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 Programm Airbus DS Geo–Intelligence, France Aleksander Chekurin, Commercial Director Aleksander Chekurin, Commercial Director Racurs, Russia From Imagery to Map: Digital Photogrammetric Technologies 15 th 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

кл The corner reflectors

Characteristics of the corner reflectors RCS (S-band), dBSize, mRCS (X-band), sq.mRCS (X-band), dB 452, ,80 402, ,549,80 351, ,444,80 301, ,9539,80 250, ,6434,80 240, ,5933,80 200,685954,89529,80 150,514301,96424,80 100,38595,489519,80 50,28930,196414,80 00,2179,548959, ,1623,019644, ,1220, , ,0680, ,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 ModeStart TimeIncidence Angle RangeOrbitBeam IDPass Direction ST T14:42: – spot_022RA ST T14:59: – spot_083RA ST T02:59: – spot_112RD HS T0325: – spot_020RD HS T03:08: – spot_082RD Organization of survey

TerraSAR-X imagery analysis Scene TSX1_SAR__SSC______ST_S_SRA_ T030011_ T A fragment with test charts of corner reflectors (green rectangle - resolution test chart, orange - radiometric test chart)

The radar imagery fragments of resolution test chart in ST mode

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 domain signal interpolation by Gaussian function Slant rangeAzimuth range

Response amplitudes of resolution test chart in 3D

Pulse response for the central point Original response Interpolated signal

16 Meaning of abbreviations used in the table: D R (F) – slant range resolution which was estimated using the signal interpolation in the frequency domain, meters; D R (G) – slant range resolution which was estimated using the signal interpolation by Gaussian function, meters; D Az (F) – azimuth resolution which was estimated using the signal interpolation in the frequency domain, meters; D Az (G) – azimuth resolution which was estimated using the signal interpolation by Gaussian function, meters; SL R (R) – first right sidelobe level in slant range; SL R (L) – first left sidelobe level in slant range; SL Az (R) – first right sidelobe level in azimuth; SL Az (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; M S – average value of characteristics over the all scenes for mode; RMS S – 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 meents Results of measurements Pulse response characteristics of TerraSAR-X measured with use of PHOTOMOD Radar

17 D R (F)D R (G)D Az (F)D Az (G)SL R (L)SL R (R)SL Az (L)SL Az (R) Scene TSX1_SAR__SSC______ST_S_SRA_ T030011_ T M 0, , , , , , , ,7229 RMS 0, , , , ,81092,24093,17254,3117 Scene TSX1_SAR__SSC______ST_S_SRA_ T145956_ T M 0, , ,236790, , ,912-28, ,0423 RMS 0, , , , , , , ,37658 Scene TSX1_SAR__SSC______ST_S_SRA_ T144249_ T M 0, ,573620, , , , , ,9516 RMS 0, , , , , , ,104027, Average values for ST mode MSMS 0, , , , , , ,677-32,2389 RMS S 0, , , , , , , , Scene TSX1_SAR__SSC______HS_S_SRA_ T032553_ T M 0, , , , , , , ,4095 RMS 0, , , , ,314434,822283, , Scene TSX1_SAR__SSC______HS_S_SRA_ T030846_ T M 0, , , , , , , ,8804 RMS 0, , ,009460, , , ,710315, Average values for HS mode MSMS 0, ,566711, , , , , ,1449 RMS S 0, , , , , , ,235165, The results of measurements of pulse response characteristics Slant range resolutionAzimuth 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. The saturation begins with RCS of 34.8 dB 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 ,007580, , , ,061, ,151730, , , ,062,9973 Mean0,079650, , , ,062,3061 MSD0,101920, , ,058230,00,97750 ST mode ,088240, , , ,054, ,129180, , , ,053, ,034670, , , ,052,1196 Mean0,084030, , , ,053,3288 MSD0,047390, , ,025210,01,139726

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

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