[Osmf-talk] Mapping trees as buildings (was: Re: Alternative Strategic Plan)

[john whelan]

Unfortunately that raises all sorts of questions.

First how do you know something has been validated.  Second what quality
standards do you suggest?  Lines up with Bing or other imagery?

Then you get to the quality of validation.  I've seen project managers in
HOT tag something as invalid when it wasn't.

HOT has done a lot of work on validation and even they struggle with the
subject.

I think the best approach is to say that the majority of mapping is
accurate and if anyone notices any problems they can correct it.

I think in general the first pass will probably be armchair mappers mapping
major highways, then HOT mapping settlements, followed locals taking
ownership and that's when you'll often see the quality improve.

There are bottom feeders such as myself that look for obvious errors, such
as a two km motorway connecting two small settlements, or a building mapped
three times and correct them but I don't mark anything in a positive way to
say I have formally validated it.

Cheerio John


On Mon, May 15, 2023, 17:45 Damilola Olufemi <olufemidamilola263 at gmail.com>
wrote:

> Hello,
>
> I had a similar experience with a Remote Sensing organization here in
> Nigeria. I was overwhelmed with questions that I was not prepared enough to
> give answers to about data quality on OpenStreetMap. My suggestion would be
> that imageries on OpenStreetMap get reviewed more often and be sure that
> the imageries are up to date with a good resolution. I once mentioned that
> data quality on OpenStreetMap is easily questionable, considering the fact
> that it is being contributed by volunteers that have other activities to
> focus on irrespective of the amount of training received. Only a few will
> be keen on delivering the best. Perhaps volunteers could map while trained
> staffs validate. My opinion.
>
> Regards
> Damilola
>
> On Mon, May 15, 2023 at 12:30 PM Andy Townsend <ajt1047 at gmail.com> wrote:
>
>> On 15/05/2023 05:47, Emerson Rocha via osmf-talk wrote:
>> > Let me give a real world example. Weeks ago on unofficial
>> > OpenStreetMap Telegram channel  (message
>> > https://t.me/OpenStreetMapOrg/101372 ) a mapper from Colombia
>> > complained that the buildings added in an area (near volcano Nevado
>> > del Ruiz) was visited by local civil defense. The building=yes (added
>> > by a human mapper, but geometry suggested
>> > Microsoft/buildingFootprints) actually was a... tree. Guayacanes and
>> > Yarumos to be more exact. He was pissed off on the chat, saying it
>> > already complained in the past.
>>
>>
>> For the avoidance of doubt this was a mistake by a human mapper
>> apparently from the same country (and with a bit of experience - 1000
>> edits or so) using "RapiD 1.1.9".  It wasn't a new contributor to OSM
>> attending a mapathon organised by an NGO abroad.  There appear to be no
>> changeset comments on their changes suggesting that people have noticed
>> problems with "trees as buildings" or similar.  If a complaint was made,
>> it doesn't appear to have been made to this mapper.  Put bluntly,
>> they're not going to know how problematic tools like "RapiD" can be
>> unless someone tells them.  That's not to say that RapiD aren't really
>> useful at finding missing buildings; just that they will also find some
>> false positives too (a quick scan locally (UK) finds around 20 missing
>> sheds and small agricultural buildings that no-one has bothered to add -
>> and one that appears to be a bit of scrap metal, that isn't.
>>
>> I'd suggest (and will suggest on Telegram) that a changeset comment
>> helping them understand how to use tools such as this would be the best
>> initial approach.
>>
>> Best Regards,
>>
>> Andy
>>
>> (as usual writing here in a personal capacity, and apologies from
>> dragging this thread even further from "strategic" things)
>>
>>
>>
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