# Data

This data section of the handbook outlines procedures for how to go about doing the quality control, the processing and the generation of data products.

## Data Directory Structure

Usually dropsonde data has a `platform` from which it was meassured and a `flight_id` from the exact flight it was taken from. After the processing each flight will have data on different levels of processing. `halodrops` uses the following levels.

| Level     | Description                                                                                    |
| --------- | ---------------------------------------------------------------------------------------------- |
| `Level_0` | raw files from the AVAPS software (A-files, D-files, ...). Some files contain auxiliary data for a measurement sequence (usually a flight) and others are per sonde. |
| `Level_1` | ASPEN-processed netCDF files per sonde. First QC applied. |
| `Level_2` | Sondes that passed additional QC tests. Still one file per sonde. All soundings with no usable data are excluded  |
| `Level_3` | One dataset (file) containing all Level_2 soundings gridded on a uniform, vertical grid, with some derived variables |
| `Level_4` | Circle products from all circles flown during flight or measurement campaign |


You can define your exact folder structure as shown in {doc}`example configs <../tutorial/configs>`