Peter, I think we should separate the discussion related to linear referencing / mileposts from the cardinal direction discussion - these are two different things really, to my mind. The notion of cardinal direction is a relatively straightforward one, and that is already cause for (cultural) confusion. Introducing the GIS concept of linear referencing into this discussion I think adds to the confusion. We should perhaps discuss that separately - I for one don't see the immediate relation between the two, but I am happy to be proven wrong.
On Wed, Nov 27, 2013 at 3:08 AM, Peter Davies <peter.dav...@crc-corp.com> wrote: > Martijn > > I, too, await your clarification for KristenK, as I'm a little confused too. > > We need to keep in mind that positive and negative GIS Linear Reference > directions (which are handy as global solutions applying everywhere in the > US at least) beginning at milepoint 0.0, usually on the southern or western > state boundary for rectangular states, are not the same as posted DOT miles > that sit on green and white pressed steel signs on the shoulder of all > Interstates and many state/US routes. DOT miles often jump and can > occasionally change directions, as route designators are altered (something > that happens quite often) and bypasses are built. The cost of reporting the > whole route is usually prohibitive. > > So GIS LRS positive and (imperfect) posted DOT miles are handy things to > keep in mind as long as we realize that there are always a few exceptions to > break our defaults. Similarly, posted cardinal directions are fairly > rules-bound but certainly not 100%. This is why I think a good OSM solution > needs to be explicit rather than implicitly inferred from highway geometry. > > Examples of state GIS definitive records are built by ESRI "Roads and > highways" (used in Indiana) and by Agile Assets (used in Idaho). Check out > http://www.esri.com/software/arcgis/extensions/roads-and-highways > > Peter > > > On Tue, Nov 26, 2013 at 5:24 PM, Kristen Kam <krist...@telenav.com> wrote: >> >> Martijn, >> >> I want to make sure I understand what you're trying to convey to the >> group. Are you saying that If a way has a member role value of "east" >> then east will mean forward and then west (it's opposite) would mean >> backward? >> >> Example logic: >> >> ** If member role = east, node direction is eastbound would mean >> forward and backward would mean 'west' >> ** If member role = west, node direction is westbound would mean >> forward and backward would mean 'east' >> ** If member role = north, node direction is northbound would mean >> forward and backward would mean 'south' >> ** If member role = south, node direction is southbound would mean >> forward and backward would mean 'north' >> >> If the logic I stated above successfully captured with your >> suggestion, then I would like to expand on it. Why not just make the >> cardinal direction value-forward/backward value relationship a bit >> more simpler? I would like to cite Peter Davies' discussion on the >> Highway Directions in the US wiki page. He stated that milepoints >> increase as highways that trend northward or eastward--say positive >> direction. So if one is traveling south or west on a highway, the >> milepoints are decreasing--say negative direction. >> >> With this in mind, couldn't we just say that north/east = forward >> (forward movement is positive!) and west/south=backward (backward >> movement is negative!)? If we're digitizing our edges, the suggestion >> would be to set the node direction of two-way, aka single-carriageway >> roads, into a positive direction and the member roles values to north >> or east. Basically what you did for >> http://www.openstreetmap.org/browse/relation/2308411, but setting the >> single-carriageway/two-way roads to 'east' instead of 'west'. >> >> Thoughts Martijn? Others?? >> >> Best, >> >> Kristen >> --- >> >> OSM Profile → http://www.openstreetmap.org/user/KristenK >> >> >> -----Original Message----- >> From: Martijn van Exel [mailto:m...@rtijn.org] >> Sent: Tuesday, November 26, 2013 2:47 PM >> To: Ian Dees >> Cc: Florian Lohoff; OpenStreetMap-Josm MailConf; OSM US Talk >> Subject: Re: [Talk-us] [josm-dev] Relation editor support for >> north/south and east/west similar to forward/backward >> >> Yes, sorry for not being clearer. As Ian indicates, this is the >> *signposted cardinal direction* of a numbered road route, which does >> not change with the actual compass direction of the road. The guiding >> principle for the United States is that the odd numbered Interstates >> are north/south, and the even numbered Interstates are east/west. This >> is independent from the local compass direction. So for example, I-80 >> is east-west, but runs almost north-south locally (for example here: >> http://www.openstreetmap.org/browse/way/203317481) but the sign would >> still say 'I-80 East' (or West as the case may be). >> >> So the relation between the east--west and north--south member roles >> is equivalent to the relation between forward--backward. >> >> Because the cardinal direction is commonly included on the road signs >> (see example >> http://www.aaroads.com/west/new_mexico010/bl-010_eb_at_i-010.jpg) >> this information is useful in the U.S. (and Canadian) context as a >> drop in replacement for the traditional forward / backward role >> members. >> >> Hope this clarifies somewhat! >> Martijn >> >> On Tue, Nov 26, 2013 at 2:57 PM, Ian Dees <ian.d...@gmail.com> wrote: >> > On Tue, Nov 26, 2013 at 3:51 PM, Florian Lohoff <f...@zz.de> wrote: >> >> >> >> On Tue, Nov 26, 2013 at 12:30:25PM -0700, Martijn van Exel wrote: >> >> > Hi all, >> >> > >> >> > I'm new to this list so please bear with me. >> >> > The relation editor currently only parses 'forward' and 'backward' >> >> > roles when considering the visual representation in the rightmost >> >> > column. In the United States, north/south and east/west are very >> >> > common as member roles for road routes, because that is how they >> >> > are officially signposted. >> >> >> >> I would be very careful in using this. Is this really "south" e.g. >> >> 180° ? Or is it more like 99° ? Or 269° ? >> >> >> >> Most streets are not strictly on the 90° raster and signposts are >> >> only rough directions. >> >> >> >> Addings this to OSM might make it much more difficult for Data >> >> Consumers to process and interpret data. >> > >> > >> > No, these aren't compass directions. They're the directionality of the >> > road. >> > For example, this way is part of the I-94 interstate going west, but a >> > compass in a car driving on it would tell the viewer they were >> > pointing >> > north: >> > >> > http://www.openstreetmap.org/browse/way/39372612 >> >> >> >> -- >> Martijn van Exel >> http://oegeo.wordpress.com/ >> http://openstreetmap.us/ >> >> _______________________________________________ >> Talk-us mailing list >> talk...@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/talk-us > > -- Martijn van Exel http://oegeo.wordpress.com/ http://openstreetmap.us/ _______________________________________________ josm-dev mailing list josm-dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/josm-dev