The result is northing and easting coordinates on the local grid. Local geodetic coordinates are transformed into local grid coordinates using the map projection. When WGS‑84 coordinates are transformed onto the local ellipsoid using a datum transformation, local geodetic coordinates result.
#TRIMBLE BUSINESS CENTER SCALE TO GROUND SOFTWARE#
Rather than project the Latitude and Longitude onto the State Plane Projection, we create a projection in the software that have less distortion (all projects include distortion). The Low Distortion Projection starts at the beginning of this post. Careful attention to metadata should be taken, and it is recommended to subtract off a significant value (such as the millions) from the coordinates to reduce the possibility of future confusion. It has the same limitations as option 2, but also adds the issue of the coordinates being similar in appearance to true State Plane, but no longer actually being State Plane. This does the same thing as option 2, but does the multiplication once, instead of with each inverse. Scale your true State Plane Grid coordinates by an average, project wide, Combined Factor. The problem with this is that in areas of substantial relief, your measured distances will vary from the scaled inverse - not as much as from the true Grid inverse, but there is distortion that can be observed. Keep your coordinates in true State Plane Grid and apply an average, project wide, Combined Factor to each inverse. The problem with this will be that in areas of substantial relief, the factors will scale to different elevations and your bearings and distances won't close (the chain will be longer for higher elevations and shorter on lower elevations). Keep your coordinates in true State Plane Grid and apply the proper, unique Combined Factor to each inverse. Modified systems should ONLY USE ONE CF.įor State Plane reduction to "Ground" Distances, there are three practical options:
NOTE this is for inverse distances and not to be applied to coordinates to develop a modified or scaled Grid coordinate system. Then an inverse is solved by averaging the unique Combined Factor for each endpoint and multiplying the reciprocal of the average to the Grid inverse distance. The most technically correct method requires determining the Grid Factor and Elevation factor (and subsequently the Combined Factor) for each point. These can be multiplied together to form the Combined Factor. Generally for small projects with relatively little elevation change a single Grid Factor and Elevation Factor can be used project wide. The distance between the projection surface (the cone or cylinder) and the ellipsoid changes as the distance from the Central Meridian (for Transverse Mercator) or the Standard Parallel changes. Note that the elevation factor is determined from the ellipsoid height, NOT the orthometric (sea level) height. The distance between the ellipsoid and projection surface produces the Grid factor while the distance between the ellipsoid and the surface produces the Elevation factor. To answer your question, there are two factors that distort any projection distance: the distance between the ellipsoid and the projection surface, and the distance from the ellipsoid to the surface. As a result, most of us start of with GPS using State Plane and arrive at the conclusion that this is what GPS operates in. This is probably due to State Plane being the most functional, largely accepted, largely supported and documented projections available to US surveyors. This is a common misconception among surveyors, and one I held in my early understanding of GPS. This is then projected onto an ellipsoid to produce latitude and longitude, which is then projected onto a conic surface (such as a cylinder or a cone for State Plane) by your data collector. GPS works in ECEF (Earth Centered Earth Fixed).