I am working on a project for aerial
mapping.The project has only 11 panels but they are spread in a large area 20 miles square, so the scale factor will male a large difference. I am wanting to compute to ground coordinates. What survey point in the survey do I use as my base point, to apply the scale factor.Do I apply it from a control monument or the middle of the job, end of job ? or does it matter, I am not sure what point to use as the base point. Thanks in advance.
David J Sgroi, PLS

Dave,

Here is how I have done what you are looking to do.
Tie into known and published SPC system, process and adjust in SPC. Print out report of sites. Flip cordinate system to geodetic, adjust and again print out site positions. Find both the low and the high of your scale factors and your elevation factors, take the mean of each and multiply to get the "combination factor". (The "fake reverse)
Pick two points in the project, about the middle East and West and at the North and South ends. Use the program (downloadable) "Inerse" from the NGS website and using the printout of your geodetic positions prove to yourself that the geodetic inverse between your two selected points agrees with the Locus processors convergence at that site on the SPC grid print out. (Statue of Liberty)
Next, use any cogo package and inverse your SPC of the two sites. Take bearing and apply convergence you got from processor in SPC and it is the same as the geodetic. Your inverse in the cogo gives the grid distance, so divide grid distance by "combination factor" and obtain ground distance. In cogo package assume coordinates of say 100,000 100,000 for your base point. Do a "point in direction" with your geodetic bearing and ground distance to get N&E of second point.
Using the instructions of "converting grid to ground" from Ashtech website, method 2, create custom grid using your new N&E of the cogo package to estimate the parameters. (The flea flicker).
Hope this helps!