Spectra Precision Survey Pro CE v3.60 GPS User Manual - Manual (Page 65)

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Projection Utilities
Projection Calculator
You can use the Projection Calculator to calculate combined scale
factor for scaling conventional distance measurements to the
mapping plane. You can also use the Projection Calculator to
calculate meridian convergence for reducing geodetic azimuths (like a
sun shot) to grid bearings.
Scale Factor Calculator
1. Go to Projection Calculator from the Survey menu.
2. Choose a point on the mapping plane for scale computation in the
Select Point control. Tap
6ROYH 6FDOH!.
3. Enter a height to compute Ellipsoid Scale Factor . This calculation
uses the height of the point above the ellipsoid to correct for the
effect of the terrain above the reference surface.
4. Tap
6ROYH! to calculate the combined scale factor with the
selected values. The combined scale factor is displayed in the
Ground to Grid box. The inverse combined factor is displayed in
the Grid to Ground box.
5. Tap
$FFHSW when you are done. Both numbers are saved in the
Past Results list so you can use them in other calculations.