class rubin_sim.maf.slicers.HealpixSlicer(nside=128, lon_col='fieldRA', lat_col='fieldDec', lat_lon_deg=True, verbose=True, badval=nan, use_cache=True, leafsize=100, radius=2.45, use_camera=True, camera_footprint_file=None, rot_sky_pos_col_name='rotSkyPos')

Bases: BaseSpatialSlicer

A spatial slicer that evaluates pointings on a healpix-based grid.

Note that a healpix slicer is intended to evaluate the sky on a spatial grid. Usually this grid will be something like RA as the lon_col and Dec as the lat_col. However, it could also be altitude and azimuth, in which case altitude as lat_col, and azimuth as lon_col. An additional alternative is to use HA/Dec, with lon_col=HA, lat_col=Dec.

When plotting with RA/Dec, the default HealpixSkyMap can be used, corresponding to {‘rot’: (0, 0, 0), ‘flip’: ‘astro’}. When plotting with alt/az, either the LambertSkyMap can be used (if Basemap is installed) or the HealpixSkyMap can be used with a modified plot_dict, {‘rot’: (90, 90, 90), ‘flip’: ‘geo’}. When plotting with HA/Dec, only the HealpixSkyMap can be used, with a modified plot_dict of {‘rot’: (0, -30, 0), ‘flip’: ‘geo’}.

nsideint, optional

The nside parameter of the healpix grid. Must be a power of 2. Default 128.

lon_colstr, optional

Name of the longitude (RA equivalent) column to use from the input data. Default fieldRA

lat_colstr, optional

Name of the latitude (Dec equivalent) column to use from the input data. Default fieldDec

lat_lon_degbool, optional

Flag indicating whether the lat and lon values in the input data are in degrees (True) or radians (False). Default True.

verbosebool, optional

Flag to indicate whether or not to write additional information to stdout during runtime. Default True.

badvalfloat, optional

Bad value flag, relevant for plotting. Default the np.nan value (in order to properly flag bad data points for plotting with the healpix plotting routines). This should not be changed.

use_cachebool, optional

Flag allowing the user to indicate whether or not to cache (and reuse) metric results calculated with the same set of simulated data pointings. This can be safely set to True for slicers not using maps and will result in increased speed. When calculating metric results using maps, the metadata at each individual ra/dec point may influence the metric results and so use_cache should be set to False. Default True.

leafsizeint, optional

Leafsize value for kdtree. Default 100.

radiusfloat, optional

Radius for matching in the kdtree. Equivalent to the radius of the FOV. Degrees. Default 2.45.

use_camerabool, optional

Flag to indicate whether to use the LSST camera footprint or not. Default True.

camera_footprint_filestr, optional

Name of the camera footprint map to use. Can be None, which will use the default.

rot_sky_pos_col_namestr, optional

Name of the rotSkyPos column in the input data. Only used if use_camera is True. Describes the orientation of the camera orientation compared to the sky. Default rotSkyPos.