AbstractFor the survey company which is completely automated, the production of topographic maps by non-photogrammetric methods means feeding raw field data consisting of stadia observations into a minicomputer linked to a plotter which prints the spotshots and draws the contours without further human intervention. However, for the survey office which has not yet reached this degree of sophistication and prepares maps with limited electronic aids for example reducing the stadia observations with a programmable calculator, the program presented here for interpolating contours between two spotshots with the aid of an HP25 should turn out to be an additional useful link in the production process.