Surveying Instruments - Practical Boundary Surveying - page 56

Fig. 5.4 Total station with data collector—the data collector is attached to the tripod and
connected to the total station with a communications cable. Note the top mounted EDM
5.3 Reflectorless Total Stations
Many total stations have Relectorless capability. A reflectorless total station
does not require a prism to reflect the light back to the EDM. The emitter in a
reflectorless EDM is much more powerful than a conventional EDM which relies
upon a prism to reflect light back to the total station. So, even when measuring to
a relatively dull surface such as a tree, some of the light will be reflected back to
the EDM. The range is dependent on the type of surface and color of the surface
which reflects the light. Because most surfaces are much less efficient at reflecting
light than a prism, the range of a reflectorless EDM will be considerably less than
when using a prism. Depending on the power of the EDM and the quality of the
reflective surface, ranges of roughly 500 feet are possible. In contrast, when meas-