Feb 25 2020

A new era of spatial analysis: AK CASC Fellow Erin Trochim hosts Google Earth Engine workshop

a woman gives a presentation in front of a classroom

Erin Trochim gives the first training in her Google Earth Engine Workshop series at IARC.

GIF of Alaska showing monthly precipitation

The summed monthly precipitation from the daily ERA5 data, created by Erin Trochim on Google Earth Engine.

Erin Trochim stands poised at the front of a dim classroom at the International Arctic Research Center. At her fingertips is a tool that could revolutionize the way we process and analyze spatial information. Google Earth Engine is a powerful online platform that combines large spatial datasets and computing power in an accessible, app-like interface. It can be used to study trends and changes across Earth’s surface over space and time, and ask complex geospatial questions without the need to spend weeks downloading and processing large spatial datasets.

Google Earth Engine (GEE) can load global satellite imagery like Modis, Landsat, and Sentinel, as well as climate, landcover, and topography layers with a single line of code, in a fraction of the time.

“You used to have to be a big expert to work with big data; that is absolutely no longer the case. You can find an entrance point that works for you,” said Trochim. Since attending a GEE workshop in Dublin, Ireland in 2018, Trochim has had a vision for how this tool could revolutionize the way scientists and managers look at spatial data and address problems that have been difficult or impossible to consider in the past. On topics from stream temperature to permafrost degradation and beyond, GEE allows users to aggregate (or summarize) decades of data over an area of interest at an unprecedented rate. She believed so much in its applications that she designed a workshop to introduce new users to the platform.

The three-part, hands-on GEE workshop Trochim created with support from the AK CASC is aimed towards GIS professionals, managers, and subject-matter experts whose work has spatial applications. On a repeated offering of her first training module on February 6th (at the request of those who couldn’t attend initially) Trochim conveyed to over 25 participants in person and online how GEE could change the landscape of their work and the kinds of questions they can ask.

This initial session taught users the basics of remote sensing and processing big datasets, starting with a simple question: why use GEE? For many in the room, GEE offers a drastic reduction in the amount of time they spend processing and managing data, leaving more time for analysis and visualization of their research. GEE provides tools for that too, allowing users to put together striking visuals like the GIF below illustrating the summed monthly precipitation from the daily climate data. “You can do very sophisticated science, and also communicate it better,” noted Trochim.

In her own work, Trochim used GEE to look at changes to surface water across the Arctic. Even at such an immense spatial scale, she could look at each lake, river, and stream and calculate whether it had grown, shrunk, or remained the same. Trochim built an app in GEE that allows users to investigate water surface changes in their area of interest, which could be used for tracking water availability, infrastructure planning, and ecosystem health. “We have so much area in the Arctic, and we don’t always have a lot of information. So these sorts of tools are really attractive,” said Trochim.

Trochim is part of a GEE group developing a curriculum to bring the tool to a wider class of professionals and students outside of the computer programing and data science world. She hopes the curriculum will empower its students to look at problems across time and space in ways they haven’t been able to due to the computing and time requirements of the past.

The workshop continued with a second training on applying algorithms and classifying data on February 20, and will culminate with a third training on visualization (date to be determined).

For more information, contact Erin Trochim at edtrochim [at] alaska.edu.