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Constellation of Airbus SAR satellites and PHOTOMOD Radar software: quality assessment of geometric and radiometric parameters of TerraSAR-X imagery
Matthieu Besnard, Head of Channel Partner ProgrammAirbus DS Geo–Intelligence, France Aleksander Chekurin, Commercial Director Racurs, Russia
15th International Scientific and Technical Conference
From Imagery to Map: Digital Photogrammetric Technologies
Yucatan. Mexico. October 2015
Some of validated parameters of satellite RSD systems
Impulse response characteristics related to the capability of RSD system to image objects with different geometrical dimensions including the critical ones (linear ground resolution)
Coordinate measuring characteristics which determine the image measurement properties and the accuracy of image key-elements
Radiometric characteristics related to the capability of RSD system to reproduce the radiometric properties of objects
General system characteristics which determine the capability of RSD space system to collect information
Resolution test chart (test object 1)
Potential test chart (test object 2)Single corner reflectors (markers):
• center marker – 1 pce• boundary markers – 4 pcs
Test object 1:• resolution test chart – 9 corner reflectors
Test object 2:• radiometric (potential) test chart – 14 corner reflectors
The set of the corner reflectors
3
Test field equipment
The layout of the test objects
Ilovlinsky District Volgograd region
The test field for evaluation of RSD system characteristics
The test field of the validation measurements
Adjustment of the corner reflectors
The corner reflectors on the test field
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The corner reflectors
Characteristics of the corner reflectors
RCS (S-band), dB Size, m RCS (X-band), sq.m RCS (X-band), dB
45 2,888 301964 54,80
40 2,166 95489,5 49,80
35 1,624 30196,4 44,80
30 1,218 9548,95 39,80
25 0,913 3019,64 34,80
24 0,862 2398,59 33,80
20 0,685 954,895 29,80
15 0,514 301,964 24,80
10 0,385 95,4895 19,80
5 0,289 30,1964 14,80
0 0,217 9,54895 9,800
-5 0,162 3,01964 4,800
-10 0,122 0,95490 -0,200
-20 0,068 0,09549 -10,20
.
The layout drawing of the corner reflectors on the test field
Radar image of the test field The layout drawing of the corner reflectors
The final acquisition plan
Mode Start Time Incidence Angle Range Orbit Beam ID Pass Direction
ST 2015-05-22T14:42:11.297 26.73 – 26.73 84 spot_022R A
ST 2015-05-21T14:59:18.484 50.35 – 50.35 69 spot_083R A
ST 2015-05-20T02:59:33.683 57.74 – 57.74 46 spot_112R D
HS 2015-05-24T0325:15.443 26.04 – 26.04 107 spot_020R D
HS 2015-05-25T03:08:08.363 49.94 – 49.94 122 spot_082R D
Organization of survey
TerraSAR-X imagery analysis
Scene TSX1_SAR__SSC______ST_S_SRA_20150520T030011_20150520T030011
A fragment with test charts of corner reflectors (green rectangle - resolution test chart, orange - radiometric test chart)
1
9
2
3
4
5
6
7
8
9
68
1
5
7
3
24 4
1
2
35
6
9
8
7
The radar imagery fragments of resolution test chart in ST mode
1
2
4
7
5
6
8
9
34
7
2
3
5
6
8
9
1
The radar imagery fragments of resolution test chart in HS mode
The pulse response sections of corner reflectors of resolution test chart
Corner reflector 1
reference signal signal interpolated in the frequency domainsignal interpolation by Gaussian function
Slant range Azimuth range
Response amplitudes of resolution test chart in 3D
Pulse response for the central point
Original response Interpolated signal
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Meaning of abbreviations used in the table:DR (F) – slant range resolution which was estimated using the signal interpolation in the frequency domain, meters;DR (G) – slant range resolution which was estimated using the signal interpolation by Gaussian function, meters;DAz (F) – azimuth resolution which was estimated using the signal interpolation in the frequency domain, meters;DAz (G) – azimuth resolution which was estimated using the signal interpolation by Gaussian function, meters;SLR (R) – first right sidelobe level in slant range;SLR (L) – first left sidelobe level in slant range;SLAz (R) – first right sidelobe level in azimuth;SLAz (L) – first left sidelobe level in azimuth;M – average value of characteristic over the scene;RMS - mean square deviation of characteristic evaluation over the scene;MS – average value of characteristics over the all scenes for mode;RMSS – mean square deviation of characteristic evaluation over the all scenes for mode.
Pulse response analysis was carried out over the area of 32 x 32 pixels with a peak response in the middle of the area.
Results of measurements
Pulse response characteristics of TerraSAR-X measured with use of PHOTOMOD Radar
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DR (F) DR (G) DAz (F) DAz (G) SLR (L) SLR (R) SLAz (L) SLAz (R)
Scene TSX1_SAR__SSC______ST_S_SRA_20150520T030011_20150520T030011M 0,601630 0,581888 0,239026 0,225880 -31,6343 -28,7160 -28,7782 -33,7229
RMS 0,005230 0,015488 0,002773 0,012264 1,8109 2,2409 3,1725 4,3117
Scene TSX1_SAR__SSC______ST_S_SRA_20150521T145956_20150521T145956M 0,601245 0,578721 0,23679 0,227369 -36,7838 -30,912 -28,9243 -30,0423
RMS 0,007106 0,006509 0,002574 0,012049 5,907095 6,002328 2,775589 6,37658
Scene TSX1_SAR__SSC______ST_S_SRA_20150522T144249_20150522T144249M 0,602674 0,57362 0,235290 0,221753 -39,0070 -32,7524 -37,3284 -32,9516
RMS 0,001569 0,015494 0,002828 0,009914 7,248753 6,095767 10,10402 7,358993
Average values for ST mode MS 0,601850 0,578076 0,237035 0,225001 -35,8084 -30,7935 -31,677 -32,2389
RMSS 0,004635 0,012497 0,002725 0,011409 4,988916 4,779665 5,350702 6,015758
Scene TSX1_SAR__SSC______HS_S_SRA_20150524T032553_20150524T032554M 0,598830 0,566533 1,185758 1,113123 -37,3204 -31,4552 -33,9937 -37,4095
RMS 0,002804 0,014189 0,012097 0,031806 9,31443 4,82228 3,760008 6,390421
Scene TSX1_SAR__SSC______HS_S_SRA_20150525T030846_20150525T030847M 0,601196 0,566887 1,184008 1,106669 -36,9381 -33,8193 -28,8693 -34,8804
RMS 0,006481 0,023267 0,00946 0,025922 9,098027 7,494723 22,71031 5,563505Average values for HS mode
MS 0,600013 0,56671 1,184883 1,109896 -37,1292 -32,6373 -31,4315 -36,1449RMSS 0,004643 0,018728 0,010778 0,028864 9,206228 6,158501 13,23516 5,976963
The results of measurements of pulse response characteristics
Slant range resolution Azimuth resolution
Dependency of pulse responses from the RCS of the reflectors
The amplitudes of the linear part of pulse responses
Three-dimensional representation of the linear part of pulse responses
In the windows are marked only the reflectors forming "the ideal response line" and participating in the evaluation of the radiometric characteristics. Red and green rectangles shows areas of the image used in the evaluating of the relative radiometric error, blue - in the evaluation of the radiometric resolution and the effective number of looks.
55,00
65,00
75,00
85,00
95,00
105,00
115,00
4,8 9,8 14,8 19,8 24,8 29,8 34,8 39,8 44,8 49,8 54,8
The saturation begins with RCS of 34.8 dB
The measurement results of radiometric characteristics of SAR TerraSAR-X
The measurement results of radiometric characteristics of SAR TerraSAR-X
Acquisition date
Radiometric error, dB
Radiometric linearity
Effective number of looks
Radiometric resolution, dB
Noise equivalent, dB
Dynamic range, dB
HS mode
24.05.2015 0,00758 0,989586 0,997827 3,01266 -19,0 61,6149
25.05.2015 0,15173 0,999080 0,925633 3,09501 -19,0 62,9973
Mean 0,07965 0,994333 0,961730 3,05383 -19,0 62,3061
MSD 0,10192 0,006713 0,051048 0,05823 0,0 0,97750
ST mode
20.05.2015 0,08824 0,998051 0,958333 3,05675 -18,0 54,3832
21.05.2015 0,12918 0,997221 0,977812 3,03473 -18,0 53,4838
22.05.2015 0,03467 0,996542 0,934033 3,08503 -18,0 52,1196
Mean 0,08403 0,997271 0,956726 3,05883 -18,0 53,3288
MSD 0,04739 0,000756 0,021934 0,02521 0,0 1,139726
Conclusions
Measurements of pulse response characteristics confirm the claimed spatial resolution of TerraSAR-X data
Measurements of radiometric parameters shows the high radiometric quality of TerraSAR-X imagery
Thank you for your attention!