Hello

I have conducted a site calibration on the site I work on, we are using a local base and streaming corrections over radio RTK to the rovers.

Our site sites on the UKs national grid (OSGB36 (15)) therefore a scale factor must be used to scale total station observations from ground to grid and vice versa. In the part of the country I am in I know the SF should be approx 0.9996xxxx.

When you examine the parameters in Trimble access for OSGB36 15 this is indeed the case, the SF displayed is "0.9996012717" this works perfectly with the total station and our set ups are very tight (>2mm) across the site (1.5km).

The issue is when the site calibration is used to set the projection parameters Access calculates the wrong scale factor and applies a 1.000092460 to total station observations which is incorrect.

I have tried re-calculating the calibration in TBC and exporting as a coordinate system but the problem persists, our GNSS measurements are perfect using this calibration however I would like to be able to use the total station in the same job.

Also where in access is the option to compute the SF every time the total station is set up as opposed to using a fixed number? this generally gives better results but I see no option for this.

Any ideas what is wrong here? I would really appreciate your help.

Cheers

Sam

Hi,

I have some questions:

Did you use Total Station or GNSS to measure control points?

Did you use this coordinate system ( UKs national grid (OSGB36 (15)) to measure control points? or was an arbitrary location?

Something similar happens here. If you measure control points using UTM 17 North WGS84 and you calibrate automatically (not using coordinate system); the calibration file will have a new coordinate system with scale factor 1. So to get the scale factor of your coordinate system, you need to calibrate using the same coordinate system where the control points were measured.

Can you attach the calibration file with points .cal?

Regards

Miguel Espinoza