CataEx: How to get started with JavaScript in Google Earth Engine?

Google Earth Engine offers a multitude of options for retrieving and analyzing satellite imagery from various satellite missions, which optimizes GIS studies, especially in the aspect of download and storage of extensive data volumes.

However, the compatibility with traditional desktop or web-based GIS software remains a gap that was attempted to overcome with the JavaScript code CataEx – a multi-functional tool that exemplifies several essential types of computations and finally exports imagery and its additionally created layers as GeoTIFFs. We presented several basic functionalities of CataEx: identifying images out of collections (e.g., the least cloudy image in a time frame), the definition of a location of interest (as coordinates and/or as a polygon), cloud masking for different collections, evaluation of satellite band properties and their projections, layer creation in Google Earth Engine, index computation, pixel-based statistics and histogram plotting, layer visualization and export to Google Drive.

CataEx is available in six versions for Landsat 4/5/7, Landsat 8/9, and Sentinel-2, each separated for top-of-atmosphere reflectance and surface reflectance collection. The code is deliberately kept simple to allow for easy brick-like recombination, adaption, and customization of code sections, and, hence, can be used as an example toolkit for students or beginners writing their first JavaScript routines for Google Earth Engine.

This work is funded by the Polish National Science Center (no. 2021/42/E/ST10/00186); the code is available on Zenodo (https://doi.org/10.5281/zenodo.8407939).