FEATURES

FEATURES

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COMPASS ooDB

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Last Updated Jan 2001

Purpose :

To compute spike and texture features to help the classifier separate objects into stars, galaxies, plate defects etc.

Procedure :

Read objects from OOP file detected by the inventory program and calculate four texture parameters for each object using the image cutouts. These are: 1) second angular moment, 2) contrast, and 3) entropy, all averaged over four directions (axis at 0, 45, 90, and 135 degrees) and 4) the range of the second angular moment (maximum in the four directions - minimum in the four directions). Texture uses a detection threshold below which pixels are not used in texture calculations for an object. Default is /didthreshobj, the same detection threshold used in inventory. Other choices are a multiple of the sky sigma (/sigmaobj=n) and an explicitly input user value (/defobj=n). Features then computes the likelihood that an object is a point source by looking for the presence of a diffraction spike. It does this by comparing the gradient of the image along the spike, which should be weak, with the gradient along the thin dimension of the spike, which should be strong. Texture features are calculated for every object in an OOP file, but spike calculations can be restricted to a limited magnitude range, or (in the future) to certain object classes. The features are written to an updated OOP file (default), or optionally to a new file with .FEA extension with the /FEA qualifier.

Calling Sequence :

FEATURES imagefile (do not include .VIM extension)

[/XRANGE=(lx,ux)]

[/YRANGE=(ly,uy)]

[/FEA] write features to FEA file instead of OOP file {def= write features to OOP file}

[/TEXT] create text file with features (not yet available)

[/DIDTHRESHOBJ] use same threshold for texture as inventory {def}

[/SIGMAOBJ=n] threshold in texture as multiple of sky sigma

[/DEFOBJ=n] in texture, user defined threshold n above sky level

[/SKYMODE=option] sky subtraction

Readoop (local sky read from CIM file) {default}
Derive (take sky map from SIM file, not yet available)
Map (user supplied sky map, not yet available)
Global (no sky subtraction)

[/SKY_VALUE=] user defined sky constant

[/BASE_SIZE=] base memory size for cutouts whose dimensions nx * ny <= basesize (larger cutouts will be handled with decreased speed) {def="2048}"

[/WIDTH=] width array for spikes {def= -2, -1, 0, 1, 2}

[/RADIUS=] spike length qualifier {def=1}

[/WEIGHT_RADIUS] use weighted moments in object radius for spikes (applied only when /CUTOUTS qualifier is also selected)

[/INTENSITY] use intensity instead of density

[/FAINT_LIMIT=] cutoff magnitude for spikes calculation

[/BRIGHT_LIMIT=] cutoff magnitude for spikes calculation

[/LIST=(i1,i2,...)] process only listed object numbers in OOP file (not yet available)

[/CUTOUTS] (not yet available)

[/INCOMPLETE] process incomplete objects (not yet available)

[/DBDINPUT] read input from deblender .DBD file instead of OOP {not yet available}

[/FPA] use fpa file with input from deblender (not yet available)

[/INCLUDE.TEMPLATE=] These four qualifiers allow spikes to be

[/INCLUDE.MATCH=] calculated only for objects with the

[/EXCLUDE.TEMPLATE=] specified bit pattern in the

[/EXCLUDE.MATCH=] object_status_flag (not yet available)

[/COMMENT="string"] comment for DID file

[/VERBOSE]

[/NOANNOTATE]

Availability :

GSSS AXP - yes
GSSS VAX - yes
PIXELS - no

History/Author :

Original Implementation - Spikes code: Vicki Laidler - Texture code: Andrea Zacchei June - Aug 96. Spikes code modified by George Hawkins for new OOP file structure and to work with the new pipeline. Also, new code written to interface the texture subroutine with the new pipeline.