[GRASS-user] harmonic analysis of time series

GRASS GRASS user
1

There is a new add-on module for GRASS 7 to perform harmonic analysis
of time series (HANTS), a kind of customized FFT, after Roerink et al
(2000). The original purpose was to reconstruct NDVI time series, but
it works with all kinds of time series that show periodicity. The
module is called r.hants.

Enjoy!

Markus M

2

Nice! Will give it a try. I’ve been using FFT transforms to help map agricultural areas using MODIS time series. So far I’ve been filtering the data using a simple procedure but I’ll now test to see if the hants filtering can improve agricultural area mapping.

Cheers
Daniel

···

On Sat, Jan 19, 2013 at 1:18 PM, Markus Metz <markus.metz.giswork@gmail.com> wrote:

There is a new add-on module for GRASS 7 to perform harmonic analysis
of time series (HANTS), a kind of customized FFT, after Roerink et al
(2000). The original purpose was to reconstruct NDVI time series, but
it works with all kinds of time series that show periodicity. The
module is called r.hants.

Enjoy!

Markus M

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3

On Saturday 19 of January 2013 16:18:59 Markus Metz wrote:

There is a new add-on module for GRASS 7 to perform harmonic analysis
of time series (HANTS), a kind of customized FFT, after Roerink et al
(2000). The original purpose was to reconstruct NDVI time series, but
it works with all kinds of time series that show periodicity. The
module is called r.hants.

Enjoy!

What a Great addition!!
Kudos Markus,

a one-way time-traveller,
Nikos

ps- can we also travel backwards in time with this? I would use it to
complete my never-ending project on MODIS time series? :D. I was checking
the possibilities 5 years ago for something like that. Looked, and still
looks, very complex to understand what's going on behind the scene.

4

Fourier series imply in their definition that the returning from the
spectral dimension is an unbounded retribution of harmonics in the
temporal dimension. In clear, the transform returns harmonics
applicable "forever" before and after, however, your temporal
constraint of origin is the realistic application of it...

On 26 January 2013 19:03, Nikos Alexandris <nik@nikosalexandris.net> wrote:

On Saturday 19 of January 2013 16:18:59 Markus Metz wrote:

There is a new add-on module for GRASS 7 to perform harmonic analysis
of time series (HANTS), a kind of customized FFT, after Roerink et al
(2000). The original purpose was to reconstruct NDVI time series, but
it works with all kinds of time series that show periodicity. The
module is called r.hants.

Enjoy!

What a Great addition!!
Kudos Markus,

a one-way time-traveller,
Nikos

ps- can we also travel backwards in time with this? I would use it to
complete my never-ending project on MODIS time series? :D. I was checking
the possibilities 5 years ago for something like that. Looked, and still
looks, very complex to understand what's going on behind the scene.
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