Contents
DEM
- Band
- 2 dimensional data array, 2-byte signed integer
- Unit conversion coefficient
- 1 m/DN
- Ellipsoid
- WGS-84
- Spatial resolution
- 15m, 30m, 90m
- Geometric accuracy
- TBD
- Dummy area data
- -9999
Orthorectified radiance
- Data format
- VNIR and SWIR
- Raster image, 1-byte unsigned integer
- TIR
- Raster image, 2 byte unsigned integer
- VNIR and SWIR
- Conversion from ASTER Data BETA DN to Radiance
- OBC Radiance = ( DN -1 ) * UCC
- UCC : Unit Conversion Coefficients
- ASTER Data BETA can be converted to onboard calibrated radiance by using UCC. Null data number (DN=0) is assigned to dummy (no data area after map projection, lack of observations, etc.). DN=255 is assigned to the maximum radiance.
- Please find further details about the algorithms and the coefficients at the following site;
http://staff.aist.go.jp/s.tsuchida/aster/cal/info/equation/index.html
- (5. Radiance calculation from DNL1B based on the results for the trend analysis)
The onboard calibration with the latest L1PGE correction tables is reflected in ASTER Data BETA (L0->L1A). GDS and LPDAAC products may not be calibrated with the latest version due to a limitation of the L0 generating timing. Our products are ideal.
- OBC Radiance = ( DN -1 ) * UCC
- VNIR/SWIR radiometric recalibration
- ASTER Data BETA can be also converted to recalibrated radiance (UOA,AIST) by using another UCC.
- Radiometric recalibrated Radiance = ( DN -1 ) * UCC
The UCC are shown in an ASCII file data1.l3a.*sh as UnitConversionCoefficients=(gain,offset,unit). They depend on the ASTER Gain mode.
AIST vicarious calibration http://staff.aist.go.jp/s.tsuchida/aster/cal/fc/index.html
- The AIST group developed an algorithm and derived coefficients for the recalibration. The coefficients are based on ground measurements from April 2000 to December 2004. They are applied to products with the onboard calibration (L1B). We are planning to update the algorithms and coefficients in near future.
UOA vicarious calibration http://www.optics.arizona.edu/rsg/index.php
- The RSG, College of Optical Sciences at University of Arizona developed the algorithms and derived the coefficients for this recalibration. These coefficients are based on the vicarious calibration works, which are the ground measurements from 2000 to the present. These are based on L1A. We are planning to update the algorithms and the coefficients in near future.
SAGA vicarious calibration http://www.ip.is.saga-u.ac.jp/~arai/aster.html
- Coming soon.
- "VICAL=NONE, UOA or AIST" is given in data1.l3a.gh. "NONE" means onboard calibrated radiance.
- TIR radiometric recalibration
As mentioned in http://terrast.aster.ersdac.or.jp/t/en/science_info/radiometric.html, GDS and LPDAAC products may not be created with the latest calibration due to a limitation of L0 generating timing. A recalibration method described in http://deco.cis.ibaraki.ac.jp/RECAL/ is generally recommended.
- "TIR_RECAL=YES" is seen in data1.l3a.gh.
Orthorectified reflectance
- Data format
- VNIR
- Raster image, 2 byte unsigned integer
- VNIR
- Conversion from radiance to reflectance
- Reflectance = DN * 0.0001
- Re-calibrated radiance is used to calculate reflectance.
- The ENVI format and the Equirectangular (geographic) projection are supported. The GeoTIFF, UTM, and Polar Stereo projections will be supported in near future.
- Orthorectified SWIR reflectance and orthorectified emissivity/temperature will be supported in near future.
The WRC solar irradiance model is used. The models of NewKur (New Kurucz), Thuillier2002, and others will be also applied later.
Detailed information is shown in http://staff.aist.go.jp/s.tsuchida/aster/cal/info/solar/index.html.
- Algorithm
- The default algorithm corrects Rayleigh scattering, ozone absorption, and/or water vapor absorption.
- Aerosol correction will be supported in near future.
More detailed info is described in http://staff.aist.go.jp/hirokazu.yamamoto/sat/sat_mate/ASTBETA_AC_Manual.pdf.
- Applied file names for the ozone and water vapor corrections and their statistic information (mean and standard deviation) are given in data.l3a.gh file.
File format of orthorectified radiance product
- Flat binary (Raw image data + ENVI header file)
GeoTiff
About GeoTiff
Files included in ASTER Data Beta
- Data files
- ASTXXXXXXXXXXXX.Y.ZZZ(.3B)
- 【X】Observation Time (YYMMDDhhmmss)
- YY Year
- MM Month（01-12）
- DD Day（01-31）
- hh Hour（00-23）
- mm Minute（00-59）
- ss Second（00-59）
- 【Y】Sensor Type *1
- V VNIR
- S SWIR
- T TIR
- 【Z】Data Type
- REF Reflectance *2
- RAD Radiance *2
- DEM Digital Elevation Model
- NVA Satellite Azimuth Direction at Band 3N
- NVZ Satellite Zenith Angle at Band 3N
- BVA Satellite Azimuth Direction at Band 3B
- BVZ Satellite Zenith Angle at Band 3B
- DQA Quality flag for DEM
- RQA Quality flag for Atmospheric correction (Reflectance)
- STP Temperature using Standard TES *2
- SEM Emissivity using Standard TES
- WTP Temperature using Water Vapor Scaling and TES *2
- WEM Emissivity using Water Vapor Scaling and TES
- BRS Browse image
- 【X】Observation Time (YYMMDDhhmmss)
*1 The letter also means a spatial resolution. ( V = 15 m/pixel, S = 30 m/pixel, T = 90 m/pixel )
*2 Images are stored in BSQ format.
- Information files
- ASTXXXXXXXXXXXX.V.sh VNIR specific header file
- ASTXXXXXXXXXXXX.S.sh SWIR specific header file
- ASTXXXXXXXXXXXX.T.sh TIR specific header file
- ASTXXXXXXXXXXXX.gh Generic header file
- ASTXXXXXXXXXXXX.Y.ZZZ.hdr ENVI header file
- options.txt Option list file