I am converting a 2m DTM to contours, and would like to have the smallest interval possible. Is there a theoretical limit, or even a rule of thumb for defining contour intervals based on the resolution of the source data?

  • what are you going to use the contours for? what will you do with them once you have them? Nov 10, 2010 at 20:37

2 Answers 2


The minimum contour interval is the double vertical error (RMSE or standard deviation) of the height model. You can find that for ASTER GDEM in:

Lang, R. Harold, and Roy Welch. 1999. “Algorithm theoretical basis document for ASTER digital elevation models.”

It's defined by the "United States National Map Accuracy Standards (NMAS)"

For example: If your DHM have a resolution of 2x2m, and the vertical error is 4m, you can extract contours of a minimum of 8m.

Late, but I hope it helps you!

  • I would be careful in that this answer's example mentions the resolution of the data, but the true relationship it is trying to convey is between the accuracy and contour interval.
    – Rex
    Nov 5, 2019 at 21:04

I would say this depends on your knowledge of the data and how it was collected as well as how the DTM was generated from the raw data (regular grid vs interpolated from irregular points or other sources) I don't think there is a rule of thumb. Personally, I choose contour intervals based on the scale, type, content, purpose of the map, etc.

  • This is a good answer and gives useful rules of thumb. I have changed the accepted answer to @MAP as it gives a documented theoretical limit. May 22, 2012 at 17:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.