[GRASS-user] How can I locate points on a river?

I'm trying to identify specific points on the centerline of a river channel
by "river mile" , that is, points along a path at specified distances from
a starting point — not at regular intervals. Any suggestions how I might
go about this?

have a look at

https://grass.osgeo.org/grass82/manuals/addons/v.fixed.segmentpoints.html

for inspiration to create an input file for v.segment.

kind regards
Helmut

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OSGeo charter member