Spectra Precision FAST Survey Reference Manual - Manual (Page 219)

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 Slope Distance to Horizontal Distance:
This option allows you to convert slope distances with zenith angles to
horizontal distances and vertical differences, and vice versa. See figure.
 Lat/Lon-SP:
This option allows you to convert from Latitude/Longitude to grid system coordinates and vice versa.
If you are configured for U.S. State Plane Coordinates, the routine conveniently displays your zone, and you can
even change zones for quick calculations without altering your GPS zone settings in Job Settings. Otherwise, the
calculation is based on your Job Settings GPS Zone. To solve for northing and easting, fill in the latitude and
longitude and press Solve N/E. To solve for latitude and longitude, fill in the northing and easting and press Solve
Lat/Long. You can set the state plane zone at the bottom of this dialog.