Leap Frog is a measured-to-measured Iterative Alignment used to relocate the measuring device in the same file, or to reenter an existing file. Select 3 to 10 point-reducible features that you have previously measured from the list box. Select DONE. You are then prompted to re-measure each of the features you selected. If you make an error while digitizing a feature, press ESCAPE and you are prompted to re-measure that same feature. If 2D features are selected, the plane in which they are located must be digitized.
To see the actual equations, please follow the linked document here.
Tips for a move device can be found here.
Keywords: move device calculation leapfrog calculation