t.sample(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💖 t.sample — GRASS GIS User's Manual, man section 1 💖

okay bestie, buckle up 🎀 this is t.sample(1) from the GRASS GIS User's Manual, and it's lowkey one of the most satisfying little tools in the temporal toolbox. it samples your space time datasets and just… tells you what's up. no cap.

🌸 NAME 🌸

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

like, that's the whole vibe. it prints to stdout. it does not gatekeep. 💅

🦋 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. yes queen, header row, we love a labelled table 👑
  • -s — Check for spatial topological overlap. turns the temporal vibe check into a full spatio-temporal vibe check 💀
  • --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 💜

So the whole point of t.sample is to compute and to show spatio-temporal relations between space time datasets of different type. You feed it several input space time datasets, and they get sampled by a sample space time dataset using temporal topological relations. and here's the cute part — the types of the input space time datasets and the type of the sample space time dataset can totally be different. mismatch is allowed. it's giving inclusivity. 🫶

This module is useful to analyze temporal relationships between space time datasets using temporal topology. And the -s flag enables a spatio-temporal topology, so that only spatio-temporal related map layers of space time datasets are considered in the analysis. so if you want the spatial receipts too, add the -s, bestie.

🌈 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. so many numbers, so organized. 😭

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. yes, None is the main character when there's nothing there 🙈

🔥 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)" -s
r.mapcalc expression="a2 = rand(0, 450)" -s
r.mapcalc expression="a3 = rand(0, 320)" -s
r.mapcalc expression="a4 = rand(0, 510)" -s
r.mapcalc expression="a5 = rand(0, 300)" -s
r.mapcalc expression="a6 = rand(0, 650)" -s
# 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

look at those tables. absolutely ate. 🧚✨

⭐ 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: Saturday Jan 17 05:41:53 2026

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

k that's the whole page bestie 🫶 this was GRASS GIS 8.4.2, and the manual got accessed on Saturday Jan 17 05:41:53 2026 — remember that date, it's giving historic. now go sample something and slay 💅✨🌈

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