Buildings and residential areas: Buldings as nodes (Q1)

classic Classic list List threaded Threaded
11 messages Options
Reply | Threaded
Open this post in threaded view
|

Buildings and residential areas: Buldings as nodes (Q1)

Bjoern Hassler

Dear all,

I've got a few questions about buildings and residential areas. Here's the first one. Can buildings be entered as nodes? This may well have been discussed before :) but I'd like to understand the situation better.

On the one hand, https://wiki.openstreetmap.org/wiki/Key:building suggests that nodes tagged as buildings are fine. However, nodes with  building=yes only are not rendered in standard carto.

https://taginfo.openstreetmap.org/keys/?key=building says there's just about 0.9m buildings as nodes (about 0.5% of buildings that are areas, which is about 220m in total). Running some overpass queries, I'd say there are around 60,000 buildings as nodes in sub-Saharan Africa (so about ~7% of the total "buildings as nodes" set), and poking around a bit, some seem to come from campaigns like these:

  • #hotosm-liberia-task-489
  • #hotosm-task-572
  • #hotosm-ebola-si-586, #MapGive #UNVolunteers

Do you have any suggestions? I guess the questions are:
  • Should nodes[building=yes][name=""] be rendered in carto?
  • If not, what about existing nodes? Should they be replaced by ways?
  • If yes, then would it not be easier to just use nodes in for some campaigns? It's obviously much faster just to copy-paste building nodes (e.g. in JOSM) rather than drawing outlines. I can see that outlines help in cities, as it indicates land-use better, but in many of the deep-rural areas, is there a strong benefit to having buildings as outlines? Sure, it tell us the size (which relates to quantity of spray), but is the exact size that relevant? Do we know that data is entered accurately enough for this to matter?
Anyway, not meant to be controversial - just trying to understand the issue!

I've also filed an issue on github here:
https://github.com/gravitystorm/openstreetmap-carto/issues/2635 in case people want to discuss there too.

_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

john whelan-2
OpenStreetMap and HOT conventions are slightly different.  In OpenStreetMap a much wider range of mapping conventions are used and it is quite acceptable for a building to be mapped as a node or outline, in HOT the convention is to map it in outline.

If the buildings are mapped accurately then you can do population estimates by adding up the area of each building although its not as accurate as counting people directly but much better than nothing.  How many doses of vaccine do we need?  There are many other uses the data can be put to.  How many children do we think there are who need schooling?

Once they are in OpenStreetMap then there are a number of ways to render them.  Some rendering systems render some things but not others.  For example OSMand renders street numbers on a node but not attached to a building outline.  Maperitive can dig anything out and render it with the right rules.

I think you can assume that if the information is in the data people who need it can dig it out.  They won't restrict themselves to what is printed or rendered on a particular web site.  They just go for the raw data.

Cheerio John

On 19 May 2017 at 07:18, Bjoern Hassler <[hidden email]> wrote:

Dear all,

I've got a few questions about buildings and residential areas. Here's the first one. Can buildings be entered as nodes? This may well have been discussed before :) but I'd like to understand the situation better.

On the one hand, https://wiki.openstreetmap.org/wiki/Key:building suggests that nodes tagged as buildings are fine. However, nodes with  building=yes only are not rendered in standard carto.

https://taginfo.openstreetmap.org/keys/?key=building says there's just about 0.9m buildings as nodes (about 0.5% of buildings that are areas, which is about 220m in total). Running some overpass queries, I'd say there are around 60,000 buildings as nodes in sub-Saharan Africa (so about ~7% of the total "buildings as nodes" set), and poking around a bit, some seem to come from campaigns like these:

  • #hotosm-liberia-task-489
  • #hotosm-task-572
  • #hotosm-ebola-si-586, #MapGive #UNVolunteers

Do you have any suggestions? I guess the questions are:
  • Should nodes[building=yes][name=""] be rendered in carto?
  • If not, what about existing nodes? Should they be replaced by ways?
  • If yes, then would it not be easier to just use nodes in for some campaigns? It's obviously much faster just to copy-paste building nodes (e.g. in JOSM) rather than drawing outlines. I can see that outlines help in cities, as it indicates land-use better, but in many of the deep-rural areas, is there a strong benefit to having buildings as outlines? Sure, it tell us the size (which relates to quantity of spray), but is the exact size that relevant? Do we know that data is entered accurately enough for this to matter?
Anyway, not meant to be controversial - just trying to understand the issue!

I've also filed an issue on github here:
https://github.com/gravitystorm/openstreetmap-carto/issues/2635 in case people want to discuss there too.

_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

cascafico

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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot

--
cascafico.altervista.org
twitter.com/cascafico
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Bjoern Hassler
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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Palolo
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Enock Seth Nyamador
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 <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

john whelan-2
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 <[hidden email]> 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 <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Jan Martinec
Hello all,

There's really no "their" where OSM is concerned - the database is made by individual contributors, without centralized oversight, and much of the mapping is by convention. But looking at the OSM wiki gives some fairly strong recommendations: http://wiki.openstreetmap.org/wiki/Key:building - to paraphrase, "in absence of better data, building-as-a-node is better than nothing at all, until it can be mapped as an area from a better source."

As far as "accurate mapping" - that's a problem and a driving force for the whole of OSM: have you seen the map in 2010? There was a very similar situation worldwide, with most buildings existing as rough outlines or not at all; requiring "perfect or nothing" would have resulted in no OSM, period.

That said, the quality of mapping does depend on feedback, especially with new mappers: is the project with badly mapped buildings representative of HOT projects? The ones I've seen (and edited) seem to match building shapes and sizes well - e.g. http://tasks.hotosm.org/project/2520 - but that's also an issue of task validation, in addition to mapper training; I do agree that takes some additional human power in return for much better map result.

So, I guess that where time is critical (or space, even though XML compresses well and data for mobile apps is compressed even more efficiently), buildings-as-nodes are an acceptable interim solution, but the ideal case is buildings as well-outlined ways (which is what "experienced OSM mappers" do prefer, btw; no retraining needed).

Cheers,
Jan "Piskvor" Martinec,
OSM and HOTOSM mapper

Dne 22. 5. 2017 17:54 napsal uživatel "john whelan" <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

john whelan-2
But you can't decide something about OSM on the HOT mailing list.  You can confer and edit the wiki but that may or may not be followed.  There are a number of instances where what is suggested in the wiki and taginfo are quite different.

Data compression was mentioned purely because of the writer showing up as a computer science / engineer person.  Having worked in computers including setting standards for some years cost is something they don't always consider and it is a major part of engineering.  No matter what compression system is used four nodes will always take up four times the space as one node.  Maybe not with .7z compression looking for strings in the long lat but its a good rule of thumb.  Again OSM is now running the largest database known in whatever it is running in, I forget the name.  It's really big which means bleeding edge as we used to call it for backups, for data retrieval etc..  Not quite where you want to be for reliability.

I've seen some areas / projects where building outlines are mapped accurately.  Ottawa, Canada is one, the data was imported from local government sources.  Lusaka, Zambia, they used motivated experienced GIS people but having said I've done a lot of validation and accurately mapped buildings are not infrequent on a HOT project.

The biggest users of nodes for buildings on HOT projects are experienced OSM mappers.  They will switch to ways when you give them feedback that that is what HOT prefers but I think they are the largest source.  The HOT training group has done a very good job on training HOT mappers to draw ways.

Cheerio John



On 22 May 2017 at 14:16, Jan Martinec <[hidden email]> wrote:
Hello all,

There's really no "their" where OSM is concerned - the database is made by individual contributors, without centralized oversight, and much of the mapping is by convention. But looking at the OSM wiki gives some fairly strong recommendations: http://wiki.openstreetmap.org/wiki/Key:building - to paraphrase, "in absence of better data, building-as-a-node is better than nothing at all, until it can be mapped as an area from a better source."

As far as "accurate mapping" - that's a problem and a driving force for the whole of OSM: have you seen the map in 2010? There was a very similar situation worldwide, with most buildings existing as rough outlines or not at all; requiring "perfect or nothing" would have resulted in no OSM, period.

That said, the quality of mapping does depend on feedback, especially with new mappers: is the project with badly mapped buildings representative of HOT projects? The ones I've seen (and edited) seem to match building shapes and sizes well - e.g. http://tasks.hotosm.org/project/2520 - but that's also an issue of task validation, in addition to mapper training; I do agree that takes some additional human power in return for much better map result.

So, I guess that where time is critical (or space, even though XML compresses well and data for mobile apps is compressed even more efficiently), buildings-as-nodes are an acceptable interim solution, but the ideal case is buildings as well-outlined ways (which is what "experienced OSM mappers" do prefer, btw; no retraining needed).

Cheers,
Jan "Piskvor" Martinec,
OSM and HOTOSM mapper

Dne 22. 5. 2017 17:54 napsal uživatel "john whelan" <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Jan Martinec
Of course this is not the place for deciding for OSM at large. Note that HOTOSM's mapping is well within the general OSM conventions - surely it is decidable "it seems that both is possible, so we could choose either for our purposes." As for differences between TI and wiki - yes, some conventions do emerge spontaneously and are codified ex post. Although this makes the data harder to parse, it lends OSM a certain flexibility.

As for scale, the entire OSM planet file with complete history takes ~60 GB: one flash disk worth of data. It is still a considerable amount of data, and in the past may have been the largest public database in pgSQL, but it's pretty far from bleeding edge these days: anything resembling Big Data is many orders of magnitude bigger today (petabytes and up - literally a million times larger). For a current extract of one country, OSM tops out at low hundreds of MBs, for less mapped countries it's rather tens of MBs. (Of course, if you are using .osm files as baseline, you'll get far larger numbers - because that's the most verbose format available for representing the data: a dataset of 33 MB in .pbf has 1.8 GB in .osm format). 

I do agree with you with regard to bandwidth; that could be an actual bottleneck.

Cheers,
Jan

Dne 22. 5. 2017 21:44 napsal uživatel "john whelan" <[hidden email]>:
But you can't decide something about OSM on the HOT mailing list.  You can confer and edit the wiki but that may or may not be followed.  There are a number of instances where what is suggested in the wiki and taginfo are quite different.

Data compression was mentioned purely because of the writer showing up as a computer science / engineer person.  Having worked in computers including setting standards for some years cost is something they don't always consider and it is a major part of engineering.  No matter what compression system is used four nodes will always take up four times the space as one node.  Maybe not with .7z compression looking for strings in the long lat but its a good rule of thumb.  Again OSM is now running the largest database known in whatever it is running in, I forget the name.  It's really big which means bleeding edge as we used to call it for backups, for data retrieval etc..  Not quite where you want to be for reliability.

I've seen some areas / projects where building outlines are mapped accurately.  Ottawa, Canada is one, the data was imported from local government sources.  Lusaka, Zambia, they used motivated experienced GIS people but having said I've done a lot of validation and accurately mapped buildings are not infrequent on a HOT project.

The biggest users of nodes for buildings on HOT projects are experienced OSM mappers.  They will switch to ways when you give them feedback that that is what HOT prefers but I think they are the largest source.  The HOT training group has done a very good job on training HOT mappers to draw ways.

Cheerio John



On 22 May 2017 at 14:16, Jan Martinec <[hidden email]> wrote:
Hello all,

There's really no "their" where OSM is concerned - the database is made by individual contributors, without centralized oversight, and much of the mapping is by convention. But looking at the OSM wiki gives some fairly strong recommendations: http://wiki.openstreetmap.org/wiki/Key:building - to paraphrase, "in absence of better data, building-as-a-node is better than nothing at all, until it can be mapped as an area from a better source."

As far as "accurate mapping" - that's a problem and a driving force for the whole of OSM: have you seen the map in 2010? There was a very similar situation worldwide, with most buildings existing as rough outlines or not at all; requiring "perfect or nothing" would have resulted in no OSM, period.

That said, the quality of mapping does depend on feedback, especially with new mappers: is the project with badly mapped buildings representative of HOT projects? The ones I've seen (and edited) seem to match building shapes and sizes well - e.g. http://tasks.hotosm.org/project/2520 - but that's also an issue of task validation, in addition to mapper training; I do agree that takes some additional human power in return for much better map result.

So, I guess that where time is critical (or space, even though XML compresses well and data for mobile apps is compressed even more efficiently), buildings-as-nodes are an acceptable interim solution, but the ideal case is buildings as well-outlined ways (which is what "experienced OSM mappers" do prefer, btw; no retraining needed).

Cheers,
Jan "Piskvor" Martinec,
OSM and HOTOSM mapper

Dne 22. 5. 2017 17:54 napsal uživatel "john whelan" <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]>:
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 <[hidden email]> 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 <[hidden email]> 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


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot



_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot


_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot




_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot
Reply | Threaded
Open this post in threaded view
|

Re: Buildings and residential areas: Buldings as nodes (Q1)

Rob Savoye
In reply to this post by john whelan-2
On 05/22/2017 01:44 PM, john whelan wrote:

> consider and it is a major part of engineering.  No matter what compression
> system is used four nodes will always take up four times the space as one
> node.  Maybe not with .7z compression looking for strings in the long lat
> but its a good rule of thumb.  Again OSM is now running the largest
> database known in whatever it is running in, I forget the name.  It's

  OSM uses PostgreSQL with the postgis and hstore extensions. I run it
locally to save on bandwidth latency, plus it works offline too cause
connectivity is poor around here. Mobile bandwidth is getting better all
the time all over the planet though. Adding data to OSM is better to be
done the way most others do it than worrying about bandwidth.

  Looking into a few OSM files, I see <node> used as a building that
hasn't been mapped as a polygon, ie.. just a waypoint. That's useful
enough for most people trying to find someplace. For a building that
actually has it's dimensions mapped, then it's a <way>, with references
to each <node>. It depends what type of info you want from your map.
When generating a display map, a <node> won't appear as a building,
it'll just be a cute icon. If you want to see a whole building shape, it
needs to be a <way>. Some buildings have both.

        - rob -

_______________________________________________
HOT mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/hot