16 replies to this topic

[Bryan Keith]

Hello,

I'm looking for FOSS software to create a TIN from contours. I have my contours in a dxf now, but I can convert to whatever format. I know that GRASS will convert contours to a gridded surfaces. Will GRASS convert directly from contours to a TIN? What about other software?

Bryan

[angel.spatial]

Hello,

I'm looking for FOSS software to create a TIN from contours. I have my contours in a dxf now, but I can convert to whatever format. I know that GRASS will convert contours to a gridded surfaces. Will GRASS convert directly from contours to a TIN? What about other software?

Bryan

GRASS is obviously the more advanced open source (and I can't wait when someone can prove me wrong on that). But I don't think it is capable, as I am sure you have found out.

IDRISI Andes is your cheapest bet as far as I have ever used in commercial. Doubt this really helps you though.

Angel

Edited by angel.spatial, 20 March 2008 - 04:04 PM.

[Hans van der Maarel]

Not FOSS, but pretty cheap: Global Mapper.

[angel.spatial]

I just stumbled upon one that may help. It will make a TIN from shapefiles.

SAGA GIS

Totally Free!

Should be able to help you out. What format are your contours in?

Angel

Edited by angel.spatial, 21 March 2008 - 08:33 AM.

[Bryan Keith]

I just stumbled upon one that may help. It will make a TIN from shapefiles.

SAGA GIS

Totally Free!

Should be able to help you out. What format are your contours in?

Angel

Well, I know I said I have contours, but they aren't really contours. They're polylines with xyz vertices. Each feature represents the ground surface, but each feature is not necessarily a single elevation.

I have the lines as a dxf right now. It should be easy enough to convert them a shapefile. However, I haven't found a tool to convert xyz lines in a dxf to a shapefile, but I could write that myself fairly quickly.

I'll check out SAGA GIS.

Bryan

[Unit Seven]

However, I haven't found a tool to convert xyz lines in a dxf to a shapefile, but I could write that myself fairly quickly.

In before Hans—FME will do this.

Prob overkill though if you are only wanting to do a conversion. Arc will also do a DXF import.

[Bryan Keith]

I just stumbled upon one that may help. It will make a TIN from shapefiles.

SAGA GIS

Totally Free!

Should be able to help you out. What format are your contours in?

Angel

Well, I know I said I have contours, but they aren't really contours. They're polylines with xyz vertices. Each feature represents the ground surface, but each feature is not necessarily a single elevation.

I have the lines as a dxf right now. It should be easy enough to convert them a shapefile. However, I haven't found a tool to convert xyz lines in a dxf to a shapefile, but I could write that myself fairly quickly.

I'll check out SAGA GIS.

Bryan

Yes, SAGA GIS can create a TIN from a shapefile that does not contain z vertices. They must be real contour lines. However, I couldn't figure out how to export the TIN out of SAGA. There's a workaround though. You can export a polygon shapefile with the triangles and the point ids (no z info stored anywhere!). Then you can export a point shapefile where the z information and point id are stored as tabular attributes. With all that information you can whatever analysis you want with the TIN (or write a tool to export it to another format).

The big bummer is that SAGA GIS doesn't seem to be able to handle shapefiles with xyz vertices.

Bryan

[Bryan Keith]

Not FOSS, but pretty cheap: Global Mapper.

Hans,

Will Global Mapper create a TIN from a polylineZ shapefile? As I mention in another post, a single feature represents a continuous line on the ground but not necessarily at a single elevation. The only software that I've actually seen do this ArcView 3.x (with Spatial and/or 3d Analyst add-ons). I assume the newer Arc stuff does this as well.

What formats will Global Mapper export TINs to?

Bryan

[angel.spatial]

I just stumbled upon one that may help. It will make a TIN from shapefiles.

SAGA GIS

Totally Free!

Should be able to help you out. What format are your contours in?

Angel

Well, I know I said I have contours, but they aren't really contours. They're polylines with xyz vertices. Each feature represents the ground surface, but each feature is not necessarily a single elevation.

I have the lines as a dxf right now. It should be easy enough to convert them a shapefile. However, I haven't found a tool to convert xyz lines in a dxf to a shapefile, but I could write that myself fairly quickly.

I'll check out SAGA GIS.

Bryan

Yes, SAGA GIS can create a TIN from a shapefile that does not contain z vertices. They must be real contour lines. However, I couldn't figure out how to export the TIN out of SAGA. There's a workaround though. You can export a polygon shapefile with the triangles and the point ids (no z info stored anywhere!). Then you can export a point shapefile where the z information and point id are stored as tabular attributes. With all that information you can whatever analysis you want with the TIN (or write a tool to export it to another format).

The big bummer is that SAGA GIS doesn't seem to be able to handle shapefiles with xyz vertices.

Bryan

Here is another one to try out if you want:

LandSerf (Handles conversion of numerous types and handles TINs)

Let us know how this one works out.

Angel

[Hans van der Maarel]

Will Global Mapper create a TIN from a polylineZ shapefile? As I mention in another post, a single feature represents a continuous line on the ground but not necessarily at a single elevation. The only software that I've actually seen do this ArcView 3.x (with Spatial and/or 3d Analyst add-ons). I assume the newer Arc stuff does this as well.

Don't know about polylineZ, but if you can send me a sample I'd be more than happy to give it a try. As for export, it supports a number of output vector formats, including Shape, DGN, DXF, MIF and KML.

[Bryan Keith]

Here is another one to try out if you want:

LandSerf (Handles conversion of numerous types and handles TINs)

Let us know how this one works out.

Angel

Angel,

Thanks for another idea. However, LandSerf does not handle polylineZ shapefiles. It doesn't appear to create a TIN from lines, only from points or gridded data.

Bryan

[Bryan Keith]

Will Global Mapper create a TIN from a polylineZ shapefile? As I mention in another post, a single feature represents a continuous line on the ground but not necessarily at a single elevation. The only software that I've actually seen do this ArcView 3.x (with Spatial and/or 3d Analyst add-ons). I assume the newer Arc stuff does this as well.

Don't know about polylineZ, but if you can send me a sample I'd be more than happy to give it a try. As for export, it supports a number of output vector formats, including Shape, DGN, DXF, MIF and KML.

Hans and I exchanged some e-mails off-list. Indeed GlobalMapper does exactly what I'm asking for. At $300 it's probably worth buying. I'm a bit surprised though that none of open-source projects include this functionality yet.

Bryan

[mdsumner]

Will Global Mapper create a TIN from a polylineZ shapefile? As I mention in another post, a single feature represents a continuous line on the ground but not necessarily at a single elevation. The only software that I've actually seen do this ArcView 3.x (with Spatial and/or 3d Analyst add-ons). I assume the newer Arc stuff does this as well.

Don't know about polylineZ, but if you can send me a sample I'd be more than happy to give it a try. As for export, it supports a number of output vector formats, including Shape, DGN, DXF, MIF and KML.

Hans and I exchanged some e-mails off-list. Indeed GlobalMapper does exactly what I'm asking for. At $300 it's probably worth buying. I'm a bit surprised though that none of open-source projects include this functionality yet.

Bryan

AFAIK, the most general way to generate a TIN from contours is to use a constrained triangulation (i.e. the algorithm used to generate the triangulation is modified so as to include the lines that exist in the input data set). The DEST algorithm uses (constrained) Delaunay triangulation: http://www.agu.org/p...4JF000150.shtml and there are open source triangulation packages to do this, but it's still that bit beyond me to use them yet. The R package tripack seems the most promising.

[cgrob]

I know I said I have contours, but they aren't really contours. They're polylines with xyz vertices

If you have lines or polylines with valid z elevations, you can open a DXF (ASCII format) in SiteTopo and it will create a TIN.

http://www.sitetopo.com

There is a video of the program here:

http://www.sitetopo....emo1/demo1.html

The program is free to download.

[Simmer]

Hans and I exchanged some e-mails off-list. Indeed GlobalMapper does exactly what I'm asking for. At $300 it's probably worth buying. I'm a bit surprised though that none of open-source projects include this functionality yet.

Sounds interesting, but I couldn't find out yet how you got it done with Global Mapper. I have a similar problem here. Downloaded some E00 files from the British Antarctic Survey into Global Mapper. They show fine there and I also can export them to DXF and see that they contain all altitude information.
Problem here is: SiteTopo can only load very limited amounts of data and crashes with most contour line files from Antarctica. Therefore I would be very interested to know how you converted your lines to a TIN (in the long run I need to get an elevation GeoTiff).

See attached sample file.

Bests,
Simmer

Attached Files

•  SP19_20cont00.zip   91.69K   24 downloads