ConvertReferenceCatalogTask

ConvertReferenceCatalogTask converts an external catalog for use as an LSST Science Pipelines reference catalog, using a Hierarchical Triangular Mesh (HTM) indexing scheme. The format and layout of the input data is configurable. The output data is a collection of lsst.afw.table.SimpleCatalog files identified by their HTM pixel. This task is not available as a pipeline task: see How to generate an LSST reference catalog for how to run the task.

Processing summary

ConvertReferenceCatalogTask uses Python multiprocessing to ingest multiple files in parallel, configured by n_processes. Once it has generated the necessary multiprocessing file locks (one per output file: ~130,000 files for HTM depth=7), it performs the following steps for each input file:

1. Reads the file using the configured file_reader subtask (default: ReadTextCatalogTask).
2. Indexes the coordinates in the input data to determine which mesh pixel they go with, and thus which output file they will be written to.
3. Loops over the output pixels in this input file (where N is the number of sources in this pixel):

1. Acquires the lock for this output file.
2. Reads an existing output file and appends N new empty rows, or generates a new empty catalog with N rows.
3. Fills in the empty rows of the catalog with the converted values from the input data.
4. Writes the output file and releases the file lock.

Python API summary

from lsst.meas.algorithms.convertReferenceCatalog import ConvertReferenceCatalogTask

classConvertReferenceCatalogTask(*, output_dir=None, **kwargs)

Class for producing HTM-indexed reference catalogs from external catalog data...

attributeconfig

Access configuration fields and retargetable subtasks.

methodrun(inputFiles)

Index a set of files comprising a reference catalog...

See also

See the ConvertReferenceCatalogTask API reference for complete details.

Butler datasets

ConvertReferenceCatalogTask does not behave in the same manner as most LSST Tasks. When run directly through the run method (e.g. via the convertReferenceCatalog commandline interface), ConvertReferenceCatalogTask reads input from a collection of non-LSST files, and writes to a specified directory. Note that configurations for ConvertReferenceCatalogTask, and its subtasks, affect what the output dataset content is.

Output datasets

ref_cat

An LSST-style reference catalog, consisting of one lsst.afw.table.SimpleCatalog per HTM pixel.

Retargetable subtasks

file_reader

Default

lsst.meas.algorithms.readTextCatalogTask.ReadTextCatalogTask

Field type

ConfigurableField

Task to use to read the files. Default is to expect text files.

manager

Default

lsst.meas.algorithms.convertRefcatManager.ConvertRefcatManager

Field type

ConfigurableField

Multiprocessing manager to perform the actual conversion of values, file-by-file.

Configuration fields

coord_err_unit

Default

None

Field type

str Field (optional)

Unit of RA/Dec error fields (astropy.unit.Unit compatible)

dataset_config

Data type

lsst.meas.algorithms.convertReferenceCatalog.DatasetConfig

Field type

ConfigField

Configuration for reading the ingested data

dec_err_name

Default

None

Field type

str Field (optional)

Name of Dec error column

dec_name

Default

None

Field type

str Field

Name of Dec column (values in decimal degrees)

epoch_format

Default

None

Field type

str Field (optional)

Format of epoch column: any value accepted by astropy.time.Time, e.g. ‘iso’ or ‘unix’

epoch_name

Default

None

Field type

str Field (optional)

Name of epoch column

epoch_scale

Default

None

Field type

str Field (optional)

Scale of epoch column: any value accepted by astropy.time.Time, e.g. ‘utc’

extra_col_names

Default

[]

Field type

str ListField

Extra columns to add to the reference catalog.

full_position_information

Default

False

Field type

bool Field

Include epoch, proper motions, parallax, and covariances between sky coordinates, proper motion, and parallax in the schema. If true, a custom ConvertRefcatManager class must exist to compute the output covariances.

id_name

Default

None

Field type

str Field (optional)

Name of column to use as an identifier (optional).

is_photometric_name

Default

None

Field type

str Field (optional)

Name of column stating if satisfactory for photometric calibration (optional).

is_resolved_name

Default

None

Field type

str Field (optional)

Name of column stating if the object is resolved (optional).

is_variable_name

Default

None

Field type

str Field (optional)

Name of column stating if the object is measured to be variable (optional).

mag_column_list

Default

None

Field type

str ListField

The values in the reference catalog are assumed to be in AB magnitudes. List of column names to use for photometric information. At least one entry is required.

mag_err_column_map

Default

{}

Field type

DictField

Key type

str

Value type

str

A map of magnitude column name (key) to magnitude error column (value).

n_processes

Default

1

Field type

int Field

Number of python processes to use when ingesting.

parallax_err_name

Default

None

Field type

str Field (optional)

Name of parallax error column

parallax_name

Default

None

Field type

str Field (optional)

Name of parallax column

parallax_scale

Default

1.0

Field type

float Field

Scale factor by which to multiply parallax values to obtain units of milliarcsec

pm_dec_err_name

Default

None

Field type

str Field (optional)

Name of proper motion Dec error column

pm_dec_name

Default

None

Field type

str Field (optional)

Name of proper motion Dec column

pm_ra_err_name

Default

None

Field type

str Field (optional)

Name of proper motion RA error column

pm_ra_name

Default

None

Field type

str Field (optional)

Name of proper motion RA column

pm_scale

Default

1.0

Field type

float Field

Scale factor by which to multiply proper motion values to obtain units of milliarcsec/year

ra_err_name

Default

None

Field type

str Field (optional)

Name of RA error column

ra_name

Default

None

Field type

str Field

Name of RA column (values in decimal degrees)

Examples

See How to generate an LSST reference catalog for a description of how to run the task to ingest the Gaia DR2 catalog.