[HOT] Buildings and residential areas: Buldings as nodes (Q1)

[john whelan]

But from your computer science background you should realise there are
costs involved.  To mark a building as a node is one line in the database.
As a way well there are four nodes for a start each with its lat and long,
then you have the connecting way.  Have you saved a bit of .OSM and opened
it in Notepad++?  Try it sometime.  Open JOSM download a tiny area ie a
building and take a look.  Download a node and take another look.

So we have time costs in mapping, plus internet costs in uploading the
additional information, storage in the main OpenStreetMap database,
additional costs in downloading, more storage required on smartphones in
the field more processing required at all stages. The time costs in mapping
mean given the number of mappers we have few projects will get mapped. We
also have experienced OpenStreetMap mappers mapping who may not follow HOT
guidelines.  These will need retraining and how will you reach them?

In Africa internet transmission costs are much higher than locally in North
America so ideally we want to minimise these.

Then you get to the added value.

Take a look at http://tasks.hotosm.org/project/2656#task/102 when I
validated it recently for a highways project it seemed to me that most
buildings=yes were twice or three times the size of the building sometimes
covering more than one building, at least they were mostly square.  For HOT
projects this is not untypical but strange shapes tagged building=yes
abound. I've seen tiles when only half the buildings have been mapped but
the tile marked done.

The true added value is being able to estimate population. How many people
are there that need to be vaccinated.  If the buildings are mapped
accurately then you stand a chance.  You may have seen some references to
the JOSM building_tool plugin, try it if you haven't.  You take the number
of buildings and their combined area and you can make some reasonable
guesses. The area data is so unreliable you might as well have asked for
nodes and to be honest you stand a better chance of them all being mapped.

I take it you took all these points into consideration before saying that
building=yes nodes should not be used?

The place to raise the issue is with OpenStreetMap, its their map and there
will be different points of view and it might be worth checking how many
there are in the map already.

Cheerio John

On 22 May 2017 at 11:18, Enock Seth Nyamador <kwadzo459 at gmail.com> wrote:

> On personal level I feel mapping buildings as nodes is very wrong so I
> avoid it.
>
> But I think tagging nodes as building should be looked at very well. I
> will recommend it is deprecated.
>
> Best,
>
> - Enock
>
> 2017-05-20 11:38 GMT+00:00 Vao Matua <vaomatua at gmail.com>:
>
>> My opinion is that buildings should be mapped as areas.
>> In un-mapped areas it would be best to create landuse=residential areas
>> first rather than quickly tagging buildings with single nodes. When it
>> comes time to trace buildings it is troublesome to convert single nodes to
>> polygons.
>> For existing single node areas they could be cleaned up on an as-needed
>> basis.
>>
>> Emmor
>> (Palolo)
>>
>> On Sat, May 20, 2017 at 2:10 PM, Bjoern Hassler <bjohas+mw at gmail.com>
>> wrote:
>>
>>> Dear both, dear all,
>>>
>>> If we're agreed that it's better to map buildings as areas - should we
>>> try to re-map node-buildings from previous campaigns as areas? Or shall we
>>> just leave it?
>>>
>>> Many thanks,
>>> Bjoern
>>>
>>> On 19 May 2017 at 17:54, Cascafico Giovanni <cascafico at gmail.com> wrote:
>>>
>>>> AFAIK Osmand renders addr: housenumber also for polygons [1].
>>>>
>>>> Anyway I agree to the general rule that rendering has to adhere to
>>>> mapping (and not VS).
>>>>
>>>> [1] cascafico.altervista.org/public/Screenshot_2017-05-19-18-40-41.png
>>>>
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