[GRASS5] projection-transformation

[Markus Neteler]

On Fri, Dec 22, 2000 at 08:59:41AM -0600, Helena Mitasova - staff wrote:
> 
> >The resulting UTM/international/eur50 datum location looks like this:
> > - GLOBE DEM 1km and GSHHS match rather good
> > - boundaries are shifted (why? - I didn't supervised their work)
> 
> Markus, I am glad that somebody else got this problem too!
> Bill and I had to import data for various locations from arc/info into UTM
> but also into state plane,
> (usually shape files) and we had the vector data often shifted
> compared to raster data - the difference is equivalent to
> the difference in datums used in US, so at least in one case Bill
> was able to re-project them through different location to get them right.
> However the input data were supposed to be in the same projection.
> I did not have time to figure out whether I am doing something wrong
> but I am suspicious that there might be a bug - I haven't seen
> people complaining about it though, so it may be my mistake
> (or your student's) too - check your datums.
> 
Hi Helena, hi all,

maybe it's a bug... (but where?). I made some further tests with my
dataset by analysing a point:

The west corner of the "norderney" island (one of those islands in the
picture I have sent the URL) has following points in the map (d.where):

UTM:
 377261 5953152 (GSHHS dataset from v.in.gshhs [new, to be submitted soon])
 377946 5953426 (GLOBE DEM 1km, generally matching to GSHHS quite well)

 379592 5952535 (Students vector data from ARC/INFO)


I took a 1:100000 map of that area and got the coordinates in Gauss-Krüger
system (tmerc, bessel):
 2575400   5953800 GK

These I transformed with m.proj to UTM to compare them with d.where results:
 377375 5953157 UTM

It seems that the ARC/INFO vector data are shifted:
 > 2km to east
 > 500m to south

-----

Then I looked back into the original lat/long database:
The shifts are identical. So it's not a *.proj problem.

May there be a bug in m.in.e00 which I used for data import?

Markus

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