How to create contour lines with SRTM DEM and field checks
Contour lines help read terrain, but they are only as reliable as the elevation model behind them.
Field takeaways
- SRTM is useful for reconnaissance and preliminary analysis, not precise elevation delivery.
- Contour interval should match terrain relief.
- Contours should not be the sole source for legal or construction elevation decisions.
- Field checks are needed around drainage, slopes, roads and structures.
- MapLab Survey combines contours, profiles and field notes.
What global elevation data can tell you
Open datasets such as SRTM or Copernicus describe terrain at roughly thirty-metre spacing. They show valleys, ridges and general slope well, and small features not at all.
Where the limit bites
A thirty-metre grid cannot represent a bund, a ditch or a terrace. Contours derived from it are a planning aid, not a design surface.
Surface, not ground
These datasets often record the top of vegetation and buildings rather than bare earth, so wooded areas read higher than they are.
Use it to plan the survey
Generate contours to understand the shape of the site and decide where to concentrate real measurements, then measure those areas properly.
See it in action
MapLab Survey | Professional Mobile GIS, GPS Surveying & Land Measurement App
Visit the YouTube channel ->Try these steps on your own phone.
MapLab Survey handles RTK/GNSS point capture, drawing, area and volume calculations and coordinate conversion, then exports to DXF, KML/KMZ, GeoJSON, Shapefile, GeoPackage, NCZ or CSV. Capture, calculation and export work offline. Live NTRIP corrections and online basemaps need a connection.
Frequently asked questions
Are SRTM contours precise?
They are useful for preliminary analysis, not precise construction elevation.
Which contour interval should I use?
It depends on terrain relief and purpose.
Can contours show drainage direction?
Generally yes, but drainage design needs field elevation checks.
Can MapLab Survey create contours?
Yes, for field interpretation and planning.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Creating an elevation profile · Terrain slope · Cut-and-fill calculation · MapLab Survey