STAR*NET V6 - Circe

Chapter 5 Preparing Input Data
Height of Instrument and Height of Target
When entering 3D data, STAR*NET allows you to input height of instrument (HI) and
the height of target (HT) information for data lines that contain zenith angles, slope
distances and elevation differences. The HI and HT information is entered as a single
entry of two values separated by a slash “/” character. For example, if your HI/HT values
are 5.65 and 5.25 respectively, your entry would be 5.65/5.25.
1. You can input an HI/HT entry for zenith angles. If the instrument and target were not
at the same height when the zenith was read, this entry allows STAR*NET to
internally correct the angle during adjustment processing.
2. Likewise, you can input an HI/HT entry for slope distances so STAR*NET can
internally correct the length of the line for the HI and HT difference.
3. The HI/HT can also be included with elevation difference readings when the
readings have not already been corrected for the HI and HT difference.
Whenever the HI/HT entry is used, it is always the last element on a data line, except for
any possible descriptor. It goes after the standard error entry, if there is one.
The examples below show a 3D “measure” line, each with HI/HT entries. The second
example includes three standard errors following the three observations, and then
directly followed by the HI/HT entry.
M 1-2-3 123-44-55 1555.666 91-22-33 5.1/5.3
M 1-2-4 142-33-24 1244.231 89-54-33 3 .05 6 5.1/5.6
Important! Older versions of STAR*NET allowed entering a single HI-HT difference
rather that entering both values. For example, using HI and HT values of 5.1 and 5.3, you
could enter a single value of -0.20 using the old method. If the HI was greater than the
HT, the value would be positive. If the HI was less than the HT, the value would be
negative. Using this method, the first line above would look like this:
M 1-2-3 123-44-55 1555.666 91-22-33 -0.20
To support these old data files, this method is still supported, but it is recommended that
it not be used for new data entry. Entering both values rather than a single HI minus HT
difference is preferable because both values are carried through all calculations for
curved earth geometry in local jobs, and combined scale in grid jobs, to produce results
that are more correct. Just as important, entering both values accurately documents the
actual instrument/target heights measured in the field!
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