[R-sig-Geo] Projections and Transformations with Garmin GPS Coordinates?

[Karl Ove Hufthammer]

Breitbach, Nils wrote:

> # assign spatial reference; via EPSG code set to WGS84
> proj4string(map)<- CRS("+init=epsg:4326")
> 
> Does anybody of you know if this is the same definition as in the Garmin
> GPS receivers? Should result in correct WGS1984 coordinates.

Yes, that’s the correct EPSG code for longitude and latitude in WGS 84.
 
> I now tried to reproject the WGS1984 coordinates into the different other
> datums and projections that I need:
> 
> # transform/reproject from WGS84 to UTM32N
> map2 <- spTransform(map,CRS("+init=epsg:32632"))
> 
> Is 32632 the correct ESPG code for "WGS 1984 / UTM Zone 32N" ?

Yes.

> # transform/reproject from WGS84 to Gauss Krueger Zone 3 (for use with
> # CORINE land-use data)
> map3a <- spTransform(map,CRS("+init=epsg:2166"))
> 
> Again, is 2166 the correct ESPG code for "Gauss Kruger zone 3"?

It’s deprecated. http://spatialreference.org/ref/epsg/2166/ says to use 2397 
instead. But as you mention, there are several EPSG codes for Gauss-Kruger 
zone 3. You can try all of them, and see which fits best with yout data 
(note that some of them have an identical proj4string, and will therefore 
give the same output).

Note that the list of codes is also available inside R:

library(rgdal)
epsg=make_EPSG()
epsg[grepl("Gauss.*zone 3(\\D|$)", epsg$note), 1:2]

I find this easier to use than the search engine at Spatial Reference.

-- 
Karl Ove Hufthammer