Re: [OSM-talk] Historical Data in OSM database
If you prefix tag keys of historic elements with past:, it will not interfere with extisting SW conserned with rendering the present state. Examples: past:building=y, past:highway=... At the same time it should be easy to render historic maps based on existing styles. I doubt that historical mapping will add significantly to the OSM database size on the global scale. But if I am wrong, it will certainly add value to OSM, IMHO. (I first thought of historic: prefix, but that can be misunderstood to mean present object of historic interest.) BR/Egil Hjelmeland ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] How inaccurate was the mapnik distance/scale marker?
Dave F. wrote: Excuse my ignorance, are you saying that it's 2x inaccurate at all zoom levels? At lattitude 60: yes. So one of the mapnik guys could implement it quite easily then? I don't think it is related to mapnik. It is the javascript code served by the web-site that wraps up the map rendered by mapnik, osmarender or what so ever. It is part of the javascript code running in your browser which handles panning, zooming and selection of map-layer. If you are thinking of the map on openstreetmap.org, that would have be done by the maintainers of that site. Cheers Dave F. Egil H ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] How inaccurate was the mapnik distance/scale marker?
I assume you are referring to the OpenLayers based slippy map at openstreetmap.org? The Openlayers 2.8 ScaleLine class has the the problem that it does not handle that the map-scale is not constant accoss the map. The slippy map uses mercators projection, where the scale increases with 1/cos(lattiude). So the scaleline is correct at equator, but a over factor 2 off where I am at 62 north. But it is trivial to make a mercator-specific variant of ScaleLine. I have made one here: http://www.egil-hjelmeland.no/kart/mercatorScaleLine.js. Anyone are free to use it. View it in action at my playground: http://www.egil-hjelmeland.no/kart/ . It is also very easy to make measurement functions in OpenLayers. And the good thing is that the OpenLayers Measure class is geodesic aware, it handles mercator out of the box. I think it would be good to include that on the OSM main map, as well. Cheers Egil H There used to be a distance indicator graphic in the bottom left of the map. I believe it was removed because it was inaccurate due to the curvature of the Earth. I can understand the point at low zoom levels, but at say, zoom 13, just how inaccurate, percentage wise, is it? I found it quite useful as a guide. Obviously I didn't do any intricate journey calculations based on it, but as a ball park figure, it came in use. Could it be reinstated for the higher level zooms, 11 maybe? Cheers Dave F. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] talk Digest, Vol 65, Issue 41
I think it does not hurt to define the exact meaning of a line-segment in OSM. And I think that great circle (in wgs84) is the natural choice, in stead of defining line to be straight relative to some arbitrary projection. Since the API (for performance reasons) can not return line segments with endpoint outside the bounding box, we (at least for some time) have to live with adding redundant nodes for every x km for great-circle lines. Then I suggest that the purists may add a tag redundant=y to the redundant nodes. To Frederik's concern about mappers getting confused about what a straight line is: I guess that there is only a tiny fraction of the mappers that ever will come across very long line segments. I suppose more than half of them can do it right in the first place if it is properly described on the Wiki. (Particulary state that a line of lattitude is not a Great circle, except for equator). And the other cases can be corrected by others who understands the concept of a great circle. That is the beauty of wiki-style mapping. Best regards Egil Message: 6 Date: Sat, 09 Jan 2010 09:58:20 -0500 From: Greg Troxel g...@ir.bbn.com Subject: Re: [OSM-talk] New Highways view in OSM Inspector To: Frederik Ramm frede...@remote.org Cc: OSM Talk talk@openstreetmap.org Message-ID: rmiskafl3zn@fnord.ir.bbn.com Content-Type: text/plain; charset=us-ascii We were discussing what exactly a straight line was. There is no such thing as a straight line in the database, because, as you correctly state, the database only stores the end points of a line. If you draw a line from point lat=10;lon=10 to lat=30;lon=30, then it is unclear whether that line visits point lat=20;lon=20. Some might think yes, some might think no. I think this is exactly the key question. When there is a line segment in the database, in WGS84 lat/lon, with points (lon1,lat1) and (lon2,lat2), then we need to have a definition of what that representation means. Obvious candidates are: 1) linear in lon,lat space 2) great circle in wgs84 3) linear in google spherical mercator 4) linear in WGS84 UTM 5) linear in your own country's local grid, or US state plane coordinate system 6) we don't define it, and if any of the above are different in any discernible way, you need more points. In the 10,10 30,30 example above, we are clearly in this state. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] New Highways view in OSM Inspector
Egil Hjelmeland wrote: Sorry, I forgot to change the subject line. I think it does not hurt to define the exact meaning of a line-segment in OSM. And I think that great circle (in wgs84) is the natural choice, in stead of defining line to be straight relative to some arbitrary projection. Since the API (for performance reasons) can not return line segments with endpoint outside the bounding box, we (at least for some time) have to live with adding redundant nodes for every x km for great-circle lines. Then I suggest that the purists may add a tag redundant=y to the redundant nodes. To Frederik's concern about mappers getting confused about what a straight line is: I guess that there is only a tiny fraction of the mappers that ever will come across very long line segments. I suppose more than half of them can do it right in the first place if it is properly described on the Wiki. (Particulary state that a line of lattitude is not a Great circle, except for equator). And the other cases can be corrected by others who understands the concept of a great circle. That is the beauty of wiki-style mapping. Best regards Egil Message: 6 Date: Sat, 09 Jan 2010 09:58:20 -0500 From: Greg Troxel g...@ir.bbn.com Subject: Re: [OSM-talk] New Highways view in OSM Inspector To: Frederik Ramm frede...@remote.org Cc: OSM Talk talk@openstreetmap.org Message-ID: rmiskafl3zn@fnord.ir.bbn.com Content-Type: text/plain; charset=us-ascii We were discussing what exactly a straight line was. There is no such thing as a straight line in the database, because, as you correctly state, the database only stores the end points of a line. If you draw a line from point lat=10;lon=10 to lat=30;lon=30, then it is unclear whether that line visits point lat=20;lon=20. Some might think yes, some might think no. I think this is exactly the key question. When there is a line segment in the database, in WGS84 lat/lon, with points (lon1,lat1) and (lon2,lat2), then we need to have a definition of what that representation means. Obvious candidates are: 1) linear in lon,lat space 2) great circle in wgs84 3) linear in google spherical mercator 4) linear in WGS84 UTM 5) linear in your own country's local grid, or US state plane coordinate system 6) we don't define it, and if any of the above are different in any discernible way, you need more points. In the 10,10 30,30 example above, we are clearly in this state. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] New Highways view in OSM Inspector
An other practical alternative: Leave the exact definition of line segments undefined (as Frederik suggests). Then tag straight ways as straight=great circle or straight=lattitude or what ever. And then tag the redundant nodes as redundant=yes. Egil Egil Hjelmeland wrote: Egil Hjelmeland wrote: Sorry, I forgot to change the subject line. I think it does not hurt to define the exact meaning of a line-segment in OSM. And I think that great circle (in wgs84) is the natural choice, in stead of defining line to be straight relative to some arbitrary projection. Since the API (for performance reasons) can not return line segments with endpoint outside the bounding box, we (at least for some time) have to live with adding redundant nodes for every x km for great-circle lines. Then I suggest that the purists may add a tag redundant=y to the redundant nodes. To Frederik's concern about mappers getting confused about what a straight line is: I guess that there is only a tiny fraction of the mappers that ever will come across very long line segments. I suppose more than half of them can do it right in the first place if it is properly described on the Wiki. (Particulary state that a line of lattitude is not a Great circle, except for equator). And the other cases can be corrected by others who understands the concept of a great circle. That is the beauty of wiki-style mapping. Best regards Egil Message: 6 Date: Sat, 09 Jan 2010 09:58:20 -0500 From: Greg Troxel g...@ir.bbn.com Subject: Re: [OSM-talk] New Highways view in OSM Inspector To: Frederik Ramm frede...@remote.org Cc: OSM Talk talk@openstreetmap.org Message-ID: rmiskafl3zn@fnord.ir.bbn.com Content-Type: text/plain; charset=us-ascii We were discussing what exactly a straight line was. There is no such thing as a straight line in the database, because, as you correctly state, the database only stores the end points of a line. If you draw a line from point lat=10;lon=10 to lat=30;lon=30, then it is unclear whether that line visits point lat=20;lon=20. Some might think yes, some might think no. I think this is exactly the key question. When there is a line segment in the database, in WGS84 lat/lon, with points (lon1,lat1) and (lon2,lat2), then we need to have a definition of what that representation means. Obvious candidates are: 1) linear in lon,lat space 2) great circle in wgs84 3) linear in google spherical mercator 4) linear in WGS84 UTM 5) linear in your own country's local grid, or US state plane coordinate system 6) we don't define it, and if any of the above are different in any discernible way, you need more points. In the 10,10 30,30 example above, we are clearly in this state. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
[OSM-talk] Tagging schema
of the rendering A language translation table on literal values: -Key name - Literal value - Language ID (ISO 639) - Localised name for value - Localised description in English Organisation: OSM is a community of volunteers. So neither bureaucracy or dictatorship is probably the way to go. I would guess that forking off a “tagging” mail group with a strict “keep-to-topic” policy would be the way to proceed. It could deal with tagging schema/policy in general, as well as core tagging, and assigning top level keys to other sub level tagging groups. Well, it is time to get some sleep before work calls tomorrow. I am not going to implement any of this. I just hope these ideas can spawn some productive debate. Best regards Egil Hjelmeland ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
[OSM-talk] [tagging] Feature Proposal - RFC - key:prominence
Here is a proposal for tagging natural=peak with its prominence (prime factor) in meters: http://wiki.openstreetmap.org/wiki/Proposed_features/key:prominence Please comment, preferably on the talk-page. Best Regards Egil Hjelmeland ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
