t.sample(1)

NAME
t.sample - Samples the input space time dataset(s) with a sample space time dataset and print the result to stdout.

KEYWORDS
temporal, sampling, time

SYNOPSIS
t.sample
t.sample --help
t.sample [-cs] inputs=name[,name,...] sample=name [intype=name] [samtype=name] [method=name[,name,...]] [separator=character] [--help] [--verbose] [--quiet] [--ui]

  Flags:

-c
    Print the column names as first row

-s
    Check for spatial topological overlap

--help
    Print usage summary

--verbose
    Verbose module output

--quiet
    Quiet module output

--ui
    Force launching GUI dialog

  Parameters:

inputs=name[,name,...] [required]
    Name of the input space time datasets

sample=name [required]
    Name of the sample space time dataset

intype=name
    Type of the input space time dataset
    Options: strds, stvds, str3ds
    Default: strds

samtype=name
    Type of the sample space time dataset
    Options: strds, stvds, str3ds
    Default: strds

method=name[,name,...]
    The method to be used for sampling the input dataset
    Options: start, during, overlap, contain, equal, follows, precedes
    Default: during,overlap,contain,equal

separator=character
    Do not use "," as this char is reserved to list several map ids in a sample granule
    Field separator between output columns, default is tabular " | "
    Default: pipe

DESCRIPTION
The purpose of t.sample is to compute and to show spatio-temporal relations between space time datasets of different type. Several input space time datasets are sampled by a sample space time dataset using temporal topological relations. The types of the input space time datasets and the type of the sample space time dataset can be different.

This module is useful to analyze temporal relationships between space time datasets using temporal topology. The flag -s enables a spatio-temporal topology, so that only spatio-temporal related map layers of space time datasets are considered in the analysis.

NOTES
The temporal relation start means that the start time of an input map layer is temporally located in an interval of a sample map layer.

The textual output at the command line shows the names of the maps, start and end time as well as the interval length in days and the temporal distance from begin in days.

The default separator is the pipe symbol.

Temporal gaps, if present, in the input and sampling space time datasets will be used in the sampling process. Gaps have no map name, instead None is printed.

EXAMPLE
In the examples below we create a space time raster dataset A and a space time vector dataset P that have different temporal layouts and number of map layers. The space time vector dataset contains a gap, that will be used in the sampling process.

We use t.sample to inspect the topological relations between the time stamped map layers in A and P.

# Set an appropriate region
g.region s=0 n=80 w=0 e=120 b=0 t=50 res=10 res3=10 -p3
# Generate the raster map layer
r.mapcalc expression="a1 = rand(0, 550)"
r.mapcalc expression="a2 = rand(0, 450)"
r.mapcalc expression="a3 = rand(0, 320)"
r.mapcalc expression="a4 = rand(0, 510)"
r.mapcalc expression="a5 = rand(0, 300)"
r.mapcalc expression="a6 = rand(0, 650)"
# Generate the vector map layer
v.random -z output=pnts1 n=20 zmin=0 zmax=100 column=height
v.random -z output=pnts2 n=20 zmin=0 zmax=100 column=height
n1=`g.tempfile pid=1 -d`
n2=`g.tempfile pid=2 -d`
cat > "${n1}" << EOF
a1
a2
a3
a4
a5
a6
EOF
cat > "${n2}" << EOF
pnts1|2001-01-01|2001-03-01
pnts2|2001-05-01|2001-07-01
EOF
# Register the maps in new space time datasets
t.create type=strds temporaltype=absolute output=A \
    title="A test with raster input files" descr="A test with raster input files"
t.create type=stvds temporaltype=absolute output=P \
    title="A test with vector input files" descr="A test with vector input files"
t.register type=raster -i input=A file="${n1}" start="2001-01-01" increment="1 months"
# Raster map layer in A
t.rast.list A
name|mapset|start_time|end_time
a1|PERMANENT|2001-01-01 00:00:00|2001-02-01 00:00:00
a2|PERMANENT|2001-02-01 00:00:00|2001-03-01 00:00:00
a3|PERMANENT|2001-03-01 00:00:00|2001-04-01 00:00:00
a4|PERMANENT|2001-04-01 00:00:00|2001-05-01 00:00:00
a5|PERMANENT|2001-05-01 00:00:00|2001-06-01 00:00:00
a6|PERMANENT|2001-06-01 00:00:00|2001-07-01 00:00:00
t.register type=vector input=P file="${n2}"
# Vector map layer in P
t.vect.list P
name|layer|mapset|start_time|end_time
pnts1|None|PERMANENT|2001-01-01 00:00:00|2001-03-01 00:00:00
pnts2|None|PERMANENT|2001-05-01 00:00:00|2001-07-01 00:00:00
# Start time of maps in A located in maps in P
t.sample method=start input=A samtype=stvds sample=P -c
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|a1@PERMANENT,a2@PERMANENT|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|a3@PERMANENT,a4@PERMANENT|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|a5@PERMANENT,a6@PERMANENT|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0
# P contains A
t.sample method=contain input=A samtype=stvds sample=P -c
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|a1@PERMANENT,a2@PERMANENT|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|a3@PERMANENT,a4@PERMANENT|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|a5@PERMANENT,a6@PERMANENT|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0
# A during P
t.sample method=during intype=stvds input=P samtype=strds sample=A -c
A@PERMANENT|P@PERMANENT|start_time|end_time|interval_length|distance_from_begin
a1@PERMANENT|pnts1@PERMANENT|2001-01-01 00:00:00|2001-02-01 00:00:00|31.0|0.0
a2@PERMANENT|pnts1@PERMANENT|2001-02-01 00:00:00|2001-03-01 00:00:00|28.0|31.0
a3@PERMANENT|None|2001-03-01 00:00:00|2001-04-01 00:00:00|31.0|59.0
a4@PERMANENT|None|2001-04-01 00:00:00|2001-05-01 00:00:00|30.0|90.0
a5@PERMANENT|pnts2@PERMANENT|2001-05-01 00:00:00|2001-06-01 00:00:00|31.0|120.0
a6@PERMANENT|pnts2@PERMANENT|2001-06-01 00:00:00|2001-07-01 00:00:00|30.0|151.0
# No Overlapping
t.sample method=overlap input=A samtype=stvds sample=P -cs
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|None|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|None|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|None|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0
t.sample method=precedes input=A samtype=stvds sample=P -c
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|a3@PERMANENT|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|a5@PERMANENT|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|None|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0
t.sample method=follows  input=A samtype=stvds sample=P -c
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|None|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|a2@PERMANENT|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|a4@PERMANENT|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0
t.sample method=precedes,follows input=A samtype=stvds sample=P -c
P@PERMANENT|A@PERMANENT|start_time|end_time|interval_length|distance_from_begin
pnts1@PERMANENT|a3@PERMANENT|2001-01-01 00:00:00|2001-03-01 00:00:00|59.0|0.0
None|a5@PERMANENT,a2@PERMANENT|2001-03-01 00:00:00|2001-05-01 00:00:00|61.0|59.0
pnts2@PERMANENT|a4@PERMANENT|2001-05-01 00:00:00|2001-07-01 00:00:00|61.0|120.0

SEE ALSO
t.create, t.info

AUTHOR
Sören Gebbert, Thünen Institute of Climate-Smart Agriculture

SOURCE CODE

Available at: t.sample source code (history)

Accessed: Monday May 11 17:55:47 2026

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