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
(attachments)
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 <tyler@plantarum.ca> 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
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Thanks, Micha.
I figured it out. I had incorrectly connected the database table to the map. The table had multiple key values for each polygon.
The dataset is the Harmonized World Soils Database. I've updated the wiki with correct instructions. I think they're correct, at least.
http://grasswiki.osgeo.org/wiki/Global_datasets#Harmonized_World_Soil_Database_.28HWSD_Database.29
Best,
Tyler
On March 17, 2014 3:08:37 PM EDT, Micha Silver <micha@arava.co.il> wrote:
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 <tyler@plantarum.ca> 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
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-- Micha Silver GIS Consultant, Arava Development Co.
http://www.surfaces.co.il 052-3665918