v.what.strds.timestamp: add example (#331)

* Update v.what.strds.timestamp.html * Update grass7/vector/v.what.strds.timestamp/v.what.strds.timestamp.html Co-authored-by: Markus Neteler <neteler@gmail.com> * Update grass7/vector/v.what.strds.timestamp/v.what.strds.timestamp.html Co-authored-by: Markus Neteler <neteler@gmail.com> Co-authored-by: Markus Neteler <neteler@gmail.com>
OSGeo · Nov 15, 2020 · fc63266 · fc63266
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commit fc63266
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diff --git a/grass7/vector/v.what.strds.timestamp/v.what.strds.timestamp.html b/grass7/vector/v.what.strds.timestamp/v.what.strds.timestamp.html
@@ -20,7 +20,74 @@ <h2>NOTES</h2>
 
 <h2>EXAMPLE</h2>
 
-TBD
+This example is based on the MODIS LST raster time series sample dataset
+(mapset "modis_lst") available for the North Carolina sample location which
+can be downloaded from the
+<a href="https://grass.osgeo.org/download/data/">GRASS GIS website</a>.
+
+<div class="code"><pre>
+# Check time MODIS LST raster time series to sample
+t.rast.list LST_Day_monthly@modis_lst
+
+# Set computational region to first raster map of the time series
+g.region -up raster=MOD11B3.A2015001.h11v05.single_LST_Day_6km \
+    align=MOD11B3.A2015001.h11v05.single_LST_Day_6km
+
+# Create sampling points map with timestamp column for sampling time
+echo "cat,sampling_time,x,y
+1,2015-01-12,-125870.664090128,591821.149756026
+2,2015-02-01,77667.7974483332,571718.585653462
+3,2015-02-27,351565.233345769,481257.047191923
+4,2015-03-10,565154.976935513,375718.585653462
+5,2015-04-07,366642.156422692,277718.585653462
+6,2015-05-22,178180.617961154,363154.483089359
+7,2015-06-12,12334.464115,395821.149756026
+8,2016-03-04,112847.28462782,204846.790781667
+9,2016-05-12,311360.105140641,26436.5343714103
+10,2017-01-03,467154.976935513,8846.79078166676
+11,2018-01-01,600334.464115,129462.175397051
+12,2016-06-07,690796.002576538,262641.662576539
+13,2016-08-16,685770.361550897,441051.918986795
+14,2016-12-11,625462.669243205,594333.970268846" > sampling_points.txt
+
+# Import sampling points
+v.in.ascii in=sampling_points.txt out=sampling_points x=3 y=4 cat=1 \
+    columns='cat int, sampling_time date, x double precision, y double precision' \
+     separator="," skip=1
+
+# Assign LST values to sampling points at time of sampling 
+v.what.strds.timestamp input=sampling_points \
+    timestamp_column=sampling_time column=lst_at_sampling_time \
+    strds=LST_Day_monthly@modis_lst
+
+# Check result
+v.db.select sampling_points
+cat|sampling_time|x|y|lst_at_sampling_time
+1|2015-01-12|-125870.664090128|591821.149756026|13811
+2|2015-02-01|77667.7974483332|571718.585653462|13486
+3|2015-02-27|351565.233345769|481257.047191923|13793
+4|2015-03-10|565154.976935513|375718.585653462|14355
+5|2015-04-07|366642.156422692|277718.585653462|14565
+6|2015-05-22|178180.617961154|363154.483089359|14864
+7|2015-06-12|12334.464115|395821.149756026|15091
+8|2016-03-04|112847.28462782|204846.790781667|14641
+9|2016-05-12|311360.105140641|26436.5343714103|14982
+10|2017-01-03|467154.976935513|8846.79078166676|
+11|2018-01-01|600334.464115|129462.175397051|
+12|2016-06-07|690796.002576538|262641.662576539|15052
+13|2016-08-16|685770.361550897|441051.918986795|15052
+14|2016-12-11|625462.669243205|594333.970268846|13920
+
+# Check result for point with category 5
+r.what -n map=MOD11B3.A2015091.h11v05.single_LST_Day_6km@modis_lst \
+    coordinates=366642.156422692,277718.585653462
+
+# add extra column for LST in degree Celsius
+v.db.addcolumn map=sampling_points column="lst_celsius double precision"
+# rescale original MODIS LST to degree Celsius
+v.db.update map=sampling_points column="lst_celsius" query_column="lst_at_sampling_time * 0.02 - 273.15" 
+v.db.select sampling_points
+</pre></div>
 
 <h2>SEE ALSO</h2>
 <em>