ExposureIdInfo

class lsst.obs.base.ExposureIdInfo(expId=0, expBits=1, maxBits=64)

Bases: object

Exposure ID and number of bits used.

Attributes include:

expId

exposure ID as an int

expBits

maximum number of bits allowed for exposure IDs

maxBits

maximum number of bits available for values that combine exposure ID with other information, such as source ID

unusedBits

maximum number of bits available for non-exposure info (maxBits - expBits)

One common use is creating an ID factory for making a source table. For example, given a data butler butler and a data ID dataId:

from lsst.afw.table import IdFactory, SourceTable
exposureIdInfo = butler.get("expIdInfo", dataId)
sourceIdFactory = IdFactory.makeSource(exposureIdInfo.expId,
                                       exposureIdInfo.unusedBits)
schema = SourceTable.makeMinimalSchema()
#...add fields to schema as desired, then...
sourceTable = SourceTable.make(self.schema, sourceIdFactory)

At least one bit must be reserved, even if there is no exposure ID, for reasons that are not entirely clear (this is DM-6664).

Attributes Summary

unusedBits

Attributes Documentation

unusedBits