In article <[email hidden]>, Roger
<[email hidden]> writes
Quoted message said:The message <[email hidden]>
from Dominic Sexton <[email hidden]> contains these words:Quoted message said:As I read it the error was in the conversion of co-ordinates from one
datum to another rather than in relation to a map.In which case I am totally lost. I thought a GPS had to convert its
position under WGS 84 to the datum of choice and thus a 45m error in
conversion would automatically be a 45m displacement on the map.
It would indeed but as you pointed out there are also errors or
deliberate distortions in the map. Therefore it would not be
easy/possible to say how much of the 45m was due to a conversion error
and how much was due to the map error(s) if relation to the map was used
to determine the error.
I thought it had been said that all of the 45m was due to the GPS
receiver's internal conversion from WGS-84 to OSGB. That was the point I
was questioning because it is an order of magnitude higher than I would
expect from the conversion errors.
Lots of people using a GPS for OS grid refs would be very disappointed
if the errors were consistently that large. No doubt there would be lots
of posts here slagging them off as useless ;-)
--
Dominic Sexton