1. Introduction

1.1. Overview

Polar2Grid is a set of command line tools for extracting data from earth-observing satellite instrument files, remapping it to uniform grids if needed, and writing that gridded data to a new file format. It provides an easy way to create high quality projected images. Polar2Grid was created by scientists and software developers at the SSEC. It is distributed as part of the CSPP LEO project for processing of data received via direct broadcast antennas. Although Polar2Grid was created to serve the direct broadcast community, it can be used on most archived data files.

The features provided by Polar2Grid are accessible via bash scripts and binary command line tools. This is meant to give scientists an easy way to use and access features that typically involve complicated programming interfaces. Linux terminal commands included in these instructions assume the bash shell is used.


A collaboration between the Polar2Grid and PyTroll team will change a majority of the low-level code in future versions of Polar2Grid. However, the bash scripts will still be available to provide the same functionality with which users are familiar. Polar2Grid terminology such as “frontend” and “backend” is now used interchangeably with the SatPy terminology “reader” and “writer”.

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1.2. Software Design

digraph glue_flow {
    rankdir = LR;
    node [shape = rectangle, fillcolor="#C3DCE7:white", gradientangle="90.0", style="filled"];
    "Reader" -> "Remapper";
    "Remapper" -> "Writer";
    "Remapper" -> "Compositors" [style=dashed];
    "Compositors" -> "Writer" [style=dashed];

Polar2Grid has a modular design operating on the idea of satellite “products” or “datasets”; data observed by a satellite instrument. These products can be any type of raster data, such as temperatures, reflectances, radiances, or any other value that may be recorded by or calculated from an instrument. There are 4 main steps or components involved when working with these products in Polar2Grid: reading, writing, compositing, and remapping. Polar2Grid makes it possible to access and configure these steps with a simple bash script called polar2grid.sh and other helper scripts. More information on accessing Polar2Grid’s features and running its scripts can be found in the Polar2Grid Basics section or the examples following each reader section. Note that although an example may be written for a specific reader the same operations can be applied to all readers unless mentioned otherwise.

For more low-level information on the design and responsibility of each component see the Software Design Overview Appendix.

In Polar2Grid a majority of the functionality is provided by the open source SatPy library created by the PyTroll group. More information on SatPy and the capabilities it provides to python users can be found in the SatPy documentation.

1.3. What’s New?

Polar2Grid Version 2.3 is now available. Changes in this version include:

  • Add FY-3C VIRR reader

  • Add MERSI-2 reader

  • Add VIIRS EDR Flood reader

  • Add VIIRS EDR Active Fire reader

  • Add “overlay.sh” script for overlaying active fire products

  • Add ‘–borders-width’ flag to “add_coastlines.sh”

  • Fix AVHRR reader not masking bad 0 values

  • Fix MIRS reader not using valid range properly

For more details on what’s new in this version and past versions see the Release Notes in the github repository.

1.4. System Requirements

System requirements for the Polar2Grid software are as follows:

  • Intel or AMD CPU with 64-bit instruction support (2+ cores - 2.4GHz)

  • 16 GB RAM (minimum)

  • CentOS 6 64-bit Linux (or other compatible 64-bit Linux distribution)

  • 5 GB disk space (minimum)

1.5. License and Disclaimer

Original scripts and automation included as part of this package are distributed under the GNU GENERAL PUBLIC LICENSE agreement version 3. Software included as part of this software package are copyrighted and licensed by their respective organizations, and distributed consistent with their licensing terms.

The University of Wisconsin-Madison Space Science and Engineering Center (SSEC) makes no warranty of any kind with regard to the CSPP LEO software or any accompanying documentation, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. SSEC does not indemnify any infringement of copyright, patent, or trademark through the use or modification of this software.

There is no expressed or implied warranty made to anyone as to the suitability of this software for any purpose. All risk of use is assumed by the user. Users agree not to hold SSEC, the University of Wisconsin-Madison, or any of its employees or assigns liable for any consequences resulting from the use of the CSPP LEO software.