[Talk-GB] bing image alignment

OpenStreetmap HADW osmhadw at gmail.com
Sat Sep 14 13:24:31 UTC 2013


On 13 September 2013 19:59, ael <law_ence.dev at ntlworld.com> wrote:

> No one has mentioned the OS gps (passive) stations: for example
> http://www.openstreetmap.org/browse/node/472420260
> http://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/surveying.html
>
> Can we not use them at least for some reference points?
>

Interesting.  Unfortunately it looks as though OS Net slipped past
their commercial people as they use the term "freely available" on
their web site without giving a precise legal definition of what that
means.  Given the intended use (all high accuracy surveys in the UK)
there seems to be an implication that they aren't claiming a database
copyright, but OSM will probably need a clearer legal statement.
OSTN02 seems to have the same licensing uncertainty.

I would note that even if a relatively restrictive licence were to
apply, OS allow checking of accuracy, as long as you don't use the
measured error to correct the inaccurate data.

Depending on exactly which ground feature represents the station, BIng
datum), Bing and the consumer grade GPS survey differ by between 5.2
and 6.2m.   Bing and StreetView agree quite well at that point, but
diverge towards the West.  The BIng error in the typical range, at
this point.

Are the ETRS89 coordinates given on the monument itself, as they would
be individual statements of fact, much like an individual address with
postcode?  (OS Net allows for movement, so the highest accuracy values
will not be fixed.)

Without survey quality GNSS receivers, these points are probably
mainly of use for calibrating imagery.

It's a pity they aren't all clearly visible on the aerial view, my
local one, which appears to be within centimetres of Bing, is only
identifiable because OS have measured the distance from the local
trees.  When the rain stops, I'll have a look at what is on the
ground, and try for a long average GPS reading.  I'll also try and get
on the ground measurements from the trees in case the station
coordinates are considered fair game, but the sketch map details
aren't  (looks like a surveyor's tape is on the shopping list - I
guess class III, at about 0.05% is good enough, compared with GPS).

I note that a lot of them are on private land and require permission
from the landowner to gain physical access.

PS.  The OSTN02 conversion tool, which presumably contains the table,
has a BSD Licence, according to
<http://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/grid-inquest.html>.
 If that is correct, I can see no reason why the os.openstreetmap
tiles should not be rectified based on OSTN02.  The data also seems to
be available in lat/long to lat/long forrmat, also with a BSD licence.



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