Simple survey figures have their limitations. If, as in intersection or resection, two angles are measured to
find the two coordinates, easting and northing, of an unknown point then only the minimum number of
observations have been taken and there is no check against error in either observations or the computations.
A fully observed traverse is a little better in that there are always three more observations than the strict
minimum. If the traverse has many stations then this redundancy of three is spread very thinly in terms of check against error. Read this topic