CN110487241B - Method for extracting elevation control points of building area by satellite laser height measurement - Google Patents
Method for extracting elevation control points of building area by satellite laser height measurement Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C11/00—Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
Abstract
The invention provides a method for extracting an elevation control point of a building area by satellite laser height measurement, which comprises the following steps: selecting laser height measurement data with qualified quality, and geometrically positioning the laser height measurement light spot center; carrying out Gaussian wavelet decomposition and integral fitting on the full-waveform echo data to accurately extract Gaussian wavelet characteristic parameters; selecting laser height measurement data containing a high plane layer with the same height in a light spot range by utilizing high-resolution images or Digital Surface Model (DSM) data and half-width parameters of Gaussian wavelets; establishing a corresponding relation between the equal-height plane layers and the reflection Gaussian wavelets thereof; positioning the center of the light spot by using the accurate distance of the center position moment of the sub-waveform characteristic parameters obtained by decomposition, and calculating the absolute elevation of the corresponding equal-height plane layer; and combining the remote sensing image with the high-resolution image to manufacture a remote sensing image elevation control point. The invention expands the field of using full-waveform large-spot laser height measurement data as a remote sensing image height control point from a flat terrain to a building area and other areas containing a high plane layer.
Description
Technical Field
The invention belongs to the field of laser radars, particularly relates to satellite-borne laser radar data-assisted remote sensing image photogrammetry processing and application technology, and particularly relates to a method for extracting elevation control points of a building area through satellite laser height measurement based on laser height measurement geometric positioning and full waveform decomposition.
Background
The laser radar, the imaging spectrum and the imaging radar are called as three leading edge technologies in the current earth observation field, some foreign developed countries start earlier in the field of satellite-borne laser radar height measurement, the American aerospace agency (NASA) launches an ICESat-1 satellite carrying a globe-in-the-earth science laser height measurement system (GLAS) in 2003, the height measurement precision of the satellite is 0.15m, a large amount of high-precision global three-dimensional space information is obtained, and due to the failure of a laser, the satellite stops data acquisition work in 2009[1]. In order to continue to complete the scientific task of ICESat-1, the United states emitted advanced laser altimetry carried by advanced terrains in 2018The system (ATLAS) ICESat-2 satellite adopts a micro-pulse photon counting laser radar for counting, which is firstly applied to a satellite-borne platform in the world, the diameter of a light spot is about 10m, the space between the light spots is about 0.7m, and the height measurement precision can reach 0.1m[2]. The research and development work of domestic laser radar software and hardware technology is late, and in 2016, China successfully transmits resource No. three 02 stars, carries the first experimental laser height measurement load of earth observation in China, but does not have the function of full waveform recording. In addition, a high-resolution seven-grade satellite which is one of the great special items of the high-resolution earth observation system in China is already in the whole satellite test stage, and the satellite has the laser height measurement capability with the precision superior to 1 m.
A key technology for extracting elevation control points of a building area by utilizing laser height measurement data relates to contents such as filtering and denoising, full waveform decomposition and the like. The GLAS filtering denoising method mainly comprises Gaussian convolution filtering, wavelet denoising and related improved algorithms thereof, such as Zhaoxin and the like[3]Denoising the original echo signal by adopting a Gaussian convolution filtering method, carrying out convolution calculation on the Gaussian kernel function and the original echo signal, and adjusting the smoothness degree of the echo signal by changing the half-width value of the Gaussian kernel function. Qiu game and the like[4]A wavelet de-noising method is adopted to process the ICESat/GLAS waveform, and the basic idea is that after wavelet decomposition, the wavelet coefficient of an approximate signal is larger, the wavelet coefficient of noise is smaller, a proper threshold value is selected, and the signal smaller than the threshold value is taken as noise and is set as zero, so that the de-noising purpose is achieved.
The most representative waveform decomposition method is a gaussian decomposition method, the laser radar emission pulse is generally considered to be in accordance with gaussian distribution, and if a single ground object target echo is also in accordance with gaussian distribution, the essence of the gaussian decomposition is to decompose an original echo signal into a plurality of superimposed gaussian wavelets. Foreign, Hoffton[5]A classical Gaussian decomposition algorithm is proposed, and Gaussian wavelets are determined through adjacent odd-even inflection points. At home, Wangcheng et al[6]And solving the center position, amplitude and half width of the Gaussian wavelet by using a second-order partial derivative to obtain an inflection point, and adjusting the peak position and half width of the Gaussian wavelet at the maximum amplitude to weaken the influence of waveform curve distortion due to saturation and forward scattering. In addition, the first and second substrates are,due to the complexity of the structure of the ground object, the learners believe that the echo signal does not conform to Gaussian distribution sometimes, and due to different spatial scales of different targets, wavelet analysis is performed by adopting wavelet basis functions of different scales to obtain the approximation strength of the Gaussian wavelet basis under different scales to the echo waveform, and the peak information of the echo waveform is further obtained through the approximation strength, such as Yang scholar and the like[7]A Gaussian progressive waveform decomposition method based on wavelet transformation is provided, and target components can be effectively detected from superposed waves.
The satellite-borne laser radar has the characteristics of high operation orbit, wide observation range, high height measurement precision and the like, can provide high-precision three-dimensional space information for different regions in the world, and is widely applied to the fields of global elevation measurement, forestry resource investigation, polar glacier monitoring and the like. Plum blossom jacket and the like[8]The method comprises the steps that GLAS laser height measurement data are used for generating a south pole ice cover DEM with high precision; li nationality Yuan, etc[9]Providing a multi-criterion constrained elevation control point screening algorithm, comprehensively utilizing an SRTM DEM to carry out gross error elimination and carrying out fine screening according to distance measurement related attribute parameters, wherein the screened laser height measurement points can reach the accuracy of 1:50000 stereo mapping; meanwhile, LI and the like[10]The ICESat/GLAS laser footprint point is used as an elevation control point to perform combined adjustment with the three-dimensional resource image III, and the result shows that the elevation precision of the image without the ground control point can be improved to 3.0 m. At present, the large-spot laser height measurement data auxiliary remote sensing image photogrammetry mainly uses a flat terrain area, and the application results of the laser height measurement data used as an elevation control point auxiliary photogrammetry in a non-flat terrain and building area are rare.
Because the laser footprint area is large, the plane positioning accuracy is low, and the original echo signal reflects the effect of comprehensively superposing a plurality of ground object target reflected signals in a light spot, the accurate elevation value in the light spot is difficult to directly extract, so that the application of laser height measurement data in areas with complex structures such as cities and the like and the auxiliary remote sensing image photogrammetry as an elevation control point are greatly restricted, and the related achievement of extracting the elevation control point of a building area by utilizing a laser height measurement full-waveform decomposition method is not available at present. The invention accurately extracts echo characteristic parameters by utilizing a full waveform decomposition method of progressive stripping and integral fitting so as to accurately represent a building vertical structure in a building area, extracts the height values of high-level layers such as a facula area and the like in high precision by combining with geometric positioning of a satellite, the position and the attitude of the satellite and related distance measurement parameters, and combines with characteristic points of images of the high-level layers to be used as a height control point.
Reference documents:
[1] yanfan, Wenjiao, ICESat and ICESat-2, application progress and prospect [ J ]. Excellent 2011,23(2): 138-.
[2] Shahao wave, Wang Cheng, Xiao Huan, etc. ICESat-2 airborne test point cloud filtering and vegetation height inversion [ J ] remote sensing academic, 2014,18(6): 1199-.
[3] Zhaoxin, Zhang Yi, Zhang Li Ming, et al. laser altimeter Gaussian echo decomposition method [ J ] infrared and laser engineering, 2012,41(3):643 and 649.
[4] Qiu Sai, Cheng Yang Qiu, Li Lidi, etc. ICESAT-GLAS waveform processing based on wavelet transforms [ J ] forest engineering, 2012,28(5):33-35.
[5]HOFTON M A,MINSTER J B,BLAIR J B.Decomposition of laser altimet-er waveforms[J].IEEE Transactions on Geoscience&Remote Sensing,2000,38(4):1989-1996.
[6] Wang, dawn, vicuna, etc. satellite-borne lidar data processing and application [ M ]. beijing scientific press 2015.
[7] Yang student Bo, Wang Cheng, Xiaohuan, etc. Gaussian progressive decomposition of large-spot LiDAR full waveform data wavelet transform [ J ] Infrared and millimeter wave academic newspaper, 2017,36(6): 749-.
[8] Plum is built, fangchun, papery sea, etc. the ICESAT satellite determines the elevation model research of the ice cover of south Pole [ J ]. Wuhan university, academic newspaper, information science edition, 2008,33(3): 226-.
[9] Lizhou Yuan, Tang Xinming, Zhang Chongyang, and the like, and the ICESat/GLAS elevation control point screening with multi-criteria constraint [ J ]. remote sensing report, 2017,21(1): 96-104.
[10]LI G Y,TANG X M,GAO X M,et al.ZY-3Block Adjustment Supported by GLAS Laser Altimetry Data[J].The Photogrammetric Record,2016,31(153):88-107.
Disclosure of Invention
The invention provides a method for extracting elevation control points of a building area by satellite laser height measurement based on laser height measurement full waveform decomposition and sub-waveform geometric positioning, aiming at the problem that large-spot satellite laser height measurement data is difficult to play a role in geometric positioning of high-resolution images of the building area, and the application range of satellite laser height measurement auxiliary image photogrammetry is expanded.
According to the method, the high-resolution remote sensing image or DSM data is utilized to find out that the spot area contains laser height measurement data with qualified quality of a high-level layer, Gaussian wavelets reflected by a characteristic elevation layer are obtained through geometric positioning, waveform decomposition and waveform fitting, the elevation of the corresponding high-level layer is calculated by utilizing the center time parameters of the wavelet, and the extraction of the elevation control point of the building area is realized by combining the high-resolution remote sensing image. The invention adopts a computer and manual assistance mode, and mainly comprises the following contents:
(1) according to an aspect of the embodiments of the present invention, there is provided a basic method for selecting quality-qualified laser height measurement data and extracting elevation control points of remote sensing images of a building area by using full-waveform laser height measurement data, including:
selecting laser height measurement data with qualified quality, calculating a corresponding accurate distance by using the peak moment of an echo waveform, and geometrically positioning the center of a laser spot by using the satellite position and the attitude of a height measuring instrument when a beam is emitted;
preprocessing and filtering and denoising an original echo signal for laser altimetry, extracting Gaussian wavelet from the processed waveform through waveform decomposition, and refining accurate characteristic parameters of each Gaussian wavelet through integral fitting, wherein the characteristic parameters comprise amplitude, central position and half-width value;
selecting laser height measurement data of a high-resolution orthographic image or DSM data and a half-width parameter of a Gaussian sub-waveform, wherein the laser height measurement data comprises a high-level layer in a spot area;
establishing a corresponding relation between the contour plane layer and the Gaussian sub-waveform by using the high-resolution orthographic image or DSM data and the half-width parameter of the Gaussian sub-waveform;
calculating the accurate distance from the equal-height plane layer to the satellite according to the extracted central position of the Gaussian sub-waveform corresponding to the equal-height plane layer in the spot area, geometrically positioning the center of the light spot according to the distance and a laser height measurement positioning principle and method, and obtaining the elevation value of the central position of the light spot through coordinate conversion, namely the absolute elevation value of the equal-height plane layer;
and combining the characteristic points of the high-resolution images of the equal-height plane layers and the elevation values of the equal-height plane layers to manufacture elevation control points for geometric positioning of the remote sensing images.
(2) According to another aspect of the embodiments of the present invention, there is provided a method for screening qualified laser height measurement data, including: and judging according to the effectiveness of the laser height measurement waveform data, the attitude quality, the cloud cover and the reflectivity obtained by measurement when the satellite performs height measurement and emits beams, and whether the parameters of the laser measurement height of the ground target, the external DSM elevation deviation degree and the like meet the laser height measurement requirement.
(3) According to another aspect of the embodiments of the present invention, there is provided a method for accurately positioning a spot center corresponding to a peak time of an echo waveform or a peak time of a wavelet waveform, including:
calculating an initial distance according to the time and the light speed of the wave beam to and from the satellite and the target corresponding to the peak time, and correcting system errors, atmospheric delay, tides and the like to obtain an accurate distance;
three-dimensional positioning of the light spot center of the elevation layer corresponding to the peak time utilizes the position of a satellite at the laser emission time and the attitude of a height measuring instrument to calculate the coordinates of a ground-fixed earth center rectangular coordinate system of the light spot center;
and converting the rectangular coordinate system coordinate of the earth-fixed geocentric of the light spot center into a coordinate of a geodetic coordinate system comprising the geodetic longitude, the latitude and the geodetic height, wherein the geodetic height is the elevation of the positioning point of the light spot center, and the coordinate of the geodetic coordinate system can be subjected to projection conversion to obtain the coordinate of a projection coordinate system.
(4) According to another aspect of the embodiments of the present invention, a method for extracting a full waveform gaussian wavelet decomposition for satellite laser altimetry by gradual stripping and integral fitting is provided, which includes:
the full-waveform progressive stripping method comprises the following steps: and preprocessing and filtering and denoising the laser altimetry original echo signal. Determining the amplitude and the central position of the first Gaussian wavelet according to the maximum value and the position of the processed waveform, and stripping the first Gaussian wavelet from the original waveform by taking the smaller time distance from the central position to the left inflection point and the right inflection point as a half-width value; then repeating the steps of the residual waveforms according to the sequence of the peak values from large to small until the maximum value of the stripped residual waveform is smaller than a preset threshold value;
overall fitting method of Gaussian wavelets: and performing overall least square fitting on all the stripped Gaussian wavelets by taking the Gaussian wavelet characteristic parameters obtained when all the wavelets are stripped as initial values and taking the condition that the sum of the echo instantaneous intensity value received at any time in the echo receiving time and the instantaneous intensity value of each Gaussian wavelet is equal to obtain the parameter values of each Gaussian wavelet with more accurate characteristic parameters.
(5) According to another aspect of the embodiments of the present invention, there is provided a method for screening laser altimetry data including a contour layer in a spot area by using auxiliary data, including:
whether the laser spot area has the high-resolution remote sensing image or the high-resolution DSM with the position information or not can be displayed by utilizing the central position and the size of the light spot, whether the high-resolution remote sensing image or the high-resolution DSM has the high-resolution remote sensing image or the high-resolution DSM with the position information or not is judged manually or machine-assisted according to the high-resolution orthographic image or the DSM in the laser spot area, and whether the laser spot area comprises the high-resolution remote sensing image or the high-resolution DSM or not is judged assisted according to whether the half.
The contour plane layer refers to a contour region which has a certain area and can form Gaussian reflected waves in the light spot region, such as a flat ground layer, a building flat top layer and the like.
(6) According to another aspect of the embodiments of the present invention, there is provided a method for establishing a correspondence between a contour layer and a sub-waveform, the method including: the corresponding relation between the high plane layer and the sub-waveshape can be found by comparing the information of the relative position, shape, intensity and the like of the decomposed sub-waveshape with the high-resolution orthographic image of the spot area and DSM, for example, the sub-waveshape with the maximum peak value corresponds to the highest elevation layer, the sub-high elevation layer corresponding to the second sub-waveshape corresponds to the second sub-elevation layer, the last sub-waveshape corresponds to the ground, the sub-waveshape with the maximum peak value corresponds to the elevation layer close to the center of the light spot and with the maximum area, and whether the sub-wave is reflected by the high plane layer or not is assisted and judged according to. Each spot area only needs to select a pair of equal-height plane layers and corresponding sub-wavelets, and usually, the building top plane layer, the first echo wavelet, the ground flat area and the last echo wavelet are a group of corresponding relation groups which are commonly selected preferentially.
(7) According to another aspect of the embodiments of the present invention, there are provided methods for extracting and using information of a laser altimetry elevation control point, including: the extracted basic information of the elevation control point comprises an accurate absolute elevation value obtained by calculation according to the center time of a wavelet peak corresponding to an elevation layer and an image feature point which is easy to identify and corresponds to the elevation value in an image area of the equal-height plane layer or is selected from the image area of the equal-height plane layer. When the subsequent process is used for the geometric processing and target positioning of the remote sensing image, the characteristic point or other characteristic points of the high plane layer images are transfixed to the corresponding image to be processed, and the elevation value of the elevation control point is used.
The method for extracting the elevation control points of the building area by satellite laser height measurement provided by the invention is a technology for extracting the elevation control points of the building area by utilizing laser height measurement full-waveform decomposition, processes the original echo signals of specific ground building targets, can accurately reflect the vertical structural characteristics of buildings in the building area, realizes the accurate extraction of elevation information of different equal-height plane layers, can effectively solve the limitation of laser height measurement data auxiliary image photogrammetry application of uneven terrain, and provides an effective way for the selection of the elevation control points in cities or other building areas.
According to the invention, the elevation control points of the high-resolution image of the building area can be extracted by using the full-waveform large-light-spot laser height measurement data, the field of using the large-light-spot laser height measurement data as the elevation control points of the remote sensing image is expanded from a flat terrain to the building area and other areas containing high-level plane layers, the application range of satellite laser height measurement data for assisting the photogrammetry of the high-resolution remote sensing image is expanded, and the geometric processing and target positioning precision of the remote sensing image is improved.
Drawings
FIG. 1 is a schematic diagram of a method for extracting elevation control points of a building area by satellite laser height measurement.
Detailed Description
As shown in fig. 1, the present invention is carried out by the following steps:
step 1, judging the quality of laser height measurement data, selecting the laser height measurement data with qualified quality, calculating a corresponding accurate distance by using the peak moment of an echo waveform, and geometrically positioning the laser spot center by using the satellite position and the attitude of a height measuring instrument when a beam is emitted.
The laser height measurement data quality is judged according to whether parameters such as attitude quality, cloud cover, reflectivity and laser measurement height of a ground target and external DSM elevation deviation obtained by measurement during satellite height measurement and beam emission meet the laser height measurement requirement or not; the accurate distance corresponding to the peak time is obtained by calculating the initial distance according to the time and the light speed of the wave beam to and from the satellite and the target and correcting system errors, atmospheric delay, tides and the like. The corresponding accurate positioning from the center of the light spot is realized by calculating the coordinate of the center of the light spot by utilizing the position of the satellite at the moment of laser emission and the attitude of the altimeter,
the calculation formula is as follows: p ═ Ps+Rc E[0,0,l]T(Ps、l、Rc EAnd P is a satellite position vector in a ground-fixed earth center rectangular coordinate system, a laser height measurement accurate distance, a conversion matrix from a laser height measurement sensor coordinate to the ground-fixed earth center rectangular coordinate system and a light spot center three-dimensional coordinate vector in the ground-fixed earth center rectangular coordinate system respectively).
And 2, preprocessing the laser altimetry original echo signal and carrying out filtering and denoising, carrying out waveform decomposition on the waveform subjected to filtering and denoising to extract a Gaussian wavelet, refining Gaussian wavelet characteristic parameters through integral fitting, and accurately extracting each wavelet characteristic parameter. The Gaussian wavelet extraction is realized by adopting a progressive stripping and integral fitting decomposition method, and comprises the following steps:
s1: and preprocessing and filtering and denoising the laser altimetry original echo signal. Determining the amplitude and the central position of the first Gaussian wavelet according to the maximum value and the position of the processed waveform, and then stripping the first Gaussian wavelet from the original waveform by taking the small span from the central position to the left inflection point and the right inflection point as a half-width value;
s2: then repeating the steps of the residual waveforms according to the sequence of the peak values from large to small until the maximum value of the stripped residual waveform is smaller than a preset threshold value, and generally taking 3 times of the standard deviation of the noise as the threshold value;
s3: and finally, taking the Gaussian wavelet parameters obtained when each wavelet is stripped as initial values, and carrying out overall least square fitting on all stripped Gaussian wavelets under the condition that the sum of the echo instantaneous intensity value received at any time in the echo receiving time and the instantaneous intensity value of each Gaussian wavelet is equal to obtain more accurate characteristic parameters of each Gaussian wavelet waveform, including amplitude, central position and half-width value.
And 3, screening out laser height measurement data of the high-plane layer in the speckle area by using the laser height measurement auxiliary data in combination with the high-resolution orthographic image or DSM data. The equal-height plane layer in the invention refers to an equal-height area which is arranged in the spot area and has a limited size and can form Gaussian reflected waves, such as a flat ground layer, a building flat top layer and the like. Whether a laser spot area has a high-level layer or not can be displayed on a high-resolution remote sensing image or a high-resolution DSM with position information by utilizing the central position and the size of a spot, whether the laser spot area has the high-level layer or not is judged according to the high-resolution orthographic image or the DSM in the laser spot area, and whether the laser spot area comprises the high-level layer or not is judged in an auxiliary mode according to whether the half-width value of Gaussian wavelet is close to the half-width value of the original emission wave or not.
And 4, comparing the corresponding relation between the contour plane layer and the reflection wavelet with a high-resolution orthographic image of a spot area and DSM (digital projection system) through information such as the relative position, the shape and the intensity of the decomposed wavelet, and finding the corresponding relation, wherein the wavelet with the maximum peak value corresponds to a highest elevation layer, the wavelet with the maximum peak value corresponds to a second next highest elevation layer, the last wavelet corresponds to the ground, the wavelet with the maximum peak value is close to the center of a light spot, the elevation layer with the maximum area and the like, and the corresponding relation can be found in an auxiliary mode according to the rule that the wavelet with the half-width value close to the half-width value of the transmission waveform is reflected by.
Each spot area only needs to select a group of equal-height plane layers and corresponding sub-wavelets, and usually the building top plane layer, the first echo wavelet, the ground flat area and the last echo wavelet are a common corresponding relation group with preference.
And 5, calculating the accurate distance from the equal-height plane layer to the satellite according to the extracted sub-waveform central position moment corresponding to the equal-height plane layer in the spot area, calculating the light spot center of the corresponding equal-height plane layer according to a laser height measurement positioning principle and method, and positioning, wherein the obtained elevation value is the absolute elevation value of the equal-height plane layer. This step can be referred to as step 1.
And 6, combining the characteristic points of the high-resolution images of the equal-height plane layers and the elevation values of the equal-height plane layers to manufacture elevation control points for geometric positioning of the remote sensing images. The basic information of the elevation control point comprises an accurate absolute elevation value obtained by calculation according to the center time of a wavelet peak corresponding to an elevation layer, and an image feature point which is easy to identify and corresponds to the elevation value in an image area of the high plane layer or is selected from the image area of the high plane layer. When the subsequent process is used for the geometric processing and target positioning of the remote sensing image, the characteristic point or other characteristic points of the high plane layer images are transfixed to the corresponding image to be processed, and the elevation value of the elevation control point is used.
Claims (8)
1. A method for extracting elevation control points of a building area by satellite laser height measurement is characterized by comprising the following steps:
(1) judging the quality of laser height measurement data in a measurement area, selecting the laser height measurement data with qualified quality, calculating a corresponding accurate distance by using the peak moment of an echo waveform, and geometrically positioning the center of a laser spot by using the satellite position and the attitude of a height gauge when a beam is transmitted;
(2) preprocessing and filtering and denoising an original echo signal for laser altimetry, extracting Gaussian wavelet from the processed waveform through waveform decomposition, and refining accurate characteristic parameters of each Gaussian wavelet through integral fitting, wherein the characteristic parameters comprise amplitude, central position and half-width value;
(3) selecting laser height measurement data of a contour plane layer contained in a spot area by utilizing high-resolution orthographic images or Digital Surface Model (DSM) data and a half-width parameter of Gaussian wavelets;
(4) establishing a corresponding relation between the contour plane layer and the Gaussian sub-waveform by using the high-resolution orthographic image or DSM data and the half-width parameter of the Gaussian sub-waveform;
(5) calculating the accurate distance from the equal-height plane layer to the satellite according to the extracted central position of the Gaussian sub-waveform corresponding to the equal-height plane layer in the spot area, geometrically positioning the center of the light spot according to the distance and a laser height measurement positioning principle and method, and obtaining the elevation value of the central position of the light spot through coordinate conversion, namely the absolute elevation value of the equal-height plane layer;
(6) and combining the characteristic points of the high-resolution images of the equal-height plane layers and the elevation values of the equal-height plane layers to manufacture elevation control points for geometric positioning of the remote sensing images.
2. The method for extracting elevation control points of a building area by satellite laser height measurement according to claim 1, wherein in the step (1), the method for judging the quality of the laser height measurement data judges according to the validity of echo data, the satellite position measurement quality, the attitude measurement quality, the cloud cover amount and the reflectivity measured when the satellite height measurement transmits beams, and whether the parameter of the elevation deviation between the laser measurement height of the ground target and the external DSM elevation meets the requirement of laser height measurement.
3. The method for extracting the elevation control points of the building area by satellite laser height measurement according to claim 1, wherein the method comprises the following steps: in the steps (1) and (5), the accurate distance corresponding to the peak time of the waveform or the Gaussian wavelet after the echo processing and the positioning of the center of the light spot are received, the initial distance is calculated according to the time and the light speed of the wave beam to and from the satellite and the target, the accurate distance is obtained through system error, atmospheric delay and tide correction, the position coordinate of the center of the light spot is calculated by utilizing the position of the satellite at the moment of laser emission, the attitude of the altimeter and high-precision geometric calibration parameters, and the accurate positioning of the center of the light spot is realized.
4. The method for extracting the elevation control points of the building area by satellite laser height measurement according to claim 1, wherein the method comprises the following steps: in the step (2), the Gaussian wavelet extraction is realized by adopting a progressive stripping and integral fitting decomposition method, and the method comprises the following steps:
s1: firstly, preprocessing and filtering denoising a laser altimetry original echo signal: determining the amplitude and the central position of the first Gaussian wavelet according to the maximum value and the position of the processed waveform, and stripping the first Gaussian wavelet from the original waveform by taking the smaller time distance from the central position to the left inflection point and the right inflection point as a half-width value;
s2: then repeating the steps of the residual waveforms according to the sequence of the peak values from large to small until the maximum value of the stripped residual waveform is smaller than a preset threshold value;
s3: and finally, taking the Gaussian wavelet parameters obtained when each wavelet is stripped as initial values, and performing overall least square fitting on all stripped Gaussian wavelet characteristic parameters according to the condition that the sum of the echo instantaneous intensity value received at any time in the echo receiving time and the instantaneous intensity value of each Gaussian wavelet is equal to obtain more accurate characteristic parameter values of each wavelet.
5. The method for satellite laser height measurement and building area elevation control point extraction according to claim 1, wherein in the step (3), the contour plane layer is a contour plane area having a certain area and size capable of forming a gaussian reflected wave, whether the contour plane layer exists in the laser spot area can be displayed on a high-resolution remote sensing image or a high-resolution DSM with position information by using a spot center position and a spot size, whether the contour plane layer exists is judged manually or by machine assistance according to a high-resolution orthographic image or the DSM in the spot area, and whether the contour plane area exists is judged by assistance according to whether a half-width value of the gaussian wavelet is close to a half-width value of an original transmitted wave.
6. The method for extracting the elevation control points of the building area by satellite laser height measurement according to claim 1, wherein the method comprises the following steps: in the step (4), the correspondence between the equal-height plane layer and the reflection wavelet thereof can be found by comparing the relative position, shape and intensity information of the decomposed wavelet with the high-resolution orthographic image of the spot area and the DSM, wherein the first echo wavelet corresponds to the highest elevation layer, the second wavelet corresponds to the second highest elevation layer, the last wavelet corresponds to the ground, and the wavelet with the maximum peak value corresponds to the elevation layer close to the center of the spot and with the maximum area.
7. The method for extracting elevation control points of a building area by satellite laser height measurement according to claim 6, wherein the method comprises the following steps: besides comparison discovery, the correspondence can be found by using the fact that the half-width value of the Gaussian wavelet reflected by the equal-height plane layer is approximately equal to the half-width value of the transmitted waveform; each spot area only needs to select a group of equal-height plane layers and corresponding sub-waveforms, wherein the building top plane layer and the first echo wavelet, the ground flat area and the last echo wavelet are a corresponding relation group which is selected preferentially.
8. The method for extracting the elevation control points of the building area by satellite laser height measurement according to claim 1, wherein the method comprises the following steps: in the step (6), the basic information of the elevation control point comprises an accurate absolute elevation value obtained by calculation according to the center time of a wavelet peak corresponding to an elevation layer, and an image feature point which is easy to identify and is selected from an image area of a high plane layer corresponding to the elevation value or an image area of the high plane layer; when the subsequent process is used for the geometric processing and target positioning of the remote sensing image, the characteristic point or other characteristic points of the high plane layer images are transfixed to the corresponding image to be processed, and the elevation value of the elevation control point is used.
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| CN108414998A (en) * | 2018-03-02 | 2018-08-17 | 国家测绘地理信息局卫星测绘应用中心 | A kind of laser satellite altitude meter echo waveform analog simulation method and equipment |
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