The selection of sources for a geodetic segment is based on constructing several possible geodetic sequences and choosing the best. The first few selected sources for each tested segment are chosen randomly from among those that can contribute to the low elevation scans at at least one station. After those, the program chooses the source that best complements those chosen so far in terms of improving the quality measure without excessive slewing. Parameter GEOTRIES sets the number of trial segments to construct and test. The algorithm for making segments comes up with reasonable ones most of the time, so it is not generally necessary to test very many. The algorithm is also moderately slow which will encourage not testing too many. The default is 10 which seems reasonable.