How does the weighting of GCPs and GPS affect the block adjustment?
The weighting of GCPs and GPS affects the influence of those values when they are used in the block adjustment. They are weighted inversely proportionately to the error value, so GCPs or photo centres with high error will affect the solution less than points with lower error. How you decide what values to use generally depends on what you want to accomplish. Usually, the first step is to put what you believe to be reasonable values in for both the GPS data and the GCPs. For the GPS, you can get an estimate from the manufacturer. For the GCPs, you have to find out where they came from, and estimate their accuracy. After you have your initial estimates, you can always change the values to force one or the other (GPS or GCPs) to have the dominant effect on the solution by setting those errors closer to zero.
