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<b>t.rast.accdetect</b> is designed to detect accumulation pattern in
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temporally accumulated space time raster datasets created by
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<a href="t.rast.accumulate.html">t.rast.accumulate</a>.
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This module expects a space time raster dataset as input that is the result
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of a <a href="t.rast.accumulate.html">t.rast.accumulate</a> run.
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The <b>start</b> time and the <b>end</b> time of the pattern detection
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process must be set, eg. <b>start="2000-03-01" end="2011-01-01"</b>.
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The <b>start</b> and <b>end</b> time do not need to be the same as for
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the accumulation run that produced the input space time raster dataset.
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In addition a <b>cycle</b>, eg. "8 months", can be specified, that
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defines after which time interval the accumulation pattern detection
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process restarts. The <b>offset</b> option specifies the time between
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two cycles that should be skipped, eg. "4 months". Please make sure
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that the <b>cycle</b> and <b>offset</b> options are same as in the
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accumulation process that produces the input space time raster dataset,
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otherwise the accumulation pattern detection will produce wrong
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The <b>minimum</b> and <b>maximum</b> values of the pattern detection
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process can be set, either by using space time raster datasets or
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by using fixed values for all raster cells and time steps.
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Using space time raster datasets allow to specify minimum and maximum
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values for each raster cell and each time step. For example, we want to
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detect the germination (minimum value) and harvesting (maximum value)
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dates for different crops in Germany using the growing-degree-day (GDD)
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method for several years. Different crops may grow in different raster
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cells and change with time because of crop rotation. Hence we need to
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specify different GDD germination/harvesting (minimum/maximum) values
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for different raster cells and different years.
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The raster maps that specifies the minimum and maximum values of the
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actual granule will be detected using the following temporal relations:
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equals, during, overlaps, overlapped and contains. First all maps with
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equal time stamps to the current granule of the input STRDS will be
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detected, the first minimum map and the first maximum map that were
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found are used as range definitions. If no equal maps are found then
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maps with a temporal during relation are detected, then maps that
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temporally overlap the actual granules, until maps are detected that
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have a temporal contain relation. If no maps are found or
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minimum/maximum STRDS are not set, then the <b>range</b> option is
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used, eg. <b>range=480,730</b>.
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The <b>base</b> name of of the generated maps must always be set.
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This module produces two output space time raster datasets. The
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<b>occurrence</b> output STRDS stores the time in days from the begin
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of a cycle for each raster cell and time step that has a value within
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the minimum and maximum definition. These values can be used to compute
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the duration of the recognized accumulation pattern. The
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<b>indicator</b> output STRDS uses three values, that can be set using
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the <b>staend</b> option, to mark raster cells with integer values that
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indicate the start, the intermediate state and the end of a
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accumulation pattern. As default specifies the value 1 the start, the
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value 2 the intermediate state and the value 3 the end of the
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accumulation pattern in a cycle.
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Please have a look at the <a href="t.rast.accumulate.html">t.rast.accumulate</a> example.
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<a href="t.rast.accumulate.html">t.rast.accumulate</a>,
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<a href="t.rast.aggregate.html">t.rast.aggregate</a>,
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<a href="t.rast.mapcalc.html">t.rast.mapcalc</a>,
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<a href="t.info.html">t.info</a>,
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<a href="r.series.accumulate.html">r.series.accumulate</a>,
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<a href="g.region.html">g.region</a>
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Sören Gebbert, Thünen Institute of Climate-Smart Agriculture
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<p><i>Last changed: $Date: 2014-11-26 14:30:48 +0100 (Wed, 26 Nov 2014) $</i>