OpenStreetMap
Looking over my area, I am proud to say that there a ridiculous number of fresh water sources. Canada is renowned as possessing one of the largest supplies of natural fresh water in the world. My province does not buck that reputation - there are a tremendous number of bodies of water, both big and small, that serve to provide all of the water needs of the population. That’s the good part.
The bad part is that most of these water sources were added via the CanVec data available from the Department of Natural Resources. This is good topographical data, but it is not completely accurate. In one case, a fresh water source is itemized in that data with no corresponding information in the satellite data available through Bing. Another has a water source that is significantly different in shape from the aerial data. I am hesitant to delete the CanVec markings as they are based on professional surveys of te region. Still, the lack of any 1 to 1 consideration in it gives me pause. For egregious examples, my instinct is to plan a visit to the site - I can probably settle the matter fairly swiftly that way.
The other interesting variance in the CanVec data is that it does not indicate the type of any of the sources of water that it outlines. Which is it - a pond or a lake? A check around the Internet provides a ridiculous amount of referencing, discussion and argument as to what the difference between these two geographical items are. Some draw distinctions in terms of size, depth, movement or content while noting quite openly numerous examples that violate those criteria. Local knowledge in lieu of naming is likewise of limited use as a enormous water body in one place is a pond while another just a kilometer away at half the size is a lake.
To combat this, I have adopted the official naming scheme for water bodies as prescribed by the OpenStreetMap Wiki. Lakes are henceforth all bodies of water that are flowing (as in a stream or river) that are natural - that is, formed by local conditions independent of the influence of man. Ponds are artificial, man-made lakes that may now compose a portion of a regular waterway, but which is no less created either intentionally or otherwise.
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Камэнтар Vincent de Phily ад 10 Ліпень 2013 у 10:34
Water bodies are difficult to map because their shape changes quickly. Tidal water is the obvious example, but the convention of mapping the high water mark is fairly well established.
Lakes may seem static but they are not. In Ireland we have a lot of turloughs that can swell to hundreds of meters length in a matter of days, stay around for a few weeks or months, and disapear again. Even for an identical “fill factor”, the shape may be different from year to year. This is an extreme case, but all the lakes of the world probably fit between “static” and “turlough”.
So how do you map such a beast ? No one outline will be correct.
Камэнтар Adam Martin ад 11 Ліпень 2013 у 14:45
Thanks for the pointers, @Vincent de Phily.
I have a related question - what do you do in circumstances where the coastline and the administrative boundary have been merged?
Камэнтар Vincent de Phily ад 11 Ліпень 2013 у 16:17
I haven’t really formed an opinion on coastline vs boundary. I expect it differs legally from country to country. To me this looks awfully silly and makes me wish for county borders away from the coast, but I can understand the argument that only the country itself, not its constituent counties has sovereignty out in the see. To think that it I’m rowing between those islands I’m in Ireland but not in Mayo nor Connaght feels weird, but I haven’t argued against the established order so far.
Камэнтар pnorman ад 12 Ліпень 2013 у 06:09
Much of the CanVec water data in many regions is over 30 years old, I’d be bold in deleting it if you can’t see any signs.
Камэнтар Andrew_F_ ад 26 Люты 2014 у 09:47
The main difference between ponds and lakes that you can notice in satellite view is depth. Lakes are deeper, and generally (but not always) bigger. Lakes because they are deeper have little vegetation and the shores are rocky while ponds have lots of vegetation and the shoreline will have a greater percentage of grass and vegetation on it. There is a large number of ponds that could be called lakes or vice versa. I wouldn’t worry too much about it and usually will go with the actual name from the Newfoundland and Labrador Geographical Names Board by the Department of Environment & Conservation. Wetland info can be found here http://www.ducks.ca/learn-about-wetlands/what-wetland/
Камэнтар Adam Martin ад 26 Люты 2014 у 12:03
That is usually the sort of difference I note for ponds and lakes as well. For OSM, any natural body of water is a lake and any man-made body is a pond. That’s for that resource - it’ll certainly help!