The ALOS PRISM/AVNIR-2 Quality Control at ADEN, a status after three years of operation

Transcription

1 The ALOS PRISM/AVNIR-2 Quality Control at ADEN, a status after three years of operation Sebastien Saunier, Aboubakr Mamabimba and Vincent Motti (GAEL Consultant) And Beatrice Berthelot (VEGA FR)

2 Content 1. ESA and the operational QC of ALOS data ESA/ADEN and SPPA, ALOS data, ESA and TPM QC Framework QC Activities 2.PRISM Product quality status Visual inspection and image artefacts, Geometry & geolocation, Image quality: Modulation function transfer. 3.AVNIR-2 Product quality status Geometry & geolocation, Radiometry; calibration & sensor intercomparison. 4.Open discussions

3 ALOS data, ESA and TPMs ESA uses its multi-mission ground systems to acquire, process, archive and distribute data from other satellites : the Third Party Missions. The data from these missions is distributed under specific agreements with the owners or operators of the missions. Proba SPOT-4 QuikSCAT IRS-P6 SciSat-1/ACE AVHRR ALOS is now considered as a GMES contributing mission,

4 FRAMEWORK ORGANISATION QC Framework & Organisation The ALOS Quality Control service is a part of ESA Sensor Performance and Product Assessment (SPPA). The QA framework applied to ALOS data distributed in Europe is the SAME as for the other ESA missions. ESA delegates responsibilities of SPPA to the IDEAS Consortium. The IDEAS Consortium relies on a wide panel of operational and experts; involved in the remote sensing domain such as, optical, radar, radar altimeter, atmospheric composition. For ALOS the ACTORS OF ADEN QC Team Operator; VEGA FR Expert Support Team; GAEL Consultant, and laboratory QC TOOLS AMALFI Multi Mission, IQ processing chains. Challenge To harmonize the QA approach between TPMs and with ESA Missions.

5 OPERATION Support the ESA User service or help desk, Check the EOLI Catalog, Support to the operational team in charged of ALOS CORE s/w, Operate the routine QC Task, Support the expert analysis. Activitydayby day&qa policy implementation CALIBRATION/VALIDATION s/w validation, ALOS CVST activities, Follow product specification DOCUMENTATIONS Quality Control Plan, Calibration/Validation Plan, Reporting such cyclic report of the mission, User documentation (FAQ, notice) Article

6 -----PRISM Product Quality Satus----- Geometry & geolocation Image quality: Modulation function transfer

7 PRISM Product QualityStatus-Visual Inspection The task of visual inspection has been set up. The following artifacts are detected and reckoned: Blurred artifact observed (Marginaly) and feedbacks of JAXA on this topic has been really appreciated the contaminated ADEN scenes are removed from the catalog. Detector over saturation, noise, gain setting is an issue. Relative calibration, ccd-to-ccd & detector-todectector, improved but cause image saturation.

8 PRISM Product Geometry performance (1/7) The PRISM geometry performance quality items focused on product geolocation accuracy, direct location accuracy, ortho product accuracy. The calibration sites are considered for reference equipment. Europe; La Crau (Fr), Bordeaux (Fr); Madrid (Sp); Saragosse (Sp); Piemont (It); Adana (Tu) South Africa; Le Cap, Wellington Since launch, a geometric database has been built, Geolocation accuracy Results about the 1B2 product geolocation accuracy are presented. The results does not reflect the real accuracy of the mission; the geolocation function embeds within the product does not account for the effects due to terrain relief. The products from PRISM data observed over the equipped sites (geometric reference) are now systematically checked based on correlation and using image chip database. Due to (1), the GCP point definition is of low height elevation and located over flat terrains. All the results are put together together in order to compute the CE90 measurements as a standard quality measurement specification. Direct/Indirect location accuracy using SENSOR MODEL The geometric model has been implemented thanks to the support of JAXA, The accuracy of the geometric model is investigated, on going studies are done on thermal distortion along with orbit (short term / long term drift), Ortho product generation The calibrated sensor model is ussd to generate RPC coefficients. In turn, this generic model is used for ortho product generation purposes. The product planimetric accuracy is assessed.

9 PRISM Geometry performance Geolocation 1BR/1B2G Plevel (2/7) Significant improvements are observed since launch along with sw version. Recentring of the Error with 5.04, north south errors have decreased.

10 PRISM Geometry performance Geolocation 1BR/1B2G Plevel (3/7) Significant improvements are observed since launch along with sw version thanks to STT realignment. About geometric parameters; the validity period is a key issue V 4.05, 2007/11/30 ~DOYSC Launch 690, V 5.04, 2008/12/12 ~ DOYSC Launch Large across track variability, degradation of the Along track location accuracy (RMSY) 30 PRISM, 1B2 product geolocation Metre RMSX RMSY Doy since launch

11 PRISM Geometry performance Geolocation 1BR/1B2G Plevel (3/7) Significant improvements are observed since launch along with sw version thanks to STT realignment. About geometric parameters; the validity period is a key issue V 4.05, 2007/11/30 ~DOYSC Launch 690, valid for the past three months observations, V 5.04, 2008/12/12 ~ DOYSC Launch 1058, valid for the past three months observations, V 5.04 looks to not correct as expected the old observed products PRISM, 1B2 product geolocation filtered RMSX 4.05 RMSY 4.05 RMSX 5.04 V.405 release V.504 release RMSY 5.04 Poly. (RMSY 4.05) Metre Doy since launch

12 PRISM Geometry performance Direct location 1B1 Plevel (4/7) Significant improvements are observed since launch along with sw version thanks to STT realignment. About geometric parameters; again the validity period is a key issue V 4.05, 2007/11/30 ~DOYSC Launch 690, V 5.04, 2008/12/12 ~ DOYSC Launch Large error in Y for the wellington product DOY1197, drift along the path. To be investigated PRISM, 1B1 direct location, all views RMSX 4.05 RMSY 4.05 RMSX 5.04 RMSY 5.04 Metre Doy since launch

13 PRISM Geometry performance InDirect location 1B1 Plevel (5/7) This is the performance we may achiveved in using five ground control points to reset the model.. The sub pixel accuracy is reached

14 PRISM Geometry performance InDirect location 1B1 Plevel (6/7) The error vector fields for ADANA North Hemisphere

15 PRISM Geometry performance InDirect location 1B1 Plevel (6b/7) The error vector fields for WELLINGTON south hemisphere. Geometric alignement between CCDs looks irregular; change of error vector fields orientation.

16 PRISM Geometry performance ortho Product generation(7/7) Test on one product, this is the planimetric accuracy for model based on RPCs generated using direct location process WITHOUT Calibration. The sub pixel accuracy is not reached RMSX m, RMSY m, RMS m.

17 PRISM Product Quality Status MTF (1/5) The PRISM MTF is now monitored using an artifical target located at Salon de Provence, The MTF measurements have been performed on various dataset in order to appreciate the effect of the viewing geometry (ccd number) and the radiometer (B/N/F) Results comparison performend with JAXA, based on a common dataset with Jaxa the last year demonstrated a good level of consistency between the both approach. The image saturation introduced with odd/even correction (5.04) makes the 1B1 not suitable for our methology The 1A product level is now considered and some preliminary results are encouraging. The MTF monitoring is one QI, the FWHM and RER are also monitored. The approach is quite automatic but required so much expertise.

18 PRISM Product Quality Status MTF (2/5) Few words about the method, this is the knife edge method, From the image of the target up to the ESF estimate Processing of the ESF to determine the LSF and MTF with parametric approach. Application of an MTF model.

19 PRISM Product Quality Status MTF (3/5) How the compression effect / equalization problem is seen when modeling ESF? Asymnetric ESF model: optical aberrations or only JPG compression effect, Non linearity of the noise.

20 PRISM Product Quality Status MTF (4/5) The FWHM is monitored and stable, see LSF «asymnetry» The cross track MTF for the nadir view is within the specification, The along track MTF for the nadir view shows more variability A same behaviour for the other view, with degradation (may be due to variation of the LSF within the FOV?)

21 PRISM Product Quality Status MTF (5/5) The MTF assessment on PRISM data is a bit difficult, The analysis on a significant number of dataset enables to distinguish coarse tendency, Here is proposed the specification we output, It would be interesting to consider more targets, to analyse the variations of the LSF across the FOV. Cross track MTF Along track MTF Backward Nadir Forward

22 -----AVNIR Product Quality Satus----- Geometry & geolocation Radiometry; calibration & sensor intercomparison ALA2A February 26, 2008 RVPN US

23 AVNIR Product Geometry performance 1BR/1B2G Plevel (1/4) The AVNIR geometry performance quality items focused on band to band registration and product geolocation accuracy. Results about the product geolocation accuracy are presented. The results does not reflect the real accuracy of the mission; the geolocation function embeds within the product does not account for the effects due to terrain relief (1). Since launch, a geometric database has been built, The products from AVNIR-2 data observed over the equipped sites (geometric reference) are now systematically checked based on correlation and using image chip database. Due to (1), the GCP point definition is of low height elevation and located over flat terrains. All the results are put together together in order to compute the CE90 measurements as a standard quality measurement specification.

24 AVNIR Product Geometry performance 1BR/1B2G Plevel (2/4) Significant improvements are observed since launch, It is better to consider product processed with 4.05 and 5.04 sw version, the alignement changes are observed. More variability wrt to the pixel direction. The CE90 is by definition above the RMS standard. For 5.04, the results comply with the JAXA one.

25 AVNIR Product Geometry performance 1BR/1B2G Plevel (3/4) All the measurements; sudden change of the geolocation (peack), to be explained and investigated, All mesurements; doy since launch 150 up to now; some peaks of degradation are observed and still unexplained. Products have been reprocessed and re evaluated the problem is still not corrected. Metre AVNIR-2, 1B2 product geolocation Doy since launch RMSX RMSY

26 AVNIR Product Geometry performance 1BR/1B2G Plevel (3/4) All the measurements; sudden change of the geolocation (peack), to be explained and investigated, Fitered measurements; again two populations distinguished. RMSX variability for the Past period, due to pointing alignement, Degradation of the In track location for the second period (RMSY) AVNIR-2, 1B2 product geolocation 100 Metre RMSX RMSY Doy since launch

27 Dx AVNIR Product Geometry performance 1BR/1B2G Plevel (4/4) Dy Past Results

28 AVNIR Radiometric calibration Stability (1/3) 36 scenes acquired over Libya from May 06 until July 07 Libya site is considered as stable and uniform, After geometric co registration of dataset, Radiometric calibration stability is studied using multi-temporal analysis of TOA reflectance measurements DN values are converted into TOA measurements in using the extraterrestrial solar spectral irradiance (Thuillier 2003), Statistical computation on TOA results from for five ROIs, Band to band calibration stability is studied using multi-temporal analysis of band radiance ratio DN values are converted into radiances, Statistical computation on ratio results from for five ROIs. Influence of the atmosphere and terrain relief are not account with methods. So that, results are checked and inconsistency discarded.

29 AVNIR- 2 is very stable over three years of operation, AVNIR Radiometric calibration Stability (2/3) Few measurements are inconsistent and should be investigated. Unfortunately, the image saturation makes some data useless for this purposes. TOA - MEAN/ STD >>Band1 0,234/0,02 >>Band2 0,334/0,02 >>Band3 0,427/0,04 >>Band4 0,483/0,03 TOA Reflectance 0,55 0,50 0,45 0,40 0,35 0,30 0,25 0,20 AVNIR-2 radiometric stability, Lybia Lybia 4 site 4 site y = 2E-06x + 0,489 y = -6E-06x + 0,441 y = -6E-06x + 0,340 y = -7E-06x + 0,238 0, Doy Doy since since Launch band band 1 1 band band 2 2 band 3band 3 band 4 band 4

30 AVNIR Radiometric calibration Stability (3/3) The Lybia 4 sites being uniform in space and stable with time, is very suitable for calibration monitoring, The method has demonstrated to be reliable, However, the directionnal effects modeling is a key point for correct understanding of the calibration drift, Some activities are on going with MERIS in order to characterize this site more accurately Lybia 4, Directionnal effects 0,55 TOA Reflectance 0,45 0,35 0,25 0,15-1,00-0,80-0,60-0,40-0,20 0,00 0,20 0,40 0,60 0,80 1,00 Delta Azimuth band 1 band 2 band 3 band 4

31 AVNIR Radiometric calibration Xcal (1/3) The AVNIR-2 radiometric calibration stability has been demonstrated, Multidate sensor intercomparison, AVNIR-2 & Landsat ETM+ Nearly simultaneous TOA reflectance observed with the two sensors are compared, Try to consider all AVNIR-2 scenes in the catalog, After geometric co registration, DN are converted into TOA reflectance, Reflectance relative difference are computed.

32 AVN/ETM+ Relative Spectral Response Comparison AVNIR Radiometric calibration Xcal (2/3)

33 AVNIR Radiometric calibration Xcal (3/3) The inter comparison with an other EO sensor is interesting but the method is very sensitive to The time lag between the both concurent observation dates The geoemtry of observation (ETM NADIR, AVNIR OFF NADIR) The site properties itself and brdf. Relative % difference [ ETM+ - AVN-2 ] Band1 = 3,46% Band2 = -4,84% CROSS CALIBRATION OVER RVPN, AVN/ETM+ Band3 = -3,75% Band4 = 1,76% %Differencece 6,00% 4,00% 2,00% 0,00% -2,00% -4,00% -6,00% Channel

34 Summary 1. General The configuration set up to follow the quality of ALOS product at ADEN has been presented. The IQ assessment of ALOS data leads to product specification that are shared with community, The presentation demonstrated that the overall system is complex. The data quality of PRISM and AVNIR- 2 is good, some efforts are still required to inform user and refine the product specification estimate. 2. Radiometry Calibration accuracy of AVNIR-2 band remains stable along with time, but more data are necessary AVNIR-2 Cross calibration with ETM+ demonstrated that the radiometric calibration agreed within 5% 3. Geometry Various methods have been proposed in order to appreciate and monitor the geometric quality of the PRISM and AVNIR-2 data. They all demonstrated that quality achieved is within specification. But some strong variability in the results is also report. This is due to the validtiy period of auxiliary file used for processing. For PRISM The drift along with the orbit has been discussed with an on going investigation. 4. The spatial resolution This presentation shows that the PRISM SR is monitored, The results are conformed with the preliminary ones and not within the specification for the Along Track MTF.

35 Thanks for your attention OPEN DISCUSSIONS.