Drainage Basins and Google Earth

I have compared it to good USGS data and fount it pretty weak. On the other hand, if you are fortunate enough to have a project that is covered by the newest, highest resolution, USGS data from the national seamless DEM models, that data is very tight.

Also, it is a pain to stitch together as you can only get small pieces at a time.

Robert,

I can't vouch for whether it's good enough, but the workflow in GEOPAK is pretty easy. There are actually two ways to do it.

When you capture the Google Earth image, you will get a mesh element. You will need to drop the mesh element and it will create a bunch shapes.

1. You can use the DTM Tools > Extract Graphics > Graphical Triangles. This will create a dat file and then you can build the TIN.

2. You can use Data Acquisition. Just create an empty surface. Then put the shapes into a MS Selection Set, then under the surface right-click on "Triangles" and select Import Selection. YOu can then export the surface to a GEOPAK TIN or InRoads DTM.

Derricke

Hi,

I also tried to use GE terrain, but it is in fact VERY weak and I have same conclusion as former answers.

Import is limited to 400 points whatever area you target, and as caddcop spotted, stiching parts is not an easy solution.

On areas I tested, GE terrain was too "smoothed" to be used as a technical input - not usable (forget about ridges/valley).

I only use it to give idea of surrounding terrain in rendering projects.

Here's a related question: Are you in a state that's covered by StreamStats?  If you're not aware, StreamStats is a USGS production that let's you click on a point, and it will give you the rough drainage area as a .shp file.  It's only good for large basins - I used it as a starting point for some 6' culverts in CT a couple years ago.   

water.usgs.gov/.../ssonline.html

-Tim