Should river lines be mapped through lakes, estuaries, gulfs, and other large water bodies?

[Minh_Nguyen (Minh Nguyễn)]

@ezekielf

It also seems like virtual waterway lines outside the natural=coastline in estuaries, gulfs, and bays are more questionable than those in large lakes.

I previously floated the idea of mapping a channel through certain linear gulfs:

Gulf of Mexico object / Rendering of Large Seas

This point-placed label may look fine by the standard of avoiding overlapping text, but the Gulf of California is actually a great example of why some mappers probably think it’s beneficial to map some seas as areas. Conventionally, whenever a body of water is long and narrow, a map strings out the label along its “centerline”, spacing out the letters to cover the entire length: [Pergamon World Atlas © 1967 Pergamon World Press & P.W.N.] OSM Americana does render line-placed labels for some …

However, I didn’t consider the implication of also extending every inflow to meet this channel. I could see that being problematic, in that the majority of a very short stream could lie within the gulf, causing an unsophisticated renderer to place its label misleadingly inside the gulf.

As others have indicated, there’s a difference between a linear representation of an elongated body of water (which some renderers can generate automatically) and a waterway channel that happens to be submerged beneath the body of water (i.e., a dammed river through a reservoir). In the latter case, the thalweg is valuable additional information that renderers can use. The geometry is nonarbitrary and not quite the same thing as a waterway=fairway.

Gulf of Mexico object / Rendering of Large Seas

In practice, it often is an eyeballed centerline, but some mappers try to make it represent the thalweg. Either way, we can think of it as an abstraction. The “centerline” of a V-shaped valley is another example of an abstraction. In that case, thankfully no one expects mappers to delineate the valley floor based on precisely where it meets the foothills. As a sidenote, mapping the thalweg is especially useful for rivers that run through reservoirs, as in the Lake Mead example earlier. An algo…