[GRASS-user] r.mapcalc: compare two maps [RESOLVED]

[Laurent C.]

2017-03-30 12:00 GMT-06:00 Rich Shepard <rshepard at appl-ecosys.com>:
> On Thu, 30 Mar 2017, Laurent C. wrote:
>
>> If you want to 'open' the culvert, you'll have to cut through the road.
>> You can do this with r.carve, for example.
>
>
>   Certainly worth doing. The r.carve manual page requires as input a vector
> map containing streams. Having only two points (culvert inlet and outlet), I
> suppose the idea is to create a stream between those two points.
>
>   Would the process be to use v.edit on a copy (called 'stream') of the
> culvert point map to generate a straight line between the two points? That
> would provide the vector input r.carve wants.

Rich,

You can create a new vector map and create a line that link the two points.
However, r.carve will interpolate the elevation between the start
point and the end point.
If you culvert invert have a lower elevation, this will not show up.
But considering the amount of simplification you're already applying,
it could be acceptable.

Regards,
Laurent