[GRASS-user] Questions on TGRASS; t.rast.gapfill , GRASS 71

Thu Feb 5 10:23:15 PST 2015

Hi
I am trying to use the module "t.rast.gapfill" to fill the gaps in my
temporal datasets. I have couple of doubts on getting my tasks done.

I am using GRASS 71 svn, latest.

##Q1:

In my temporal data , there are multiple continuous gaps. In this case, I
am not getting the interpolated results. Please check the below work flow:

*r.mapcalc expr="map1 = 1" --or.mapcalc expr="map2 = 3" --or.mapcalc
expr="map3 = 5" --or.mapcalc expr="map4 = 7" --or.mapcalc expr="map5 = 9"
--ot.register type=raster maps=map1 start=2012-08-20 end=2012-08-21
--ot.register type=raster maps=map2 start=2012-08-22 end=2012-08-23
--ot.register type=raster maps=map3 start=2012-08-25 end=2012-08-26
--ot.register type=raster maps=map4 start=2012-08-29 end=2012-08-30
--ot.register type=raster maps=map5 start=2012-09-03 end=2012-09-04
--ot.create type=strds temporaltype=absolute output=mapT1 title="test for
all the gaps filled together" description="test for all the gaps filled
together"t.register type=raster input=mapT1 maps=map1,map2,map3,map4,map5
--ot.rast.list input=mapT1 columns=name,start_time,min,maxt.rast.list
input=mapT1 method=gran*
*id|name|mapset|start_time|end_time|interval_length|distance_from_begin*
*map1 at testtgrass|map1|testtgrass|2012-08-20 00:00:00|2012-08-21
00:00:00|1.0|0.0*
*None|None|None|2012-08-21 00:00:00|2012-08-22 00:00:00|1.0|1.0*
*map2 at testtgrass|map2|testtgrass|2012-08-22 00:00:00|2012-08-23
00:00:00|1.0|2.0*
*None|None|None|2012-08-23 00:00:00|2012-08-24 00:00:00|1.0|3.0*
*None|None|None|2012-08-24 00:00:00|2012-08-25 00:00:00|1.0|4.0*
*map3 at testtgrass|map3|testtgrass|2012-08-25 00:00:00|2012-08-26
00:00:00|1.0|5.0*
*None|None|None|2012-08-26 00:00:00|2012-08-27 00:00:00|1.0|6.0*
*None|None|None|2012-08-27 00:00:00|2012-08-28 00:00:00|1.0|7.0*
*None|None|None|2012-08-28 00:00:00|2012-08-29 00:00:00|1.0|8.0*
*map4 at testtgrass|map4|testtgrass|2012-08-29 00:00:00|2012-08-30
00:00:00|1.0|9.0*
*None|None|None|2012-08-30 00:00:00|2012-08-31 00:00:00|1.0|10.0*
*None|None|None|2012-08-31 00:00:00|2012-09-01 00:00:00|1.0|11.0*
*None|None|None|2012-09-01 00:00:00|2012-09-02 00:00:00|1.0|12.0*
*None|None|None|2012-09-02 00:00:00|2012-09-03 00:00:00|1.0|13.0*
*map5 at testtgrass|map5|testtgrass|2012-09-03 00:00:00|2012-09-04
00:00:00|1.0|14.0*

# Doing the gapfill:

*t.rast.gapfill input=mapT1 base=gapt.rast.list input=mapT1 method=gran*
*id|name|mapset|start_time|end_time|interval_length|distance_from_begin*
*map1 at testtgrass|map1|testtgrass|2012-08-20 00:00:00|2012-08-21
00:00:00|1.0|0.0*
*gap_10 at testtgrass|gap_10|testtgrass|2012-08-21 00:00:00|2012-08-22
00:00:00|1.0|1.0*
*map2 at testtgrass|map2|testtgrass|2012-08-22 00:00:00|2012-08-23
00:00:00|1.0|2.0*
*gap_11 at testtgrass|gap_11|testtgrass|2012-08-23 00:00:00|2012-08-24
00:00:00|1.0|3.0*
*gap_11 at testtgrass|gap_11|testtgrass|2012-08-24 00:00:00|2012-08-25
00:00:00|1.0|4.0*
*map3 at testtgrass|map3|testtgrass|2012-08-25 00:00:00|2012-08-26
00:00:00|1.0|5.0*
*gap_12 at testtgrass|gap_12|testtgrass|2012-08-26 00:00:00|2012-08-27
00:00:00|1.0|6.0*
*gap_12 at testtgrass|gap_12|testtgrass|2012-08-27 00:00:00|2012-08-28
00:00:00|1.0|7.0*
*gap_12 at testtgrass|gap_12|testtgrass|2012-08-28 00:00:00|2012-08-29
00:00:00|1.0|8.0*
*map4 at testtgrass|map4|testtgrass|2012-08-29 00:00:00|2012-08-30
00:00:00|1.0|9.0*
*gap_13 at testtgrass|gap_13|testtgrass|2012-08-30 00:00:00|2012-08-31
00:00:00|1.0|10.0*
*gap_13 at testtgrass|gap_13|testtgrass|2012-08-31 00:00:00|2012-09-01
00:00:00|1.0|11.0*
*gap_13 at testtgrass|gap_13|testtgrass|2012-09-01 00:00:00|2012-09-02
00:00:00|1.0|12.0*
*gap_13 at testtgrass|gap_13|testtgrass|2012-09-02 00:00:00|2012-09-03
00:00:00|1.0|13.0*
*map5 at testtgrass|map5|testtgrass|2012-09-03 00:00:00|2012-09-04
00:00:00|1.0|14.0*

For example; between *2012-08-29 and **2012-09-03 *there are 4 days of gap,
but the gap filling is providing the same image at all the 4 gaps. It seems
to be generating only one image between two valid temporal images, no
matter how long the gap is!!

So is the gap filling will work only for *one gap* between *2 valid
temporal images*?

###2.

When I try to do gap fill with the "where" condition, I am getting no
results in some cases.
For example when I try:

t.rast.gapfill input=mapT1 where="start_time = '2012-08-21 00:00:00'"
base=gap
*No gaps found*

OR when I try;

*t.rast.gapfill input=mapT1 where="start_time > '2012-08-20 00:00:00'"
base=gap*

It misses the first gap and fills the other gap, see below:

*t.rast.list input=mapT1 method=gran*
*id|name|mapset|start_time|end_time|interval_length|distance_from_begin*
*map1 at testtgrass|map1|testtgrass|2012-08-20 00:00:00|2012-08-21
00:00:00|1.0|0.0*
*None|None|None|2012-08-21 00:00:00|2012-08-22 00:00:00|1.0|1.0*
*map2 at testtgrass|map2|testtgrass|2012-08-22 00:00:00|2012-08-23
00:00:00|1.0|2.0*
*gap_8 at testtgrass|gap_8|testtgrass|2012-08-23 00:00:00|2012-08-24
00:00:00|1.0|3.0*
*gap_8 at testtgrass|gap_8|testtgrass|2012-08-24 00:00:00|2012-08-25
00:00:00|1.0|4.0*
*map3 at testtgrass|map3|testtgrass|2012-08-25 00:00:00|2012-08-26
00:00:00|1.0|5.0*
*gap_9 at testtgrass|gap_9|testtgrass|2012-08-26 00:00:00|2012-08-27
00:00:00|1.0|6.0*
*gap_9 at testtgrass|gap_9|testtgrass|2012-08-27 00:00:00|2012-08-28
00:00:00|1.0|7.0*
*gap_9 at testtgrass|gap_9|testtgrass|2012-08-28 00:00:00|2012-08-29
00:00:00|1.0|8.0*
*map4 at testtgrass|map4|testtgrass|2012-08-29 00:00:00|2012-08-30
00:00:00|1.0|9.0*
*gap_10 at testtgrass|gap_10|testtgrass|2012-08-30 00:00:00|2012-08-31
00:00:00|1.0|10.0*
*gap_10 at testtgrass|gap_10|testtgrass|2012-08-31 00:00:00|2012-09-01
00:00:00|1.0|11.0*
*gap_10 at testtgrass|gap_10|testtgrass|2012-09-01 00:00:00|2012-09-02
00:00:00|1.0|12.0*
*gap_10 at testtgrass|gap_10|testtgrass|2012-09-02 00:00:00|2012-09-03
00:00:00|1.0|13.0*
*map5 at testtgrass|map5|testtgrass|2012-09-03 00:00:00|2012-09-04
00:00:00|1.0|14.0*

Here it works if I give one day before the actual valid temporal image in
the where condition. So if I give *"start_time > '2012-08-19 00:00:00'", *the
first gap will also get filled*.* But It would be great if we can query on
the missing dates/time.

All suggestions welcome.

Thanks in advance

Regards

Sajid

--

http://gis.cri.fmach.it/pareeth/

Fondazione Edmund Mach
Research and Innovation Centre
GIS and Remote Sensing Unit/Limnology and River ecology
Via Mach 1, 38010 San Michele all'Adige (TN) - Italy
Phone +39 461 615 669
spareeth at gmail.com
sajid.pareeth at fmach.it
skype: spareeth
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