[GRASS-user] weird results from v.distance's to_angle

[Hamish]

Moritz wrote:
> While I'm not sure which of the to_angle descriptions I
> prefer (in your version it is not unambiguously clear where
> the angle is measured as I image that the 'to' feature is a
> line, not a line segment) 

However we word it, I expect adding a small graphic to the help
page is ultimately going to do the best job of explaining it.


> Here would be my go for both of them:
> 
> "to_along;distance to the nearest point on 'from' feature
> along linear feature, measured from 'start' point of that
> linear feature;"

sounds fine. (it really is from the start node of that line not the
start of that line segment, right?) maybe add a note about
v.build.polylines to the help page?

> "to_angle;angle of linear feature at the point nearest to
> point/centroid in 'from' map, counterclockwise from positive
> x axis, in radians, which is between -PI and PI inclusive;"

one of my goals was to have it be a brief description (goal < 60 chars!)
not a full paragraph, which is why I tried to remove as many
words as possible without letting it get too ambiguous.
so:
 * "point/centroid in " isn't strictly needed
 * "positive x axis" -> "+x axis"
 * counterclockwise -> CCW
 * "which is " -> ""
 * In this context Pi is a proper name not a C macro or acronym, so
   the "I" is lowercased.

otherwise '--help' on the command line looks crappy with the line-wrap.
perhaps extending the indentation code could help that, but the art of
concise technical writing is always good to practice. :-)


the main bug was that it's not the angle of the line _to_ the nearest
point, it's the angle _of the line_ at the nearest point. as long as that's
clear+correct I'm not too worried about the exact wording of it, have fun.


cheers,
Hamish