As it was a test file I forgot to copy my normal statements across.

I tend to use a line like

 

declination xx degrees  # xx.x degrees (based on Grid Bearing of 18.5 deg to Llangattock Church)

 

to show the location of the calibrated bearing we have used. This line was set out over 40 years ago and most of the calibrations have been an average of 6 or so readings taken. I have now adapted a tripod so I can calibrate the distox on the same line. (most tripods have quite a bit of iron in them, so replace all with suitable non magnetic nuts and bolts, discarding any springs etc.)

I have been taking calibration in each orientation of the distox, rotating one way then the other to get 8 hopefully similar readings. Then average to produce

 

declination -1.8 degrees  # 20.31 degrees (based on Grid Bearing of 18.5 deg to Llangattock Church)

calibrate compass 0.9280    # meridian convergence for OSGB:SO location

 

with the actual calibration readings in with the cave survey data but commented out.

 

Maybe this is more how to use the distox and pda than Therion

 

John

 

Do you mean adding some option, that would specify, that given declination is not against true but grid north?

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