3. Getting Started

Getting started with Polar2Grid can be simple once you’ve decided what you actually want to do. Polar2Grid comes with a lot of options and there is a lot that can be customized with little work. Each section below describes the basic operations that a user should take to achieve their processing goals. The information is split in to 3 sections:

• For CSPP Software Bundle Users
• For Command Line Tool Users
• For Python Library Users

3.1. For CSPP Software Bundle Users

Users of the CSPP Software Bundle can find all of the tools they may want to use in the bin directory of the extracted tarball. As mentioned in the installation instructions, the following line can be added to your .bash_profile to simplify calling Polar2Grid scripts. This line allows you to remove the $POLAR2GRID_HOME/bin/ portion of the commands mentioned elsewhere in the documentation.

export PATH=$POLAR2GRID_HOME/bin:$PATH

The majority of the scripts in the software bundle are wrappers around python command line tools. Due to the modular design of Polar2Grid a user only needs to decide on a Frontend and a Backend to find the script to run. For example, to convert VIIRS SDR files to Geotiffs a user should run the following:

$POLAR2GRID_HOME/bin/viirs2gtiff.sh -f /path/to/my_sdrs/

This method of finding and calling scripts applies to all basic Polar2Grid features. Each Frontend comes with a logical set of default products to be created. If it can’t find all the necessary data then it will continue on with what could be created.

To see a full list of the available command line arguments provide the -h argument to a script. See the frontends documentation for available frontends and backends documentation for available backends. Some of the more advanced features provided by Polar2Grid are decribed in the below sections. It is recommended that users searching for a feature not explained on this page look at the rest of the Polar2Grid documentation. For users looking to make their own custom RGB products, see the Compositor’s documentation.

3.1.1. Creating True Color as Geotiffs and KML/KMZ

To create a true color image you must first have the SDRs for the proper instrument. Traditional true color images are created using the CREFL (Corrected Reflectance) Frontend. See the frontend documentation for which instruments are supported at this time (VIIRS and MODIS at the moment). Even if you want a KMZ, a geotiff must be created first:

$POLAR2GRID_HOME/bin/crefl2gtiff.sh -f /path/to/my_sdrs/

This will create a series of geotiff files with the .tif file extension. To create a KMZ file (a compressed KML) to show in Google Earth or other program use the gtiff2kmz.sh script provided in the software bundle:

$POLAR2GRID_HOME/bin/gtiff2kmz.sh input_true_color.tif output_true_color.kmz

Where the input_true_color.tif file is one of the files created from the crefl2gtiff.sh command and output_true_color.kmz is the name of the KMZ file to create.

For more information see the documentation for the CREFL Frontend, the Geotiff Backend, and the True Color Compositor.

3.1.2. Creating False Color as Geotiffs and KML/KMZ

A false color image is any combination of 3 bands that isn’t a true color image, but by default Polar2Grid uses a default set of bands. See the False Color Compositor for more information on those defaults. To make a false color image geotiff run:

$POLAR2GRID_HOME/bin/crefl2gtiff.sh false_color --false-color -f /path/to/my_sdrs/

Now while these command arguments may seem redundant there is a good reason for them. The --false-color portion of the command tells the frontend that you want the products used in a false color image. The false_color portion says that you actually want to make a false color image product. Without the false_color part, no RGB image would be created.

Just like for the true color image, use the following to create a KMZ file:

$POLAR2GRID_HOME/bin/gtiff2kmz.sh input_false_color.tif output_false_color.kmz

3.1.3. Custom Grid Utility

The Polar2Grid software bundle comes with a wrapper script for the Custom Grid Utility for easily creating Polar2Grid grids over a certain longitude and latitude. To run it from the software bundle wrapper run:

$POLAR2GRID_HOME/bin/p2g_grid_helper.sh ...

See the script’s documentation for more information on how to use this script and the arguments it accepts.

3.2. For Command Line Tool Users

TODO

3.3. For Python Library Users

TODO