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lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask Class Reference

Assemble a coadded image from a set of warps (coadded temporary exposures). More...

Inheritance diagram for lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask:
lsst.pipe.tasks.assembleCoadd.SafeClipAssembleCoaddTask

Public Member Functions

def __init__
 Initialize the task. More...
 
def run
 Assemble a coadd from a set of Warps. More...
 
def getTempExpRefList
 Generate list data references corresponding to warped exposures that lie within the patch to be coadded. More...
 
def getBackgroundReferenceScaler
 Construct an image scaler for the background reference frame. More...
 
def prepareInputs
 Prepare the input warps for coaddition by measuring the weight for each warp and the scaling for the photometric zero point. More...
 
def backgroundMatching
 Perform background matching on the prepared inputs. More...
 
def assemble
 Assemble a coadd from input warps. More...
 
def assembleMetadata
 Set the metadata for the coadd. More...
 
def assembleSubregion
 Assemble the coadd for a sub-region. More...
 
def addBackgroundMatchingMetadata
 Add metadata from the background matching to the coadd. More...
 
def readBrightObjectMasks
 
def setBrightObjectMasks
 

Public Attributes

 brightObjectBitmask
 
 warpType
 

Static Public Attributes

 ConfigClass = AssembleCoaddConfig
 

Detailed Description

Assemble a coadded image from a set of warps (coadded temporary exposures).

Contents

Description

We want to assemble a coadded image from a set of Warps (also called coadded temporary exposures or coaddTempExps. Each input Warp covers a patch on the sky and corresponds to a single run/visit/exposure of the covered patch. We provide the task with a list of Warps (selectDataList) from which it selects Warps that cover the specified patch (pointed at by dataRef). Each Warp that goes into a coadd will typically have an independent photometric zero-point. Therefore, we must scale each Warp to set it to a common photometric zeropoint. By default, each Warp has backgrounds and hence will require config.doMatchBackgrounds=True. When background matching is enabled, the task may be configured to automatically select a reference exposure (config.autoReference=True). If this is not done, we require that the input dataRef provides access to a Warp (dataset type coaddName + 'Coadd' + warpType + 'Warp') which is used as the reference exposure. WarpType may be one of 'direct' or 'psfMatched', and the boolean configs config.makeDirect and config.makePsfMatched set which of the warp types will be coadded. The coadd is computed as a mean with optional outlier rejection. Criteria for outlier rejection are set in AssembleCoaddConfig. Finally, Warps can have bad 'NaN' pixels which received no input from the source calExps. We interpolate over these bad (NaN) pixels.

AssembleCoaddTask uses several sub-tasks. These are

ScaleZeroPointTask
create and use an imageScaler object to scale the photometric zeropoint for each Warp
MatchBackgroundsTask
match background in a Warp to a reference exposure (and select the reference exposure if one is not provided).
InterpImageTask
interpolate across bad pixels (NaN) in the final coadd

You can retarget these subtasks if you wish.

Task initialization

Initialize the task. Create the interpImage, matchBackgrounds, & scaleZeroPoint subtasks.

Invoking the Task

Assemble a coadd from a set of Warps. Coadd a set of Warps. Compute weights to be applied to each Warp and find scalings to match the photometric zeropoint to a reference Warp. Optionally, match backgrounds across Warps if the background has not already been removed. Assemble the Warps using assemble. Interpolate over NaNs and optionally write the coadd to disk. Return the coadded exposure.

Parameters
[in]dataRef,:Data reference defining the patch for coaddition and the reference Warp (if config.autoReference=False). Used to access the following data products:
  • [in] self.config.coaddName + "Coadd_skyMap"
  • [in] self.config.coaddName + "Coadd_ + <warpType> + "Warp" (optionally) - [out] self.config.coaddName + "Coadd"
[in]selectDataList[in],:List of data references to Warps. Data to be coadded will be selected from this list based on overlap with the patch defined by dataRef.
Returns
a pipeBase.Struct with fields:
  • coaddExposure: coadded exposure

Configuration parameters

See AssembleCoaddConfig_

Debug variables

The command line task interface supports a flag -d to import debug.py from your PYTHONPATH; see baseDebug for more about debug.py files. AssembleCoaddTask has no debug variables of its own. Some of the subtasks may support debug variables. See the documetation for the subtasks for further information.

A complete example of using AssembleCoaddTask

AssembleCoaddTask assembles a set of warped images into a coadded image. The AssembleCoaddTask can be invoked by running assembleCoadd.py with the flag '–legacyCoadd'. Usage of assembleCoadd.py expects a data reference to the tract patch and filter to be coadded (specified using '–id = [KEY=VALUE1[^VALUE2[^VALUE3...] [KEY=VALUE1[^VALUE2[^VALUE3...] ...]]') along with a list of Warps to attempt to coadd (specified using '–selectId [KEY=VALUE1[^VALUE2[^VALUE3...] [KEY=VALUE1[^VALUE2[^VALUE3...] ...]]'). Only the Warps that cover the specified tract and patch will be coadded. A list of the available optional arguments can be obtained by calling assembleCoadd.py with the –help command line argument:

1 assembleCoadd.py --help

To demonstrate usage of the AssembleCoaddTask in the larger context of multi-band processing, we will generate the HSC-I & -R band coadds from HSC engineering test data provided in the ci_hsc package. To begin, assuming that the lsst stack has been already set up, we must set up the obs_subaru and ci_hsc packages. This defines the environment variable $CI_HSC_DIR and points at the location of the package. The raw HSC data live in the $CI_HSC_DIR/raw directory. To begin assembling the coadds, we must first

processCcd
process the individual ccds in $CI_HSC_RAW to produce calibrated exposures
makeSkyMap
create a skymap that covers the area of the sky present in the raw exposures
makeCoaddTempExp
warp the individual calibrated exposures to the tangent plane of the coadd

We can perform all of these steps by running

1 $CI_HSC_DIR scons warp-903986 warp-904014 warp-903990 warp-904010 warp-903988

This will produce warped exposures for each visit. To coadd the warped data, we call assembleCoadd.py as follows:

1 assembleCoadd.py --legacyCoadd $CI_HSC_DIR/DATA --id patch=5,4 tract=0 filter=HSC-I --selectId visit=903986 ccd=16 --selectId visit=903986 ccd=22 --selectId visit=903986 ccd=23 --selectId visit=903986 ccd=100 --selectId visit=904014 ccd=1 --selectId visit=904014 ccd=6 --selectId visit=904014 ccd=12 --selectId visit=903990 ccd=18 --selectId visit=903990 ccd=25 --selectId visit=904010 ccd=4 --selectId visit=904010 ccd=10 --selectId visit=904010 ccd=100 --selectId visit=903988 ccd=16 --selectId visit=903988 ccd=17 --selectId visit=903988 ccd=23 --selectId visit=903988 ccd=24

that will process the HSC-I band data. The results are written in $CI_HSC_DIR/DATA/deepCoadd-results/HSC-I You may also choose to run:

1 scons warp-903334 warp-903336 warp-903338 warp-903342 warp-903344 warp-903346
2 assembleCoadd.py --legacyCoadd $CI_HSC_DIR/DATA --id patch=5,4 tract=0 filter=HSC-R --selectId visit=903334 ccd=16 --selectId visit=903334 ccd=22 --selectId visit=903334 ccd=23 --selectId visit=903334 ccd=100 --selectId visit=903336 ccd=17 --selectId visit=903336 ccd=24 --selectId visit=903338 ccd=18 --selectId visit=903338 ccd=25 --selectId visit=903342 ccd=4 --selectId visit=903342 ccd=10 --selectId visit=903342 ccd=100 --selectId visit=903344 ccd=0 --selectId visit=903344 ccd=5 --selectId visit=903344 ccd=11 --selectId visit=903346 ccd=1 --selectId visit=903346 ccd=6 --selectId visit=903346 ccd=12

to generate the coadd for the HSC-R band if you are interested in following multiBand Coadd processing as discussed in High-level Overview of Multi-Band Coadd Processing (but note that normally, one would use the SafeClipAssembleCoaddTask rather than AssembleCoaddTask to make the coadd.

Definition at line 184 of file assembleCoadd.py.

Constructor & Destructor Documentation

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.__init__ (   self,
  args,
  kwargs 
)

Initialize the task.

Create the interpImage, matchBackgrounds, & scaleZeroPoint subtasks.

Definition at line 293 of file assembleCoadd.py.

Member Function Documentation

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.addBackgroundMatchingMetadata (   self,
  coaddExposure,
  tempExpRefList,
  backgroundInfoList 
)

Add metadata from the background matching to the coadd.

Parameters
[in]coaddExposure,:Coadd
[in]tempExpRefList,:List of data references for temp exps to go into coadd
[in]backgroundInfoList,:List of background info, results from background matching

Definition at line 736 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.assemble (   self,
  skyInfo,
  tempExpRefList,
  imageScalerList,
  weightList,
  bgInfoList = None,
  altMaskList = None,
  mask = None 
)

Assemble a coadd from input warps.

.assemble_

Assemble the coadd using the provided list of coaddTempExps. Since the full coadd covers a patch (a large area), the assembly is performed over small areas on the image at a time in order to conserve memory usage. Iterate over subregions within the outer bbox of the patch using assembleSubregion to stack the corresponding subregions from the coaddTempExps with the statistic specified. Set the edge bits the coadd mask based on the weight map.

Parameters
[in]skyInfo,:Patch geometry information, from getSkyInfo
[in]tempExpRefList,:List of data references to Warps (previously called CoaddTempExps)
[in]imageScalerList,:List of image scalers
[in]weightList,:List of weights
[in]bgInfoList,:List of background data from background matching, or None
[in]altMaskList,:List of alternate masks to use rather than those stored with tempExp, or None
[in]mask,:Mask to ignore when coadding
Returns
coadded exposure

Definition at line 565 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.assembleMetadata (   self,
  coaddExposure,
  tempExpRefList,
  weightList 
)

Set the metadata for the coadd.

This basic implementation simply sets the filter from the first input.

Parameters
[in]coaddExposure,:The target image for the coadd
[in]tempExpRefList,:List of data references to tempExp
[in]weightList,:List of weights

Definition at line 628 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.assembleSubregion (   self,
  coaddExposure,
  bbox,
  tempExpRefList,
  imageScalerList,
  weightList,
  bgInfoList,
  altMaskList,
  statsFlags,
  statsCtrl 
)

Assemble the coadd for a sub-region.

For each coaddTempExp, check for (and swap in) an alternative mask if one is passed. If background matching is enabled, add the background and background variance from each coaddTempExp. Remove mask planes listed in config.removeMaskPlanes, Finally, stack the actual exposures using statisticsStack with the statistic specified by statsFlags. Typically, the statsFlag will be one of afwMath.MEAN for a mean-stack or afwMath.MEANCLIP for outlier rejection using an N-sigma clipped mean where N and iterations are specified by statsCtrl. Assign the stacked subregion back to the coadd.

Parameters
[in]coaddExposure,:The target image for the coadd
[in]bbox,:Sub-region to coadd
[in]tempExpRefList,:List of data reference to tempExp
[in]imageScalerList,:List of image scalers
[in]weightList,:List of weights
[in]bgInfoList,:List of background data from background matching
[in]altMaskList,:List of alternate masks to use rather than those stored with tempExp, or None
[in]statsFlags,:afwMath.Property object for statistic for coadd
[in]statsCtrl,:Statistics control object for coadd

Definition at line 674 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.backgroundMatching (   self,
  inputData,
  refExpDataRef = None,
  refImageScaler = None 
)

Perform background matching on the prepared inputs.

Each Warp has a different background level that must be normalized to a reference level before coaddition. If no reference is provided, the background matcher selects one. If the background matching is performed sucessfully, recompute the weight to be applied to the Warp (coaddTempExp) to be consistent with the scaled background.

Parameters
[in]inputData,:Struct from prepareInputs() with tempExpRefList, weightList, imageScalerList
[in]refExpDataRef,:Data reference for background reference Warp, or None
[in]refImageScaler,:Image scaler for background reference Warp, or None
Returns
Struct:
  • tempExprefList: List of data references to warped exposures (coaddTempExps)
  • weightList: List of weightings
  • imageScalerList: List of image scalers
  • backgroundInfoList: result from background matching

Definition at line 494 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.getBackgroundReferenceScaler (   self,
  dataRef 
)

Construct an image scaler for the background reference frame.

Each Warp has a different background level. A reference background level must be chosen before coaddition. If config.autoReference=True, backgroundMatching will pick the reference level and this routine is a no-op and None is returned. Otherwise, use the scaleZeroPoint subtask to compute an imageScaler object for the provided reference image and return it.

Parameters
[in]dataRef,:Data reference for the background reference frame, or None
Returns
image scaler, or None

Definition at line 403 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.getTempExpRefList (   self,
  patchRef,
  calExpRefList 
)

Generate list data references corresponding to warped exposures that lie within the patch to be coadded.

Parameters
[in]patchRef,:Data reference for patch
[in]calExpRefList,:List of data references for input calexps
Returns
List of Warp/CoaddTempExp data references

Definition at line 386 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.prepareInputs (   self,
  refList 
)

Prepare the input warps for coaddition by measuring the weight for each warp and the scaling for the photometric zero point.

Each Warp has its own photometric zeropoint and background variance. Before coadding these Warps together, compute a scale factor to normalize the photometric zeropoint and compute the weight for each Warp.

Parameters
[in]refList,:List of data references to tempExp
Returns
Struct:
  • tempExprefList: List of data references to tempExp
  • weightList: List of weightings
  • imageScalerList: List of image scalers

Definition at line 431 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.readBrightObjectMasks (   self,
  dataRef 
)
Returns None on failure

Definition at line 759 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.run (   self,
  dataRef,
  selectDataList = [] 
)

Assemble a coadd from a set of Warps.

Coadd a set of Warps. Compute weights to be applied to each Warp and find scalings to match the photometric zeropoint to a reference Warp. Optionally, match backgrounds across Warps if the background has not already been removed. Assemble the Warps using assemble. Interpolate over NaNs and optionally write the coadd to disk. Return the coadded exposure.

Parameters
[in]dataRef,:Data reference defining the patch for coaddition and the reference Warp (if config.autoReference=False). Used to access the following data products:
  • [in] self.config.coaddName + "Coadd_skyMap"
  • [in] self.config.coaddName + "Coadd_ + <warpType> + "Warp" (optionally) - [out] self.config.coaddName + "Coadd"
[in]selectDataList[in],:List of data references to Warps. Data to be coadded will be selected from this list based on overlap with the patch defined by dataRef.
Returns
a pipeBase.Struct with fields:
  • coaddExposure: coadded exposure

Definition at line 320 of file assembleCoadd.py.

def lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.setBrightObjectMasks (   self,
  exposure,
  dataId,
  brightObjectMasks 
)
Set the bright object masks

exposure:          Exposure under consideration
dataId:            Data identifier dict for patch
brightObjectMasks: afwTable of bright objects to mask

Definition at line 767 of file assembleCoadd.py.

Member Data Documentation

lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.brightObjectBitmask

Definition at line 306 of file assembleCoadd.py.

lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.ConfigClass = AssembleCoaddConfig
static

Definition at line 290 of file assembleCoadd.py.

lsst.pipe.tasks.assembleCoadd.AssembleCoaddTask.warpType

Definition at line 313 of file assembleCoadd.py.


The documentation for this class was generated from the following file: