[Tagging] tagging of ele / elevation data e.g. in the context of towers
On the German ML we are currently discussing how to applicate ele to towers (and similar situations). There is consensus that the key height is describing the height of the structure from the ground to the top. There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). There are 2 alternatives: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). b) ele is the elevation of the highest point at the tagged spot, i.e. the top of the tower Comments welcome. The idea is to clarify this aspect on the wiki page for the key ele. cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
2012/2/20 Martin Koppenhoefer dieterdre...@gmail.com On the German ML we are currently discussing how to applicate ele to towers (and similar situations). There is consensus that the key height is describing the height of the structure from the ground to the top. There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). There are 2 alternatives: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). +1 I believe ele=* should be applied only to the terrain, and height would be the physical distance between the point at ele=* elevation and the one at ele+height elevation. b) ele is the elevation of the highest point at the tagged spot, i.e. the top of the tower -1 Comments welcome. The idea is to clarify this aspect on the wiki page for the key ele. For istance if there would ever be a DEM compatible with OSM licenses, I think it would be imported in ele=* tags. cheers, Martin cheers, Stefano. ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
As I understand it option a) is correct. If put on a building it would mean that the ground level is at this height. In some specific cases this might bring problems though: imagine a lot of stones and earth is transported on the hilltop, the elevation clearly changes. If you build a building there the elevation is unchanged. Now what if you cover this building with earth to look more natural? How thick layer of earth is required for the elevation to change? But these cases will be uncommon and I still vote for a) Lukáš Matějka (LM_1) 2012/2/20 Martin Koppenhoefer dieterdre...@gmail.com: On the German ML we are currently discussing how to applicate ele to towers (and similar situations). There is consensus that the key height is describing the height of the structure from the ground to the top. There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). There are 2 alternatives: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). b) ele is the elevation of the highest point at the tagged spot, i.e. the top of the tower Comments welcome. The idea is to clarify this aspect on the wiki page for the key ele. cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Hi, On 02/20/2012 01:06 PM, LM_1 wrote: As I understand it option a) is correct. If put on a building it would mean that the ground level is at this height. Should one not then, to avoid misunderstandings, use ele only on ground-level features? We can define away on the wiki all we want; there will always be people who read ele on a building to mean its height. Bye Frederik -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09 E008°23'33 ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Generelly yes, but if there is a tower on the summit, there is not really any other way. Lukáš 2012/2/20 Frederik Ramm frede...@remote.org: Hi, On 02/20/2012 01:06 PM, LM_1 wrote: As I understand it option a) is correct. If put on a building it would mean that the ground level is at this height. Should one not then, to avoid misunderstandings, use ele only on ground-level features? We can define away on the wiki all we want; there will always be people who read ele on a building to mean its height. Bye Frederik -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09 E008°23'33 ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Hi, On 02/20/2012 01:26 PM, LM_1 wrote: Generelly yes, but if there is a tower on the summit, there is not really any other way. You would normally put a natural=peak tag next to the tower anyway. Or if you don't, then attach ele to the bench near the base of the tower or so ;) Bye Frederik -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09 E008°23'33 ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
At 2012-02-20 03:44, Martin Koppenhoefer wrote: On the German ML we are currently discussing how to applicate ele to towers (and similar situations). There is consensus that the key height is describing the height of the structure from the ground to the top. There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). This is the standard for FCC (communications) and FAA (airspace) in the US. Well, close at least - elevations are generally above mean sea level - I don't know how that relates to the WGS84/GPS and/or survey elevation but I'd expect them to be close. -- Alan Mintz alan_mintz+...@earthlink.net ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
At 2012-02-20 04:06, LM_1 wrote: As I understand it option a) is correct. If put on a building it would mean that the ground level is at this height. I might add that, if you put a tower on top of the building, I'd expect the ele tag on the tower to be the sum of the building's ele and height tags. -- Alan Mintz alan_mintz+...@earthlink.net ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
At 2012-02-20 04:26, someone wrote: We can define away on the wiki all we want; there will always be people who read ele on a building to mean its height. I think this may be a language issue. In American English at least, one would not use/read the word elevation to mean the height of an object - one would always use/expect to read height for that. The words are not synonymous. -- Alan Mintz alan_mintz+...@earthlink.net ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Alan Mintz alan_mintz+...@earthlink.net writes: This is the standard for FCC (communications) and FAA (airspace) in the US. Well, close at least - elevations are generally above mean sea level - I don't know how that relates to the WGS84/GPS and/or survey elevation but I'd expect them to be close. above mean sea level (not claiming the FCC doesn't use it; I've seen it too) is basically sloppy from a surveying/geodesy viewpoint; the notion of mean sea level only applies at a specific tide gauge. The modern concept is orthometric height relative to a given vertical datum (in the US, NAVD88). This is more or less the same conceptually as MSL except that it doesn't presume that mean sea level at all tide gauges is the same (as NGVD29 did). Orthometric height is based on gravity, rather than geometry, and is more or less distance normal to the geoid, a surface of constant potential that sort of matches sea level. WGS84 proper measures locations relative to the ellipsoid. One would refer to the measured height (transformed to lat/lon/height from XYZ in earth-centered earth-fixed) as an ellipsoidal height. But because what everyone wants is orthometric height (partly because of tradition and existing data, and partly because water flows downhill relative to orthometric height), one uses a geoid model that estimates the distance From the ellipsoid to the geoid. From that one gets an estimate of orthometric height. On every GPS receiver I've seen, the altitude is intended to match orthometric height, and is ellipsoidal height adjusted by the geoid model. So it's ok to talk about WGS84 elevations, but we should be clear that we mean elevations intended to be usable as orthometric heights using the geoid model. ellipsoid/geoid separates are large; around me it's ~30m. But errors in geoid models and differences in semi-modern (20th century and newer) vertical datums are a meter or so, at least in North America. So despite my ranting, this is mostly ignorable for OSM. pgpQpUXswOprE.pgp Description: PGP signature ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Martin Koppenhoefer wrote: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). In practice, this is closest to how I would have interpreted it. I would usually expect ele to define the elevation of the base of the feature that carries the tag. If an object stands on the ground, then this is identical to the elevation of the ground at that point. But in the case of e.g. a tunnel, it would refer to the surface of the road running through the tunnel - and therefore an elevation below the ground elevation. The road running on top of the hill would have different ele values than the tunnel running through it. So no, ele is imo not the elevation of the ground, it is the elevation of _the object mapped with the ele tag_. However, in the case of a building, that building's elevation is given at ground level. As a result, the ele tags on features on the ground will be the same as ground ele. The ele tags on features above or below the ground, such as bridges or tunnels, will be different from ground ele, though. Tobias ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Martin There is consensus that the key height is describing the height of the structure from the ground to the top. +1 (I think there is no other way of doing it) There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). I do not understand what that means. For me height is always in meters, and meters don't change with the system of reference (unless they move close to the speed of light ) There are 2 alternatives: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). +1 b) ele is the elevation of the highest point at the tagged spot, i.e. the top of the tower I would say abolutely not, even though there are examples where, say a restaurant on top of a tower gives the elevation from see level, but that most likely be altitude and not elevation. I would stick to this terminology: The tip of a tower with *height* x meters on top of a mountain peak at * elevation* y meters is at an *altitude* of y+x meters. Volker Comments welcome. The idea is to clarify this aspect on the wiki page for the key ele. cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging -- Volker SCHMIDT Via Vecchia 18/ter 35127 Padova Italy mailto:vosc...@gmail.com office phone: +39-049-829-5977 office fax +39-049-8700718 home phone: +39-049-851519 personal mobile: +39-340-1427105 skype: volker.schmidt ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Am 20. Februar 2012 14:21 schrieb Volker Schmidt vosc...@gmail.com: There is consensus that the key height is describing the height of the structure from the ground to the top. +1 (I think there is no other way of doing it) well, you could say that height is the maximum vertical extension and thus also comprising the underground part of a structure. There is also consensus to tag elevation data in WGS84 (so that numbers in local systems would typically have to be converted before you can enter them). I do not understand what that means. For me height is always in meters, and meters don't change with the system of reference (unless they move close to the speed of light ) It's not the meters that change, it is where you set your 0.00 level that is changing b) ele is the elevation of the highest point at the tagged spot, i.e. the top of the tower I would say abolutely not, even though there are examples where, say a restaurant on top of a tower gives the elevation from see level, but that most likely be altitude and not elevation. well, this is what one could read from the current wiki definition (which we could make less ambiguous after this discussion). cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Simple solution: use ele:top=* for the elevation of the top. ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Martin Koppenhoefer wrote: Am 20. Februar 2012 14:21 schrieb Volker Schmidt vosc...@gmail.com: There is consensus that the key height is describing the height of the structure from the ground to the top. +1 (I think there is no other way of doing it) well, you could say that height is the maximum vertical extension and thus also comprising the underground part of a structure. You could say that, but I've never met a person who takes a shovel and goes dig up some roots when they are asked about the height of the tree. And the same goes for other man made/natural structures standing around us. Cheers, Petr Morávek aka Xificurk signature.asc Description: OpenPGP digital signature ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
On 20.02.12 12:44, Martin Koppenhoefer wrote: a) ele is the elevation of the ground around/below the tower (in the case of a mountain summit it would be the elevation of the mountain, not the tower). elevation vs altitude vs height: http://en.wikipedia.org/wiki/File:Vertical_distances.svg /al ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Frederik Ramm frede...@remote.org wrote: Hi, On 02/20/2012 01:06 PM, LM_1 wrote: As I understand it option a) is correct. If put on a building it would mean that the ground level is at this height. Should one not then, to avoid misunderstandings, use ele only on ground-level features? We can define away on the wiki all we want; there will always be people who read ele on a building to mean its height. Bye Frederik Also, if the building is built into a slope, both the elevation of the ground level and the height of the building above the ground will depend on which specific part of the building you are discussing. -- John F. Eldredge -- j...@jfeldredge.com Reserve your right to think, for even to think wrongly is better than not to think at all. -- Hypatia of Alexandria ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
From what has been written here it seems that elevation clearly does not contain buildings. Frederik Ramm: You would normally put a natural=peak tag next to the tower anyway. Or if you don't, then attach ele to the bench near the base of the tower or so ;) Most peaks with some construction on them have a pile of stones or some other marking with some elevation label. Yes, I usually would put natural=peak there. Not always there is a peak nearby. Imagine an end-station of a ski lift that does end under the peak. It seems sensible to put elevation tag on it, but there is no suitable natural object nearby. Therefore it should be clear how to map this. Lukas ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
OK, following this discussion it seems clear that either nobody interprets the wiki literally (the elevation at a given point), or that the English term elevation never refers to man_made structures. In each of these cases the tagged value for ele would be the elevation of the surrounding ground. I suggest to improve the wiki. http://wiki.openstreetmap.org/wiki/Key:ele reads: Elevation (height above sea level) of a point in metres. This is mainly intended for mountain peaks but could also be used for elevation of airport runways and many other objects. For OpenStreetMap, please use the elevation above sea level defined by the World Geodetic System, revision WGS 84. I amended this: In the case of buildings and other man_made structures use the elevation of the surrounding ground, not of the structure itself. cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Am 20. Februar 2012 14:43 schrieb Nathan Edgars II nerou...@gmail.com: Simple solution: use ele:top=* for the elevation of the top. if top is a reference system for elevation data... cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Martin Koppenhoefer dieterdre...@gmail.com wrote: OK, following this discussion it seems clear that either nobody interprets the wiki literally (the elevation at a given point), or that the English term elevation never refers to man_made structures. In each of these cases the tagged value for ele would be the elevation of the surrounding ground. I suggest to improve the wiki. http://wiki.openstreetmap.org/wiki/Key:ele reads: Elevation (height above sea level) of a point in metres. This is mainly intended for mountain peaks but could also be used for elevation of airport runways and many other objects. For OpenStreetMap, please use the elevation above sea level defined by the World Geodetic System, revision WGS 84. I amended this: In the case of buildings and other man_made structures use the elevation of the surrounding ground, not of the structure itself. cheers, Martin If a structure is located on sloping ground, do you record the elevation of the highest point in contact with the structure, the lowest point, halfway between the highest and lowest points, or what? -- John F. Eldredge -- j...@jfeldredge.com Reserve your right to think, for even to think wrongly is better than not to think at all. -- Hypatia of Alexandria ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
John F. Eldredge: If a structure is located on sloping ground, do you record the elevation of the highest point in contact with the structure, the lowest point, halfway between the highest and lowest points, or what? This is related to the question: Where do you measure the structure's height from? To allow the top = ele + height calculation that has been mentioned in this thread, it would be desirable if the answer to both was the same. At the last 3D rendering workshop I attended, the general idea appeared to be to measure height from the lowest point in contact with the ground. But it's indeed not properly documented anywhere afaict. And while it seems intuitive enough for height, it might not appear that way for ele. Tobias ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] tagging of ele / elevation data e.g. in the context of towers
Am 20. Februar 2012 21:09 schrieb John F. Eldredge j...@jfeldredge.com: If a structure is located on sloping ground, do you record the elevation of the highest point in contact with the structure, the lowest point, halfway between the highest and lowest points, or what? The lowest point would be OK for standard situations* (and for structures which are not accessible). It could also be the ground level at the entrance (and if its more entrances the main one, and if that is not clear the lower entrance) or the floor level of the lowest normal floor. I think we will anyway at some point have to decide where is the 0-level for buildings (in the context of 3D and building details). cheers, Martin * a non-standard situation might be atop a cliff with supporting beams that run down the cliff or something like this. ___ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
