IRAM Memo 2016-2 Gridding spectra with CLASS
Keywords: class-gridding

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# IRAM Memo 2016-2
Gridding spectra with CLASS

S. Bardeau, J. Pety

March, 1st 2018
Version 1.1

1. IRAM (Grenoble)

### Abstract:

In the sep16a CLASS release, the internal code of the `XY_MAP` command was refurbished to ensure that datasets larger than the available RAM memory can be processed by slicing the data in intervals of channels. The command is now also able to read direct or transposed input XY tables and/or to write direct (LMV) or transposed (VLM) output cubes. The latter feature is useful to easily reimport data when a 2nd step of baselining is desired on the gridded data cube. The online help was upgradeed accordingly (see in particular the output of `LAS> HELP XY_MAP MEMORY`).

This memo describes how the gridding is performed in CLASS, from the collection of spectra to the spectral cube. It focuses on the file access efficiency, memory consumption, and how the user choices can impact them.

Commands: `TABLE, XY_MAP, TRANSPOSE`

Keywords: gridding, transposition, memory, large files

Related documents: CLASS documentation

- Contents
- Quick overview
  - Efficient table reading
  - Efficient cube writing
  - Efficient transpositions
- CLASS tables in details
- Gridding with `XY_MAP`
  - Gridding engine
  - Output cube in details
- Implementation
  - Memory management
  - In practice
- About this document ...