Ken Sibley ksibley at
Wed Aug 17 12:15:45 EDT 1994

> Hi Folks,
> I am trying to fully integrate GRASS database support into the PCI software
> product, and I am somewhat confused about projections support.  I am basing
> my work on the GRASS 4.0 Programmer's Manual (DRAFT) dated August 11, 1992.
> I am primarily utilizing the chapter on ``Database Structure'' which 
> defines the directory tree, and file formats within it.
> Recently I have discovered that some of our customers using GRASS have raster
> layers with a ``proj'' code of 99 in the ``cellhd'' files, and projection
> information in a file called PROJ_INFO in the PERMANENT directory.  The
> following is an example of one of these files:
> -------------------------------------------------------------------------------
> Frank Warmerdam | Who can give them back their lives | warmerda at    
> Software Artist | and all those wasted years? - Rush | 
    The customers that have a 99 in the cellhd files are either SCS sites
    or are co-operators that have received grass from SCS or are running
    grass4.1.  In grass4.0 SCS modified the projection information.  CERL
    did not change theirs until grass4.1.  SCS has already converted to
    grass4.1 for 85% of its operations.

    The 99 is also in the WIND file which indicates you need to look in
    the PROJ_INFO file for the true projection.  This is where the 
    differences between SCS and CERL grass come into play.  If you need
    more details about SCS modifications for grass4.0 let me know.

Ken Sibley
USDA-SCS/NCG		"Hell, if you understand everything I say,
ksibley at   you'd be me!"  - Miles Davis

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