Originally Posted by
Layer zero and three-quarters
Hello everyone. Obviously, you can see I'm new around here. Most of my work is in the Denver, CO area. I have been a C3D user for about three years now and have wondered about this question for a few months, but did not see any previous discussion here regarding this topic or at any other support sites:
Like many surveyors, one of my workflows involves creating a model from an existing subdivision or a metes & bounds parcel description for the purpose of creating search coordinates to export to my field equipment as a tool for finding, then surveying the actual position of corner monuments. My deliverables mostly involve boundaries and rarely topo or grading. I've not seen it to cause an issue, but does anyone have pros or cons either way I should be considering regarding the input elevation for COGO points being created for this purpose. More often than not my jobs are of limited geographic extent and are set as "No Datum, No Projection". Only when I'm working in mountainous areas, where the relief from one end of the job can be substantial do I go to the trouble of taking an aproximate elevation for points from Google Earth. Otherwise, when the terrain is fairly flat, I export my points with the elevation set as either a null value or 0.00. When I'm using a conventional total station, I can work in either 2D or 3D mode and there is no issue; however, when doing this with GPS and the Z value for all of my points is 0, my coordinate delta display as I near a given point might show something along the lines of "N: 0.17 ft, E: -0.05 ft, Z: -5127.78 ft". My thinking is that as long as I don't attempt to use the point for a vertical calibration (for those of you who work with Trimble gear and are familar with the meanings of horizontal and vertical calibration) there should be no problem, aside from that huge delta for the Z value stored in my data collector. Of course the new coordinate from the field location of the monument will have new values, including a correct Z relative to the elevation datum I've selected by that time. I also normally create an offset, such that search Pt. #152 becomes field Pt. #1152. So, should using the bogus value of 0 for a preliminary elevation cause me to lose any sleep?