[OSM-talk-ie] Water depth in lake

[John Whitmore]

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


> 
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> 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 <dan at post.com>
> > To: Discussion of OpenStreetMap in Ireland <talk-ie at openstreetmap.org>
> > 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?
> > 
> 
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