On 20/09/2012 3:49 PM, Brett Russell signalled:
Been reading up on GPS accuracy and playing with averaging waypoints on the Garmin 62S and have realised that WAAS does not work outside the USA and
for some units better to have it switched off. If I wrong in my understanding please let me know. I can be rather a precision freak but be nice to
get thing right.
Discovering the accuracy of a unit is easy. Find a convenient spot near your house and with your GPS record its position. Come back next day (or at
least a few hours later) and do it again. Repeat daily until you are sick of it and you will then have a good idea of how accurate any particular
observation is likely to be. No technical expertise required.
The question of absolute accuracy is complex. Survey marks mostly were placed before the current modelling of the earth was developed. While these
may now have GDA coordinates (typically about 100 mm different from WGS in Australia) there are complexities that arise (eg from continental drift and
the instability of the earth's axis of rotation) which are significant variables. There are many assumptions in the modelling.
WAAS also works in Europe and Japan. There is no likelihood of it being implemented in Australia as our population density is too low. Switch it
off. If it is left switched on there is some risk that spurious signals from other systems may degrade the accuracy of your device.
Regards, Peter
--
There are no problems more difficult to overcome than those which are merely
imagined.
We never approach the truth in what we say unless that includes the expectation
of being wrong
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