Scale Factors

Posted by: @dave92983

↑

Is it ok to set your scale factor based on a derived point?

StarNet computes "Project Average" scale factors, in addition to those for the individual points. That average is not attached to any particular point. It would be the appropriate value for some point that, very probably, does not exist within the dataset. 

Under the adjustment settings that's true. Under other files settings you can you can set a ground scale coordinate file by 3 ways: a given factor, computed at a station or computed average.

If you're scaling from a close location, use a physical monument and keep good records. The scale factor wouldn't normally be the monument's, it should be a rough mean across the site. It doesn't really matter at the scale from point, that point will have the same grid and ground coordinates no matter what scale is applied. 

If you're scaling around 0, 0, a mean factor also makes more sense.