Coordinate distances are derived from cartesian coordinates (Northings / Eastings) as opposed to Geodetic distances which are derived from geodetic positions (Latitude / Longitude). When you are doing a typical boundary or topo survey, you are using coordinate distances.
A survey can have one Coordinate Reference System (CRS) that relates it's geodetic positions and cartesian coordinates. TPC computes coordinate distances by inversing between coordinates on the current CRS and applying the appropriate scale factor (converts between the coordinate plane and ellipsoid surface) and elevation factor (converts between the ellipsoid surface and the ground elevation). Since the CRS releates the coordinates of a point to its geodetic position, TPC can compute both a coordinate distance and a geodetic distance between any two points.
TPC refers to coordinate distances as Grid when no scaling is applied and Ground distance where one or more factors are applied. Ground distances are further qualified with the factors that are applied (as shown below).
Coordinate distances use the equation: grid distance = ground
distance x (scale factor) x (elevation factor)
where: scale factor converts between the coordinate plane and the
ellipsoid surface and elevation factor converts between the elliipsoid surface
and the ground elevation.
TPC will use the word Grid to refer to the coordinate plane.
Advanced Traverse View Format dialog - you can choose which coordinate distance to use for a particular traverse, allowing you to enter ground distance and compute grid coorindates or recall grid coordinates and display ground distance. See Traverse View Distance Factors.
Miscellaneous Drawing Settings dialog - you can choose which coordinate distance to use for line labels.
COGO dialogs - some COGO dialogs allow you to select which coordinate or geodetic distance to display.
Here are the definitions of the different coordinate distance types Traverse PC uses.
In each of these cases, TPC combines the factors listed below with any unit conversions. So if you are entering chains in a traverse, each of the definitions listed below would further multiply the chains you enter by 66.0 to convert to feet provided your survey coordinates are in feet.
This is the distance computed by inversing between grid coordinates. This is a planar computation of X/Y coordinate pairs using simple cartesian trigonometry.
The Traverse View status bar displays “inversed grid dist”
This options applies the project combined factor you enter in the CRS dialog. The combined factor includes both a scale factor and an elevation factor. It is appropriate when the area covered by the survey is small and there is not much elevation change within the survey.
grid distance = ground distance x (project combined factor)
The Traverese View status bar displays "Combined Factor = 0.9999865".
This works much like the combined factor in that it is a combination of scale factor and elevation factor. For this type however, the project elevation factor is computed internally based on the project elevation you enter in the Survey Factors dialog, but the scale factor is computed for each survey point based on its geodetic position.
grid distance = ground distance x (project elevation factor) x (mean course scale factor)
The mean course scale factor is the average of the scale factor computed for each end point of the course. The mean scale factor of a short course will be very nearly the scale factor of either end. For a long course, the mean may vary more significnatly from the scale factors at each end.
If the elevation change within the survey is not great, this can be a simple and acceptable way of relating grid and ground distances.
The Traverse View status bar displays "Project Elevation = 1,500".
The option computes a mean scale factor and mean elevation factor for each course. It disregards any combined factor or project elevation you may have entered for the CRS and uses the geodetic position and elevation of each end point of the course to compute the respective factors. This is most rigorous computation for ground distance.
grid distance = ground distance x (mean course elevation factor) x (mean course scale factor)
The Traverse View status bar displays “Mean Course Elevation”
You may choose to enter your own distance factor manually. If you have a special situation where the distances you are entering or reporting do not match the survey, you can enter a manual factor that will be used in place of any of the other methods listed here.
grid distance = ground distance x (manual factor)
The Traverse View status bar displays "Manual Factor = 1.0000000123"
Personal, Premium, Professional
Choosing a Coordinate Reference
System
CRS dialog
Scale Factors