Contour map generator: from an area on the map to AutoCAD and Civil 3D
Pick an area on the map and get its contour lines in seconds. Download them as DXF, in UTM coordinates with their elevations, or download a grid of points to build the surface in Civil 3D. Free, nothing to install, no Global Mapper.
- Free, no sign-up
- DXF with elevations
- Points for Civil 3D
- For preliminary studies
Contour line generator from the map
Pick the area on the map
Pan the map: the square follows the center.
Elevation data: Terrain Tiles (AWS Open Data), from SRTM, 3DEP, EU-DEM, ETOPO1 and other sources. Full attribution
Result
Pick an area and press “Generate contours”.
In short
To get contour lines for an area without a survey, you use an open digital elevation model. In the US that's USGS 3DEP, at 10 m resolution (3 m in places); elsewhere it's usually SRTM, at about 30 m. This generator downloads the model for the area you pick, traces the contours in your browser and delivers them as DXF for AutoCAD and Civil 3D, in UTM coordinates with elevations. Use them for planning and feasibility, not for final design.
How these contours are generated
The tool uses Terrain Tiles, an open elevation model published on AWS that blends public sources. In the United States it relies on USGS 3DEP (formerly NED) at 10 m, and 3 m in select areas. In most of the rest of the world it uses NASA's SRTM, on a grid of about 30 m, and EU-DEM (30 m) in Europe.
- Pan the map until the square covers your area and pick its size (500 m to 5 km per side).
- The tool downloads the elevation tiles for that area and builds the elevation grid.
- It traces contours with the marching squares method used by GIS software.
- It converts them to UTM WGS 84 coordinates for the zone at the center and clips them to the square.
Everything runs in your browser. Elevations are heights above mean sea level, in meters.
How accurate they are, and what they're good for
Accuracy depends on the source. 3DEP 10 m data in the US is far better than SRTM, whose specified vertical accuracy is ±16 m (90%). Steep slopes, dense vegetation and buildings make any radar-based model worse, because it measures the visible surface.
- Good for: site selection, feasibility studies, preliminary road and channel alignments, slope estimates and academic work.
- Not for: final design, construction documents or earthwork quantities.
How to bring the contours into Civil 3D
- Set the drawing to the UTM WGS 84 zone the tool reports (for example, UTM84-10N for San Francisco).
- Recommended, the points: download the PNEZD point grid, import it with Insert > Points from File, and build a surface from that point group. Civil 3D then draws contours with your style, interval and labels.
- Direct, the DXF: contours arrive as 3D polylines on MAJOR-CONTOURS and MINOR-CONTOURS layers, at their elevations. Use them as linework or add them to a surface definition (Contours > Add).
Civil 3D can also build a surface straight from an elevation file (DEM): it accepts .dem, GeoTIFF (.tif), ESRI ASCII (.asc) and ESRI binary (.adf). The full walkthrough is in the guide to contours in Civil 3D.
What about contour lines from Google Earth?
Google Earth Pro shows the elevation under the cursor, but it doesn't export contour lines or terrain. Civil 3D once had a command to import a Google Earth surface, but current versions no longer include it. That's why the usual workaround involves paid software like Global Mapper, or add-ins.
This generator does the same job in the browser: pick the area and interval, then download the DXF. To convert a Google Earth point to UTM, use the UTM to lat long converter.
How to choose the contour interval
A rule of thumb: aim for about 20 contours across the area, an interval close to the relief divided by 20, rounded to 1, 2, 5, 10, 20 or 50 m. Index (major) contours go every 5 intervals.
Example: the 2 km area preloaded in the tool, around Twin Peaks in San Francisco, runs from about 41 to 279 m. With 238 m of relief, the automatic interval is 20 m (about 66 ft), with index contours every 100 m.
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Frequently asked questions
How do I get contour lines for an area without a survey?
From an open digital elevation model: USGS 3DEP in the US, SRTM in most of the world. In this tool you pick the area on the map and download the contours as DXF, in UTM coordinates with elevations. Use them for planning, not final design.
Can I export contour lines from Google Earth?
No. Google Earth Pro doesn't export contour lines or terrain; it only shows the elevation under the cursor. To get contours for an area, use an open elevation model, as this generator does.
How accurate are these contours?
It depends on the source: USGS 3DEP data in the US is 10 m resolution (3 m in places); SRTM elsewhere is about 30 m, with a specified vertical accuracy of ±16 m. Good for planning, not for design or quantities.
How do I create contours in Civil 3D?
Build a surface from points, contours or a DEM file, then set the minor and major contour intervals in its style. This tool gives you a PNEZD point grid ready to build that surface.
Can I download contour lines as DWG?
The tool downloads DXF, which AutoCAD and Civil 3D open directly and can save as DWG. Contours come as 3D polylines at their elevations, on major and minor layers.
Can I get contours in feet?
The tool works in meters. For feet-based drawings, import the point grid into Civil 3D, build the surface and set the contour interval in feet in the surface style.
Is there a cost or a limit?
It's free, with no sign-up. Each run covers a square up to 5 km per side; for larger areas, run several and combine them in Civil 3D.
Go deeper before you decide
Civil 3D import points from CSV, Excel or TXT: formats, latitude and longitude, duplicates and the most common errors
How to import points into Civil 3D from Excel: preparing the CSV, picking the PNEZD format, lat/long points, duplicates and why points don't show up.
Contours in Civil 3D: from Google Earth and satellite elevation models to your survey, step by step
How to get contours in Civil 3D: why Google Earth won't export terrain, which elevation model to use and how to build the surface step by step.
Automating Civil 3D: The Complete Guide (2026)
What you can automate in Civil 3D and how: Dynamo, Python, C# and AutoLISP compared, the 15 automations with the best ROI, and which to build first.
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