The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Level 1 Precision Terrain Corrected Registered At-Sensor Radiance (AST_L1T) data contains calibrated at-sensor radiance, which corresponds with the ASTER Level 1B (AST_L1B), that has been geometrically corrected, and rotated to a north-up UTM projection. The AST_L1T is created from a single resampling of the corresponding ASTER L1A (AST_L1A) product. The bands available in the AST_L1T depend on the bands in the AST_L1A and can include up to three Visible and Near Infrared (VNIR) bands, six Shortwave Infrared (SWIR) bands, and five Thermal Infrared (TIR) bands. The AST_L1T dataset does not include the aft-looking VNIR band 3.
The precision terrain correction process incorporates GLS2000 digital elevation data with derived ground control points (GCPs) to achieve topographic accuracy for all daytime scenes where correlation statistics reach a minimum threshold. Alternate levels of correction are possible (systematic terrain, systematic, or precision) for scenes acquired at night or that otherwise represent a reduced quality ground image (e.g., cloud cover).
For daytime images, if the VNIR or SWIR telescope collected data and precision correction was attempted, each precision terrain corrected image will have an accompanying independent quality assessment. It will include the geometric correction available for distribution in both as a text file and a single band browse images with the valid GCPs overlaid.
This multi-file product also includes georeferenced full resolution browse images. The number of browse images and the band combinations of the images depends on the bands available in the corresponding AST_L1A dataset.
|File Size||~115 MB|
|Temporal Extent||2000-03-04 to Present|
|Coordinate System||Universal Transverse Mercator (UTM)|
|Datum||World Geodetic System (WGS84)|
|File Format||HDF-EOS or GeoTIFF|
|Geographic Dimensions||~60 km x 60 km|
|Number of Science Dataset (SDS) Layers||14|
|Columns/Rows||Varies by scene|
|Pixel Size||15 m (VNIR), 30 m (SWIR), and 90 m (TIR)|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|VNIR_Band1||15 meter resolution VNIR Band 1(0.52 to 0.60 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||VNIR_Band2||15 meter resolution VNIR Band 2 (0.63 to 0.69 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||VNIR_Band3N||15 meter resolution VNIR Band 3N (0.78 to 0.86 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band4||30 meter resolution SWIR Band 4 (1.600 to 1.700 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band5||30 meter resolution SWIR Band 5 (2.145 to 2.185 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band6||30 meter resolution SWIR Band 6 (2.185 to 2.225 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band7||30 meter resolution SWIR Band 7 (2.235 to 2.285 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band8||30 meter resolution SWIR Band 8 (2.295 to 2.365 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||SWIR_Band9||30 meter resolution SWIR Band 9 (2.360 to 2.430 µm)||W/m²/sr/μm||8-bit unsigned integer||N/A||N/A||0 to 255||N/A||TIR_Band10||90 meter resolution TIR Band 10 (8.125 to 8.475 µm)||W/m²/sr/μm||16-bit unsigned integer||N/A||N/A||0 to 65535||N/A||TIR_Band11||90 meter resolution TIR Band 11 (8.475 to 8.825 µm)||W/m²/sr/μm||16-bit unsigned integer||N/A||N/A||0 to 65535||N/A||TIR_Band12||90 meter resolution TIR Band 12 (8.925 to 9.275 µm)||W/m²/sr/μm||16-bit unsigned integer||N/A||N/A||0 to 65535||N/A||TIR_Band13||90 meter resolution TIR Band 13 (10.25 to 10.95 µm)||W/m²/sr/μm||16-bit unsigned integer||N/A||N/A||0 to 65535||N/A||TIR_Band14||90 meter resolution TIR Band 14 (10.95 to 11.65 µm)||W/m²/sr/μm||16-bit unsigned integer||N/A||N/A||0 to 65535||N/A|
|TIF||Bands Available||Red band||Green band||Blue band|
|_V.tif||15 meter resolution VNIR (bands 1, 2, 3N) and resampled 15 meter resolution pre-April 2008 SWIR (band 4)||4||3N||2|
|_V.tif||15 meter resolution VNIR only (bands 1, 2, 3N)||2||3N||1|
|_T.tif||90 meter resolution TIR (bands 10, 12, 14)||14||12||10|
¹Reduced resolution browse thumbnail images assume the same band combination and spatial resolution as their full resolution counterparts; Visible Infrared Full Resolution Images are 15 meters and Thermal Infrared Full Resolution Images are 90 meters.
|Report sections||Information contained in report sections|
|GLS 2000 Ground Control Points (GCPs) used to correct the scene||Listing of GCPs|
|Summarized correlation of comparison GCPs pixel offset from AST_L1T to a GLS2000 Standard Scene.||Mean, median, standard deviation|
|Quadrant RMSE||Mean, median, standard deviation|
|Full scene RMSE||Mean, median, standard deviation|
²Refer to ASTER Level 1T User Guide for additional information on the Quality Assurance Files.
|Color Code||Range for the number of pixels off nominal|
|Yellow||≤ 3 and > 2|
|Blue||≤ 2 and > 1|
|Cyan||≤ 1 and > 0.5|
|Green||≤ 0.5 pixel|
A modification has been incorporated within the processing of the AST_L1T data product for correcting zero-filled scans that appear in the processing of low-latitude, ascending orbit (night) thermal infrared (TIR) data acquisitions. This correction has been implemented for the historical archive of the ASTER L1T data product and for newly processed scenes as of October 1, 2017. Additional information can be found in the ASTER L1T User Advisory for more details.
Users are advised that ASTER SWIR data acquired from April 2008 to the present exhibit anomalous saturation of values and anomalous striping. This effect is also present for some prior acquisition periods. Please refer to the ASTER SWIR User Advisory Document for more details.