Absolute positions in XYZ require full metadata. Delta XYZ information only requires basic information. These are point to point relationships applied to whatever realization you want. Positions may change but relationships are (for all practical purposes in a small area) constant...
> Indeed. But software could be written with the philosophy that the XYZ coordinates are the values to be stored, and any sort of projection you want could be derived from that at any time. You would need to give it the ellipsoid, geoid, datum, and epoch, and then it could do the translation.
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> Every terrestrial measurement or local detail map could be translated using what would essentially be a LDP centered on that measurement or map. Instead of the total station measuring slope distance and vertical angle, converting to horizontal and vertical offsets, and considering those to be the measurement data, it would store the mark-to-mark (slope) distance and use the local projection to get a 3-D vector for direction.
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I agree. I think this will be the case for sophisticated users in the very, very near future. At the core, the coordinate of a surveyor's entire body of work will be stored in database(s) composed of XYZ positions at some Epoch and Realization that will be visualized in a projection. The XYZ positions will be largely transparent to the user, but will all be related to a common coordinate system.
The new Javad LS software works this way. Of course, this is GNSS only, but terrestrial measurements could be incorporated in such a model.
very true
Jim:
Aren't you required to utilize the Navajo Nation Coordinate System for this work?
James
I need to build a little diagram to really put the answer you need into perspective (it can be kind of confusing without a "picture"). If you haven't seen (and read) Shawn's recent articles in American Surveyor, you should!
I'm really buried under work right now (14-18 hour days EVERY day), so it might be awhile...sorry.
Loyal