Re: [talk-au] Direction of flow, rivers and streams
On Wed, Jul 28, 2010 at 4:56 PM, Liz wrote: > On Wed, 28 Jul 2010, Craig Feuerherdt wrote: >> In some cases it is pretty difficult to >> determine which way streams flow as pointed out by Liz and in these >> instances it may be worth putting a "fixme=direction" tag onto the stream. > > If the flow is in either direction, depending on rainfall, fixme is not going > to work, unless you speak to the Diety of Your Choice. Is there a term for these bidirectional streams? I couldn't find anything on wikipedia. Are you describing a flood plain from a dry stream (gultch or wadi)? So it might flood from any direction, but because it is so dry, water evaporates or is absorbed except in extreme flood conditions when it might flow? Surely in this case it would only flow downhill? I can imagine a system that looks like a dinner plate and can be flooded from any side, but does flow really describe what is happening there? Perhaps this is a dry lake? If these can be classified some way it sounds like we should have a distinct tag for them waterway=stream; oneway=no doesn't seem sufficient. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Direction of flow, rivers and streams
On Wed, 28 Jul 2010, Craig Feuerherdt wrote: > In some cases it is pretty difficult to > determine which way streams flow as pointed out by Liz and in these > instances it may be worth putting a "fixme=direction" tag onto the stream. If the flow is in either direction, depending on rainfall, fixme is not going to work, unless you speak to the Diety of Your Choice. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Direction of flow, rivers and streams
The stream direction is very handy if you are doing network analysis, just like one way streets are important to routing vehicles through a street network. As with any data, its always best to code objects correctly in the first instance to save time later. In some cases it is pretty difficult to determine which way streams flow as pointed out by Liz and in these instances it may be worth putting a "fixme=direction" tag onto the stream. Having said that I doubt anyone would be using OSM data for streamflow analysis because topographic features are not the main focus of OSM. Craig On Wed, Jul 28, 2010 at 1:39 PM, John Henderson wrote: > I note the wiki says that "Direction of the way should be downstream." > > Most streams I look at on OSM have been drawn uphill, and I've been > reversing the direction of ones I notice as wrong. ?Indeed, I find it more > natural to draw streams that way myself, and then reverse them. Yep, the only way to draw them facing downstream is to start at the source, and that's pretty hard. I usually find them where they join another river, so am probably contributing to the backward mapping. Anyone know of any applications that use the direction of streams? Steve ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Direction of flow, rivers and streams
On Wed, 28 Jul 2010, John Henderson wrote: > I note the wiki says that "Direction of the way should be downstream." > > Most streams I look at on OSM have been drawn uphill, and I've been > reversing the direction of ones I notice as wrong. Indeed, I find it > more natural to draw streams that way myself, and then reverse them. > > This is just to point out the direction issue to those who may have > missed it. > > John H > I know that seems eminently sensible but i live in a place so flat that streams do flow in either direction which way will I map those? I'm thoroughly guilty of starting the trace at the big end of the river and following it upstream off landsat imagery. If you wish to reverse the directions feel free but when some of the rivers hardly flow, I find the need to define the flow is little ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Direction of flow, rivers and streams
On Wed, Jul 28, 2010 at 1:39 PM, John Henderson wrote: > I note the wiki says that "Direction of the way should be downstream." > > Most streams I look at on OSM have been drawn uphill, and I've been > reversing the direction of ones I notice as wrong. Indeed, I find it more > natural to draw streams that way myself, and then reverse them. Yep, the only way to draw them facing downstream is to start at the source, and that's pretty hard. I usually find them where they join another river, so am probably contributing to the backward mapping. Anyone know of any applications that use the direction of streams? Steve ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Direction of flow, rivers and streams
On 28 July 2010 13:39, John Henderson wrote: > Most streams I look at on OSM have been drawn uphill, and I've been > reversing the direction of ones I notice as wrong. Indeed, I find it more > natural to draw streams that way myself, and then reverse them. Sometimes it's hard to figure out which way the water flows in creeks etc, that is unless you are mapping them to the mouth of that water way etc... ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
[talk-au] Direction of flow, rivers and streams
I note the wiki says that "Direction of the way should be downstream." Most streams I look at on OSM have been drawn uphill, and I've been reversing the direction of ones I notice as wrong. Indeed, I find it more natural to draw streams that way myself, and then reverse them. This is just to point out the direction issue to those who may have missed it. John H ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
