1t.rast.what(1)              GRASS GIS User's Manual             t.rast.what(1)
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NAME

6       t.rast.what   -  Sample  a space time raster dataset at specific vector
7       point coordinates and write the output to stdout using  different  lay‐
8       outs
9

KEYWORDS

11       temporal, sampling, raster, time
12

SYNOPSIS

14       t.rast.what
15       t.rast.what --help
16       t.rast.what     [-niv]      [points=name]      [coordinates=east,north]
17       strds=name   [output=name]    [where=sql_query]     [null_value=string]
18       [separator=character]    [order=string[,string,...]]    [layout=string]
19       [nprocs=integer]    [--overwrite]   [--help]   [--verbose]    [--quiet]
20       [--ui]
21
22   Flags:
23       -n
24           Output header row
25
26       -i
27           Use stdin as input and ignore coordinates and point option
28
29       -v
30           Show the category for vector points map
31
32       --overwrite
33           Allow output files to overwrite existing files
34
35       --help
36           Print usage summary
37
38       --verbose
39           Verbose module output
40
41       --quiet
42           Quiet module output
43
44       --ui
45           Force launching GUI dialog
46
47   Parameters:
48       points=name
49           Name of input vector map
50           Or data source for direct OGR access
51
52       coordinates=east,north
53           Comma separated list of coordinates
54
55       strds=name [required]
56           Name of the input space time raster dataset
57
58       output=name
59           Name for the output file or "-" in case stdout should be used
60           Default: -
61
62       where=sql_query
63           WHERE  conditions  of SQL statement without ’where’ keyword used in
64           the temporal GIS framework
65           Example: start_time > ’2001-01-01 12:30:00’
66
67       null_value=string
68           String representing NULL value
69
70       separator=character
71           Field separator
72           Special characters: pipe, comma, space, tab, newline
73           Default: pipe
74
75       order=string[,string,...]
76           Sort the maps by category
77           Options: id,  name,  creator,  mapset,   creation_time,   modifica‐
78           tion_time,   start_time,   end_time,   north,  south,  west,  east,
79           min,  max
80           Default: start_time
81
82       layout=string
83           The layout of the output. One point per row (row),  one  point  per
84           column (col), all timsteps in one row (timerow)
85           Options: row,  col,  timerow
86           Default: row
87
88       nprocs=integer
89           Number of r.what processes to run in parallel
90           Default: 1
91

DESCRIPTION

93       t.rast.what  is  designed  to sample space time raster datasets at spe‐
94       cific point coordinates using r.what internally. The output  of  r.what
95       is  transformed to different output layouts.  The output layouts can be
96       specified using the layout option.
97
98       Three layouts can be specified:
99
100row - Row order, one vector sample point value per row
101
102col - Column order, create a  column  for  each  vector  sample
103               point of a single time step/raster layer
104
105timerow  - Time order, create a column for each time step, this
106               order is the original r.what output,  except  that  the  column
107               names are the timestamps
108       Please have a look at the example to see the supported layouts.
109
110       This  module  is  designed to run several instances of r.what to sample
111       subsets of a space time raster dataset in parallel. Several  intermedi‐
112       ate  text  files  will be created that are merged into a single file at
113       the end of the processing.
114
115       Coordinates can be provided as vector map using the points option or as
116       comma separated coordinate list with the coordinates option.
117
118       An  output  file can be specified using the output option.  Stdout will
119       be used if no output is specified or if the output  option  is  set  to
120       "-".
121

EXAMPLES

123   Data preparation
124       In  the  following  examples we sample a space time raster dataset that
125       contains 4 raster map layers. First we create the STRDS  that  will  be
126       sampled with t.rast.what.
127       g.region s=0 n=80 w=0 e=120 b=0 t=50 res=10
128       # Generate data
129       r.mapcalc expression="a_1 = 1" -s
130       r.mapcalc expression="a_2 = 2" -s
131       r.mapcalc expression="a_3 = 3" -s
132       r.mapcalc expression="a_4 = 4" -s
133       t.create type=strds output=A title="A test" descr="A test"
134       t.register -i type=raster input=A maps=a_1,a_2,a_3,a_4 \
135           start=’1990-01-01’ increment="1 month"
136
137   Example 1
138       The first approach uses text coordinates as input and stdout as output,
139       the layout is one coordinate(point per column:
140       t.rast.what strds=A coordinates="115,36,79,45" layout=col -n
141       start|end|115.0000000000;36.0000000000|79.0000000000;45.0000000000
142       1990-01-01 00:00:00|1990-02-01 00:00:00|1|1
143       1990-02-01 00:00:00|1990-03-01 00:00:00|2|2
144       1990-03-01 00:00:00|1990-04-01 00:00:00|3|3
145       1990-04-01 00:00:00|1990-05-01 00:00:00|4|4
146
147   Example 2
148       A vector map layer can be used as input to sample the STRDS. All  three
149       available layouts are demonstrated using the vector map for sampling.
150       # First create the vector map layer based on random points
151       v.random output=points n=3 seed=1
152       # Row layout using a text file as output
153       t.rast.what strds=A points=points output=result.txt layout=row -n
154       cat result.txt
155       115.0043586274|36.3593955783|1990-01-01 00:00:00|1990-02-01 00:00:00|1
156       115.0043586274|36.3593955783|1990-02-01 00:00:00|1990-03-01 00:00:00|2
157       115.0043586274|36.3593955783|1990-03-01 00:00:00|1990-04-01 00:00:00|3
158       115.0043586274|36.3593955783|1990-04-01 00:00:00|1990-05-01 00:00:00|4
159       79.6816763826|45.2391522853|1990-01-01 00:00:00|1990-02-01 00:00:00|1
160       79.6816763826|45.2391522853|1990-02-01 00:00:00|1990-03-01 00:00:00|2
161       79.6816763826|45.2391522853|1990-03-01 00:00:00|1990-04-01 00:00:00|3
162       79.6816763826|45.2391522853|1990-04-01 00:00:00|1990-05-01 00:00:00|4
163       97.4892579600|79.2347263950|1990-01-01 00:00:00|1990-02-01 00:00:00|1
164       97.4892579600|79.2347263950|1990-02-01 00:00:00|1990-03-01 00:00:00|2
165       97.4892579600|79.2347263950|1990-03-01 00:00:00|1990-04-01 00:00:00|3
166       97.4892579600|79.2347263950|1990-04-01 00:00:00|1990-05-01 00:00:00|4
167       # Column layout order using stdout as output
168       t.rast.what strds=A points=points layout=col -n
169       start|end|115.0043586274;36.3593955783|79.6816763826;45.2391522853|97.4892579600;79.2347263950
170       1990-01-01 00:00:00|1990-02-01 00:00:00|1|1|1
171       1990-02-01 00:00:00|1990-03-01 00:00:00|2|2|2
172       1990-03-01 00:00:00|1990-04-01 00:00:00|3|3|3
173       1990-04-01 00:00:00|1990-05-01 00:00:00|4|4|4
174       # Timerow layout, one time series per row
175       # using the where statement to select a subset of the STRDS
176       # and stdout as output
177       t.rast.what strds=A points=points \
178           where="start_time >= ’1990-03-01’" layout=timerow -n
179       x|y|1990-03-01 00:00:00;1990-04-01 00:00:00|1990-04-01 00:00:00;1990-05-01 00:00:00
180       115.004358627375|36.3593955782903|3|4
181       79.681676382576|45.2391522852909|3|4
182       97.4892579600048|79.2347263950131|3|4
183

SEE ALSO

185         g.region,  r.mask  r.neighbors,  r.what, t.info, t.rast.aggregate.ds,
186       t.rast.extract, v.what.strds
187

AUTHOR

189       Sören Gebbert, Thünen Institute of Climate-Smart Agriculture
190

SOURCE CODE

192       Available at: t.rast.what source code (history)
193
194       Accessed: Saturday Jan 21 21:17:05 2023
195
196       Main index | Temporal index | Topics index | Keywords index | Graphical
197       index | Full index
198
199       © 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
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203GRASS 8.2.1                                                     t.rast.what(1)
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