[GRASS-user] gps import: definition of WGS84

Nikos Alexandris nikos.alexandris at felis.uni-freiburg.de
Fri May 23 12:45:38 EDT 2008

On Fri, 2008-05-23 at 18:39 +0200, Moritz Lennert wrote:
> Hello,
> I'm trying to figure out why we are seeing different results when 
> importing GPS data into different software (GRASS is doing great, it's 
> the others that are having the trouble). It must be linked to the 
> definition of the projection the GPS data comes in.
> v.in.gpsbabel defines the default projection as
> IN_PROJ="+proj=longlat +towgs84=0.000,0.000,0.000"
> Now my question: is this equivalent to EPSG 4326, which is defined as
> <4326> +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs  <>
> ?

Dear Moritz,

I think the first definition is not complete. If the  "+datum=WGS84"
parameter was at least present it should be ok since a datum includes
(or should include) all required information.

> And if not, which EPSG code would be the equivalent of the v.in.gpsbabel 
> line ?

Not sure about that. I don't think that an incomplete definition has an
EPSG code.

There are of course EPSG codes for
.the Spheroid

.transformation parameters from ??? to wgs84

.the prime meridian

.the unit of measure

.specific datums (which should include all above normally).

Maybe I am wrong,
please correct me.



> Moritz
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