Crash when creating elevation grid

dmontgomery

Good afternoon-

I have a reproducible crash in Global Mapper when trying to create an elevation grid from a TIN.

I've uploaded a section of the TIN that provokes the crash to ftp.globalmapper.com/dmontgomery-badTin.7z.

Repro steps:
1. Uncompress dmontgomery-badTin.7z into dmontgomery-badTin.xyz.
2. Open dmontgomery-badTin.xyz. (Use normal settings for a GlobalMapper Simple Ascii Text File: "Point, Line, and Area Features", "X / Easting / Longitude Coordinate First", etc.)
3. Create an elevation grid from the terrain, using the default settings.
4. A dialog will pop-up, warning that "an error occurred adding the constraint line". Select "Yes" to continue.
5. Crash!

I'm using Global Mapper 64-bit version 11.01. I've tried getting the most recent global_mapper11.exe file; my build time is Jan 12 2010 19:24:12.

This TIN file was generated in Global Mapper by combining several data sets. I was able to successfully run "Create Elevation Grid" on those data sets directly, which is how I created the TIN. Perhaps saving the TIN to Simple ASCII Text file caused the problem? (I'm not sure where the contraint violation came from.)

Any help you could offer would be greatly appreciated.

Thanks,
-David

global_mapper

David,

I am able to reproduce the issue as well and have seen this issue before on a handful of data sets. There is a known problem in the triangulation library that we have that causes this error when there are some very tight constraints. They are supposedly working on it.

In this case since you are starting with a TIN you really don't need the constraints, so just uncheck the option to use constraints when generating the grid and the operation should complete successfully.

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

dmontgomery

Hi Mike-

Thank you for the prompt response. I'm not sure that your workaround solves the problem for us, though.

Part of our workflow involves exporting the TIN to an XYZ file, making some modifications in another tool, then reimporting it to GlobalMapper for rasterization, etc. To prevent GlobalMapper from modifying the triangulation exported by the other tool, we convert each triangle of the TIN into three separate line features and use the Breakline constraint when generating the elevation grid. (I believe this was suggested on another thread in the GlobalMapper forums.) This worked well until the triangulation bug started occuring.

A few more questions for you:

Are there any other workarounds? (i.e. would reverting to a previous revision of Global Mapper help? We didn't have this problem with 9.0, but our datasets have become a bit more complex since then.)

Do you have an ETA on a fix for the triangulation library?

Thanks,
-David

global_mapper

David,

Unfortunately there really isn't another good workaround. You could remove the actual line segment that causes the error to be displayed and try triangulating again to see if it is just the one segment that is bad.

We have tried working with our triangulation library vendor on this and they came up with a partial fix a while ago, but it only worked for some data sets. For others (like yours) the operation still fails. The worst thing is that instead of failing in a nice way it actually crashes, sometimes in a non-recoverable way. They were still supposed to be looking into it further, but I haven't heard anything from them in a while so I'm guessing they decided it was too difficult to fix.

In general if you have just the points from a TIN generated in some other application I would expect the same TIN to be generated in Global Mapper from that collection of points, at least assuming that Delaunay triangulation was used to generate the TIN in the other application. Are you seeing different TINs from Global Mapper than the original TIN from the other software?

Thanks,

Mike
Global Mapper Support
support@globalmapper.com