[postgis-users] DEM importing

[Frank Warmerdam]

jeremy pierre wrote:
> Hi all,
> 
> Apologies if this is an extremely newbie-ish post but here goes:
> 
> I'm working(to scratch an itch) on a library and utility in Scala to
> import USGS format DEM files into PostGIS as points(probably
> multipoints really).  I'm working with the CDED files from geobase.ca
> at present and the quadrangle coordinates are all laid out in
> arc-seconds.  The question is:  for the x and y coordinates of each
> elevation point would it be better(across the board, given various
> types of DEM data) to keep points as lat/long floats(convert from the
> arc seconds) or stick to arc-seconds as a standard unit for importing?
>  Anyone care to weigh in on this?
> 
> Again, apologies if I'm being a terrible newbie...

Jeremy,

My position would be that you are better off converting from arcseconds
to decimal degrees as it gives you the opportunity to use the reprojection
mechanisms of PostGIS if you want.  The PostGIS transform code does not
understand geographic (angular) units other than decimal degrees.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent