On 17/03/2018 21:44, George Booth wrote:
On 17/03/2018 21:36, N_Cook wrote:
On 17/03/2018 20:55, George Booth wrote:
On 17/03/2018 18:21, Nicholas Randall wrote:

This afternoon, I have searched for the height of Meir Heath on the
website elevation.net. It states that the height is 250 m. They have
improved their website and when I searched previously, it stated 250 m
last year and 251 m earlier this year.

Nicholas
Meir Heath, Stoke-On-Trent 250 m above sea level.
That's the first really useful web based altitude resource I've come
across. When I moved up here I ended up using the OS 1:25000 map (how
old fashioned) which came up with 175m wich is what
https://elevationmap.net does (don't forget the map bit otherwise you
end up at a property company in Colorado).
Thanks for the link


Archaeologists when setting out the primary datum reference for a new
dig, cough up 20GBP to OS, for the data to an optically surveyed local
nearby reference point. After that they don't mind using
dGPS/Total-Station around their site. They've come a-cropper too much
with even the dGPS nonsense, to not trust it.

Yes, the old ones are still the best. We discussed this some years ago
and I pointed out that whilst GPS was fine for position data (once the
Americans tweaked the info publicly available) it was not particualrly
useful for altitude


I forget the number of corrections routinely applied to GPS, something
like 30 ISTR. Gravity changes (molten Earth core/snow cover/sea level
variation etc)) , atmosphere temperature and humidity fair enough for
radio propogation variability, but a lot that you would not consider,
like relativity, oxygen/nitrogen ratio in the atmosphere and changes in
the ionosphere. All dGPS does is average out some of those variables,
but come back to the same spot a year later and the "measured" altitude
is something completely different.