Garmin GPSMap 60CSx Topo \ Memory Map Co-ordinate issue

[Fraserp]

Anyone experienced with importing waypoints to Garmin GPS from topo maps and in particular Memory Map? I'm finding discrepancies on data transferred between applications. For example, the paths or summit points on Garmin Topo map on the GPS are correct when actually walking but i find the waypoints imported from MM are well out of position. Even a straight forward tfr of a summit trig point from MM to Garmin Topo differs. For example Snowdon summit co-ordinates are 48m difference between MM and Garmin Topo. The discrepancy appears comsistant throughout the different formats.

On the summit the Garmin Topo is accurate (20 ft ish) but waypoint imported from MM is 40+m out. On Ben Nevis, with that sort of discrepancy could have you in 5 fingers gully, or off the north face.

I'm not expecting inch perfect, but 48m?

Sorry if i'm being dim or missing something simple. Maybe i'm expecting too much? Any advice appreciated. Thanks.
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Fraserp
TomTom 1000
GPSmap 60CSx
SatMap

[philpugh]

Sounds like a map datum issue to me, especially if you are getting a consistent error. ~50metres is what you would get by mixing WGS84 and British Grid datums in the UK.

As far as I can recall waypoint info is exported to your GPS from MemoryMap with WGS84 datum. Check your GPS60 settings. You should have WGS84 datum set but can choose to display position in OSGB grid ref format - this should correct the problem. I would hazard a guess that you have your GPS60 set for OSGB datum and display. It caught me out the very first few times I used a computer to load waypoints into my first GPS unit. And it still catches me out occasionally!
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Phil

[briwy]

Phil

My GPS 60 wont allow this.
If you have it set to British Grid position format then it automatically reverts to British Grid map datum.

Is yours different?

Brian

[philpugh]

Sorry - you are correct - the GPS60 links the two. My older GPSII+ and my newer BGT-11 logger/GPS allow this.

To Fraserp

How do you have your MM set up? The problem still points to a datum mismatch. As far as I know MM does all transfers with WGS84 datum.

Try setting your GARMIN to WGS84 with Lat/Long - do the transfer - then switch to OSGB / OS Grid settings.
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Phil

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