[Talk-GB] Tracing buildings under trees

[SK53]

It's worth pointing out that some of these buildings will be available in
OS OpenMap Local open data. The outline will be generalised (in a way
similar to OS StreetView) but will be pretty accurately located. If you
just want a point then there ought to be a UPRN node as well. Also worth
looking at EA Lidar data (not sure of detail of current coverage) and I
haven't really checked for buildings in treed areas, because I was more
disappointed that the signal from trees does not provide canopy height
(probably because captured when trees not in leaf). Mapping other things
which might be visible on imagery (e.g. lampposts, rubbish bins) may help
with triangulation. Lastly you could persuade someone with an RTK receiver
to collect points round the building (if it is accessible).

Jerry

PS. I'd love to see some more ideas on simple photogrammetry using naive
principles.

On Thu, 31 Dec 2020 at 16:22, Alan Mackie <aamackie at gmail.com> wrote:

> If you know it's there, but don't have the information to do it asn an
> outline, map it as a single node. If you think you have the information to
> do it as an approximate rectangle/relevant shape then do it as a way and
> leave a note.
>
> I'd really like some software for assisted photogrammetry in these sorts
> of situations, but haven't found any yet. In many cases I'd be happy to add
> points/corners manually if the automated feature detection failed (you
> don't need too many for an outline), but most of the projects seem entirely
> focused on automated detection. Maybe someone on this list is familiar with
> software that's more for assisted "photo-triangulation" rather than object
> reconstruction?
>
> On Wed, 30 Dec 2020 at 14:43, ndrw6 <ndrw6 at redhazel.co.uk> wrote:
>
>> Same as with poor quality imagery that was rather common until recently.
>> If you are certain there is a building in there - map it, just reduce the
>> level of details. A simple rectangle will do. If not - skip it. At some
>> point the imagery will improve (in your case photos taken in the winter
>> would help) and the building can be added/refined.
>>
>> Surveys are helpful but, as they are time consuming, I reserve them for
>> PoIs and addresses rather than using them for mapping building shape
>> details.
>>
>> -ndrw
>>
>>
>> On 30 December 2020 18:49:30 GMT, Mat Attlee <mattattlee at gmail.com>
>> wrote:
>>>
>>> What approaches do people have for tracing buildings under trees? Today
>>> I noticed a shelter in one of my local parks which hasn't been traced and I
>>> took some photos of it but when I got home and had a look on the Bing
>>> satellite images it's obscured by all the trees.
>>>
>>> Now that I think about it I could just create a GPS trace walking around
>>> the structure and then create its shape from that or use Vespucci and my
>>> phone's GPS to determine the coordinates for the building's corners?
>>>
>>>
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