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The factors in this dialog determine how TPC displays distances and directions. You can choose from the grid, ground and geodetic options available for your edition of the program. See Survey Distance and Direction.
Default Distance and Direction Types
The Distance Type and Direction Type you select in this dialog become the default types for this survey. Until you choose an alternate type, TPC will use these default types for Traverses, Drawings and COGO.
So lets say you are doing a public lands survey. You would do the following:
•Enter a project elevation
•From the Distance Type pulldown, choose 'Geodetic Distance (project elevation x,xxx,xx)'
•From the Direction Type pulldown, choose 'True Bearing/Azimuth (mean course convergence)'
That's it. TPC now thinks like you do, in geodetic ground distance at the specified project elevation and true bearings or azimuths. Pretty simple.
Public Lands Survey System (PLSS)
In the pulldown lists for Distance and Direction, TPC adds 'PLSS" to the options prescribed in the Bureau of Land Management, Manual of Survey Instruction.
Mapping Angle
Enter a mapping angle correction you want to keep track for this project. In any Direction Type pulldown, like the one in this dialog, select the 'True Bearing/Azimuth (project mapping angle x°xx'x")'. The mapping angle you enter here will appear in this list and be available anywhere you can choose a direction type.
Compute from location
Turn this option on to use the Convergence angle of the project location as the mapping angle. TPC updates the mapping angle any time you turn this option on or modify the project location so that it computes a new convergence angle.
Combined Factor
Enter a combined factor for this project. You can now select 'Ground Distance (combined factor x.xxxxxxx)' from the any Distance Type pulldown.
The Combined Factor relates ground distances to grid distances using the following equation: Ground Distance x Combined Factor = Grid Distance.
Think of this as the combined factor for the project. It is a combination of the project's grid factor and elevation factor.
You can enter an equation in this field to compute the factor you want. For example, entering the equation 1/2 would produce the factor 0.5.
Compute from location
Turn this option on to compute the Combined factor from both the Z Factor (elevation of the project location) and Grid factor of the project's Location.
Location
Use this section to specify the location of your survey.
Point [>]
Enter an existing point label or select [>] then left-click the point from the current drawing.
Enter an existing point label
Enter an existing point label to use the position of that point as the survey's project location. TPC copies the position of the point and uses it as the new project location.
Once you enter a coordinate or geodetic position, TPC will remove the point label (it will be blank) indicating that the position is now different than the existing point.
Entering coordinates vs geodetic positions
When you enter coordinates, TPC holds those coordinates as the project location. TPC is free to transform that coordinate position into a geodetic position as needed and will use whatever CRS is current at the time to do the transformation.
When you enter a geodetic position, TPC holds that geodetic position as the project location. TPC is free to transform that geodetic position into grid coordinates as needed and will use whatever CRS is current at the time to do the transformation.
Elevation
Enter a project elevation. You can now select the 'Ground Distance (project elevation x,xxx.xx)' from any Distance Type pulldown.
Beginning in TPC Desktop 2011, if you specify a project elevation and set the default distance type to geodetic or ground distance at project elevation, the default elevation for any new survey points you create will be the project elevation.
If you have recalled an existing point to establish the project location, you can still enter an alternate elevation.
Preferences
Choose the Distance and Direction types you want to use as the defaults for this survey.
OK
Select OK to accept the changes you have made and return to the previous view.
Cancel
Select Cancel to return to the previous view without making any changes.
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