Re: Garmin launches UK OS maps

Dave Fawthrop wrote:

>>> Out of interest, are the contour labels on a topo map switchable
>>> between feet and metres?
>>
>> Yes, on the GPS and in the software, but the contour lines remain
>> the same.
>
> Then which one is inaccurate? or perhaps both?

Well since the contours were surveyed in metres I presume that would be the
most accurate, but only as accurate as the survey was in the first place.

Conversion to feet is subject to rounding errors, and metres are a lower
resolution measurement than feet anyway. For example, the 2460ft contour
line shown on the Garmin Map viewer displays as 2461ft on my GPS. I don't
think such small errors make much difference anyway.

Regarding the free contours that I'm using, there are places where they are
probably much less accurate than the OS data. I've seen discrepancies of
over 20m in deep forested valleys - perhaps the tree heights affected the
data?

Paul


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