I want to make a DEM with a vertical resolution of 1-2 feet. What are the different variables that come into play in obtaining this?
1. Generally speaking, from traditional film based aerial photography (9 inch format) you would expect accuracies of approximately 30-40 microns in the vertical direction. In other words, for 1:10,000 scale photography you would expect 30-40cm residuals for your bundle adjustment (1:5,000 -> 15-20cm; 1:20,000 -> 60-80cm; and so on). To obtain a DEM that is suitable for 1 or 2 foot contour intervals you would aim for a better ground accuracy (maybe better than half the desired vertical resolution -> 15 cm or 30 cm) so that it will accurately represent 1 or 2 foot deviations in the terrain. The flying height that this corresponds to for a standard aerial camera and different scales are: 1:10,000 -> 5,000 feet above ground level; 1:5,000 -> 2,500 feet AGL; 1:20,000 -> 10,000 feet; and so on. 2. As for angular separation of the two images, it is most efficient to collect vertical photography with a base to height ratio of 0.6 to optimize the geometry of the intersecting rays from which the
