CN100344948C - Aviation high spectrum remote sensing flight ground synchronous scaling and reflectivity conversion method - Google Patents

Abstract

The present invention relates to an aviation high spectrum remote sensing flight ground synchronous calibration and reflectivity conversion method. The method comprises three subprocesses: generally laying out a ground synchronous calibration test, obtaining ground synchronous calibration data and converting an indoor reflectance ratio. The present invention selects a sun altitude angle as a reference according to the ground synchronous calibration data obtained by the ground synchronous calibration test so as to convert the reflectance ratio of aviation high spectrum remote sensing data. Accurate and reliable ground calibration data can be obtained by the method of the present invention, and the influence of time on the radiance of ground objects is also considered in converting the reflectance ratio; thus, the accuracy of reflectance ratio conversion is improved; at the same time, the problem that the acquisition time of air route images is overlong or the images do not contain ground calibration points is solved. The present invention lays a foundation for applying and analyzing high spectrum remote sensing information.

Description

A kind of method that realizes aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion

Technical field

The present invention relates to the sensor information process field, particularly a kind of method that realizes aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion.

Background technology

High-spectrum remote sensing data has higher resolution on the spectrum dimension, the comparatively detailed spectral characteristic of complete sum of ground object target can be provided.Because be subjected to the influence of atmosphere, spectral signal that remote sensor receives and atural object real spectrum characteristic have certain deviation; The reflectance spectrum characteristic is intrinsic physics of atural object and chemical feature index in addition, the intrinsic propesties that more can reflect atural object than radiation wave spectrum.Therefore, have only high-spectrum remote sensing data is converted to reflectivity, could more effectively carry out follow-up applied analysis.For high-spectrum remote-sensing was used, reflectivity conversion was a very important element task.

Reflectivity conversion method commonly used at present comprises utilizes radiation transfer equation to carry out reflectivity conversion, utilize image itself to carry out reflectivity conversion such as flat field model, inherent average relative reflectance model, logarithm residual error model etc., and the method for carrying out reflectivity conversion by ground actual measurement reflectance spectrum data.These three class methods respectively have characteristics: radiation transfer theory is comparatively ripe, but needs to know atmospheric parameter and relevant data in concrete the application, and attitude instability in the airborne remote sensing system operational process does not have real-time atmospheric parameter record, is difficult to use.It is fairly simple to utilize image itself to carry out the method for reflectivity conversion, but what obtain is relative reflectance.Therefore carrying out reflectivity conversion by the ground synchronous calibration measured data is easy, the most effective and the most practical method that operates.Analyze to have now and test the method for carrying out reflectivity conversion, in concrete the application, generally also have following problem by ground synchronous calibration:

1) ground synchronous calibration experimental arrangement error or unreasonable

The ground synchronous calibration experiment is the important content that carries out reflectivity conversion by ground data, does not have ground synchronous calibration data accurately and reliably, just can not obtain high-precision reflectivity.This is a very numerous and diverse job, comprises artificial and the determining, manually calibrate the layout of atural object, calibrate layouting of atural object naturally of calibration type of ground objects naturally, and the obtaining etc. of ground synchronous calibration data.But in real world applications, exist such as causing the selection of calibration type of ground objects improper without wave spectrum experiment fully and analysis, calibration atural object size design is improper to make the influence that can't effectively eliminate mixed pixel in application, and the ground data synchronism of obtaining is crossed problem such as difference and made the ground calibration data of obtaining not accurate enough reliably.Therefore press for that a cover is complete, system arrange the ground synchronous calibration experiment carrying out ground synchronous calibration according to aviation flight, and then obtain the method for accurately reliable ground scalar number certificate.

2) the reflectivity conversion method is not considered the influence of time factor

Having now utilizes the ground synchronous data to carry out the method for reflectivity conversion, generally be that entire image is done as a whole the processing, do not consider the influence of time factor to atural object target emanation characteristic, this disposal route is comparatively suitable for the little small size test site of aerial remotely-sensed data acquisition time span.Aviation high-spectrum remote sensing data spatial resolution is generally higher, can not be to the large area region instantaneous imaging, and common aviation flight experiment can cover many course lines; And because the restriction of experiment condition, ground synchronous calibration can only concentrate on the nearer several representative points of certain bar airline distance.If therefore course line, ground calibration point place is long, when perhaps utilizing the ground calibration data to look like to carry out reflectivity conversion, consider that or else the influence of time factor will cause bigger deviation to not containing ground calibration point enroute chart.

Summary of the invention

The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of method that realizes aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion is provided, to obtain accurately reliable ground scalar number certificate, and when reflectivity conversion, will the time influence of ground object target spoke brightness be taken into account, improve the precision of reflectivity conversion.

For achieving the above object, the invention provides a kind of method that realizes aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion, its characteristics are to comprise the following steps:

(1) determines the latitude and longitude coordinates of flight path and major control point;

(2) determine the scope and the ground calibration thing type of ground scaling point according to flight path;

(3) time of determining ground experiment is the moment that aircraft is crossed ground calibration point;

(4) carry out the ground synchronous calibration experiment, obtain ground synchronous calibration data, this synchronous calibration data comprises ground spectral data and ground calibration auxiliary data, and wherein the ground calibration auxiliary data comprises the longitude and latitude of time that each spectral data obtains and each calibration thing position;

(5) reflectivity conversion step:, make benchmark with the sun altitude of choosing the aviation high-spectrum remote sensing data is carried out reflectivity conversion according to the ground synchronous calibration data of obtaining.Described reflectivity conversion step comprises the following steps:

When determining that i. the aviation high-spectrum remote sensing carried out reflectivity conversion, be elected to be the sun altitude of benchmark;

Ii. basis is the reflectivity when entire image is converted to same sun altitude, still image pixel value is converted to the reflectivity constantly of imaging separately, determines the spoke brightness value L of each pixel of image _{S λ}

Iii. determine the inverting coefficient k of reflectivity _λAnd b _λ

Iv. with the inverting coefficient k _λAnd b _λBe applied to the spoke brightness value L of step I i gained according to the form of ρ=kL+b _{S λ}, can obtain reflectivity data ρ _{G λ}

Described ground calibration thing comprises artificial and natural ground calibration thing, and wherein artificial ground calibration thing comprises as the byssus of bright body with as the black cotton of black matrix; Naturally the calibration thing comprises concrete floor as bright body, water body and as the dump of black matrix, the area of described ground calibration thing all is not less than 10 * 10 pixel areas, and is positioned at point under the machine.

Described inverting coefficient k _λAnd b _λBe the spoke brightness value of the respective regions that extracts according to ground actual measurement synchronous calibration data and from image, utilize least square method to calculate.

Described aviation high-spectrum remote sensing data is the enroute chart picture that comprises ground calibration point, and when corresponding sun altitude was benchmark during with the imaging of ground calibration point, described reflectivity conversion step comprised the following steps:

(1) determine the sun altitude of each pixel of enroute chart picture, selecting the corresponding pixel area of ground scaling point on image is the interesting image district, determines and with the pairing average sun altitude h of all images region of interest _tBe benchmark;

(2), determine that entire image calculating entire image is at average sun altitude h according to following formula _tSpoke brightness value L under the image-forming condition _{S λ t}:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·\sin h_t$

H wherein _tBe the pairing sun altitude of pixel i; L _{S λ t}It is the original spoke brightness value of entire image correspondence;

(3) the spoke brightness calculation inverting coefficient that utilizes ground synchronous calibration data and extract from the interesting image district comprises the following steps:

1. extracting each interesting image district sun altitude is h _tThe time each passage pairing spoke brightness value;

2. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

3. pairing image wave spectrum in each interesting image district and ground wave spectrum are matched, and set up system of equations, and try to achieve the inverting coefficient k of λ wave band correspondence by following equation _λAnd b _λ:

ρ _gλR＝k _λ·L _sλR+b _λ

ρ wherein _{G λ R}Be the ground wave spectrum after resampling; L _{S λ R}The sun altitude that extracts for image respective image region of interest is h _tThe spoke brightness value;

(4) the inverting coefficient k _λAnd b _λEquation shown in (3) is used for the simulation spoke brightness value L that step (2) obtains set by step _{S λ t}, can obtain entire image is h at sun altitude _tReflectivity ρ _{G λ t}

Described aviation high-spectrum remote sensing data is the course line image pixel that comprises ground calibration point, and with each pixel imaging of image when corresponding sun altitude is benchmark constantly, described reflectivity conversion step comprises the following steps:

(1) determine the sun altitude of each pixel of enroute chart picture, selecting the corresponding pixel area of ground scaling point on image is the interesting image district, extracts the spoke brightness value L in each interesting image district from image _{S λ t}, determine and with the average sun altitude h of its imaging _tBe benchmark;

(2) calculate each interesting image district at the corresponding sun altitude h of pixel i according to following formula _iSimulation spoke brightness value L under the condition _{S λ Oi}:

$L_{\mathrm{s\λOi}}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·\sin h_i;$

(3) utilize ground synchronous calibration data and the spoke brightness value that extracts from the interesting image district calculates the inverting coefficient of each pixel, comprise the following steps:

1. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

2. for pixel i, the simulation spoke brightness value and resampling ground, the ground wave spectrum in each interesting image district matched, and set up system of equations by following relation, try to achieve the corresponding inverting coefficient of each pixel:

ρ _gλO＝k _i·L _sλOi+b _i

Wherein, ρ _{G λ O}Be the ground wave spectrum after resampling; L _{S λ Oi}Simulation spoke brightness value from the extraction of respective image region of interest; k _iAnd b _iBe the pairing reflectivity inverting of the pixel i that is asked coefficient.

(4) trying to achieve inverting coefficient k _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain the reflectivity ρ of pixel i _{G λ i}:

ρ _gλi＝k _i·L _sλi+b _i

L wherein _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

Described aviation high-spectrum remote sensing data is not for containing the course line image pixel of ground calibration point, and with image each when pixel imaging moment, corresponding sun altitude was benchmark, described reflectivity conversion step may further comprise the steps:

(1) determines the sun altitude of each pixel of enroute chart picture, from containing the spoke brightness value L in each interesting image district that the ground calibration dot image reads _{S λ t}And corresponding sun altitude h _t

(2) for pixel i, establishing its sun altitude is h _i, calculate each interesting image district as follows at this sun altitude h _iCorresponding down simulation radiance L _{S λ Oi}:

$L_{\mathrm{s\λOi}}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·\sin h_i;$

(3) utilize the spoke brightness value in ground synchronous calibration data and interesting image district to calculate the inverting coefficient, comprise the following steps:

1. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

2. for pixel i, the simulation spoke brightness value and resampling ground, the ground wave spectrum in each interesting image district matched, and set up system of equations by following relation, try to achieve the corresponding reflectivity inverting of each pixel i coefficient k _iAnd b _i:

ρ _gλO＝k _i·L _sλOi+b _i；

Wherein, ρ _{G λ O}Be the ground wave spectrum after resampling; L _{S λ Oi}Simulation spoke brightness value for the respective image region of interest;

(4) with the inverting coefficient k that obtains _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain the reflectivity ρ of pixel i _{G λ i}:

ρ _gλi＝k _i·L _sλi+b _i

L wherein _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

Described aviation high-spectrum remote sensing data is not for containing the enroute chart picture of ground calibration point, and when corresponding sun altitude was benchmark during with the imaging of ground calibration point, described reflectivity conversion step may further comprise the steps:

(1) determines the sun altitude of each pixel of enroute chart picture, read existing inverting coefficient k _λAnd b _λAnd pairing imaging sun altitude h _t

(2), entire image is converted to sun altitude h according to following formula _tSimulation spoke brightness value L under the image-forming condition _{S λ t}:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_t$

H wherein _iSun altitude for pixel i; L _{S λ i}Be the original spoke brightness value of entire image;

(3) with the inverting coefficient k _λAnd b _λBe applied to the simulation spoke luminance picture of above-mentioned steps (2) gained according to the form of ρ=kL+b, can obtain entire image is h at altitude of the sun _tReflectivity.

Described sun altitude is that promptly the imaging time of each pixel correspondence and latitude and longitude information calculate according to remote sensing flight auxiliary data.

The present invention tests ground synchronous calibration before ground synchronous calibration experiment and has carried out scientific and reasonable general layout, select suitable calibration type of ground objects through wave spectrum experiment and analysis, suitably the atural object size is calibrated in design, effectively subdue the influence of mixed pixel, assurance obtains the synchronism of ground data, thereby guaranteed the accurately reliable of the ground synchronous calibration data obtained in the ground synchronous calibration experiment; The ground synchronous calibration data that the present invention simultaneously utilizes the ground synchronous calibration realization to obtain is carried out reflectivity conversion to the aviation high-spectrum remote sensing data, corresponding sun altitude is that benchmark carries out reflectivity conversion to the aviation high-spectrum remote sensing data during promptly with the imaging of ground calibration point, to the time influence of ground object target spoke brightness be taken into account, it is long or when not containing ground calibration point enroute chart and look like to carry out reflectivity conversion to have overcome course line, ground calibration point place, do not consider that time factor will bring the problem than large deviation, improve the precision of reflectivity conversion.

The present invention is further illustrated below in conjunction with accompanying drawing and embodiment.

Description of drawings

Fig. 1 is a workflow diagram of the present invention.

Fig. 2 is the workflow diagram of airborne remote sensing flight ground synchronous calibration experimental set-up of the present invention.

Fig. 3 is the process flow diagram that the aviation high-spectrum remote sensing data is carried out the embodiment 1 of reflectivity conversion of the present invention.

Fig. 4 is the process flow diagram that the aviation high-spectrum remote sensing data is carried out the embodiment 2 of reflectivity conversion of the present invention.

Fig. 5 is the method flow diagram of calculating sun altitude of the present invention.

Fig. 6 is the process flow diagram that the aviation high-spectrum remote sensing data is carried out the embodiment 3 of reflectivity conversion of the present invention.

Fig. 7 is the process flow diagram that the aviation high-spectrum remote sensing data is carried out the embodiment 4 of reflectivity conversion of the present invention.

Embodiment

A kind of method of aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion that realizes of the present invention utilizes ground synchronous calibration that the aviation high-spectrum remote sensing data is carried out reflectivity conversion, as shown in Figure 1, this method comprises obtaining and three subprocess of indoor reflection rate conversion of ground synchronous calibration experimental set-up, ground synchronous calibration data.

Wherein ground synchronous calibration experimental set-up process is earlier determined flight path according to application demand as shown in Figure 2, and provides the latitude and longitude coordinates of major control point, particularly turning point or the latitude and longitude coordinates of interesting target particularly.

Secondly determine the scope of ground scaling point and suitable ground calibration thing type (abbreviation type of ground objects), wherein the ground calibration thing comprises artificial and calibrates two kinds of atural objects naturally.In conjunction with the line of flight, choose the suitable position of layouting, as the crossing on the not too crowded harbour of traffic, road, park etc. so that artificial calibration thing is put in existing enough spaces, comprise again satisfy condition calibrate atural object naturally.The atural object that can be used as scaling point requires to meet the following conditions: significantly do not absorb or reflection, have good lambert's bulk properties; Spectral characteristic is vary stable in time; Size is suitable, and the area that is not less than 10 * 10 pixels is arranged, to reduce the area of mixed pixel; The scaling point number is 5～7, and its reflectivity covers high, medium and low reflectivity range; Scaling point is positioned at point under the machine, to avoid how much and radiometric distortion; The distance of scaling point distance will guarantee synchronism to greatest extent testing in the acceptable scope synchronously.Choose artificial calibration atural object through the preparation of indoor wave spectrum comparative analysis and man-made features; Through field reconnaissance and ground-object spectrum comparative analysis, choose nature calibration atural object, determine the position that it is concrete, and the longitude and latitude of this position is in time fed back to aviation flight organization unit cover this zone to guarantee the course line.

Determine the time of ground experiment at last: flight was accurately obtained the concrete time of taking off on same day, spent the moment of ground calibration point to determine aircraft.

Then carry out the ground synchronous calibration experiment, enter the acquisition process of ground synchronous calibration data, this is the prerequisite of the aviation high-spectrum remote sensing data being carried out reflectivity conversion.This synchronous calibration data comprises ground spectral data and ground calibration auxiliary data, and wherein the ground calibration auxiliary data comprises time that each spectral data obtains and the longitude and latitude that each calibrates the thing position etc.

Obtaining of above ground synchronous calibration experimental set-up and ground synchronous calibration data can describe in detail by following examples.

Carry out the high-spectrum remote-sensing flight experiment of OMIS (practical modularization imaging spectrometer) and PHI (pull-broom type area array CCD hyperspectral imager) in the area, Shanghai, before the flight, determine following several contents:

1) determine flight path according to application demand, Dianshan Lake → Xu Pu bridge → Nanpu bridge → Yangpu Bridge (along Pudong) → Jiang Wan airport (area) → Yangpu Bridge → Nanpu bridge (Yan Puxi), and provide the latitude and longitude coordinates of major control point.

2) determine the approximate range of scaling point and suitable type of ground objects

In order to select ground synchronous calibration experiment man-made features, white, the black cloth of differing textures such as polyester-cotton blend, cotton yarn card, Nylon Taffeta, velveteen, cotton textiles, Lycra, silk, silk fabric carried out indoor spectrum comparative analysis experiment, 12 * 12m is processed in selection at last ²Black cotton and byssus respectively as calibration with black matrix and bright body.

Through field reconnaissance and ground-object spectrum comparative analysis, select concrete floor, vegetation, floor tile, marble, dump, soil, water body as calibrating atural object naturally, determine the position that it is concrete, and the longitude and latitude of position is in time fed back to aviation flight organization unit.

3) step is determined the time of ground experiment

Flight was accurately obtained the concrete time of taking off on same day, spent the moment of ground calibration point to determine aircraft.

4) carry out the ground synchronous calibration experiment, obtain ground synchronous calibration data

Aviation flight same day, utilize black, bright body and various natural feature on a map, ground such as section, Jiang Wan airport and park, square, Nanpu have carried out the ground synchronous calibration experiment in the thing outbeach, on the south the Xu Pu bridge, obtain the wave spectrum and the associated auxiliary data of various natural feature on a map targets such as concrete floor, vegetation, floor tile, marble, dump, soil, water body, for the processing of aviation high-spectrum remote sensing data provides data source.

After obtaining ground synchronous calibration data,, make benchmark with the sun altitude of choosing the aviation high-spectrum remote sensing data is carried out reflectivity conversion according to this ground synchronous calibration data.An aviation high-spectrum remote-sensing flight generally can cover several course lines, and because the restriction of experiment condition, ground synchronous calibration often can only concentrate on the nearer several representative points of certain bar airline distance.Therefore utilize reflectivity conversion method proposed by the invention to look like to contain or do not contain the ground calibration point with regard to the enroute chart of proofreading and correct respectively below and provide concrete example.

1, the enroute chart picture that contains ground calibration point

For the reflectivity conversion that contains ground calibration point enroute chart picture, corresponding sun altitude is that benchmark carries out reflectivity conversion to entire image in the time of can the imaging of ground calibration point, and the specific implementation step is seen Fig. 3; Image pixel can also be converted to the reflectivity under the image-forming condition separately, the specific implementation step is seen Fig. 4.

Details are as follows for it:

1) corresponding sun altitude is benchmark (embodiment 1) during the imaging of ground calibration point

Each pixel sun altitude of computed image at first; Next select the ground scaling point, calculate the average sun altitude of ground calibration point, as the benchmark of entire image reflection conversion; Calculate the spoke brightness value of entire image under this benchmark altitude of the sun corner condition; Utilize ground synchronous calibration data and (Region of Interest, be called for short ROI) extracts from the interesting image district spoke brightness value calculates the inverting coefficient by least square method; At last the inverting coefficient is applied to entire image and obtains reflectivity.As shown in Figure 3, it specifically may further comprise the steps:

Step 1: read the enroute chart picture that contains ground calibration point that will carry out reflectivity conversion, requirement is the spoke brightness value.

Step 2: according to the corresponding remote sensing of reading images flight auxiliary data, obtain the imaging time and the latitude and longitude information of each pixel correspondence, and calculate the pairing sun altitude of every pixel, its calculation procedure as shown in Figure 5:

Step 21: the year, month, day according to imaging is calculated a day angle J;

Step 22: calculate declination angle δ by day angle J;

Step 23: calculate solar hour angle τ, performing step is:

Step 231: according to longitude information, S changes local time S into during with Beijing of imaging _d,

Step 232: calculate the time difference by day angle J, and local time is carried out the time difference correct, get the true solar time,

Step 233: calculate solar hour angle τ;

Step 24: calculate sun altitude h according to latitude information and gained declination angle δ, solar hour angle τ.

Generally speaking, the auxiliary data precision of airborne remote sensing flight is limited, but interpolation is obtained the supplementary of every row or every pixel necessary the time.

Step 3: display image, select the corresponding pixel area of ground scaling point on image, i.e. interesting image district (ROI district).

Step 4: the pairing average sun altitude h in all ROI districts of statistical computation _t

Step 5:, entire image is converted to average sun altitude h according to following formula _tSpoke brightness value L under the image-forming condition _{S λ t}:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_t$

Wherein, h _iBe the pairing sun altitude of pixel i; L _{S λ i}It is the original spoke brightness value of entire image correspondence; L _{S λ t}For entire image is h at sun altitude _tThe time pairing spoke brightness value.

Step 6: extracting each ROI district sun altitude is h _tThe time each passage correspondence the spoke brightness value.

Step 7: read each ROI district corresponding ground return wave spectrum data that the ground synchronous calibration experiment is obtained.

Step 8: the channel parameters according to imaging spectrometer resamples to the ground return wave spectrum data that it obtained, and makes ground wave spectrum and image wave spectrum have identical wave band number.

Step 9: the ground return wave spectrum after obtaining to resample.

Step 10: pairing image wave spectrum in each ROI district and ground wave spectrum are matched.

Step 11: according to step 10, set up system of equations, and try to achieve the inverting coefficient k by following equation _λAnd b _λ:

ρ _gλR＝k _λ·L _sλR+b _λ

Wherein, ρ _{G λ R}Be the ground actual measurement reflectance spectrum after resampling; L _{S λ R}The sun altitude that extracts for the corresponding ROI of image district is h _tThe spoke brightness value; k _λAnd b _λInverting coefficient for the λ wave band correspondence that requires.

Step 12: at last again k _λAnd b _λEquation shown in 11 is used for the spoke brightness value that obtains of step 5 set by step, and can obtain entire image is h at sun altitude _tReflectivity.

2) image pixel is converted to reflectivity (embodiment 2) under each pixel image-forming condition

At first calculate each pixel sun altitude; Select the ground scaling point, calculate the spoke brightness value and the average sun altitude in each ROI district; For every pixel, calculate the simulation spoke brightness value of each ROI district under this sun altitude; Utilize ground calibration data and simulation spoke brightness value to calculate the inverting coefficient of each pixel; At last the inverting coefficient is used for each pixel and promptly gets reflectivity.As shown in Figure 4, it specifically may further comprise the steps:

Step 1: read the enroute chart picture that contains ground calibration point that will carry out reflectivity conversion, requirement is the spoke brightness value.

Step 2: by the sun altitude of the every pixel of step computed image shown in Figure 5.

Step 3: display image, select the corresponding pixel area of ground scaling point on image, i.e. interesting image district (ROI district).

Step 4:, extract its spoke brightness value L from image for each ROI district _{S λ t}, and the average sun altitude h of its imaging of statistical computation _t,

Step 5: calculate it as follows at the corresponding sun altitude h of pixel i _iSimulation spoke brightness value L under the condition _{S λ Oi}:

$L_{\mathrm{s\λOi}}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·\sin h_i$

Step 6: read each ROI district corresponding ground return wave spectrum data that the ground synchronous calibration experiment is obtained.

Step 7: the channel parameters according to imaging spectrometer resamples to the ground return wave spectrum data that it obtained, and makes ground wave spectrum and image wave spectrum have identical wave band number.

Step 8: the ground return wave spectrum after obtaining to resample.

Step 9: for pixel i, resampling ground, the ground wave spectrum that simulation spoke brightness value that the step 5 in each ROI district is obtained and step 8 obtain matches.

Step 10: according to step 9, set up system of equations, try to achieve the corresponding inverting coefficient of each pixel by following relation:

ρ _gλO＝k _i·L _sλOi+b _i

Wherein, ρ _{G λ O}Be the ground calibration point actual measurement reflectance spectrum after resampling; L _{S λ Oi}The simulation spoke brightness value that extracts from corresponding ROI district; k _iAnd b _iBe the pairing reflectivity inverting of the pixel i that is asked coefficient.

Step 11: the last k that tries to achieve _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain its reflectivity:

ρ _gλi＝k _i·L _sλi+b _i

Wherein, ρ _{G λ i}Be the pairing reflectivity of pixel i; L _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

2, the enroute chart picture that does not comprise ground calibration point

For the reflectivity conversion that does not contain ground calibration point enroute chart picture that flight experiment obtained the same day, can import according to the user, entire image is converted to reflectivity under certain sun altitude image-forming condition, its specific implementation step is seen Fig. 6; Image pixel can also be converted to the reflectivity under the image-forming condition separately, its specific implementation step is seen Fig. 7.

1), entire image is converted to reflectivity (embodiment 3) under certain sun altitude image-forming condition according to user input

At first read existing reflectivity inverting coefficient and the pairing sun altitude of this inverting coefficient; The radiance value of computed image under this sun altitude image-forming condition; Utilize linear model, obtain the reflectivity of new enroute chart picture under this altitude of the sun corner condition that view picture does not contain ground calibration point.As shown in Figure 6, it specifically may further comprise the steps:

Step 1: read the enroute chart picture that contains ground calibration point that will carry out reflectivity conversion, requirement is the spoke brightness value.

Step 2: by the sun altitude of the every pixel of step computed image shown in Figure 5.

Step 3: read existing reflectivity conversion coefficient k _λAnd b _λ, and pairing imaging sun altitude h _t

Step 4:, entire image is converted to sun altitude h according to following formula _tSimulation spoke brightness value under the image-forming condition:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_t$

Wherein, h _iSun altitude for pixel i; L _{S λ i}Be the original spoke brightness value of its image; L _{S λ t}For it is h at sun altitude _tThe time pairing spoke brightness value.

Step 5: with conversion coefficient k _λAnd b _λ, be applied to the simulation spoke brightness value that step 4 obtains according to the form of ρ=kL+b, can obtain entire image is h at sun altitude _tReflectivity.

2) image pixel is converted to reflectivity (embodiment 4) under each pixel image-forming condition

At first calculate each pixel sun altitude; Read then by containing each ROI district spoke brightness value and sun altitude that ground calibration point enroute chart picture extracts; For each pixel, calculate the simulation spoke brightness value of each ROI district under this sun altitude; Utilize ground calibration data and simulation spoke brightness value to calculate the inverting coefficient of each pixel; At last the inverting coefficient is used for each pixel and promptly gets reflectivity.As shown in Figure 7, it specifically may further comprise the steps:

Step 1: read the enroute chart picture that contains ground calibration point that will carry out reflectivity conversion, requirement is the spoke brightness value.

Step 2: by the sun altitude of the every pixel of step computed image shown in Figure 5.

Step 3: read from containing the radiation wave spectrum and the corresponding sun altitude in each ROI district that the ground calibration dot image obtains.

Step 4: for pixel i, establishing its sun altitude is h _i, calculate each ROI district as follows at this sun altitude h _iCorresponding down simulation spoke brightness value:

$L_{\mathrm{s\λOi}}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·{\sinh }_i$

Wherein, L _{S λ t}For being h at sun altitude from containing the ROI district that the ground calibration dot image extracts _tThe time the spoke brightness value, L _{S λ Oi}For this ROI district is h at sun altitude _iThe time the spoke brightness value.

Step 5: read each corresponding ground, ROI district spectral data that the ground synchronous calibration experiment is obtained.

Step 6: the channel parameters according to imaging spectrometer resamples to it, makes ground wave spectrum and image wave spectrum have identical wave band number.

Step 7: the ground return wave spectrum after obtaining to resample.

Step 8: for pixel i, resampling ground, the ground wave spectrum that simulation spoke brightness value that the step 4 in each ROI district is obtained and step 7 obtain matches.

Step 9: according to step 8, set up system of equations, try to achieve the corresponding inverting coefficient of each pixel by following relation:

ρ _gλO＝k _i·L _sλOi+b _i

Wherein, ρ _{G λ O}Be the ground actual measurement reflectance spectrum after resampling; L _{S λ Oi}Simulation spoke brightness value for corresponding ROI district; k _iAnd b _iBe the pairing reflectivity inverting of pixel i coefficient.

Step 10: last k _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain its reflectivity:

ρ _gλi＝k _i·L _sλi+b _i

Wherein, ρ _{G λ i}Be the pairing reflectivity of pixel i; L _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

The present invention before ground synchronous calibration experiment to ground synchronous calibration experiment carried out scientific and reasonable general layout, guaranteed the ground synchronous calibration data obtained in the ground synchronous calibration experiment accurately not reliably; The ground synchronous calibration data that the present invention simultaneously utilizes the ground synchronous calibration experiment to obtain is carried out reflectivity conversion to the aviation high-spectrum remote sensing data, to the time influence of ground object target spoke brightness be taken into account, it is long or when not containing ground calibration point enroute chart and look like to carry out reflectivity conversion to have overcome course line, ground calibration point place, do not consider that time factor will bring the problem than large deviation, improve the precision of reflectivity conversion.When the present invention has proposed with the imaging of ground calibration point when reflectivity conversion in addition corresponding sun altitude to be benchmark carry out reflectivity conversion and image pixel be converted to the method for reflectivity under the image-forming condition separately entire image, and look like to contain ground calibration point according to desire conversion enroute chart and handle respectively.

Claims (8)

1, a kind of method that realizes aviation high-spectrum remote-sensing flight ground synchronous calibration and reflectivity conversion is characterized in that comprising the following steps:

(1) determines the latitude and longitude coordinates of flight path and major control point;

(2) determine the scope and the ground calibration thing type of ground scaling point according to flight path;

(3) time of determining ground experiment is the moment that aircraft is crossed ground calibration point;

(4) carry out the ground synchronous calibration experiment, obtain ground synchronous calibration data, this synchronous calibration data comprises ground spectral data and ground calibration auxiliary data, and wherein the ground calibration auxiliary data comprises the longitude and latitude of time that each spectral data obtains and each calibration thing position;

(5) reflectivity conversion step: according to the ground synchronous calibration data of obtaining, make benchmark with the sun altitude of choosing the aviation high-spectrum remote sensing data is carried out reflectivity conversion, described reflectivity conversion step comprises the following steps:

When determining that i. the aviation high-spectrum remote sensing carried out reflectivity conversion, be elected to be the sun altitude of benchmark;

Ii. basis is the reflectivity when entire image is converted to same sun altitude, still image pixel value is converted to the reflectivity constantly of imaging separately, determines the spoke brightness value L of each pixel of image _{S λ}

Iii. determine the inverting coefficient k of reflectivity _λAnd b _λ

Iv. with the inverting coefficient k _λAnd b _λBe applied to the spoke brightness value L of step I i gained according to the form of ρ=kL+b _{S λ}, can obtain reflectivity data ρ _{G λ}

2, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 1 and reflectivity conversion, it is characterized in that described ground calibration thing comprises artificial and natural ground calibration thing, wherein artificial ground calibration thing comprises as the byssus of bright body with as the black cotton of black matrix; Naturally the calibration thing comprises concrete floor as bright body, water body and as the dump of black matrix, the area of described ground calibration thing all is not less than 10 * 10 pixel areas, and is positioned at point under the machine.

3, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 1 and reflectivity conversion is characterized in that described inverting coefficient k _λAnd b _λBe the spoke brightness value of the respective regions that extracts according to ground actual measurement synchronous calibration data and from image, utilize least square method to calculate.

4, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 3 and reflectivity conversion, it is characterized in that described aviation high-spectrum remote sensing data is the enroute chart picture that comprises ground calibration point, and when corresponding sun altitude was benchmark during with the imaging of ground calibration point, described reflectivity conversion step comprised the following steps:

(1) determine the sun altitude of each pixel of enroute chart picture, selecting the corresponding pixel area of ground scaling point on image is the interesting image district, determines and with the pairing average sun altitude h of all images region of interest _tBe benchmark;

(2), determine that entire image calculating entire image is at average sun altitude h according to following formula _tSpoke brightness value L under the image-forming condition _{S λ t}:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_t$

Wherein, h _iBe the pairing sun altitude of pixel i; L _{S λ i}It is the original spoke brightness value of entire image correspondence;

(3) the spoke brightness calculation inverting coefficient that utilizes ground synchronous calibration data and extract from the interesting image district comprises the following steps:

1. extracting each interesting image district sun altitude is h _tThe time each passage pairing spoke brightness value;

2. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

3. pairing image wave spectrum in each interesting image district and ground wave spectrum are matched, and set up system of equations, and try to achieve the inverting coefficient k of λ wave band correspondence by following equation _λAnd b _λ:

ρ _gλR＝k _λ·L _sλR+b _λ

ρ wherein _{G λ R}Be the ground wave spectrum after resampling; L _{S λ R}The sun altitude that extracts for image respective image region of interest is h _tThe spoke brightness value;

(4) the inverting coefficient k _λAnd b _λEquation shown in (3) is used for the simulation spoke brightness value L that step (2) obtains set by step _{S λ t}, can obtain entire image is h at sun altitude _tReflectivity ρ _{G λ t}

5, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 3 and reflectivity conversion, it is characterized in that described aviation high-spectrum remote sensing data is the course line image pixel that comprises ground calibration point, and when corresponding sun altitude was benchmark constantly with each pixel imaging of image, described reflectivity conversion step comprised the following steps:

(1) determine the sun altitude of each pixel of enroute chart picture, selecting the corresponding pixel area of ground scaling point on image is the interesting image district, extracts the spoke brightness value L in each interesting image district from image _{S λ t}, determine and with the average sun altitude h of its imaging _tBe benchmark;

(2) calculate each interesting image district at the corresponding sun altitude h of pixel i according to following formula _iSimulation spoke brightness value L under the condition _{S λ 0i}:

$L_{\mathrm{s\λ}0i}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_i;$

(3) utilize ground synchronous calibration data and the spoke brightness value that extracts from the interesting image district calculates the inverting coefficient of each pixel, comprise the following steps:

1. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

2. for pixel i, the simulation spoke brightness value and resampling ground, the ground wave spectrum in each interesting image district matched, and set up system of equations by following relation, try to achieve the corresponding inverting coefficient of each pixel:

ρ _gλ0＝k _i·L _sλ0i+b _i

Wherein, ρ _{G λ 0}Be the ground wave spectrum after resampling; L _{S λ 0i}Simulation spoke brightness value from the extraction of respective image region of interest; k _iAnd b _iBe the pairing reflectivity inverting of the pixel i that is asked coefficient.

(4) trying to achieve inverting coefficient k _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain the reflectivity ρ of pixel i _{G λ i}:

ρ _gλi＝k _i·L _sλi+b _i

L wherein _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

6, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 3 and reflectivity conversion, it is characterized in that described aviation high-spectrum remote sensing data is not for containing the course line image pixel of ground calibration point, and when corresponding sun altitude was benchmark constantly with each pixel imaging of image, described reflectivity conversion step may further comprise the steps:

(1) determines the sun altitude of each pixel of enroute chart picture, from containing the spoke brightness value L in each interesting image district that the ground calibration dot image reads _{S λ t}And corresponding sun altitude h _t

(2) for pixel i, establishing its sun altitude is h _i, calculate each interesting image district as follows at this sun altitude h _iCorresponding down simulation radiance L _{S λ 0i}:

$L_{\mathrm{s\λ}0i}=\frac{L_{\mathrm{s\λt}}}{\sin h_t}\·\sin h_i;$

(3) utilize the spoke brightness value in ground synchronous calibration data and interesting image district to calculate the inverting coefficient, comprise the following steps:

1. channel parameters each corresponding ground, the interesting image district spectral data that experiment is obtained to ground synchronous calibration according to imaging spectrometer resamples, and makes ground wave spectrum and image wave spectrum have identical wave band number, the ground wave spectrum after obtaining to resample;

2. for pixel i, the simulation spoke brightness value and resampling ground, the ground wave spectrum in each interesting image district matched, and set up system of equations by following relation, try to achieve the corresponding reflectivity inverting of each pixel i coefficient k _iAnd b _i:

ρ _gλ0＝k _i·L _sλ0i+b _i；

Wherein, ρ _{G λ 0}Be the ground wave spectrum after resampling; L _{S λ 0i}Simulation spoke brightness value for the respective image region of interest;

(4) with the inverting coefficient k that obtains _iAnd b _iBe applied to the original spoke brightness value of pixel i as follows, promptly obtain the reflectivity ρ of pixel i _{G λ i}:

ρ _gλi＝k _i·L _sλi+b _i

L wherein _{S λ i}The spoke brightness value that receives for pixel i position remote sensor.

7, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 1 and reflectivity conversion, it is characterized in that described aviation high-spectrum remote sensing data is not for containing the enroute chart picture of ground calibration point, and when corresponding sun altitude was benchmark during with the imaging of ground calibration point, described reflectivity conversion step may further comprise the steps:

(1) determines the sun altitude of each pixel of enroute chart picture, read existing inverting coefficient k _λAnd b _λAnd pairing imaging sun altitude h _t

(2), entire image is converted to sun altitude h according to following formula _tSimulation spoke brightness value L under the image-forming condition _{S λ t}:

$L_{\mathrm{s\λt}}=\frac{L_{\mathrm{s\λi}}}{\sin h_i}\·\sin h_t$

H wherein _iSun altitude for pixel i; L _{S λ i}Be the original spoke brightness value of entire image;

(3) with the inverting coefficient k _λAnd b _λBe applied to the simulation spoke luminance picture of above-mentioned steps (2) gained according to the form of ρ=kL+b, can obtain entire image is h at altitude of the sun _tReflectivity.

8, the method for realization aviation high-spectrum remote-sensing flight ground synchronous calibration according to claim 1 and 2 and reflectivity conversion, it is characterized in that described sun altitude is that promptly the imaging time of each pixel correspondence and latitude and longitude information calculate according to remote sensing flight auxiliary data.

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