Hidden Point TPS1200+/TS30/TM30 83
7 Hidden Point
7.1 Overview
Description Hidden points cannot be measured directly by TPS. This is because they are not
directly visible.
• A hidden point can be calculated from measurements to prisms mounted on a
hidden point rod with a known spacing and a known length of the hidden point
rod. The hidden point rod may be held at any angle, as long as it is stationary for
all measurements.
• Measurements for the hidden point are calculated as if the hidden point was
observed directly. These calculated measurements can also be recorded.
• The hidden point rod can have either two or three reflectors. Refer to "7.2 Config-
uring Hidden Point" for information on configuring the hidden point rod.
• If three reflectors are used the average will be calculated.
Hidden point rod The reflectors on the hidden point rod are also called auxiliary points after they have
been measured.
Hidden point tasks The Hidden Point application program can be used for the following tasks:
• The hidden point program may be used to obtain accurate three dimensional
coordinates for a point that is currently blocked from direct measurement by an
obstruction between the point and the instrument.
• Determination of flow line locations and elevations in manholes, without meas-
uring from the rim of the manhole to the flow line and estimating corrections for
nonverticality of the measuring tape and eccentricity from the measurement on
the rim to the horizontal location of the flow line;
• Determination of recesses in building corners for detailed surveys, without esti-
mating right angle offsets, with or without taping of the dimensions;
• Measurements behind overhangs, buttresses and columns for quantity determi-
nations in underground construction or mining, without estimating right angle
offsets, with or without taping of the dimensions;
• Measurements of industrial process piping or other equipment in close quarters;
• Detailed architectural surveys for remodeling or cultural preservation or restora-
tion work
• Any place where accurate measurements would require many more instrument
setups in order to achieve line of sight from the instrument to the points being
measured.
1 Reflector 1
2 Reflector 2
3 Reflector 3
d1 Rod length
d2 Distance from reflector 1 to reflector 2
d3 Distance from reflector 1 to reflector 3
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