Hi, well, I was just about to pull the trigger and upload the import wiki page and send the formal import plan email when I (possibly stupidly!) thought to myself 'better just check what really goes in the "ele" tag'... well, that opened a can of worms! Seems that although it is detailed on the wiki that it should be in the form of EGM96 in metres (https://wiki.openstreetmap.org/wiki/Key:ele). And what I currently have from the OS trig data is I believe OS ODN ( https://docs.os.uk/more-than-maps/a-guide-to-coordinate-systems-in-great-britain/ordnance-survey-coordinate-systems/ordnance-datum-newlyn ).
It seems there is a long-ish history debating what should go in 'ele' - for instance one thread with a number of other relevant references buried in it: https://community.openstreetmap.org/t/irish-mountains/65758/9 I guess I have a couple of questions: Q1. Is there a consensus in the UK as to what should be put in 'ele'. I have a feeling most if not all current OSM nodes (for peaks for instance as well as trigpoints) will be in ODN metres. Q2. Is there any problem with me adding elevations with three decimal place precision? That is the data I have, but it seems the majority (but by no means all) current node data is integer only. And a statement: S1. At a minimum I'd intend to put the ODN in 3 decimal point metres into the 'ele:local' tag, as also recommended on the 'ele' wiki page And an observation: I still see a few 'ele's with 'ft' in them - I'll see if I can add that to my list of things to potentially clean up on the way past... Right, well, I'm currently struggling to find a method to actually convert ODN -> EGM96 - I'll keep looking at that. If anybody just happens to have a tool, or PROJ/GDAL command or some R/sf code with appropriate EPSG codes...? I've got the OS data loaded as EPSG:7405 which gives me 'OSGB36 + ODN', but am struggling to get that into 'WGS84 + EGM96' if that makes sense. Oh, if anybody wants a visual preview of the data I now have a slippy map up and running: https://grahamwhaley.github.io/OSM_UK_trigpoints/web/index.html thanks, Graham On Tue, 16 Jun 2026 at 17:35, Graham Whaley <[email protected]> wrote: > Hi all, > thanks to everybody for the feedback and questions. I didn’t hear any > objections, so I’ll plough on with the work. I’ve written out most of the > wiki page (locally) and am preparing the official email to the list (as per > the import guidelines) to formally lay out details and kick off the 14 day > review period. I’ve been refining the code and am just tickling a slippy > map to show the current status of the data (HTML and JS not really my > thing, but I think I can hack something together with leaflet…). Once > things here are fairly stable I’ll load up the wiki page and send the > formal email. > > Many thanks, > Graham > > >
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