The atlas is provided as files in Mapped Vector Library (MVL) format:
the main data set O3a_binary_atlas1.mvl
the summary data set O3a_binary_atlas1_summary.mvl
the spatial index O3a_binary_atlas1_spatial_index.mvl
The MVL format specification and description of data layout is in the file data_format.txt.
The main data set O3a_binary_atlas1.mvl contains upper limits (for circular, linear polarization as well as new parametetric upper limits) and signal-to-noise ratios (SNR), parameterized by sky position and frequency.
The sky resolution increases with frequency. The sky coordinates are in radians, J2000.
The summary data set O3a_binary_atlas1_summary.mvl also has upper limits and signal-to-noise ratios, but it has been mapped onto a uniform sky grid that is the same for all frequencies. The summary data set is used by the script view_summary.R.
Once in the R environment, a script runs with the following command:
source("SCRIPT_NAME.R")
Before running any of the scripts in R the RMVL package has to be installed using the following R command:
install.packages("RMVL")
A number of example R scripts that make use of the atlas data are provided. The user is encouraged to open the scripts and modify them as needed.
view_summary.R - generates a skymap and a frequency plot from any sub-band of the atlas, plus some summary information. There are examples of how to make plots and extract data at the end of the script.
create_spatial_index.R - creates spatial index allowing fast queries by sky location. The size of the generated index is 56GB. Instead of running this script you can download the spatial index.
MD5 checksums of MVL files:
c2c02331a1b23a8f0d1f721bcb382f91 - O3a_binary_atlas1.mvl
991707d8ed58c59cb382b0cbb38febc3 - O3a_binary_atlas1_summary.mvl
dcd2d8b1d7d3c93bb3a2d11cead0708a - O3a_binary_atlas1_spatial_index.mvl