Introduction to GEE

Digital Soil Mapping

José Padarian
University of Sydney

Outline

  • What is GEE and how it works
  • Explore GEE API (Javascript and Python)
  • DSM workflow (with examples)
    • Compile covariates
    • Extract data from covariates
    • Model training
    • Generate map
    • Export

Google Earth Engine

Features

  • Access to over 40 years of Satellite Imagery (with daily updates)
  • Algorithms to analyse that data
  • Google's computer clusters to analyse the data at scale
  • A web-based tool for interactive data exploration

How does it work?

Features

  • Access to over 40 years of Satellite Imagery (with daily updates)
  • Algorithms to analyse that data
  • Google's computer clusters to analyse the data at scale
  • A web-based tool for interactive data exploration

DSM workflow

Compile covariates

> 200 public datasets
> 4000 new images every day
> 5 million images
> 5 petabytes of data

Examples

Extract data from covariates

  • At the moment only using Fusion Tables
  • Another alternative is using GeoJSON (usually for small datasets)
  • Limit of 500,000 rows (also a size limit)

We will be using data SOC from Edgeroi

Let's import data into

Examples

Model training

  • Classification and Regression algorithms
  • Limited number of algorithms available
    • Tree-like (CART, Random Forest)
    • Perceptron
    • Support Vector Machine
    • Others
  • Alternative to use expressions (tree-like structures, linear models)

Examples

Generate map

This is the step where we can get most speed gain

  • The predicion is made at the viewport
    • It depends on the extent
    • It depends on the zoom level (resolution)

It's not always necessary to view the prediction (lazy evaluation)

Examples

Export

There are multiple alternatives:

It is also possible to export images as Assets

Examples