Leica Geosystems TPS1100 Professional Series - Applikation - Feldhandbuch (Teil 1) - Manual (Page 76)

76 Hidden Point
The program allows measurements to a point that is not directly
visible using a special hidden-point rod.
The data for the hidden point are calculated from measurements to
the reflectors mounted on the rod with a known spacing and a
known rod length. The rod may be held at any angle as long as it is
stationary for all measurements.
“Measurements” are calculated as if the hidden point was observed
directly. These “calculated measurements” can also be recorded.
Typical uses are:
Measurement of inverts, building corner details of measurement of
points behind overhangs.
Introduction