DL1 Data Model

The DL1 files are HDF5 format files, with the following data set hierarchy. The tables should be written with pytables (not h5py), ideally with the ctapipe.io.HDF5TableWriter, which ensures the unit and other descriptive metadata are attached to the output. Containers marked with a + should be written without their prefix (all others should use column prefixes).

The following describes the contents of data level 1 (DL1) output files generated by ctapipe (e.g. the ctapipe-stage1-process tool).

DL1/Event Data Model

This describes data that change per-event. The following datasets will be written to the group /dl1/event/ in the output file:





event-wise data pertaining to a subarray



subarray trigger information

EventIndexContainer +, CentralTriggerContainer


true shower parameters from Monte-Carlo simulation

EventIndexContainer +, MCEventContainer


Per-telescope Per-event information



tables of image parameters (one per telescope)

TelEventIndexContainer +, HillasParametersContainer, TimingParametersContainer, LeakageContainer, ConcentrationContainer, MorphologyContainer, IntensityContainer


tables of telescope images (one per telescope)

TelEventIndexContainer +, DL1CameraContainer, ExtraImageContainer

Configuration Data Model

The output file should also contain serializations of the instrument, observation (if applicable), simulation (if applicable) configuration information, written to the /configuration group:





Serialized SubarrayDescription



Subarray layout info

result of SubarrayDescription.to_table() output as HDF5 using astropy.table functionality


telescope optics information

result of SubarrayDescription.to_table(kind='optics') output as HDF5 using astropy.table functionality


camera geometry information

result of CameraGeometry.to_table() output as HDF5 using astropy.table functionality


Monte-Carlo simulation configuration information



Monte-Carlo simulation run information

ExtraMCInfo +, MCHeaderContainer +


simulated shower distribution histograms


Core Provenance

The root group of the file shall contain all of thethe “CTA Core Provenance Metadata” headers as user attributes, with the hierarchy flattened and separated by spaces (e.g. "CTA ACTIVITY NAME" = "ctapipe-stage1-process")