I have posted an extensive entry on my geofictician blog to discuss the OGF Topo Layer, including the new procedures to support topo going forward. Rather than replicate that long write-up here, please visit my blog to read all about it.
https://blog.geofictician.net/index.php/2022/03/05/the-state-of-the-ogf-topo-layer/
Thank you to all the mappers who have contributed to topo so far, and looking forward to lots more and much-improved topo in the future!
Comments welcome below, rather than at the blog (where they’re also welcome but people are less likely to see them).
Comment from SwissCrusader on 10 March 2022 at 08:48
Many thanks Luciano for uploading my topo layer. As far as I understand, the layer is generated by an interpolation between anything having an “ele” tag. Also, it doesn’t seem to be a problem if the countour=elevation tags are not closed. Which means, it works well with mountains with simple curves like every 25 or even 50 meters, but as long as the terrain is flatter there can be glitches. For example all the places where I have let’s say a curve at a base of a hill at ele=100 and several smaller hills at ele=125, without any other curves in between, it generated a glitch, I should have added more curves in between like 105, 110, 115 - or maybe even single dots with ele tag like on summits, rivers, etc. - in order to limit the number of small hills between each step (sorry if not clear, can’t find the right words to explain). This is what I’ll try to do the next time if I’ve ever got time to work on it again.
Comment from Luciano on 10 March 2022 at 12:45
@SwissCrusader
Your understanding is correct. You need more “density” of contours for flatter areas. For extremely flat areas that I’ve done, I have contour lines every 1 meter. And there is no harm and some help to the interpolation process if you use multiple lines with the same ele= value, too.
I recommend you download some of the degree squares I’ve drawn for my territory Makaska, which is quite flat in parts. You can see how the contour density prevents glitches (including “filler” contours - diagonal lines - across lake surfaces for example).
https://ogfsrtm.rent-a-planet.com/osm-squares/zone-makaska/
Comment from Luciano on 10 March 2022 at 13:05
I also wanted to be sure you understood, when updating your contours, please download the existing “osm-squares” for your zone from my ogfsrtm server and edit those files. I have added tagging to those files.
Your zone’s contour files are downloadable from here:
https://ogfsrtm.rent-a-planet.com/osm-squares/zone-alved/
