[GRASS-user] Create and analyse scatter plots against two rasters

GRASS GRASS user
1

Dear Grass community,

our objective is to monitor the soil moisture index (SMI) of small catchments in Mali and the impact of irrigation structures.

We have taken note of the many articles on this subject and as it looks now we can utilize the huge Landsat archive available on the web.

With the Landsat bands and the GRASS modules we’re able to produce rasters for the surface temperature and for the NDVI values. To determine th SMI value it’s necessary to do a regression analyses (the so called ‘wet edge’ and ‘dry edge’ in a scatter plot between the two mentioned rasters. How can we achieve this?

Thanks

Huub Munstege
Bamako
Rép. du Mali

2

* Huub Munstege <hmunstege@yahoo.com> [2015-06-11 08:12:51 +0000]:

Dear Grass community, our objective is to monitor the soil moisture
index (SMI) of small catchments in Mali and the impact of irrigation
structures. We have taken note of the many articles on this subject
and as it looks now we can utilize the huge Landsat archive available
on the web. With the Landsat bands and the GRASS modules we're able
to produce rasters for the surface temperature

For LST from Landsat 8, you might find this interesting:
<https://github.com/NikosAlexandris/i.landsat8.swlst&gt;\. Plan is to
move it in the addons repository after more testing (anyone willing to
test is welcome, feedback is essential)

and for the NDVI
values. To determine th SMI value it's necessary to do a regression
analyses (the so called 'wet edge' and 'dry edge' in a scatter plot
between the two mentioned rasters. How can we achieve this?

Have a look at

- d.correlate
- r.series
- r.regression.line (and maybe r.regression.multi)
- r.regression.series

though I am pretty sure you'll love the t.* modules for time seris
analyes:

- http://grass.osgeo.org/grass70/manuals/temporalintro.html /
  http://www.geostat-course.org/system/files/Presentation_0.pdf

- http://ncsu-osgeorel.github.io/grass-temporal-workshop/

- http://grasswiki.osgeo.org/wiki/Temporal_data_processing

Of course, you can also use R to do the work for it and get results/maps
back in GRASS for further processing.

Kind regards, Nikos