View source for plaid

{{DavinciWiki_Glossary|Plaid is column- and row-correlated band-independent noise in [[THEMIS]] IR images with a width on the order of 30 pixels.  It is most evident in [[decorrelation stretch]] images where a multi-color plaid pattern can be seen overlaying the data.
 
The <i>row-correlated component</i> of plaid is caused by electronic noise in the instrument compounded by artifacts created by the convolution steps in the [[destripe]] process.  Voltage fluctuations in the instrument electronics manifest themselves as increased or decreased signal over a row as the detector array is read out and stored in memory.  These fluctuations are both positive and negative  and follow a binomial distribution centered at zero.  [[destripe]] accurately identifies line-to-line noise and spatially smears the effects over a small (15 pixel) range.  The result is that the data retains a low-pass filtered version of the original line-to-line noise.  
 
The <i>column-correlated component</i> of plaid is caused by leftover variations across the samples of the detector that was not removed by the instrument response function.  These variations were also spatially convolved by [[destripe]] and also follow the same binomial distribution as the row-correlated plaid component.
 
[[thm.deplaid]] is used to remove this line correlated noise.  It utilizes knowledge about the statistics of the noise and separation between row- and column-correlated information and band-correlated information such as surface features.

An example image is shown below.

[[Image:nodeplaid.png]]}}

[[category:Glossary]]