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

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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!