Gradient pattern analysis: Difference between revisions

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Besides <math>G_{A}</math> other measurements (called ''gradient moments'') can be calculated from the gradient lattice.<ref name=rosa03>Rosa, R.R.; Campos, M.R.; Ramos, F.M.; Vijaykumar, N.L.; Fujiwara, S.; Sato, T. ''Braz. J. Phys.'' '''33''', 605 (2003).</ref> Considering the sets of local norms and phases as discrete compact groups, spatially distributed in a square lattice, the gradient moments have the basic property of being globally invariant (for rotation and modulation).

The primary research on gradient lattices applied to characterize [[Wave turbulence|weak wave turbulence]] from X-ray images of [http://solar.physics.montana.edu/canfield/papers/EAA.2023.pdf solar active regions] was developed in the Department of Astronomy at [[University of Maryland, College Park]], USA. A key line of research on GPA's algorithms and applications has been developed at Lab for Computing and Applied Mathematics (LAC) at [[National Institute for Space Research]] ([[INPE]]) in Brazil.

== Relation to other methods ==

When GPA is conjugated with [[wavelet analysis]], then the method is called ''Gradient spectral analysis'' (GSA), usually applied to short time series analysis.<ref name=rosa08>Rosa, R.R. et al., ''Advances in Space Research'' '''42''', 844 (2008), {{doi|10.1016/j.asr.2007.08.015}}.</ref>

== Code ==

Recently, a new implementation of the method was done. This was called GPA++, a C/C++ implementation of GPA. It is a Linux app that can run both under a Text based console or in a Graphical User Interface like KDE or GNOME. We developed it in Slackware 13

for KDE and this is the recommend platform to run it. GPA++ can be downloaded from [https://sourceforge.net/projects/gpaplusplus/ Sourceforge.net].

== References ==