[GRASS-user] v.stream.* questions

[Rich Shepard]

On Fri, 4 Oct 2019, Micha Silver wrote:

> The v.stream.* modules all take vector maps as input.

Micha,

That's what the manual pages suggest.

> Maybe yes, but if this refers to the project that you've posted about
> recently, then you have a high resolution LIDAR-based DEM of the basin.
> These v.stream.* modules are intended to work with vector outputs from the
> r.stream.* modules.

I thought so.

> If you are going to ignore that and use a vector stream network from some
> other source, then be aware:
> 
> 1- This alternate stream network must be topologically correct
> 
> 2- Stream vector segments should all be in downstream direction (the
> outlet reach *must* be directed downstream).
> 
> 3- You might not be able to make use of the DEM for other analyses, since
> it won't match the stream network.

This answers all my questions. I've no idea how the vector river network
data were created. I've also decided that for the intended audience the
results of the v.stream.* are overkill.

Thanks very much,

Rich