I am interested in adding detailed topographic terrain to a model for the purpose of modeling retaining walls and other landscape features at a lakeside property. Looking for recommendations on where to download detailed elevation/contour data (down to 1’ or more in detail). Data must be accurate for the purpose of design, materials estimating, etc. Any advice and experience shared will be appreciated.
I expect to get that kind of resolution in terrain data in most locations you will need to find a local surveyor or survey the site yourself. Maybe the local GIS agency would have that but I’d guess not likely.
Please complete your profile with SketchUp version and graphics card.
At the low end, you can add geo location inside SketchUp. If you do that, zoom to 18X before importing, that will give you the most terrain detail. If you need the surrounding area, use Add More Imagery, and import the area next to the first one.
At the high end there are the Trimble scanner devices. See this page:
https://buildings.trimble.com/field-technologies/layout/trimble-field-points
I don’t think the open data anywhere has that kind of accuracy. Here in Finland we have National Survey scans that are, I think, at about 2m intervals, but they have started a giant project to re-scan the country at something like 3 points to a square meter. That would be almost enough. The current data is not detailed enough for accurate planning.
We have an 8 pt per square meter dataset that’s public available for heights, but you would need some steps to import (layers via GIS can create Shape files, which could be imported in SketchUp by extension.
Pretty acurate, but then, we don’t have much difference in elevation 
(Netherlands)
THAT’s pretty accurate! Ok, Finland has 8 times the territory with 1/3 of the people…
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