on December 31, 2022

GEE-Select pixels whose values equal to a given value in an image

Hiking & Activities

Diving into Google Earth Engine: How to Snag Pixels with Specific Values

Google Earth Engine (GEE) is like this incredible treasure chest for anyone working with geospatial data. It’s got tons of satellite images and all sorts of cool tools to play around with. One thing you’ll often want to do is pick out specific pixels in an image based on their values. Think of it like finding all the blue candies in a bag of mixed sweets! This lets you zoom in on particular features, like lakes, forests, or areas hit by a recent storm. So, how do we do it? Let’s break it down.

The Core Idea: Masks

The basic idea is to create a “mask.” Imagine cutting out a shape from a piece of paper. That shape is your mask. In GEE, this mask highlights the pixels you’re interested in, letting you isolate them from the rest. It’s all about comparing pixel values to what you’re looking for and using the result to create that mask.

Getting Down to Business: Picking Those Pixels

Here’s the lowdown on selecting pixels with specific values in Google Earth Engine:

  • The .eq() Trick: This is your go-to method for finding pixels that exactly match a certain value. It’s super simple. You tell GEE, “Hey, find me all the pixels in this band that are equal to, say, 3.” GEE then creates a new image where matching pixels are marked as “true” (1), and everything else is “false” (0). This “true/false” image becomes your mask.

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