Of course, keeping good notes is also important so that you can return these pseudo SPC's to real SPC's as needed. If this is the approach used it's often a good idea to subtract the millions value from the coordinates so they don't have the appearance of real State Plane Coordinates.
The coordinates no longer have any real meaning, but the distances and area will approach real surface values instead of values at some imaginary surface. Method 2 is the least technically correct, and frankly I abhor it.
So plat distances will be along some imaginary grid, acreages will be at some imaginary grid, directions will have a possibly high mapping angle, reducing their correlation to North. The down side to Method 1 is that your coordinates will be State Plane, which means the results of your survey will be State Plane (unless you apply some scale factor to bring the results back to something resembling the surface). Method 1 is technically highly correct, particularly if scale factors are determined at each station. This allow the GPS positions to closely match total station distances directly with no application of a scale factor.Įach technique has some merit. By creating a projection that is suited to the project's elevation, combined scale factors can be mitigated to being negligible. The reason State Plane or UTM produces such high scale factors in some locations is that the imaginary projection surface is so far from the actual working elevation of the project. If the elevation differences aren't severe, the CSF should be fairly homogeneous. Distances should match GPS position inverses as closely as the single combined factor will allow. Perform the total station survey as normal. In this you would use GPS to determine positions of your control (RTK or static) and scale the coordinates using a project combined scale factor applied from some origin (either a point in the project which results in smaller differences from the true grid values or from the origin which results in larger differences with but is a simpler coordinate to recall). End result is a coordinate file that is truly State Plane Grid.
Perform the total station survey (raw data will store the actual measurements while coordinates will be based on the scaled distances). Input a project wide combined scale factor in the data collector to apply to all collected distances (or if the collector is sophisticated enough, use the calculate combined factor at each station setting to determine the precise scale factor for each instrument set-up). Use true State Plane Coordinate values (no scaling). Use GPS to determine positions of control (RTK or static) for total station survey.
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