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To see if NASA provides the geolocation files for your own swath files using the dimension map, for Aqua MODIS, go to ftp://ladsweb.nascom.nasa.gov/allData/5/MYD03 to find the corresponding geolocation files; for Terra MODIS, go to ftp://ladsweb.nascom.nasa.gov/allData/5/MOD03 to find the corresponding geolocation files. You may also use http://ladsweb.nascom.nasa.gov/data/search.html to search the "Geolocation" product from Terra or Aqua MODIS. So far, NASA only provides some 1KM resolution Geolocation data for swath files using the dimension maps.
For 250/500 meter resolution and unavailable "Geolocation" product for 1KM
resolution swath files using the dimension maps, you may need to use the
HDF-EOS2 Dumper
to generate the corresponding latitude and longitude. The command you need is
./dump -a1m filename
for the latitude and
./dump -a2m filename
for the longitude. Some people claimed that the generated latitude and
longitude based on the HDF-EOS2 swath dimension map parameters may not be
accurate. So please use it with caution.
Please note that you may need to compare part of the file names to ensure the geolocation file you obtained from the NASA provides the latitude and longitude for your file. For example, an HDF-EOS2 Swath using the dimension map has the name MYD05_L2.A2009001.0000.005.2009033182605.hdf. The 12 characters after MYD05_L2.A, in this case, 2009001.0000 represent the data observed time. The corresponding geolocation file is MYD03.A2009001.0000.005.2009330051638.hdf. Notice the 12 characters after MYD03.A is the same as the 12 characters after MYD05_L2.A in the previous swath file. For more information about MODIS HDF names, please visit NASA MODIS atmosphere website.