[postgis-users] 3D maps

[Randy George]

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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