DEBLENDER

DEBLENDER

STScI • ACDSD • MAST • CASB • Documentation

Products

GSC

DSS

GSPC

Science

Publications

Data Access

Related Science

Missions

HST

GEMINI

VLT

NGST

Virtual Observatory

XMM

Facilities

Plate Scanning

COMPASS ooDB

Staff Pages

Last Updated Jan 2001

Purpose :

Detect blended objects in the image cutouts, computes basic parameters and other additional image features.

Procedure :

This is based upon the published ROE COSMOS deblender algorithm which connects a minimum number of pixels that are brighter than a threshold level above sky. Objects are separated by looking for segmentation at upper thresholds and using a gaussian fit to the slope to assign fractional pixels to each object. Once an object has been completed, its size, integrated density and moments are computed from which parameters such as x,y and shape are calculated.

Calling Sequence :

DEBLENDER imagefile: [/XRANGE=(lx,ux); [/YRANGE=(ly,uy); [/MINAREA=m] minimum connected pixels for object; [/THRESHOLDS=n] Detection threshold; {default is 16 levels from inventory threshold to saturation}; [/BASE_SIZE=] base memory size for cutouts whose dimensions nx * ny <= basesize (larger cutouts will be handled with decreased speed) {def="2048}"; [/MAX_CUTOUT_SIZE=] Max cutout size in 1 dim that will be deblended {def=256}; [/SMOOTH=n] Smooth image before deblend, with scale of n pixels from start point. n=0 nosmooth {def=0}; [/CENTER_WEIGHT=n] weight for central pixel in smoothing; [/STAR] Deblend all stars; [/BRIGHT_STAR=X] Deblend only stars with integrated density > X; [/NON_STAR] Deblend non stars {default}; [/DEFECT] Deblend defects {default}; [/UNCLASSIFIED] Deblend unclassified objects; [/ALL_CLASS] Deblend all objects, regardless of class; [/DECISION_TREE] Take class from decision tree classifier, Default take from final classification; [/FPA] Write FPA files {def}; [*********APPEND DISABLED DO NOT USE**********]; [/APPEND] Append FPA to previous FPA file {def noappend}; [/WEIGHT_AREA_FPA] Weight areas of deblends by FPA {default}; [/MAXZERO=x] Fraction 0.-1. of cutout pixels that can be zero; [/NEW] Create and write to new DID file; [/VERBOSE] Get extra printout of variables; [/DEBUG] Debug mode

History :

Version:1 Date: around 1990 Developers: Istvan Szapudi, Marc Postman, Brian Mclean, Vicki Laidler. This fortran main deblender program is mainly a wrapper for the deblend routines written in C by Istvan Szapudi and Marc Postman.

Version: 2 Date:Sep 97 Developer:G Hawkins. Extensive modifications for use with gsc II pipeline. Added new oop structure. Added most cld qualifiers. Corrected C code bug in smoothing. Added automatic smoothing for all cutouts larger than 100x100. Program now write FPA files. Added call to connect_object, which weeds out most objects duplicated in Inventory and Deblender. Added processing based on classification. Added most error codes.

Version: 3 Date:Feb 98 Developer: V Laidler. Modified to change handling of "found N objects, kept only 1" to be identical to "found only 1 object": ie, preserve inventory oop record rather than writing deblender info; and don't count such objects as "parents".

Availability :

GSSS AXP - yes
GSSS VAX - yes
PIXELS - no

History/Author :

Original Implementation - Istvan Szapudi
Integrated into pipeline - Brian McLean, G Hawkins