[Gvsig_english] Coordinate Transformations

[Antonio Gennarini]

Hi Victoria,

many thanks for your very detailed reply. I have figured out that every
transformation from 4326 to other projected coord systems will
necessarily imply an error which is estimate in the 7-8m region. DO you
think that programs such as DNRGarmin do worse that gvSIG, which I
assume uses PROJ4 code?

Cheers
Antonio


Il giorno lun, 11/08/2008 alle 10.29 +0200, Victoria Agazzi ha scritto:
> Hi Antonio,
> if you are able to convert the *.gpx file to a *.shp file, then gvSIG 
> transform the CRS from EPSG: 4326 to various OSGB reference systems:
> 1. you will need to generate an shp file with your data (more than one 
> if you have points, tracks, routes and texts). You can do this with [1]. 
> These *.shp files will be in EPSG:4326.
> 2. With gvSIG you need to create a new View in the CRS OSGB. To do this, 
> create a new view, go to its Properties and select current projection. 
> Search into the EPSG type, by name OSGB. Select one of them.
> I searched into the CRS manager and found  6  CRS  that are OSGB: 4 that 
> are geographic, 1 projected and another one compound.
> 3. After that, you have to add your *.shp files which are in EPSG:4326. 
> Open the View, Add data icon,  and select  the files.  For each one, you 
> will have to change its CRS into 4326 (this is the way gvSIG "knows" in 
> which CRS is your data). Click the current projection button, and look 
> for the EPSG Type and 4326 code. Remember to define a transformation (in 
> the Selec transformation list) between both CRS because they don`t have 
> the same datum. You can select EPSG transformations, and also you can 
> define a manual one if you know the parameters involved in your 
> geographic area.
> 4. At this point you will have your data in the OSGB projection but only 
> in the actual view. Next step is to export the gvSIG layers into your 
> hard disc. To do this, go to Layer/Export to/SHP.
> 
> Regards,
> Viqui-.
> 
> [1] http://gpx2shp.sourceforge.jp/
> 
> 
> Antonio Gennarini escribió:
> > Hi.
> >
> > I'm in the process of learning howto deal with GPS data and have now the
> > difficulty of transforming WGS84 coordinates in my *.gpx files to OSGB
> > stored in a shapefile.
> >
> > ANybody now a relaxed way of doing this. I've been searching the web and
> > have only found standalone applications that will allow me to convert
> > the coordinates one by one and without reading directly from the gpx
> > file.
> >
> >
> > Thanks in advance for your help.
> >
> > REgards
> > ANtonio
> >
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> >
> >