Page 1 of 1

Calibrating Memory Map screenshots

Posted: Tue Jun 06, 2006 10:01 pm
by goon
Can someone give me some advice calibrating screen shots from Memory Map OSGB for Pathaway 4?

As I use a Palm, and Memory Map only exports to PPC, I have a method where I screenshot the area I want, and calibrate in map manager, before exporting to the Palm. I use the special OSGB settings in the manual.
I'm noticing a consistent inaccuracy in my calibrated maps when using them 'live', which I can usually sort out by nudging the map once a track has started to form. Not really a problem

However, when taking some coordinates from Cetus GPS for a geocache I was placing, I noticed the DD.MM.mmm were slightly different from the ones Pathaway was reporting, and consistently so for other locations during my trip.

When looking later, I noticed that the coords reported by Memory Map on the PC were in WSG84 format. The question therefore, is which settings do I need in map manager to calibrate Ordnance Survey GB maps from Memory Map for use in Pathaway? The special OSGB ones in the manual, or WSG84 settings?

Sorry for long winded posst, and thanks for any help!

Gareth Evans

Posted: Wed Jun 07, 2006 2:14 am
by TheSnake
Hi Gareth,

In MapManager set..

Projection: Transverse Mercator
Map Datum: Ord Srvy Grt Britn
Coordinate Grid: OSGB

Then in Pathaway preferences for co-ordinates, uncheck 'use current map datum' and set the datum to WGS84. Save this and exit.

This will give you really accurate positioning on OS maps if your initial calibration points were good - I would use 4 widely spaced calibration points.

Good Luck,

Posted: Wed Jun 07, 2006 4:53 pm
by goon
Hi TheSnake, and thanks for replying. I think I am not following your instructions correctly. I have attached a screenshot of my map manager to show my settings.
I am putting in the grid letters SJ and the OSGB coords from Memory Map eg 36000 88000. However, as you can see, when I return to point 1 from point 2 the coords have changed. I'm not sure where I'm going wrong.

If you are calibrating maps from Memory Map for Pathaway I would really appreciate a walkthrough of the process.

Thanks for any help,
Gareth Evans

Posted: Wed Jun 07, 2006 7:26 pm
by TheSnake
Hi Gareth,

That looks & sounds correct, except that your screen shot has latitude/longitude instead of Northing/Easting.

I'm running MapManager 4.00.02, and your screen looks slightly different to mine, so I'd check what version you are running first.

Posted: Wed Jun 07, 2006 7:54 pm
by goon
Hmmm, it's 4.04 here, which is now crashing to desktop when I try to save the map.
This is the only thing I find disappointing about Pathaway, the rather convoluted and mysterious calibration process.

Thanks for your help so far!

Posted: Wed Jun 07, 2006 8:27 pm
by goon
I managed to get a map off the PC without it crashing. Now opening the map in Pathaway causes an immediate lock with a divide by zero error.
Going back in to Map Manager, and looking at the map I calibrated, shows that all the Northings and Eastings I entered are now exactly the same for each point, and bear no resemblance to the ones I entered. eg, 36000 88000 is now 08576 -00016. Any idea what this means?

This is beginning to get very frustrating!

Posted: Thu Jun 08, 2006 1:46 am
by TheSnake
Gareth, if you clear some space in your mailbox I can send you a calibrated map to load up, so you can view its values and settings.

Posted: Thu Jun 08, 2006 2:09 am
by goon
Thanks TheSnake, have you tried to send the file? I'm nowhere near my quota on the e-mail address in my profile, and there is nothing in my message service here.

Thanks for your help.
Gareth Evans

Posted: Thu Jun 08, 2006 4:47 am
by TheSnake
Try this one...

Posted: Fri Jun 09, 2006 5:12 pm
by goon
Hi mate,
I got your email. The calibration settings look the same as I was using before, but I think the original problem (Pathaway coordinates not matching the actual GPS ones read by another program) was coming from the fact that I had 'use current map datum' ticked in Pathaway itself. I'll give it a whirl over the weekend.

Thanks for all your help,