topic Re: Terrain Datasets - Contours in 3D Questions

Terrain Datasets - Contours

PeterWilson — Mon, 04 Oct 2010 19:36:33 GMT

I'm trying to find out the most suitable format to store my data that will be used to generate a terrain dataset. I have 20m contours for the entire country and would like to use it to generate a terrain dataset that will be used with Arc Hydro to calculate catchment characteristics i.e. area, longest water course, 10/85 slope etc. I'm considering generating a DEM for each contour sheet using a 10m cell size and then converting the DEM into a point shapefile. I'll then convert the point shapefile into a multi-part point shapefile, thereby reducing the records per point. Is my approach going to produce a better terrain than using the contour lines to generate the surface. Any advice will be appreciated. If anyone has converted contour lines into multi-part points to generate a terrain, any advice and workflow suggestions will truly be appreciated.

Regards

Re: Terrain Datasets - Contours

DonovanCameron — Mon, 04 Oct 2010 22:02:37 GMT

The help has some good starter documentation on some terrain best practices.

Overview of Terrain Design

Best Practices

Re: Terrain Datasets - Contours

PeterWilson — Wed, 06 Oct 2010 07:11:24 GMT

The help has some good starter documentation on some terrain best practices.

Overview of Terrain Design

Best Practices

Hi Saul

Thanks for the pointers, I read much of the help on Terrain Datasets, I'm looking for some advice from the users experience in utilizing contours to generate terrains, the most efficient way to represent topography and storage methods.

Regards

Re: Terrain Datasets - Contours

JakubSisak — Wed, 06 Oct 2010 13:02:32 GMT

I have 20m contours for the entire country and would like to use it to generate a terrain dataset that will be used with Arc Hydro to calculate catchment characteristics i.e. area, longest water course, 10/85 slope etc. I'm considering generating a DEM for each contour sheet using a 10m cell size and then converting the DEM into a point shapefile. I'll then convert the point shapefile into a multi-part point shapefile, thereby reducing the records per point. Is my approach going to produce a better terrain than using the contour lines to generate the surface. Regards

Personally, i don't find terrain datasets particularly useful for anything other that cartography at the moment. In the future as ESRI adds more functionality terrain datasets might replace TIN but currently if you would like to any kind of geo-processing TIN is probably a better option.
I do not use ArcHydro but often generate very large watershed models and stream networks with Spatial Analyst. From what i understand ArcHydro uses much of Spatial Analyst functionality for its purposes so I believe what you need is a DEM not terrain dataset or TIN. You can probably generate hydrologically correct DEM from the 20m contours with "Topo to Raster" but it will be a huge job to do this for the entire country of South Africa. You might also run into problems with merging the individual datasets. I am almost certain you would not be able to do the entire model at once.
Instead of doing this i would recommend to try using DEM such as SRTM 1 arc-second which is equivalent to about 30m resolution but on such a large scale you might even consider 3 arc-second (90m resolution). For Africa, this can be found here: http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Africa/ (Source: USGS)
Not sure if 1-arc-second data is freely available for your area. Often there is a cost involved with the higher resolution DEM.