On 2018-08-28, at 07:44, Richard Lamprey <lamprey.richard@gmail.com> wrote:
> I would be truly grateful to anyone in UK with an aviation Garmin, especially
Garmin 96, 196, 295/6, 396 or 495/6 who can help me. Do you live by the sea?
Can you walk on your beach (when convenient!), turn on your GPS, let it settle,
and tell me what altitude/ elevation above / below mean sea level (MSL) that
your unit reads? It would be best if, beforehand, you can set the coordinates
to latitude/ longitude, datum to WGS84, turn off WAAS or EGNOS augmentation
Richard - I had hoped I might have a chance for a walk on the beach soon but it
hasnt turned up yet (and the nearest beach on the Bristol Channel has a huge
tidal range so timing might be an issue!). However, I have done some testing at
home in Gloucestershire. I dont know if it will be of any use to you but here
is my data anyway.
At about 63m AMSL (207) according to the OS 1:25000 map, my Garmin 296 shows an
altitude that wanders between 180 and 220 - I gave it a while and it doesnt seem
to settle any better, which surprises me (Ive not noticed that in the air).
The accuracy of position was shown as about 24. The datum is WGS84 and the
display
is lat/lon. Beside it, my Airbox Aware shows a very steady 164, and my
Dynon D2 shows about 185. My Garmin Dakota 20 hiking GPS uses WGS84 datum and
WGS84 spheroid and in the same spot it shows an altitude of 68m (223') with a
positional accuracy of 3m (10).
Hope this is of some sort of use. Ill try to get to sea level with both Garmin
units and repeat the test at some time.
in friendship
Rowland
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