ASTER Lat/Lon Adjustment Tool
Entry ID: NASA_JPL_ASTERWEB_LATLON
Abstract: Geographic coordinates for each ASTER scene are stored in various places in the
HDF and *.met files. Latitude/longitude values are assigned to certain image
pixels, based on knowledge of spacecraft attitude and pointing, instrument
pointing, and line of sight vectors for each detector. Over the last 5 years,
we have discovered several small errors that can affect the accuracy of these
1. An error in the value of the Earth rotation rate caused a geolocation
error in the daytime scenes of up to 300 m near the poles, but less than 100 m
below 70 degrees latitude; for nighttime observations, the longitude error is
largest at the equator, and decreases to 100 m at the poles.
2. Not compensating for nutation of the Earth's rotation axis caused an
acquisition-date-dependent longitude error of up to 200 m.
3. Altitude compensation: ASTER coordinates are projected to the WGS-84
ellipsoid, rather than the real Earth's surface. In the most extreme case for
areas of high relief (Tibet, for example), and maximum off-nadir viewing, the
relief displacement in longitude can be 400 m. Compensation requires a digital
Corrections for errors 1 and 2 were incorporated into the Level 1 processing
software at the time they were identified. For all Level 1 processing, no
compensation is made for elevation displacement.
For older data, we have made available a web-based tool that will prompt you to
upload your ASTER HDF files to our ftp server. We will apply all of the
appropriate coordinate adjustments to your data, dependent on date of
acquisition and processing. You will also have the option to convert your
scenes to GeoTiff format. Then you will download your adjusted GeoTiff and/or
[Summary provided by JPL]
Access Constraints Users must register to access the ASTER Lat/Long Adjustment Tool.
Use Constraints Use only on level 1B data, with a HDF extension.
Creation and Review Dates