MatchPessimisticBTask¶
MatchPessimisticBTask
matches sources to reference objects. This is often
done as a preliminary step to fitting an astrometric or photometric solution.
The algorithm is based on a more “Pessimistic” version of the Optimistic Pattern Matcher B as described in DMTN-013.
Optimistic Pattern Matching is described in [Tabur2007]
[Tabur2007] | Fast algorithms for matching CCD images to a stellar catalogue* arxiv:0710.3618 |
Processing summary¶
MatchPessimisticBTask
runs this sequence of operations:
- Flags sources with bad centroids and low signal to noise and remove them from the matching.
- Match the usable sources with an input reference catalog using the updated V. Tabur 2007 algorithm.
- Further remove sources detected on the edge of the image and those that are saturated.
- Return these sources matched to the references.
Python API summary¶
from lsst.meas.astrom.matchPessimisticB import MatchPessimisticBTask
-
class
(**kwargs)MatchPessimisticBTask
Match sources to reference objects
...
-
attribute
config
Access configuration fields and retargetable subtasks.
See also
See the MatchPessimisticBTask
API reference for complete details.
Retargetable subtasks¶
No subtasks.
Configuration fields¶
matcherIterations¶
- Default
5
- Field type
int
RangeField
- Range
- [1,inf)
maxOffsetPix¶
- Default
300
- Field type
int
RangeField
- Range
- [-inf,4000)
maxRefObjects¶
- Default
65536
- Field type
int
RangeField
- Range
- [0,65537)
maxRotationDeg¶
- Default
1.0
- Field type
float
RangeField
- Range
- [-inf,6.0)
minFracMatchedPairs¶
- Default
0.3
- Field type
float
RangeField
- Range
- [0,1)
minMatchDistPixels¶
- Default
1.0
- Field type
float
RangeField
- Range
- [0.0,6.0)
minMatchedPairs¶
- Default
30
- Field type
int
RangeField
- Range
- [2,inf)
numBrightStars¶
- Default
200
- Field type
int
RangeField
- Range
- [2,inf)
numPatternConsensus¶
numPointsForShapeAttempt¶
numRefRequireConsensus¶
Examples¶
MatchPessimisticBTask is a subtask of AstrometryTask, which is called by PhotoCalTask.
See lsst.pipe.tasks.photoCal.PhotoCalTask
.. note:: Pipe task will require conversion before this link is usable.
Debugging¶
The lsst.pipe.base.CmdLineTask
command line task interface supports a flag -d to import debug.py from your PYTHONPATH; see lsstDebug
for more about debug.py files.
The available variables in MatchOptimisticB are
- display (bool)
- If True display information at three stages: after finding reference objects, after matching sources to reference objects, and after fitting the WCS; defaults to False
- frame (int)
- frame to use to display the reference objects; the next two frames are used to display the match list and the results of the final WCS; defaults to 0
To investigate the meas_astrom_astrometry_Debug, put something like
import lsstDebug
def DebugInfo(name):
debug = lsstDebug.getInfo(name) # N.b. lsstDebug.Info(name) would call us recursively
if name == "lsst.meas.astrom.astrometry":
debug.display = True
return debug
lsstDebug.Info = DebugInfo
into your debug.py file and run this task with the –debug flag.