Class lsst::meas::base::BaseTransform

class BaseTransform

Abstract base class for all C++ measurement transformations

Measurement plugins return results in raw, uncalibrated units (eg fluxes or positions in pixels). The transformation system provides a mechanism for post-processing those results into a calibrated form (magnitudes, celestial coordinates, etc).

A measurement transformation should derive from BaseTransform. It should implement a constructor which takes three arguments:

• A Control object describing the configuration of the measurement plugin.

• The name of the measurement plugin whose outputs are to be transformed (std::string);

• An lsst::afw::table::SchemaMapper which links the input and output catalogs;

The constructor should use the SchemaMapper to map fields from the input to output schemas and add additional keys to the output as required. For example:

Derived classes should also implement operator() following the interface below. This will be called with a catalog containing the results of the measurement plugin and a catalog to be populated with transformed quantities, as well as WCS and calibration information. For example:

Note that it is safe to assume that both catalogs passed to operator() are contiguous in memory. It is good practice to ensure that they are equal in size: this may be conveniently achieved by calling BaseTransform::checkCatalogSize().

operator() may throw LengthError if the transformation is impossible to complete. In this case, the contents of outputCatalog is not guaranteed.

Subclassed by lsst::meas::base::ApertureFluxTransform, lsst::meas::base::CentroidTransform, lsst::meas::base::FluxTransform, lsst::meas::base::SdssShapeTransform