Get ID for each single v.to.points point in GRASS?

Question

How do I get for each v.to.points point an ID in the database (DB).

So far I splited the line (each 10m) but it returns only one DB entry for each original line.

v.db.select line
cat|Id|Name
1|1|Line 1
2|2|Line 2

# split the lines every 10m
v.to.points in=line out=line_points dmax=10

# check the result
v.db.select line_points
cat|Id|Name
1|1|Line 1
2|2|Line 2

Each point should have its own DB entry. The result should be:

v.db.select line_points
cat|Id|Name
1|1|Line 1
2|1|Line 1
3|2|Line 2
4|2|Line 2

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Workaround: So far my workaround is, to export (v.out.ogr) the points as shape and import (v.in.ogr) it again. Then each point has his own ID. But there must be a smarter way to do that!

Answer 1

v.to.points creates a vector with 2 layers. With the second layer you should have unique ID.

You should thus simply specify the second layer with v.db.select or write into a new feature with v.category.

# return unique IDs
v.db.select line_points layer=2

# change layer 2 to 1
v.category input=line_points output=line_points2 option=chlayer layer=2,1

For more details see v.to.points description:

v.to.points creates points along input lines. The output is a vector with 2 layers. Layer 1 holds the category and attributes of the input lines; all points created along the same line have the same category, equal to the category of that line. In layer 2 each point has it's unique category; other attributes stored in layer 2 are lcat - the category of the input line and along - the distance from line's start.