[R-sig-Geo] 3d-Shapefile in R

[Roger Bivand]

On Fri, 13 Nov 2009, Siber Rosi wrote:

> Dear list,
>
> I would like to have the z-values of a river shapefile in R (sp). So 
> that I have at the end a list of x,y and z-coordinates, for which I do 
> further analysis.

> Is there a way of importing a 3d-shapefile direct in R?

Yes, but only for points. The objects used to represent lines and polygons 
are 2D. To move forward, a Line3D representation with downstream Lines3D 
and SpatialLines3D classes would be needed. However, analysis on 3D lines 
may be hard to do - so something more like GPX track_points might be more 
useful, or the representation of sequences of points from the trip or 
adehabitat (ltraj class) packages. Just being able to read the data is 
only the first step, finding an adequate representation with convenient 
analysis tools is probably harder.

Using the Z dimension in shapefiles is arguably not a portable way of 
representing this, using points with a constant lineID and sequence 
numbers increasing downstream, with elevation at the points, may be easier 
to handle. (Untried) Convert to say GPX and read as track_points, trying 
to retain the necessary attributes.

Hope this helps,

Roger

> When I was using the readOGR command,  the following message appear.
> ****************
> riv_CH <- readOGR(".", "riverz")
> OGR data source with driver: ESRI Shapefile
> Source: ".", layer: "riverz"
> with 13 features and 13 fields
> Feature type: wkbLineString with 3 dimensions
> Warnmeldung:
> In readOGR(".", "riverz") : Z-dimension discarded
> *****************
>
> Do you have any suggestion for handling the z-dimension?
>
> Thanks a lot in advance, Rosi
>
> ???
> Rosi Siber
> Swiss Federal Institute of Aquatic Science and Technology (Eawag)
> Siam
> Ueberlandstrasse 133
> 8600 Duebendorf
> Switzerland
> Phone: +41 (0)44 823 5566
> Fax:   +41 (0)44 823 5375
> rosi.siber at eawag.ch
> http://www.eawag.ch/~siberros
>
>
>
>
>
>
> 	[[alternative HTML version deleted]]
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no