I want to take measurements to create a topographic map of an acre of land for residential building design.
This requires height measurements to be taken over a grid on the order of every two meters. The resolution of each measurement (x, y, z) should be no worse than 10cm. All measurements need only be placed with respect to an arbitrary point of reference – i.e., absolute GPS location is not necessary.
I believe this is possible using a smartphone's camera and inertial sensors. For example, I could do it manually by going to each sample point and logging the angle and direction of the phone when its camera has centered a static reference target placed somewhere in the plot of land. But functionality similar to this has already been automated in software that uses the same data to, for example, stitch full-sphere panoramas and "VR" views.
Are there any apps that can automate the creation of a topographic map of this type? Solutions are welcome for iOS or Android. No price constraints.