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Up Topic Frequently Asked Questions / SeaDAS 6 FAQ / What are utcpole.dat and leapsec.dat? How do I keep them up-to-date? (locked)
- By mike Date 2005-10-21 16:26 Edited 2008-04-21 15:58
What are utcpole.dat and leapsec.dat? How do I keep them up-to-date?

- SeaDAS now automatically checks the dates of these files and if they are not recent, automatically downloads new versions during processing. For this reason there is likely no need for you to manually update the files yourself. -

The Earth motion file "utcpole.dat" and the leap seconds file "leapsec.dat" are required for MODIS geolocation processing and are included with SeaDAS in the $SEADAS/var/modis/static/ directory. It is recommended that the utcpole and leapsec files be updated weekly, but it depends on how much error is tolerable. To quantify the errors caused by not updating these files (called "latency") Peter Noerdlinger has prepared an excellent document.

To update both of these files, simply use the [Update -> Update utcpole.dat and leapsec.dat] GUI function. It is also highly recommended that you set up a unix cron job to automatically download these files in order to keep them up-to-date. The modis_update_utcpole_leapsec.csh SeaDAS script will download these files for you. When running this script within cron, remember to invoke a shell in order for the SeaDAS environment variables to be set. Here is an example crontab line for csh shell installations that will run this script every Sunday:

0 0 * * 0 /bin/csh -c "/PATH_TO_SEADAS/scripts/modis_update_utcpole_leapsec.csh -quiet"
Up Topic Frequently Asked Questions / SeaDAS 6 FAQ / What are utcpole.dat and leapsec.dat? How do I keep them up-to-date? (locked)



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