Radiant.Earth allows you to build analyses of imagery, particularly with raster algebra, where you can calculate new pixel values from existing values. These calculations can be used to compare how much light from different bands is reflected.

This tutorial will walk you through creating an analysis from a new template. For an example of analysis, read about NDVI.

To run analysis, you need to have at least one project with ingested imagery that you can use for your analysis. You can find instructions on how to create projects here.  

Then, navigate to the Lab. There are two sections within the Lab--Templates and Analyses. A template is a generalized model that can be applied to any project, and an analysis is a filled-out template that performs the calculations and gives you a result.

In the lab, click on the Templates tab, where you can browse your templates as well as all publicly available templates. Click on New Template and name it.

Then, define the template by writing out an algebraic expression (in this case, NDVI). Normal strings with letters will be used as variables. Numbers and standard algebraic notation (including ( ) + - * / ^) will be used as normal parts of the equation. You can also add a variable constant by putting an underscore (_) before a string, and you can make a default value by making it equal to a number (e.g. _G=9.8

You can also decide whether or not you'd like it to become public (available to all users).

In this case, we're doing NDVI, using the formula (NIR - Red) / (NIR + Red).

Once you've defined your template, click Create Tool and you'll be brought to a visual layout for how that tool is interpreted by Radiant.Earth. You can choose to rename the template or edit any of the inputs, constants, or operations.

Now you're ready to create your first analysis. 

Go to Templates and click Use Template under the tool you want to use. Then, click Create Analysis. You'll be able to edit the values of constants as well as choose the project and band number for each input that you need. In this case, we're using Landsat 8 imagery, so Band 4 is "Red" and Band 5 is "NIR").

Once you have your projects and bands specified, you can view the output of your analysis on a map by clicking the map icon on the node you are interested in inspecting or clicking the large map icon on the left-hand side of the canvas and subsequently choosing the node you're interested in viewing:

(You can hold shift and drag to zoom-in to a specific area.)

You can also change the color map and masking of values by clicking on the histogram icon of any node, which is especially helpful when there are null values outside of the area of focus.

Or view a statistical summary of the values in a node by clicking the Stats  icon.

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