Veronica Andreo:
Don't know exactly which parameters you would like to extract from your time series, Nikos, but if helpful, what I did was to use a combination of r.hants and temporal modules to get some phenological indicators such as, number of cycles per year,...
Nikos Alexandris:
Vero, Is the number of cycles per year in the Wiki as well? Going through, last time, I think I didn't grasp that. Can you pin-point? It's exactly what we need at the moment.
Veronica Andreo:
Yes, maybe it is not well explained, but it is here: https://grasswiki.osgeo.org/wiki/Temporal_data_processing#Filling_and_reconstructing_time_series_data_with_gaps_-_HANTS and also in the manual under "NOTES" https://grass.osgeo.org/grass70/manuals/addons/r.hants.html The idea is, once you are happy with the result of hants, you ask for amplitude outputs and with those amplitude maps (you'll have one map per frequency) you run r.series method=max_raster. This will give you the most important frequency (according to amplitude value of that frequency) in each pixel. If the result is that the most important frequency is 0, then you have one cycle per year (that, if you use a base period of one year of course). Hope it is clearer now :)
Yes. It was even before -- just me read through quickly. r.hants is awesome! We have 24 Landsat 8 derived EVI2 maps (2 for each month) for one year. Clouds and Water surfaces removed. Another set of "relatively normalised images, using `i.histo.match` is also ready. We really need to "fix" `i.histo.match` to crunch floats directly. The resulting ranges worry me a bit -- I just followed the "old" way as discussed some years ago in a relevant thread (floats > integers > histo-matching > floats). Anyhow, I am testing the following: for NF in 4 5 6 7 8 ;do r.hants file=evi2_maps nf=$NF fet=0.05 dod=3 base_period=24 suffix=_hants_nf_$NF amplitude=amplitude_hants_nf_$NF phase=phase_hants_nf_$NF ;done (thinking loudly... it would be super-nice to have `t.rast.hants`) Not sure about `dod`. Perhaps it should also follow a patten like 3 4 5 6 and 7 for the above? for NF in 5 6 7 8 ; do t.rast.series evi2_hants_nf_$NF method=max_raster output=dominant_frequencies_hants_nf_$NF --o "Dominant" frequencies 0, 1, 2 and 3 appear to be within the areas of our interest (agricultural surfaces). Very good. And convincing. Yet I am learning to interpret this correctly. And the "phase" as well. Reminds math studies, years ago. As I am working this out in a remote workstation, it's a bit annoying not to be able to play an animation directly. The GUI runs fine, though slow, of course (via ssh -CY). Awesome to have all this in our fingertips :-) Cheers, Nikos [rest deleted] _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
