During my visit to Indianapolis, several people asked me about sideshots and RPA. While sideshots can be used in the computation of RPA, the computed coordinate position of these points might be close to their true value or very far off the mark (due to a blunder). The coordinate difference errors (between each station pair) could be much larger than the uncertainty computed during a minimally-constrained network adjustment. With no independent check on sideshots, a small relative error ellipse (and passable ALTA test) may give the surveyor an overly-optimistic assessment of their work.
- Scott Wallace, Chief Technology Officer (January 2009)