[Gvsig_english] problems with on-the-fly projection

[Moritz Lennert]

On Sun, May 25, 2008 17:59, Marcus C. England wrote:
> Sorry... I cued in on the topographic map which is usually a raster (and
> I just woke up and haven't had my coffee yet!). Are you sure you are
> using the correct transformation? If so, are you running gvSIG on the
> correct version of java? When I first started using gvSIG I had problems
> with some transformations and it had something to do with me running it
> on java 1.6. When I reinstalled using java 1.5 the problem went away. I
> use gvSIG daily for all my GIS and have not run into any problems with
> vector projections.

I installed and use the java that came with the gvSIG installer, so I
would hope that this shouldn't be the reason.

Moritz

>
> -Marcus
>
> Moritz Lennert wrote:
>> On Sun, May 25, 2008 17:26, Marcus C. England wrote:
>>
>>> Hi Moritz,
>>>
>>> GvSIG only reprojects vector data, not raster data. My understanding is
>>> that they hope to have this for rasters soon.
>>>
>>
>> The two shapefiles I speak about below are vectors... And in the example
>> with the topo raster map, I reproject the GPS points/tracks (i.e.
>> vectors)
>> to the projection of the topo map. And it works, but only more or less,
>> since the result is off by +/- 100m.
>>
>> As I mentioned, QGIS has the same problem. See:
>> http://trac.osgeo.org/qgis/ticket/1079.
>>
>> Moritz
>>
>>
>>> -Marcus
>>>
>>> Moritz Lennert wrote:
>>>
>>>> Hello,
>>>>
>>>> I have some trouble with on-the-fly projection: using gps data coming
>>>> in
>>>> WGS84 (epsg 4326) and a topographic map in Belgian Lambert (epsg
>>>> 31370),
>>>> the two do not superpose correctly.
>>>>
>>>> When importing the data into GRASS, I get perfect superposition. And
>>>> when
>>>> I import the gps data into a GRASS 4326 location and the same data
>>>> into
>>>> a
>>>> 31370 location, then reproject from one to the other, I also get
>>>> perfect
>>>> superposition of the two versions of the gps data. However, when I
>>>> export
>>>> to shapefiles from both locations and then load them in gvSIG
>>>> indicating
>>>> their respective projections, I get a difference of about 100m.
>>>>
>>>> Hamish Bowman suggested on the GRASS-users list that such a difference
>>>> hints at an issue with datum transformation.
>>>>
>>>> I get the same kind of error using on-the-fly projection in QGIS.
>>>>
>>>> Moritz
>>>>
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>>>>
>>>>
>>>>
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>>>
>>
>>
>>
>>
>
>