[GRASS-user] Problems getting unique categories with v.category

[Eric Patton]

Hi,

I have created a point vector from a coastline using v.to.points:

v.to.points input=CanCoast_Shoreline  type=line
output=CanCoast_Shoreline_points
use=vertex --v

This works fine, and the next thing I want to do is upload raster slope
values from a DEM to the attribute table of the points vector using
v.what.rast, but I get tons of warnings like these:

WARNING: Multiple points (12) of category 16, value set to 'NULL'

I assume this is telling me the points have duplicate categories?

So to get around this, I tried recreating the points, this time without an
attribute table, using v.to.points -t, then adding the table and categories
manually:

v.to.points input=CanCoast_Shoreline  type=line
output=CanCoast_Shoreline_points
use=vertex -t --v --o
v.db.addtable map=CanCoast_Shoreline_points columns="Slope_percent integer"
v.category input=CanCoast_Shoreline_points option=add
output=CanCoast_Shoreline_points_with_cat

But running v.what.rast still gives me the same error as before.

I ran v.categories in report mode to see what is going on:

v.category input=CanCoast_Shoreline_points_with_cat option=report
Layer/table: 1/CanCoast_Shoreline_points_with_cat
type       count        min        max
point     105427          1       1692
line           0          0          0
boundary       0          0          0
centroid       0          0          0
area           0          0          0
face           0          0          0
kernel         0          0          0
all       105427          1       1692
Layer: 2
type       count        min        max
point     105427          1     105427
line           0          0          0
boundary       0          0          0
centroid       0          0          0
area           0          0          0
face           0          0          0
kernel         0          0          0
all       105427          1     105427

Where did the two layers come from? I thought v.to.points -t *wasn't*
supposed to make an attribute table. And the fact that the 'max' value
reported above is '1692' seems to be a hangover from the line features they
were created from.

In this case, I don't care about the IDs or categories of the lines the
points originated from; I want unique categories for the 105427 points that
were made so I can then successfully run v.what.rast and upload my DEM
slope values.

It's been a while since I've used these tools, so I'm a little rusty. Is
there a way to do this?


~ Eric.
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