[GRASS-user] v.what.vect confusion

[Tyler Smith]

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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