DynamicDetectionTask¶
DynamicDetectionTask detects sources on an image with a dynamic threshold.
Processing summary¶
DynamicDetectionTask runs this sequence of operations:
Detects sources using a lower threshold than normal in order to identify good sky regions.
Performs forced PSF photometry on identified sky regions.
Sets threshold so that the standard deviation of measurements matches median estimated error using PSF flux measurements and estimated errors.
Python API summary¶
from lsst.meas.algorithms.dynamicDetection import DynamicDetectionTask
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class
DynamicDetectionTask(*args, **kwargs) Detection of sources on an image with a dynamic threshold
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- attributeconfig
Access configuration fields and retargetable subtasks.
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method
run(table, exposure, doSmooth=True, sigma=None, clearMask=True, expId=None, background=None) Detect sources and return catalog(s) of detections
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See also
See the DynamicDetectionTask API reference for complete details.
Retargetable subtasks¶
background¶
Background re-estimation; ignored if reEstimateBackground false
skyObjects¶
- Default
- Field type
Generate sky objects.
tempLocalBackground¶
A local (small-scale), temporary background estimation step run between detecting above-threshold regions and detecting the peaks within them; used to avoid detecting spuerious peaks in the wings.
tempWideBackground¶
A wide (large-scale) background estimation and removal before footprint and peak detection. It is added back into the image after detection. The purpose is to suppress very large footprints (e.g., from large artifacts) that the deblender may choke on.
Configuration fields¶
adjustBackground¶
Fiddle factor to add to the background; debugging only
bisectFactor¶
Factor by which to increase thresholds in brightMaskFractionMax loop.
brightGrowFactor¶
Factor by which to grow the footprints of sources detected in the “bright” detections stage (want this to be large to mask wings of bright sources).
brightMaskFractionMax¶
Maximum allowed fraction of masked pixes from the “bright” detection stage (to mask regions unsuitable for sky sourcess). If this fraction is exeeded, the detection threshold for this stage will be increased by bisectFactor until the fraction of masked pixels drops below this threshold.
brightMultiplier¶
Multiplier to apply to the prelimThresholdFactor for the “bright” detections stage (want this to be large to only detect the brightest sources).
brightNegFactor¶
Factor by which to multiply the threshold for the negative polatiry detections for the “bright” detections stage (this needs to be fairly low given the nature of the negative polarity detections in the very large positive polarity threshold).
combinedGrow¶
Grow all footprints at the same time? This allows disconnected footprints to merge.
doBackgroundTweak¶
Tweak background level so median PSF flux of sky objects is zero?
doBrightPrelimDetection¶
Do initial bright detection pass where footprints are grown by brightGrowFactor?
doTempLocalBackground¶
Enable temporary local background subtraction? (see tempLocalBackground)
doTempWideBackground¶
Do temporary wide (large-scale) background subtraction before footprint detection?
excludeMaskPlanes¶
Mask planes to exclude when detecting sources.
includeThresholdMultiplier¶
- Default
1.0- Field type
- Range
[0.0,inf)
Multiplier on thresholdValue for whether a source is included in the output catalog. For example, thresholdValue=5, includeThresholdMultiplier=10, thresholdType=’pixel_stdev’ results in a catalog of sources at >50 sigma with the detection mask and footprints including pixels >5 sigma.
isotropicGrow¶
Grow pixels as isotropically as possible? If False, use a Manhattan metric instead.
minFractionSources¶
Minimum fraction of the requested number of sky sources for dynamic detection to be considered a success. If the number of good sky sources identified falls below this threshold, a NoWorkFound error is raised so that this dataId is no longer considered in downstream processing.
minPixels¶
- Default
1- Field type
- Range
[0,inf)
detected sources with fewer than the specified number of pixels will be ignored
nPeaksMaxSimple¶
The maximum number of peaks in a Footprint before trying to replace its peaks using the temporary local background
nSigmaForKernel¶
Multiple of PSF RMS size to use for convolution kernel bounding box size; note that this is not a half-size. The size will be rounded up to the nearest odd integer
nSigmaToGrow¶
Grow detections by nSigmaToGrow * [PSF RMS width]; if 0 then do not grow
prelimNegMultiplier¶
Multiplier for the negative (relative to positive) polarity detections threshold to use for first pass (to find sky objects).
prelimThresholdFactor¶
Factor by which to multiply the main detection threshold (thresholdValue) to use for first pass (to find sky objects).
reEstimateBackground¶
Estimate the background again after final source detection?
returnOriginalFootprints¶
Grow detections to set the image mask bits, but return the original (not-grown) footprints
statsMask¶
Mask planes to ignore when calculating statistics of image (for thresholdType=stdev)
thresholdPolarity¶
- Default
'positive'- Field type
- Choices
'positive'detect only positive sources
'negative'detect only negative sources
'both'detect both positive and negative sources
Specifies whether to detect positive, or negative sources, or both.
thresholdType¶
- Default
'pixel_stdev'- Field type
- Choices
'variance'threshold applied to image variance
'stdev'threshold applied to image std deviation
'value'threshold applied to image value
'pixel_stdev'threshold applied to per-pixel std deviation
Specifies the meaning of thresholdValue.
thresholdValue¶
- Default
5.0- Field type
- Range
[0.0,inf)
Threshold for detecting footprints; exact meaning and units depend on thresholdType.