[postgis-users] 3D maps

[Randy George]

Hi Paul,

Andreas is right about using Google Earth as a simple rendering viewer. You
have to use GE DTM and GE to view it but it's pretty easy to write vectors
to KML. It's especially easy if you can drop Geoserver onto your server and
ask for KML formatted output from your PostGIS table.

If rendering is sufficient you could also use some more flexible rendering
tools like Java3D or WPF. This way you can use your existing DTM as a 3DMesh
and draw the vectors over it. This approach is the ultimate densifier since
the vectors are typically rasterized and then draped on the mesh surface. If
you have field surveyed DTM or Lidar this is probably a good way to go.

The draw back of any rendering approach, though, is the loss of the 3D
vectors, which in some cases are useful.

randy
 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Andreas
Neumann
Sent: Tuesday, November 20, 2007 1:13 AM
To: PostGIS Users Discussion
Subject: RE: [postgis-users] 3D maps

alternatively you could output your 2d data as KML and visualize it in
Google Earth. I know that the DTM is not too good in GE, but it is a quick
and cheap solution.

Andreas

> Hi Paul,
>
>
>
> I'm not aware of any built in procedures available in PostGIS. Something
> could be worked out possibly but you would need to pull out the triangles
> as
> line segments and intersect individual lines before interpolating a z
> value.
> This is a lot of work and I doubt that it could be done efficiently. You
> would have to write the splitting and interpolation yourself.
>
>
>
> Perhaps you should look at one of the open source terrain modeling tools.
> I'm thinking of grass.
>
> http://grass.itc.it/ or  http://www.jgrass.org/cgi-bin/moin.cgi
>
>
>
> Here is a potential work flow:
>
> 1. Convert your TIN to a surface
>
> http://grass.itc.it/grass63/manuals/html63_user/v.surf.idw.html
>
> I believe Grass is memory limited so if the TIN is very large you may have
> to tile and iterate through a tile set.
>
> You could possibly work out something using the pg driver
> http://grass.itc.it/grass63/manuals/html63_user/grass-pg.html
>
>
>
> 2. Use the resulting surface to process 2D polyline into 3D polyline
>
> http://grass.itc.it/grass63/manuals/html63_user/v.drape.html
>
> You may want to densify the 2D first with
> http://grass.itc.it/grass63/manuals/html63_user/v.split.html
>
>
>
>
>
> Hope this is helpful
>
>
>
> Randy
>
> http://cadmaps.com/gisblog/ <http://www.cadmaps.com/gisblog.htm>
>
>   _____
>
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Malm
> Paul
> Sent: Monday, November 19, 2007 7:53 AM
> To: PostGIS Users Discussion
> Subject: [postgis-users] 3D maps
>
>
>
> Hi!
> I have a geometry set of triangles (e.g land area), including elevations.
> To
> be able to view e.g roads ontop those triangles I must insert points in
> the
> road polylines with the correct elevation in each intersection (roadline -
> triangle border). Att the same time I would like to insert the correct
> elevation of the original points of the road-polyline. is there a command
> in
> PostGIS that could do this for me?
>
> Kind regards,
>
> Paul
>
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> postgis-users mailing list
> postgis-users at postgis.refractions.net
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>


-- 
Andreas Neumann
Böschacherstrasse 6, CH-8624 Grüt/Gossau, Switzerland
Email: a.neumann at carto.net, Web:
* http://www.carto.net/ (Carto and SVG resources)
* http://www.carto.net/neumann/ (personal page)
* http://www.svgopen.org/ (SVG Open Conference)
* http://www.geofoto.ch/ (Georeferenced Photos of Switzerland)

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