CN110132223A - A kind of image terrain radiant correction of high and device - Google Patents
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Abstract
The application proposes a kind of image terrain radiant correction of high, this includes: the solar zenith angle and solar azimuth for reading image to be corrected；The gradient and slope aspect is calculated using digital elevation model, and refers to shadowing factor；The sky observation factor is calculated according to the gradient, and the effective incidence angle of the sun is calculated according to solar zenith angle, the gradient, slope aspect and solar azimuth；The shadow region of image to be corrected is extracted, and shadow region is corrected using reference shadowing factor, determines shadowing factor；Atmosphere coherent radiation amount is calculated using radiative transfer model；The reflectivity of each pixel of image to be corrected is calculated using preset reflectivity calculation formula or relative reflectance calculation formula according to solar zenith angle, the sky observation factor, the effective incidence angle of the sun, shadowing factor and atmosphere coherent radiation amount.The above method can be used in carrying out terrain radiant correction to image, realize the terrain radiant correction to image.
Description
Technical field
This application involves image radiation processing technology fields, and more specifically more particularly to a kind of image landform radiates school
Correction method and device.
Background technique
With development of remote sensing, high-definition picture is increasing, and related application is more and more extensive.But with resolution ratio
Raising, the distortion performance of the image radiation as caused by hypsography is more and more obvious, for example massif Schattenseite and tailo is same
A kind of atural object shows significant difference on the image, brings very big difficulty to image classification or other quantitative remote sensing applications.
Therefore, terrain radiant correction processing is carried out to image, it is urgent to be that high-definition picture is applied in remote sensing technology
Demand.
Summary of the invention
Based on the demand, the application proposes a kind of image terrain radiant correction of high and device, can be realized to image
Terrain radiant correction processing.
A kind of image terrain radiant correction of high, comprising:
Read the solar zenith angle and solar azimuth of image to be corrected；
The terrain slope and slope aspect of the image to be corrected are calculated using digital elevation model, and utilizes the number
Word elevation model is calculated in conjunction with the solar zenith angle and the solar azimuth with reference to shadowing factor；
The sky observation factor of the image to be corrected is calculated according to the gradient, and according to the sun zenith
The effective incidence angle of the sun is calculated in angle, the gradient, the slope aspect and the solar azimuth；
The shadow region of the image to be corrected is extracted, and school is carried out to the shadow region with reference to shadowing factor using described
Positive processing, determines shadowing factor；
The atmosphere coherent radiation amount of the image to be corrected is calculated using radiative transfer model；Wherein, the atmosphere
Coherent radiation amount includes atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and ground scatter irradiation level；
According to the solar zenith angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor with
And institute is calculated using preset reflectivity calculation formula or relative reflectance calculation formula in the atmosphere coherent radiation amount
State the reflectivity of each pixel of image to be corrected.
Optionally, before the solar zenith angle and solar azimuth for reading image to be corrected, the method also includes:
Re-projection is carried out to digital elevation model referring to the projection pattern of image to be corrected, makes the throwing of the image to be corrected
Shadow mode is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the digital elevation model
Geographic range cover the image whole image to be corrected.
Optionally, the terrain slope and slope aspect that the image to be corrected is calculated using digital elevation model, with
And using the digital elevation model in conjunction with the solar zenith angle and the solar azimuth, be calculated with reference to masking because
Son, comprising:
When digital elevation model is identical as the resolution ratio of the image to be corrected, the digital elevation model is directly utilized
The terrain slope and slope aspect of the image to be corrected is calculated, and using the digital elevation model in conjunction with the sun day
Apex angle and the solar azimuth, are calculated with reference to shadowing factor；
When resolution ratio of the high resolution of digital elevation model in the image to be corrected, first according to the figure to be corrected
The resolution ratio of picture carries out resampling processing to the digital elevation model, is then calculated using the digital elevation model after resampling
The terrain slope and slope aspect of the image to be corrected are obtained, and using the digital elevation model after resampling in conjunction with the sun
Zenith angle and the solar azimuth, are calculated with reference to shadowing factor；
When the resolution ratio of digital elevation model is lower than the resolution ratio of the image to be corrected, the digital elevation is being utilized
Model is calculated the terrain slope and slope aspect of the image to be corrected, and using the digital elevation model in conjunction with it is described too
Positive zenith angle and the solar azimuth are calculated with reference to after shadowing factor, according to the resolution ratio pair of the image to be corrected
The gradient, slope aspect and the reference shadowing factor being calculated carry out resampling processing.
Optionally, the shadow region for extracting the image to be corrected, and using the reference shadowing factor to described
Shadow region is corrected processing, determines shadowing factor, comprising:
The shadow region in the image to be corrected is extracted using histogram method, obtains image itself shadowing factor；
Using the water body and Yun Yinying with reference in shadowing factor rejecting described image itself shadowing factor, masking is determined
The factor.
Optionally, described according to the solar zenith angle, the sky observation factor, the effective incidence angle of the sun, institute
Shadowing factor and the atmosphere coherent radiation amount are stated, is calculated using preset reflectivity calculation formula or relative reflectance public
The reflectivity of each pixel of image to be corrected is calculated in formula, comprising:
When the image to be corrected has radiation calibration coefficient, according to the radiation calibration coefficient and the sun
Zenith angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount,
Using preset reflectivity calculation formula, the pixel reflectivity of the image to be corrected is calculated；
When the image to be corrected does not have radiation calibration coefficient, according to the solar zenith angle, the sky observation
The factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount, utilize preset relative reflection
The pixel reflectivity of the image to be corrected is calculated in rate calculation formula.
Optionally, the preset relative reflectance calculation formula are as follows:
Wherein, DN (x, y) indicates pixel gray value, DNbaIndicate that journey radiates corresponding pixel value, τvIndicate that atmosphere uplink is saturating
Rate is crossed, b (x, y) indicates shadowing factor, EdirIndicate ground direct projection irradiation level, τsIndicate downward atmospheric transmitance, β indicates the sun
Effective incidence angle, EdifIndicate ground scatter irradiation level, θsIndicate solar zenith angle, Vsky(x, y) indicates the sky observation factor,
EiterIndicate the multiple reflections irradiation level of neighbouring pixel.
Optionally, the method also includes:
Processing is corrected to the reflectivity of the image non-hatched area pixel to be corrected.
Optionally, the method also includes:
The image shadow edge to be corrected region is smoothed.
A kind of image terrain radiant correction device, comprising:
Data-reading unit, for reading the solar zenith angle and solar azimuth of image to be corrected；
First computing unit, for terrain slope and the slope of the image to be corrected to be calculated using digital elevation model
To, and using the digital elevation model in conjunction with the solar zenith angle and the solar azimuth, be calculated with reference to screening
Cover the factor；
Second computing unit, for the sky observation factor of the image to be corrected to be calculated according to the gradient, with
And the effective incidence angle of the sun is calculated according to the solar zenith angle, the gradient, the slope aspect and the solar azimuth；
Third computing unit refers to shadowing factor for extracting the shadow region of the image to be corrected, and using described
Processing is corrected to the shadow region, determines shadowing factor；
4th computing unit, for the atmosphere coherent radiation of the image to be corrected to be calculated using radiative transfer model
Amount；Wherein, the atmosphere coherent radiation amount includes atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and ground
Scattering irradiance；
5th computing unit, for effectively incident according to the solar zenith angle, the sky observation factor, the sun
Angle, the shadowing factor and the atmosphere coherent radiation amount, utilize preset reflectivity calculation formula or relative reflectance meter
Formula is calculated, the reflectivity of each pixel of image to be corrected is calculated.
Optionally, described device further include:
Pretreatment unit carries out re-projection to digital elevation model for the projection pattern referring to image to be corrected, makes institute
The projection pattern for stating image to be corrected is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the digital elevation model
Geographic range cover the image whole image to be corrected.
Optionally, the landform slope of the image to be corrected is calculated using digital elevation model for first computing unit
Degree and slope aspect, and be calculated using the digital elevation model in conjunction with the solar zenith angle and the solar azimuth
When with reference to shadowing factor, it is specifically used for:
When digital elevation model is identical as the resolution ratio of the image to be corrected, the digital elevation model is directly utilized
The terrain slope and slope aspect of the image to be corrected is calculated, and using the digital elevation model in conjunction with the sun day
Apex angle and the solar azimuth, are calculated with reference to shadowing factor；
When resolution ratio of the high resolution of digital elevation model in the image to be corrected, first according to the figure to be corrected
The resolution ratio of picture carries out resampling processing to the digital elevation model, is then calculated using the digital elevation model after resampling
The terrain slope and slope aspect of the image to be corrected are obtained, and using the digital elevation model after resampling in conjunction with the sun
Zenith angle and the solar azimuth, are calculated with reference to shadowing factor；
When the resolution ratio of digital elevation model is lower than the resolution ratio of the image to be corrected, the digital elevation is being utilized
Model is calculated the terrain slope and slope aspect of the image to be corrected, and using the digital elevation model in conjunction with it is described too
Positive zenith angle and the solar azimuth are calculated with reference to after shadowing factor, according to the resolution ratio pair of the image to be corrected
The gradient, slope aspect and the reference shadowing factor being calculated carry out resampling processing.
Optionally, the third computing unit extracts the shadow region of the image to be corrected, and using described with reference to screening
It covers shadow region described in factor pair and is corrected processing, when determining shadowing factor, be specifically used for:
The shadow region in the image to be corrected is extracted using histogram method, obtains image itself shadowing factor；
Using the water body and Yun Yinying with reference in shadowing factor rejecting described image itself shadowing factor, masking is determined
The factor.
Optionally, the 5th computing unit has according to the solar zenith angle, the sky observation factor, the sun
Incidence angle, the shadowing factor and the atmosphere coherent radiation amount are imitated, it is using preset reflectivity calculation formula or relatively anti-
Rate calculation formula is penetrated, when the reflectivity of each pixel of image to be corrected is calculated, is specifically used for:
When the image to be corrected has radiation calibration coefficient, according to the radiation calibration coefficient and the sun
Zenith angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount,
Using preset reflectivity calculation formula, the pixel reflectivity of the image to be corrected is calculated；
When the image to be corrected does not have radiation calibration coefficient, according to the solar zenith angle, the sky observation
The factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount, utilize preset relative reflection
The pixel reflectivity of the image to be corrected is calculated in rate calculation formula.
Optionally, the preset relative reflectance calculation formula are as follows:
Wherein, DN (x, y) indicates pixel gray value, DNbaIndicate that journey radiates corresponding pixel value, τvIndicate that atmosphere uplink is saturating
Rate is crossed, b (x, y) indicates shadowing factor, EdirIndicate ground direct projection irradiation level, τsIndicate downward atmospheric transmitance, β indicates the sun
Effective incidence angle, EdifIndicate ground scatter irradiation level, θsIndicate solar zenith angle, Vsky(x, y) indicates the sky observation factor,
EiterIndicate the multiple reflections irradiation level of neighbouring pixel.
Optionally, described device further include:
Correction processing unit is corrected processing for the reflectivity to the image non-hatched area pixel to be corrected.
Optionally, described device further include:
Smoothing processing unit, for being smoothed to the image shadow edge to be corrected region.
The image terrain radiant correction of high that the application proposes successively obtains pixel reflectivity by digital elevation model
Parameters needed for calculating utilize preset reflectivity calculation formula or relative reflectance then according to acquired parameter
The reflectivity of each pixel of image is calculated in calculation formula, achievees the purpose that image terrain radiant correction, i.e., the method achieve
To the terrain radiant correction of image.
It further, can also be with since the reflectivity of pixel can be calculated in the application by emissivity calculation formula
Be calculated the relative reflectance of pixel by relative reflectance calculation formula, thus the embodiment of the present application technical solution for
Correction image has radiation calibration coefficient and does not have the case where radiation calibration coefficient, can carry out terrain radiant correction to it
Processing.
Detailed description of the invention
In order to illustrate the technical solutions in the embodiments of the present application or in the prior art more clearly, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
The embodiment of application for those of ordinary skill in the art without creative efforts, can also basis
The attached drawing of offer obtains other attached drawings.
Fig. 1 is a kind of flow diagram of image terrain radiant correction of high provided by the embodiments of the present application；
Fig. 2 is the flow diagram of another image terrain radiant correction of high provided by the embodiments of the present application；
Fig. 3 is the schematic diagram of the image provided by the embodiments of the present application containing mountainous shade；
Fig. 4 is image histogram schematic diagram provided by the embodiments of the present application；
Fig. 5 is a kind of structural schematic diagram of image terrain radiant correction device provided by the embodiments of the present application.
Specific embodiment
Below in conjunction with the attached drawing in the embodiment of the present application, technical solutions in the embodiments of the present application carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of embodiments of the present application, instead of all the embodiments.It is based on
Embodiment in the application, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall in the protection scope of this application.
The embodiment of the present application discloses a kind of image terrain radiant correction of high, shown in Figure 1, this method comprises:
S101, the solar zenith angle and solar azimuth for reading image to be corrected；
Specifically, general remote sensing images can all directly give solar zenith angle θsWith solar azimuth φsInformation, therefore,
Solar zenith angle and solar azimuth are read directly from above-mentioned image to be corrected.
General pattern (such as Landsat TM or ETM+ image) only provides the solar zenith angle θ at center pelsWith
Solar azimuth φsNumerical value, the solar zenith angle θ of all pixels of full figuresWith solar azimuth φsIt is all made of the numerical value.For width
Width image provides solar zenith angle and azimuth generally according to certain pixel number interval, needs to carry out resampling at this time and obtain often
θ at a pixelsAnd φsNumerical value.Such as Sentinel-2 data provide one group of solar zenith angle and bearing data every 5KM
(respectively 22*22 pixel), for 10
S102, the terrain slope and slope aspect that the image to be corrected is calculated using digital elevation model, and utilize
The digital elevation model is calculated in conjunction with the solar zenith angle and the solar azimuth with reference to shadowing factor；
Illustratively, by calling Envi to mention using digital elevation model (Digital Elevation Model, DEM)
Figure to be corrected is calculated in tool Topographic > Topographic Modeling of confession, or the respective function provided
Gradient S, the slope aspect A of picture, and combine above-mentioned solar zenith angle θsWith solar azimuth φs, it is calculated with reference to shadowing factor b0
(x,y).Wherein, (x, y) indicates cell coordinate, and it is cell coordinate that the meaning of each (x, y) is identical hereinafter.
Further, the embodiment of the present application also discloses, it is above-mentioned, be calculated using digital elevation model it is described to be corrected
The terrain slope and slope aspect of image, and using the digital elevation model in conjunction with the solar zenith angle and the solar azimuth
Angle is calculated with reference to three kinds of situation processing of shadowing factor point:
When digital complex demodulation is identical as the resolution ratio of the image to be corrected, the digital elevation is directly utilized
The terrain slope S and slope aspect A of the image to be corrected is calculated in model DEM, and utilizes the digital complex demodulation knot
Close the solar zenith angle θsWith solar azimuth φs, it is calculated with reference to shadowing factor b0(x,y)；
When resolution ratio of the high resolution of digital complex demodulation in the image to be corrected, first according to described to school
The resolution ratio of positive image carries out resampling processing to the digital complex demodulation, then utilizes the digital elevation after resampling
The terrain slope S and slope aspect A of the image to be corrected is calculated in model DEM, and utilizes the digital elevation mould after resampling
Type DEM is in conjunction with the solar zenith angle θsWith solar azimuth φs, it is calculated with reference to shadowing factor b0(x,y)；
When the resolution ratio of digital complex demodulation is lower than the resolution ratio of the image to be corrected, the number is being utilized
The terrain slope S and slope aspect A of the image to be corrected is calculated in elevation model DEM, and utilizes the digital elevation model
DEM is in conjunction with the solar zenith angle θsWith solar azimuth φs, it is calculated with reference to shadowing factor b0After (x, y), according to described
The resolution ratio of image to be corrected is to gradient S, the slope aspect A being calculated and refers to shadowing factor b0(x, y) carries out resampling processing.
It is appreciated that the embodiment of the present application technical solution is fully considered when calculating the image gradient, slope aspect and shadowing factor
Whether the resolution ratio to digital elevation model matches with image resolution ratio, for unmatched situation, according to image resolution ratio pair
The resolution ratio of digital elevation model carries out resampling, or carries out resampling according to image resolution ratio to calculated result, thus makes
The parameter that must be calculated is image actual parameter, solves image resolution ratio and digital elevation model resolution ratio is inconsistent asks
Topic.
S103, the sky observation factor that the image to be corrected is calculated according to the gradient, and according to it is described too
The effective incidence angle of the sun is calculated in positive zenith angle, the gradient, the slope aspect and the solar azimuth；
Wherein, the above-mentioned sky observation factor can be calculated according to above-mentioned gradient S by following trigonometric calculations formula
It arrives:
Vsky(x, y)=cos2(S(x,y)/2)
Wherein, Vsky(x, y) indicates the sky observation factor of pixel, and S (x, y) indicates Slope of pixel.
The above-mentioned effective incident angle β of the sun, can be according to above-mentioned solar zenith angle θs, gradient S, slope aspect A and solar azimuth
φs, it is calculated by following calculation formula:
Cos β=cos θs cosS+sinSsinθs cos(φs-A)
S104, the shadow region for extracting the image to be corrected, and using the reference shadowing factor to the shadow region
It is corrected processing, determines shadowing factor；
With reference to shadowing factor it is the shadowing factor being only calculated by digital elevation model specifically, above-mentioned, is not
The shadowing factor directly determined by image to be corrected.In order to keep the shadowing factor obtained more acurrate, the embodiment of the present application is to school
Shadowing factor is directly extracted in positive image, and school then is carried out to the shadowing factor directly extracted with reference to shadowing factor using above-mentioned
Just, the shadowing factor finally determined.
The shadow region of above-mentioned image to be corrected, the shade and non-shade zone for as treating correction image distinguish knowledge
Not, recognition result is denoted as b i.e. as the shadowing factor directly extracted from image to be corrected1(x,y)。
The embodiment of the present application distinguishes identification to the shade and non-shade zone of above-mentioned image to be corrected, obtains above-mentioned
Shadowing factor b1After (x, y), above-mentioned reference shadowing factor b is recycled0(x, y) is to b1(x, y) is corrected, and is rejected therein
Erroneous judgement factor etc., the shadowing factor b (x, y) finally determined.
S105, the atmosphere coherent radiation amount that the image to be corrected is calculated using radiative transfer model；Wherein, described
Atmosphere coherent radiation amount includes atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and ground scatter irradiation level；
Specifically, being based on above-mentioned image to be corrected itself (such as dark pixel algorithm, bright ground table algorithm) or other supplementary numbers
According to (such as actual measurement or MODIS data) estimation image aerosol optical depth, moisture content, while figure is provided according to priori knowledge
The input that the radiative transfer models such as Atmospheric models when as obtaining need.Using atmospheric radiation transmission MODTRAN, 6S or
Person 6SV calculates following atmospheric parameters: atmosphere uplink transmitance τv, downward atmospheric transmitance τs, ground direct projection irradiation level EdirThe ground and
Area scattering irradiation level Edif。
S106, according to the solar zenith angle, the sky observation factor, the effective incidence angle of the sun, the masking
The factor and the atmosphere coherent radiation amount are calculated using preset reflectivity calculation formula or relative reflectance calculation formula
Obtain the reflectivity of each pixel of image to be corrected.
Specifically, respectively obtaining above-mentioned solar zenith angle θ by executing above-mentioned steps S101~S105s, sky observation
Factor ⅤskyThe effective incident angle β of (x, y), the sun, shadowing factor b (x, y) and every atmosphere coherent radiation amount: atmosphere uplink is saturating
Cross rate τv, downward atmospheric transmitance τs, ground direct projection irradiation level EdirWith ground scatter irradiation level EdifAfterwards, the embodiment of the present application benefit
With preset reflectivity calculation formula or relative reflectance calculation formula, the reflection of above-mentioned each pixel of image to be corrected is calculated
Rate.
Wherein, above-mentioned reflectivity calculation formula are as follows:
Wherein, c0And c1For image radiation calibration coefficient, DN (x, y) indicates pixel gray value, LbaIt is the radiation pair of image journey
The effective pixel region minimum value of the spoke brightness answered, i.e. image, τvIndicating atmosphere uplink transmitance, b (x, y) indicates shadowing factor,
EdirIndicate ground direct projection irradiation level, τsIndicate downward atmospheric transmitance, β indicates the effective incidence angle of the sun, EdifIndicate that ground dissipates
Penetrate irradiation level, θsIndicate solar zenith angle, Vsky(x, y) indicates the sky observation factor, EiterIndicate the multiple reflections of neighbouring pixel
Irradiation level.
The multiple reflections irradiation level E of neighbouring pixeliterCalculation formula it is as follows:
In formula: EgFor the sum of the direct projection irradiation level of the received sun of horizontal surface and diffusing scattering irradiation level；VskyFor sky sight
Survey the factor.Indicate average reflectance (the i.e. formula before this formula of (general 0.5KM) in a certain range of pixel periphery
The ρ (x, y) calculated is in a certain range of average value), belong to intermediate result.Wherein subscript i indicates the number of iterations, opens from 0
Begin, multiple reflections irradiation level EiterCan finally determine E the usual iteration of calculating 2~3 timesiterValue.
It should be noted that since above-mentioned reflectivity calculation formula needs the radiation calibration coefficient of image, when upper
Image to be corrected is stated with radiation calibration coefficient c0And c1When, it can be according to radiation calibration coefficient c0And c1And it is above-mentioned too
Positive zenith angle θs, sky observation factor ⅤskyThe effective incident angle β of (x, y), the sun, shadowing factor b (x, y) are related to every atmosphere
Amount of radiation: atmosphere uplink transmitance τv, downward atmospheric transmitance τs, ground direct projection irradiation level EdirWith ground scatter irradiation level Edif,
Using above-mentioned preset reflectivity calculation formula, the pixel reflectivity of image to be corrected is calculated.
On the other hand, when above-mentioned image to be corrected does not have radiation calibration coefficient, above-mentioned reflectivity calculation formula
It can not then apply.At this point, the embodiment of the present application designs relative reflectance calculation formula, for calculating the relatively anti-of image to be corrected
Rate is penetrated, the formula is specific as follows:
Wherein, ρt(x, y) indicates that the relative reflectance of pixel, DN (x, y) indicate pixel gray value, DNbaIndicate journey radiation
Corresponding pixel value, τvIndicate atmosphere uplink transmitance, b (x, y) indicates shadowing factor, EdirIndicate ground direct projection irradiation level, τs
Indicate downward atmospheric transmitance, β indicates the effective incidence angle of the sun, EdifIndicate ground scatter irradiation level, θsIndicate sun zenith
Angle, Vsky(x, y) indicates the sky observation factor, EiterIndicate the multiple reflections irradiation level of neighbouring pixel.
As it can be seen that above-mentioned relative reflectance calculation formula does not need the radiation calibration coefficient of image, therefore, when it is above-mentioned to
When correction image does not have radiation calibration coefficient, according to the solar zenith angle θ obtained in above-mentioned steps S101~S105s, sky
Observe factor ⅤskyThe effective incident angle β of (x, y), the sun, shadowing factor b (x, y) and every atmosphere coherent radiation amount: atmosphere uplink
Transmitance τv, downward atmospheric transmitance τs, ground direct projection irradiation level EdirWith ground scatter irradiation level Edif, using above-mentioned opposite
The pixel reflectivity of image to be corrected is calculated in reflectivity calculation formula, which is the relative reflectance of pixel.
It should be noted that real surface reflectivity, therefore such case can not be acquired due to lacking radiation calibration coefficient
Under above-mentioned neighbouring pixel multiple reflections irradiation level EiterIt can not iterate to calculate to obtain.At this point, the embodiment of the present application setting week
The average reflectance for enclosing pixel is 0.1, and neighbouring pixel multiple reflections irradiation level is calculated by following calculation formula:
Eiter=(Edir+Edif)ξ2/(1-ξ)
ξ=0.1 (1-Vsky(x,y))
By above-mentioned introduction as it can be seen that the embodiment of the present application propose image terrain radiant correction of high, by digital elevation
Model successively obtains the parameters needed for pixel reflectivity calculates and utilizes preset reflection then according to acquired parameter
The reflectivity of each pixel of image is calculated in rate calculation formula or relative reflectance calculation formula, reaches image terrain radiant correction
Purpose, i.e., the method achieve the terrain radiant corrections to image.
Further, since the reflectivity of pixel can be calculated in the embodiment of the present application by emissivity calculation formula,
The relative reflectance of pixel, therefore the embodiment of the present application technical solution can also be calculated by relative reflectance calculation formula
There is radiation calibration coefficient for image to be corrected and do not have the case where radiation calibration coefficient, can carry out landform spoke to it
Penetrate correction process.
Also, when the embodiment of the present application parameters needed for obtaining terrain radiant correction, digital height is fully taken into account
The resolution ratio of journey model and image to be corrected whether unanimous circumstances, to the parameter of digital elevation model or acquisition according to be corrected
Image resolution ratio carries out resampling, and, shadowing factor is directly extracted from image when calculating shadowing factor, so that obtain
Parameter suits image resolution ratio, and then guarantees more acurrate to the radiant correction of image.
Optionally, it is also disclosed in another embodiment of the application, in the solar zenith angle for reading image to be corrected
Before solar azimuth, the method also includes:
Re-projection is carried out to digital elevation model referring to the projection pattern of image to be corrected, makes the throwing of the image to be corrected
Shadow mode is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the digital elevation model
Geographic range cover the image whole image to be corrected.
Specifically, the application is implemented before being preordained angle and solar azimuth angle information from the reading sun in image to be corrected
Example carries out consistency check to digital elevation model and image to be corrected first, can mainly execute in terms of two:
On the one hand, image to be corrected is subjected to geometric accurate correction or ortho-rectification, it is ensured that digital elevation model with to school
Registration accuracy between positive image, and check digital elevation model projection pattern and image to be corrected projection pattern whether
Unanimously, if it is inconsistent, the projection pattern referring to image to be corrected makes to be corrected digital elevation model progress re-projection
The projection pattern of image and the projection pattern of digital elevation model are consistent.
On the other hand, check whether the geographic range of digital elevation model covers entire image to be corrected, if do not covered
Entire image to be corrected is covered, then correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, make number
The geographic range of elevation model covers image whole image to be corrected.
It should be noted that above-mentioned both sides processing, can select to execute or do not execute according to the actual situation, be elected to
It single can execute, can also all execute when selecting execution.
Optionally, shown in Figure 2, it is also disclosed in another embodiment of the application, to school described in the extraction
The shadow region of positive image, and processing is corrected to the shadow region with reference to shadowing factor using described, determine shadowing factor,
Include:
S204, the shadow region in the image to be corrected is extracted using histogram method, obtains image itself shadowing factor；
Specifically, the image containing mountainous shade shows as apparent bimodal distribution on the histogram, such as to shown in Fig. 3
The image containing mountainous shade, obtain that its histogram is available shown in Fig. 4 as a result, histogram distribution situation is obviously in double
Peak is distributed, and the gray value at valley between two peak values can be used as the threshold value for distinguishing shade and non-shadow, and gray value is less than should
The region of threshold value can be judged as shadow region.
According to the method described above, the embodiment of the present application obtains the histogram of above-mentioned image to be corrected, searches from histogram
Valley between two peak values determines the division threshold value of the shade and non-shade zone in image to be corrected, then utilizes the threshold
Value identifies the shade and non-shade zone in image to be corrected, and the shade and non-shade zone of identification is marked, such as
Shadow region is labeled as 0, and nonshaded area is labeled as 1, obtains image itself shadowing factor of image to be corrected, is denoted as b1(x,y)。
S205, using it is described with reference to shadowing factor reject described image itself shadowing factor in water body and Yun Yinying, really
Determine shadowing factor.
Specifically, since the gray value of water body and cloud shade on the image is lower, be easy when above-mentioned histogram judges with
Massif shielded area is obscured, and image shadow region is identified as, it is therefore desirable to reject water body from itself shadowing factor of above-mentioned image
And Yun Yinying, obtain final shadowing factor.
Above-mentioned image itself shadowing factor b of the embodiment of the present application to be extracted from image to be corrected1Based on (x, y), knot
Close the reference shadowing factor b stated0(x, y) removes the erroneous judgement for water body, Yun Yinying, it is final determine shadowing factor be b (x,
y)。
Step S201~S203, S206~S207 in the present embodiment are respectively corresponded in embodiment of the method shown in FIG. 1
Step S101~S103, S105~S106, the content of particular content embodiment of the method shown in Figure 1, herein no longer
It repeats.
Optionally, it is also disclosed in another embodiment of the application, each pixel of image to be corrected is being calculated
After reflectivity, the method also includes:
Processing is corrected to the reflectivity of the image non-hatched area pixel to be corrected.
Specifically, being reflected when larger solar zenith angle incidence nonshaded area pixel in the case of assuming in order to avoid lambert's property
Correction factor is added to the relative reflectance of above-mentioned image non-hatched area pixel to be corrected in the overcorrect of rate, the embodiment of the present application
G is corrected, the reflectivity ρ after being correctedt_mm(x, y) are as follows:
ρt_mm(x, y)=ρt(x,y)·G
Wherein, the calculating of correction factor G is as follows:
Show that g is set as proper between 0.2~0.25 according to the most experiments corrected in complex area.βTAccording to
Solar zenith angle θsWith following empirical relation:
Exponential factor b is arranged according to wavelength and ground mulching, is set as b=1/2 for nonvegetated area domain；Vegetation region but wave
Section central wavelength is less than 720nm and is set as b=3/4；Vegetation region but central wavelength are more than or equal to 720nm and are set as b=1/3.
Optionally, it is also disclosed in another embodiment of the application, each pixel of image to be corrected is being calculated
After reflectivity, the method also includes:
The image shadow edge to be corrected region is smoothed.
Specifically, the case where image resolution ratio is lower than for digital elevation model resolution ratio, in order to avoid because of shadow edge
The overcorrect problem that error may cause is extracted, the embodiment of the present application carries out above-mentioned image shadow edge to be corrected region smooth
Processing.
Above-mentioned smoothing process specifically: set buffering range (example in above-mentioned image shadow edge to be corrected area first
Such as 5 pixels in left and right), then to the ratio result ρ of the pixel reflectance value within the scope of this and original pixel valuet(x,y)/DN
(x, y) carries out mean filter and handles to obtain mean_filter [ρt(x, y)/DN (x, y)], finally handled with above-mentioned mean filter
As a result again multiplied by original pixel value mean_filter [ρt(x, y)/DN (x, y)] DN (x, y), completes to treat correction image
The smoothing processing in shadow edge region.
Corresponding with above-mentioned image terrain radiant correction of high, another embodiment of the application also discloses a kind of image
Terrain radiant correction device, shown in Figure 5, which includes:
Data-reading unit 100, for reading the solar zenith angle and solar azimuth of image to be corrected；
First computing unit 110, for the terrain slope of the image to be corrected to be calculated using digital elevation model
And slope aspect, and ginseng is calculated in conjunction with the solar zenith angle and the solar azimuth using the digital elevation model
Examine shadowing factor；
Second computing unit 120, for the sky observation factor of the image to be corrected to be calculated according to the gradient,
And according to the solar zenith angle, the gradient, the slope aspect and the solar azimuth sun to be calculated effectively incident
Angle；
Third computing unit 130, for extracting the shadow region of the image to be corrected, and using it is described with reference to masking because
Son is corrected processing to the shadow region, determines shadowing factor；
4th computing unit 140, the atmosphere for the image to be corrected to be calculated using radiative transfer model are related
Amount of radiation；Wherein, the atmosphere coherent radiation amount include atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and
Ground scatter irradiation level；
5th computing unit 150, for effective according to the solar zenith angle, the sky observation factor, the sun
Incidence angle, the shadowing factor and the atmosphere coherent radiation amount, utilize preset reflectivity calculation formula or relative reflection
The reflectivity of each pixel of image to be corrected is calculated in rate calculation formula.
Optionally, it is also disclosed in another embodiment of the application, described device further include:
Pretreatment unit carries out re-projection to digital elevation model for the projection pattern referring to image to be corrected, makes institute
The projection pattern for stating image to be corrected is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the digital elevation model
Geographic range cover the image whole image to be corrected.
Wherein, as a kind of optional implementation, first computing unit 110 is calculated using digital elevation model
To the terrain slope and slope aspect of the image to be corrected, and using the digital elevation model in conjunction with the solar zenith angle and
The solar azimuth is specifically used for when being calculated with reference to shadowing factor:
When digital elevation model is identical as the resolution ratio of the image to be corrected, the digital elevation model is directly utilized
The terrain slope and slope aspect of the image to be corrected is calculated, and using the digital elevation model in conjunction with the sun day
Apex angle and the solar azimuth, are calculated with reference to shadowing factor；
When resolution ratio of the high resolution of digital elevation model in the image to be corrected, first according to the figure to be corrected
The resolution ratio of picture carries out resampling processing to the digital elevation model, is then calculated using the digital elevation model after resampling
The terrain slope and slope aspect of the image to be corrected are obtained, and using the digital elevation model after resampling in conjunction with the sun
Zenith angle and the solar azimuth, are calculated with reference to shadowing factor；
When the resolution ratio of digital elevation model is lower than the resolution ratio of the image to be corrected, the digital elevation is being utilized
Model is calculated the terrain slope and slope aspect of the image to be corrected, and using the digital elevation model in conjunction with it is described too
Positive zenith angle and the solar azimuth are calculated with reference to after shadowing factor, according to the resolution ratio pair of the image to be corrected
The gradient, slope aspect and the reference shadowing factor being calculated carry out resampling processing.
As a kind of optional implementation, the third computing unit 130 extracts the shadow region of the image to be corrected,
And processing is corrected to the shadow region with reference to shadowing factor using described, when determining shadowing factor, it is specifically used for:
The shadow region in the image to be corrected is extracted using histogram method, obtains image itself shadowing factor；
Using the water body and Yun Yinying with reference in shadowing factor rejecting described image itself shadowing factor, masking is determined
The factor.
As a kind of optional implementation, the 5th computing unit 150 is according to the solar zenith angle, the sky
The factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount are observed, preset reflection is utilized
Rate calculation formula or relative reflectance calculation formula are specific to use when the reflectivity of each pixel of image to be corrected is calculated
In:
When the image to be corrected has radiation calibration coefficient, according to the radiation calibration coefficient and the sun
Zenith angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount,
Using preset reflectivity calculation formula, the pixel reflectivity of the image to be corrected is calculated；
When the image to be corrected does not have radiation calibration coefficient, according to the solar zenith angle, the sky observation
The factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount, utilize preset relative reflection
The pixel reflectivity of the image to be corrected is calculated in rate calculation formula.
As a kind of optional implementation, the preset relative reflectance calculation formula are as follows:
Wherein, DN (x, y) indicates pixel gray value, DNbaIndicate that journey radiates corresponding pixel value, τvIndicate that atmosphere uplink is saturating
Rate is crossed, b (x, y) indicates shadowing factor, EdirIndicate ground direct projection irradiation level, τsIndicate downward atmospheric transmitance, β indicates the sun
Effective incidence angle, EdifIndicate ground scatter irradiation level, θsIndicate solar zenith angle, Vsky(x, y) indicates the sky observation factor,
EiterIndicate the multiple reflections irradiation level of neighbouring pixel.
Optionally, it is also disclosed in another embodiment of the application, described device further include:
Correction processing unit is corrected processing for the reflectivity to the image non-hatched area pixel to be corrected.
Optionally, it is also disclosed in another embodiment of the application, described device further include:
Smoothing processing unit, for being smoothed to the image shadow edge to be corrected region.
Specifically, the specific works content of each unit in each embodiment of above-mentioned image terrain radiant correction device,
The content of above method embodiment is referred to, details are not described herein again.
For the various method embodiments described above, for simple description, therefore, it is stated as a series of action combinations, but
Be those skilled in the art should understand that, the application is not limited by the described action sequence because according to the application, certain
A little steps can be performed in other orders or simultaneously.Secondly, those skilled in the art should also know that, it is retouched in specification
The embodiment stated belongs to preferred embodiment, necessary to related actions and modules not necessarily the application.
It should be noted that all the embodiments in this specification are described in a progressive manner, each embodiment weight
Point explanation is the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.
For device class embodiment, since it is basically similar to the method embodiment, so being described relatively simple, related place ginseng
See the part explanation of embodiment of the method.
Step in each embodiment method of the application can be sequentially adjusted, merged and deleted according to actual needs.
Each embodiment kind device of the application and module in terminal and submodule can be merged according to actual needs, be drawn
Divide and deletes.
In several embodiments provided herein, it should be understood that disclosed terminal, device and method, Ke Yitong
Other modes are crossed to realize.For example, terminal embodiment described above is only schematical, for example, module or submodule
Division, only a kind of logical function partition, there may be another division manner in actual implementation, for example, multiple submodule or
Module may be combined or can be integrated into another module, or some features can be ignored or not executed.Another point is shown
The mutual coupling, direct-coupling or communication connection shown or discussed can be through some interfaces, between device or module
Coupling or communication connection are connect, can be electrical property, mechanical or other forms.
Module or submodule may or may not be physically separated as illustrated by the separation member, as mould
The component of block or submodule may or may not be physical module or submodule, it can and it is in one place, or
It may be distributed on multiple network modules or submodule.Some or all of mould therein can be selected according to the actual needs
Block or submodule achieve the purpose of the solution of this embodiment.
In addition, each functional module or submodule in each embodiment of the application can integrate in a processing module
In, it is also possible to modules or submodule physically exists alone, it can also be integrated with two or more modules or submodule
In a module.Above-mentioned integrated module or submodule both can take the form of hardware realization, can also use software function
Energy module or the form of submodule are realized.
Professional further appreciates that, unit described in conjunction with the examples disclosed in the embodiments of the present disclosure
And algorithm steps, can be realized with electronic hardware, computer software, or a combination of the two, in order to clearly demonstrate hardware and
The interchangeability of software generally describes each exemplary composition and step according to function in the above description.These
Function is implemented in hardware or software actually, the specific application and design constraint depending on technical solution.Profession
Technical staff can use different methods to achieve the described function each specific application, but this realization is not answered
Think beyond scope of the present application.
The step of method described in conjunction with the examples disclosed in this document or algorithm, can directly be held with hardware, processor
The combination of capable software unit or the two is implemented.Software unit can be placed in random access memory (RAM), memory, read-only deposit
Reservoir (ROM), electrically programmable ROM, electrically erasable ROM, register, hard disk, moveable magnetic disc, CD-ROM or technology
In any other form of storage medium well known in field.
Finally, it is to be noted that, herein, relational terms such as first and second and the like be used merely to by
One entity or operation are distinguished with another entity or operation, without necessarily requiring or implying these entities or operation
Between there are any actual relationship or orders.Moreover, the terms "include", "comprise" or its any other variant meaning
Covering non-exclusive inclusion, so that the process, method, article or equipment for including a series of elements not only includes that
A little elements, but also including other elements that are not explicitly listed, or further include for this process, method, article or
The intrinsic element of equipment.In the absence of more restrictions, the element limited by sentence "including a ...", is not arranged
Except there is also other identical elements in the process, method, article or apparatus that includes the element.
The foregoing description of the disclosed embodiments makes professional and technical personnel in the field can be realized or use the application.
Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein
General Principle can be realized in other embodiments without departing from the spirit or scope of the application.Therefore, the application
It is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein phase one
The widest scope of cause.
Claims (10)
1. a kind of image terrain radiant correction of high characterized by comprising
Read the solar zenith angle and solar azimuth of image to be corrected；
The terrain slope and slope aspect of the image to be corrected are calculated using digital elevation model, and high using the number
Solar zenith angle described in journey models coupling and the solar azimuth, are calculated with reference to shadowing factor；
Be calculated the sky observation factor of the image to be corrected according to the gradient, and according to the solar zenith angle,
The effective incidence angle of the sun is calculated in the gradient, the slope aspect and the solar azimuth；
The shadow region of the image to be corrected is extracted, and place is corrected to the shadow region with reference to shadowing factor using described
Reason, determines shadowing factor；
The atmosphere coherent radiation amount of the image to be corrected is calculated using radiative transfer model；Wherein, the atmosphere is related
Amount of radiation includes atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and ground scatter irradiation level；
According to the solar zenith angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor and institute
State atmosphere coherent radiation amount, using preset reflectivity calculation formula or relative reflectance calculation formula, be calculated it is described to
Correct the reflectivity of each pixel of image.
2. the method according to claim 1, wherein in the solar zenith angle and the sun side that read image to be corrected
Before parallactic angle, the method also includes:
Re-projection is carried out to digital elevation model referring to the projection pattern of image to be corrected, makes the projection side of the image to be corrected
Formula is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the ground of the digital elevation model
It manages range and covers the image whole image to be corrected.
3. the method according to claim 1, wherein it is described be calculated using digital elevation model it is described to school
The terrain slope and slope aspect of positive image, and using the digital elevation model in conjunction with the solar zenith angle and the sun side
Parallactic angle is calculated with reference to shadowing factor, comprising:
When digital elevation model is identical as the resolution ratio of the image to be corrected, directly calculated using the digital elevation model
The terrain slope and slope aspect of the image to be corrected are obtained, and using the digital elevation model in conjunction with the solar zenith angle
With the solar azimuth, it is calculated with reference to shadowing factor；
When resolution ratio of the high resolution of digital elevation model in the image to be corrected, first according to the image to be corrected
Resolution ratio carries out resampling processing to the digital elevation model, is then calculated using the digital elevation model after resampling
The terrain slope and slope aspect of the image to be corrected, and using the digital elevation model after resampling in conjunction with the sun zenith
Angle and the solar azimuth, are calculated with reference to shadowing factor；
When the resolution ratio of digital elevation model is lower than the resolution ratio of the image to be corrected, the digital elevation model is being utilized
The terrain slope and slope aspect of the image to be corrected is calculated, and using the digital elevation model in conjunction with the sun day
Apex angle and the solar azimuth are calculated with reference to after shadowing factor, according to the resolution ratio of the image to be corrected to calculating
The obtained gradient, slope aspect and reference shadowing factor carries out resampling processing.
4. the method according to claim 1, wherein the shadow region for extracting the image to be corrected, and
Processing is corrected to the shadow region with reference to shadowing factor using described, determines shadowing factor, comprising:
The shadow region in the image to be corrected is extracted using histogram method, obtains image itself shadowing factor；
Using it is described with reference to shadowing factor reject described image itself shadowing factor in water body and Yun Yinying, determine masking because
Son.
5. the method according to claim 1, wherein described according to the solar zenith angle, the sky observation
The factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount, utilize preset albedometer
Formula or relative reflectance calculation formula are calculated, the reflectivity of each pixel of image to be corrected is calculated, comprising:
When the image to be corrected has radiation calibration coefficient, according to the radiation calibration coefficient and the sun zenith
Angle, the sky observation factor, the effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount utilize
The pixel reflectivity of the image to be corrected is calculated in preset reflectivity calculation formula；
When the image to be corrected does not have radiation calibration coefficient, according to the solar zenith angle, the sky observation factor,
The effective incidence angle of the sun, the shadowing factor and the atmosphere coherent radiation amount, utilize preset relative reflectance meter
Formula is calculated, the pixel reflectivity of the image to be corrected is calculated.
6. according to the method described in claim 5, it is characterized in that, the preset relative reflectance calculation formula are as follows:
Wherein, DN (x, y) indicates pixel gray value, DNbaIndicate that journey radiates corresponding pixel value, τvIndicate that atmosphere uplink penetrates
Rate, b (x, y) indicate shadowing factor, EdirIndicate ground direct projection irradiation level, τsIndicate downward atmospheric transmitance, β indicates that the sun has
Imitate incidence angle, EdifIndicate ground scatter irradiation level, θsIndicate solar zenith angle, Vsky(x, y) indicates the sky observation factor, Eiter
Indicate the multiple reflections irradiation level of neighbouring pixel.
7. the method according to claim 1, wherein the method also includes:
Processing is corrected to the reflectivity of the image non-hatched area pixel to be corrected.
8. the method according to claim 1, wherein the method also includes:
The image shadow edge to be corrected region is smoothed.
9. a kind of image terrain radiant correction device characterized by comprising
Data-reading unit, for reading the solar zenith angle and solar azimuth of image to be corrected；
First computing unit, for the terrain slope and slope aspect of the image to be corrected to be calculated using digital elevation model,
And using the digital elevation model in conjunction with the solar zenith angle and the solar azimuth, be calculated with reference to masking because
Son；
Second computing unit, for the sky observation factor of the image to be corrected, Yi Jigen to be calculated according to the gradient
The effective incidence angle of the sun is calculated according to the solar zenith angle, the gradient, the slope aspect and the solar azimuth；
Third computing unit, for extracting the shadow region of the image to be corrected, and the utilization reference shadowing factor to institute
It states shadow region and is corrected processing, determine shadowing factor；
4th computing unit, for the atmosphere coherent radiation amount of the image to be corrected to be calculated using radiative transfer model；
Wherein, the atmosphere coherent radiation amount includes atmosphere uplink transmitance, downlink transmitance, ground direct projection irradiation level and ground scatter
Irradiation level；
5th computing unit, for according to the solar zenith angle, the sky observation factor, the effective incidence angle of the sun,
The shadowing factor and the atmosphere coherent radiation amount are calculated public using preset reflectivity calculation formula or relative reflectance
The reflectivity of each pixel of image to be corrected is calculated in formula.
10. device according to claim 9, which is characterized in that described device further include:
Pretreatment unit carries out re-projection to digital elevation model for the projection pattern referring to image to be corrected, make it is described to
The projection pattern for correcting image is consistent with the projection pattern of the digital elevation model；
And/or
Correction image is treated according to the geographic range of digital elevation model and carries out cutting processing, makes the ground of the digital elevation model
It manages range and covers the image whole image to be corrected.
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| CN111667432A (en) * | 2020-06-09 | 2020-09-15 | 中国电子科技集团公司第五十四研究所 | Remote sensing image shadow removing method based on physical model |
| CN114782829A (en) * | 2022-06-22 | 2022-07-22 | 浙江甲骨文超级码科技股份有限公司 | Method and system for constructing yield estimation model and yield estimation method and system |
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| CN111667432A (en) * | 2020-06-09 | 2020-09-15 | 中国电子科技集团公司第五十四研究所 | Remote sensing image shadow removing method based on physical model |
| CN111667432B (en) * | 2020-06-09 | 2022-08-02 | 中国电子科技集团公司第五十四研究所 | Remote sensing image shadow removing method based on physical model |
| CN114782829A (en) * | 2022-06-22 | 2022-07-22 | 浙江甲骨文超级码科技股份有限公司 | Method and system for constructing yield estimation model and yield estimation method and system |
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