Problems to use v.what.vect in GRASS7

Question

I have problems to use the function v.what.vect and I'm not sure what is the issue. I have a simple forest polygon and try to determine if a point is in the forest or not.

# check the output of the feature nature
v.db.select nature col=landuse where="cat<5"
# function returns
landuse
forest
forest
forest
forest
# add column to points
v.db.addcolumn map=points col="landuse varchar(50)"
# use function v.what.vect
v.what.vect map=points column=landuse query_map=nature query_column=landuse
# function returns
Finding nearest features ...
 100%
 100%
Update vector attribute...
 100%
2696 categories - no nearest feature found
v.distance complete. 2696 records updated.

For me its looks like everything worked fine, just the that the result 0 is wired. Any idea what went wrong or how to check it?

---

EDIT

I checked again the notes of the grass manual:

In case of a multipoint input map map, with several points having the same category number, it can happen, that the query result is NULL, if the same category number falls into different query_map polygons.

But that is also given:

v.db.select points col=cat where="cat<5"
# function output:
cat
1
2
3
4
5

Answer 1

The problem is that the two features are not matching in the 3rd dimension!

A quick look at the manual give the explanation:

In case that one or both input vector maps are 3D, features need to touch also in the 3rd dimension (z coordinate) in order to transfer attributes.

And the check:

v.info -g nature
# check the top and the bottom
top=0.000000
bottom=0.000000

v.info -g points
# 3rd dimension is given
top=474.388580
bottom=205.511824