Timeline for Determine if points fall upstream or downstream from a point on a line (river)
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
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| Jan 27, 2014 at 8:21 | comment | added | simpleuser001 | Indeed, didn't notice that example handled only one direction (i usually handle both directions ) | |
| Jan 24, 2014 at 16:10 | comment | added | whuber | @simplexio You're on the right track, but this is more than an issue of topology: the topology can be perfectly consistent while having all directions reversed. In such cases this solution will work without failure or any warning messages but it will produce incorrect results. | |
| Jan 24, 2014 at 7:46 | comment | added | simpleuser001 | I assume that @whuber means network topology cleaning. Yes, it is hard to fix network perfectly, getting it good enough is easier. | |
| Jan 23, 2014 at 18:25 | comment | added | whuber | It appears this solution assumes the river coordinates are stored in a consistent order (from their 'start') in every reach of the river. Ensuring that is the case actually is the hardest part of this question! | |
| Jan 23, 2014 at 17:04 | comment | added | sckott | Thanks so much @Zbynek for the thorough answer. I will try this out and see if it helps | |
| Jan 23, 2014 at 12:49 | history | edited | Zbynek | CC BY-SA 3.0 |
added 14 characters in body
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| Jan 23, 2014 at 12:45 | comment | added | simpleuser001 | You could use something similiar to this : blog.cleverelephant.ca/2010/07/network-walking-in-postgis.html , to solve correct order of linestring from start point ( river exit to ocean or dam ) | |
| Jan 23, 2014 at 12:35 | history | answered | Zbynek | CC BY-SA 3.0 |