|
After reading your first post, I tried
on a small contrived sample of polygons and points. I moved the
polygon centroids to "un-natural" positions, to try to get the
wrong values uploaded to the points attrib table. The bottom line
was that v.what.vect seemed to work fine.
Can you share a sample of your data?
On 03/17/2014 06:42 PM, Tyler Smith wrote:
Hi again,
I'm still struggling with how to add the attribute values from a polygon map to the table for a point map. I've tried v.what.vect, as documented in my previous message. Any suggestions would be appreciated!
Thanks,
Tyler
On March 14, 2014 2:29:49 PM EDT, Tyler Smith <[email protected]> wrote:
Hello,
I have a vector point map, amelanchier, and a vector polygon map,
hwSoil. I tried to extract data from hwSoil for each point in
amelanchier as follows:
v.db.addcol map=amelanchier columns="T_GRAVEL double precision"
v.what.vect vector=amelanchier qvector=hwSoil qcolumn=T_GRAVEL \
column=T_GRAVEL
I've repeated this process for a few dozen columns.
However, I'm not getting the right values. If I investigate a single
point using d.what.vect, notice that the values for T_GRAVEL in
amelanchier is not the same as that in hwSoil. I've included some of
the other columns that also show small discrepancies.
d.what.vect -t
82:13:46.5625W(E) 36:23:46.875N(N)
hwSoil in PERMANENT Area
Size - Sq Meters: 10269585820.955 Hectares: 1026958.582
Acres: 2537669.922 Sq Miles: 3965.1093
Layer: 1
category: 4608
driver: sqlite
database: /home/tws/grassdata/hwSoilsDB/PERMANENT/sqlite.db
table: hwsdData
key column: MU_GLOBAL
ADD_PROP : 0
T_GRAVEL : 10
T_SAND : 49
T_SILT : 27
T_CLAY : 24
T_USDA_TEX_CLASS : 10
T_REF_BULK_DENSITY : 1.4
T_BULK_DENSITY : 1.4
amelanchier in PERMANENT Point
Layer: 1
category: 668
driver: sqlite
database: /home/tws/grassdata/hwSoilsDB/PERMANENT/sqlite.db
table: amelanchier
key column: cat
cat : 668
accession : 10-217
species : ARB
country : USA
state : TN
y : 36.3966
x : -82.22792
ADD_PROP : 0
T_GRAVEL : 11
T_SAND : 44
T_SILT : 33
T_CLAY : 23
T_USDA_TEX_CLASS : 9
T_REF_BULK_DENSITY : 1.39
T_BULK_DENSITY : 1.35
What have I done wrong here? Is v.what.vect doing some kind of
interpolation? I've attached a small section of my map, so you can see
that the individual points are placed within large polygons, so I
don't think there's a chance that I'm clicking in a different polygon
than the one the point is in.
Thanks for your help!
Tyler
------------------------------------------------------------------------
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
This mail was received via Mail-SeCure System.
--
Micha Silver
GIS Consultant, Arava Development Co.
http://www.surfaces.co.il 052-3665918
|
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
