This command allows you to set configuration options for data collection. These options remain set from job to job. Some options may only apply to GPS or to Total Station use. If an option is not applicable, it is grayed out. This figure shows the options available when the Units tab is selected.

• Distance: Select the units that you want to use. Choices include US Feet, International Feet, and Metric. If US Feet or International Feet is selected, the user has the option to display distances as decimal feet (Dec Ft) or Feet and Inches (Inches). This is a display property only and will not change the format of the data recorded to the raw file.
• Scale Factor:  For most applications, the Scale Factor should be set to 1.0.  The scale factor represents the “combined” grid/elevation factor that reduces ground distances to grid.  Therefore, for total stations, the scale factor acts as a multiplier.  All distance measurements, taken by a total station will be multiplied by the scale factor. For GPS, the scale factor acts as a divisor. All GPS coordinates will also be divided by the scale factor.  In this way, the same “ground to grid” number can be used to convert total station shots to the grid, or alternately to convert GPS shots to the ground.

To match the coordinates of any standard transformation (e.g. UTM, NAD83), the scale factor should be set to 1.0.  When configured to total stations, the Calculate option will calculate the combined grid/elevation factor from any entered coordinate—based on your current state plane zone setting.  This can allow you to go “ground to grid,” to typically reduce the distance measured by total station to the sea level grid distance of GPS.  If set to a GPS configuration, Calculate becomes Read GPS.  The Read GPS option is ghosted if a multi-point localization is active.  In that case, the scale factor is fixed by the localization itself, and is the inverse of the value appearing in localization, because within Units, we display the “ground to grid” number, whereas in localization, we display the “grid to ground” multiplier.  But for base or 1-point rover localizations, Read GPS applies.  After converting the LAT/LONG from the GPS to the state plane coordinates and computing the grid and elevation factors, the Scale Factor is applied as the final adjustment to the coordinates. This adjustment is used on the X,Y and not the Z. In GPS, the Scale Factor is applied by dividing the distance between the coordinate and a base point by the Scale Factor. The coordinate is then set by starting from the base point and moving in the direction to the coordinate for the adjusted distance.

The base point is the first point appearing in the GPS Localization option. If there are no points specified in Localization, then 0,0 is used as base point. The Scale Factor can be entered directly or calculated using the grid factor and elevation for the current position. When using the current position, the program will read the LAT/LONG from the GPS receiver. The scale factor is then calculated as: (State Plane Grid Factor - (Elevation/Earth Radius)).  A scale factor can be used to make grid-to-ground conversions between identical points, to adjust the lesser sea level distances of GPS to the ground (greater) distances measured by total stations whenever you are above sea level.  The grid to ground scale factor is lower at higher elevations because it acts as a divisor (the scale factor is always defined as “ground to grid”).  In summary, when configured to GPS, the scale factor (typically <1) can be used to go “grid to ground” through division and when configured to total stations, the scale factor (typically <1) can be used to go “ground to grid” through multiplication.  It can also be used for any other scaling purpose desired, but be advised that any scale factor used for GPS is used as a divisor.  Because there are two potential uses of the scale factor (to adjust GPS measurements and to adjust total station measurements), two distinct scale factors are stored and recalled for any job, one for when you are configured to a GPS instrument and one for when you are configured to total stations.

Choosing Calculate will give you this dialog.

• Sea Level Correction: This is either Off or On.  It applies only to total station work.  If turned On, the distances that are measured will be reduced the higher the elevation of the survey.  This is, in effect, a ground to grid conversion.  When using a total station and surveying between state plane coordinates (coordinates based on a sea level grid), distances at elevation must be reduced.  This will occur automatically when sea level correction is turned on.  Distance effects are negligible under 1000 feet (300 meters) but do become geometrically larger over greater distances.
• C & R (Curvature and Refraction): This option applies only to total station configurations and will be unavailable when your instrument is configured to any GPS option. When selected, options are On or Off.  This factor causes an adjustment in distance measurement.  Effects are negligible except over long distances.  It is recommended that this factor be set On, except in those very rare cases where the instrument factors in curvature and refraction.
• Angle Unit: This offers the option of degrees (360 circle, 60 minutes to a degree and 60 seconds to a minute) or gons, often referred to as grads (the 400 circle and fully decimal).  An angle of 397.9809 gons is equivalent to 358 degrees, 10 minutes and 58 seconds. (Note: you can verify this in Cogo, Calculator, Conversion tab).  The Angle Unit configuration impacts commands such as Inverse, Traverse, Sideshot, Input-Edit Centerline and other commands where a direction is displayed or entered.
• Station:  This option impacts the display of centerline stationing, sometimes referred to as “chainage”.  In the U.S., for example, roads designed in feet are “stationed” by every 100 feet, so that a road at linear position 14280.5 is given a station of 142+80.50.  Metric roads in the U.S. are often stationed by kilometers, where the same road position has a station of 14+280.500.  You can configure the placement of the “+” as desired, independent of your configuration for metric vs feet units.  You can also configure for a purely decimal display of stationing/chainage, as in 14280.500.   This display form shows up in such commands as Input-Edit Centerline, within the Start Station dialog box.  However, you should enter stationing in purely numeric form, without the “+” convention.  Only the display is impacted by this option.
• Zero Azimuth: Allows you to specify the direction for zero azimuth, North or South.
• Vertical Obs: Allows you to set the default prompting to Zenith (0 degrees up, 90 degrees level), Vertical Angle (90 degrees up, 0 degrees level) or Elevation Difference (up is positive in absolute units, down is negative). ).  Normally combine Elevation Difference with Horizontal Distance.  If combined with Slope Distance, the non-zero Elevation Difference will be used to compute the equivalent zenith angle and will reduce the Slope Distance to a lesser Horizontal Distance.  (Applies to entries in Manual Total Station mode).
• Angle: Options are Bearing or Azimuth.  This applies to numerous commands, such as prompting and displays in Sideshot Traverse (the backsight as azimuth or bearing), Intersections and Inverse.
• Distance Obs: Options are Slope or Horizontal.  This applies to the values displayed from total station readings.
• Slope: Whenever slopes are reported or prompted, the user has the option to specify the default in Percent, Degrees or Ratio.  Some commands such as 3D Inverse will, however, automatically report both slope and ratio and are unaffected.