John Aldridge wrote:
I have a question regarding the OS Opendata. How accurately aligned is
it? I've noticed that in some places the bing orphophotos match up
almost perfectly to the buildings below, and it other areas there can be
some difference (sometimes up to a meter of).
I don't know how accurate OS Opendata is, but I do know that Bing is sometimes
several metres off (and sometimes differently off depending on how far you are
zoomed in).
I've had carefully surveyed data buggered up a few times by people 'correcting'
it to match the Bing photography!
It's often interesting when imagery is updated. Zooming in and seeing old and
new versions at different zoom levels. Often these simply don't line up well
with one another. I've even resorted now to popping out and taking GPS readings
in the hope of establishing a better reference, which with an external aerial
should be accurate to 1mt. The result is that with the large vertical variations
around here one can see the effect of a satellite not being directly over head
quite clearly and different passes give different offsets to landmarks. One can
see the different side walls much of the time.
I don't find the OS Opendata any more accurate. If anything it tends to be a
little 'artistic' ignoring a lot of fine detail so I have no problem moving
objects where originally sourced from Opendata. That is once the new data is
proven to be more accurate. Altitude *IS* an important element of determining
accuracy and is something we need to take more seriously ... the flat earth
society has been proven wrong long ago :)
--
Lester Caine - G8HFL
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