Satellite Data > Satellite FAQ > Question

Question

How do I navigate GOES Imager AREA files provided by CLASS?

Answer


What is navigation

Satellite imagery in its raw format is simply what the sensor observes. To use the data quantitatively (or even to simply overlay a map) requires the calculation of the Earth location for each pixel. Generally, the Earth location is described in latitude/longitude pairs.

How does one navigate imagery?

CLASS automatically navigates...
  • GIF/JPG imagery by overlaying map coordinates on the image.
  • netCDF files by providing latitude and longitude as variables in the file
However, McIDAS Area files will need to be navigated by the user, which depends on whether the data originates from the:
  • Mode Files: GOES-1,2,3,4,5,6,7 (i.e., pre GOES-8)
  • GVAR Files: GOES-8,9,10,11,12,... (GOES-Next in GVAR format)

Mode Navigation

Mode data was just recently made available from CLASS. A description of the navigation will be included here at a later date.

GVAR Navigation

  • The GVAR navigation is described in the NESDIS Earth Location User's Guide (ELUG) available from NESDIS or here.
  • The ELUG describes a navigation algorithm which has been coded in Fortran 77 and is available via ftp at the GOES Project Science Office.
NCDC scientists have brought this code up-to-date by upgrading it to Fotran95 and also converting it to IDL.

Navigation Tools

  • sat2netcdf - This tool converts files in their raw format to netCDF. Since it is a Java tool, it is compatible with most systems.
  • The weather and climate toolkit developed at NCDC will calibrate and remap CLASS-Area files to various output formats, some of which can be used with GIS software.
  • IDL - NCDC has a library of routines which can be used to navigate GOES Area files. The routines are provided as part of a tarball distribution which includes IDL code to read and navigate GOES GVAR McIDAS Area files.
  • Fortran - If you are interested in the Fortran code for GVAR navigation, please contact NCDC.Satorder@noaa.gov to request the code. The Fortran code has some compiler-specific calls (Lahey Fortran 95) which may preclude it from working with all Fortran compilers.