Contour Maps

 Contour Maps indicates elevation by showing lines of equal elevation. The elevation difference between adjacent contour lines is called the contour interval. The smaller the map scale larger should be the contour interval. The area of steep relief should also have a larger contour interval so that the lines are not close together.

To estimate the maximum flying height required to produce the map of the desired contour interval. Photogrammetrists use the C-Factor i.e the ratio of flying height and the contour interval. The c-factor is influenced by all parts of the mapping system including the camera, the quality of imagery,the stereo plotter, and the operator.

To produce a contour map an operator places a floating mark at the desired elevation in an absolutely oriented stereo model and guides it along the ground surface, tracing each contour line in turn. The raw contour lines produced muset be edited so that no contour lines cross and they are consistent with the linear features on the map. For, instance, contours should cross the road perpendicular to the direction of the road and the bend of the contour should align with the drainage line.