On Sat, May 30, 2015 at 05:47:18PM +0100, Colm Moore wrote: > Hi, > > This is potentially life or death information, so I'm not sure if it is > approved for OSM. > > Different datums (measurements) are used: > http://en.wikipedia.org/wiki/Chart_datum However, with lakes, you might find > novel effects on water depth, like flows from higher rivers / lakes, > reservoirs, currents, etc. > > Colm
Thanks for all the responses to my message and it's certainly food for thought. I was actually talking with a boat person about it and they were saying that it wasn't simple at all. If I did have a depth at a position I'd also have to get my hands on the official water level at that time. He wasn't sure who keeps that info but basically all water depths are measured relative to a set water level. If the current level is below or above that then you have to adjust all figures. Guess it's something I've never thought about before, but sure now I know. Thanks again. John > > --------------------------------------------------------------------------------------------------------------- > Never doubt that a small group of thoughtful, committed citizens can change > the world. Indeed, it is the only thing that ever has. Margaret Mead > > > > Message: 2 > > Date: Fri, 29 May 2015 15:10:51 +0100 > > From: Daniel Cussen <[email protected]> > > To: Discussion of OpenStreetMap in Ireland <[email protected]> > > Subject: Re: [OSM-talk-ie] Water depth in lake > > > > > 3) Depth is normally displayed on maps as mean tide level (I think), > > are you taking into account tide (off shore) or recent rain for rivers > > to calculate the actual depth below mean level? > > > > > _______________________________________________ > Talk-ie mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-ie _______________________________________________ Talk-ie mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk-ie
