LiDAR contours vs a topographic survey
Modern USGS 3DEP LiDAR (Quality Level 2 or better) is specified to about 10 cm (4 in) vertical accuracy in open, non-vegetated ground, which makes it good for 1 to 2 ft contours and early grading studies. It's weaker under dense vegetation, smooths out curbs, walls and narrow swales, and is only as current as its collection date. A topographic survey adds exact spot elevations on hard surfaces and breaklines, which you need for detailed grading and drainage.
Side by side
| 3DEP LiDAR DEM | Topographic survey | |
|---|---|---|
| Vertical accuracy | About 10 cm RMSE in open ground (QL2); worse under canopy | Typically a few hundredths of a foot on hard surfaces |
| Detail | 1 m grid; features narrower than a couple of meters smoothed | Breaklines at curbs, walls, top and toe of slope |
| Currency | Collection date, sometimes 10+ years old | Current |
| Buildings, trees | Removed (bare earth) | Located, with finished floors and tree sizes |
Good enough for
- Overall slope, drainage direction and steep areas
- Siting buildings, parking and paths at concept level
- Rough cut and fill comparisons between options
Not good enough for
- ADA routes, curb and gutter, finished floor tie-ins
- Wall heights and stair counts
- Detailed drainage near buildings
Always check the collection date and resolution. Basesheet records both in each download's provenance file and widens the contour interval when the data is coarse. See how to get contours.
Everything here is planning-level public data. Confirm boundaries, topography, wetlands and flood status with a licensed surveyor and the right specialists before design decisions depend on them.
Basesheet does all of this for any US address in about 30 seconds, free, with no account.
Build a base planRelated
- How to get contour lines for a property
- Public-data base plan vs a boundary survey
- How to get real topography into SketchUp
Updated October 2026.