Self scanned map calibration

[Oldie]

Before going on holiday to the Greek island Samos I scanned a walk map, calibrated it by matching three locations with those on the Garmin MapSource World map. Next I set up four routes and exported them to my Garmin eTrex Legend.

I realise that this was all very approximate, but my intention was to record the tracks that I walked and then recalibrate my map when I got back home. To my great surprise the start point of my first walk was spot on :D. However, it was the only point that was correct so I could not use my pre-planned routes to guide me. This was a pity, especially when lost Really I was not lost as I knew my position to 4 decimal places, but that is of no help when trying to find the right track to follow. At one time I knew that, as the crow flies, I was just 1 mile from Vourliotes but I could not see how to get there. Luckily some German walkers coming from Vourliotes put me on the right track

Back home I have been adding my tracks to three different scanned maps of the area that I walked and I am disappointed with the match that I have achieved.

Does anyone know how MMN 3.1.6 calculates the transformation when more than 3 calibration points are used. My GPS points are WGS84, the paper maps are an unknown quantity, although one of them (a road map) does have a grid with lat/long values. The road map gives me the best match, but I have to use the MMN WGS84 datum shift values, both N and E, to achieve a good match.

We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
Have you considered making a donation towards website running costs?.
Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!