I'm in a new field of research and I'm having troubles following a procedure with QGIS. I'm extremely new to all this since I'm a chemist.

The aim is to calculate the total green cover from a photo. Since this data isn't available through satellite, I have to use normal .jpg photography.

I start with raster > calculator and add in the open box this equation: BAND2(green) * 2 – BAND1(Red) – BAND3(Blue)

This comes out:

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Now in the search box on the right, I'm told to search for "RECLASSIFY VALUES(SIMPLE)" but this is all that appears.

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This is the reference photo I've been given of the tool that should appear:

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And this is the version of QGIS I'm using

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on this version of Windows.

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I've installed SAGA with QGIS in this version

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3 Answers 3


If you have GRASS GIS installed, there is the r.reclass tool which does the same thing, reclassify raster values based on given rules.


Some tools from SAGA toolbox are not available anymore. My recommendation would be to use these instead:

Part 37: r.null from GRASS toolbox

Part 38: r.resample from GRASS toolbox

Part 39: simple Raster Calculator from raster menu. Use if statement -> if (condition, option if true, option if false)

Part 40: In this specific case the SAGA tool existed for me. It looked not available but it still worked.

Part 43: Raster Calculator from GDAL toolbox

Part 50: Use simple Raster Calculator twice. The first time for the reclassifying process use the expression: total costs raster < 5000. Then use the tool as shown by the instructor.


The information provided seems mostly accurate, but there are some considerations to keep in mind:

  1. SAGA Toolbox Changes: It's true that some tools from the SAGA toolbox may not be available due to changes in software versions or configurations. However, the specific tools mentioned for replacement can vary based on the software version and the GIS environment you are using. Make sure to check the available tools in your software and use the suggested alternatives if the corresponding tools are unavailable.

  2. GRASS Toolbox: Using tools like "r.null" and "r.resample" from the GRASS toolbox can be good alternatives if certain SAGA tools are missing.

  3. Simple Raster Calculator: Using the Raster Calculator in your GIS software with conditional statements (if-else) is a common approach for performing calculations that may have been done using SAGA tools.

  4. SAGA Tool Availability: It's important to note that the availability of SAGA tools can vary depending on the GIS software you are using and its version. If you find that a SAGA tool is still available even though it appears to be missing, it could be due to the configuration of your GIS software.

  5. GDAL Toolbox: Using the Raster Calculator from the GDAL toolbox can be a suitable alternative for specific tasks.

In summary, while the recommendations provided are generally correct, it's crucial to adapt them based on your specific GIS software version and configuration. Verify the availability of tools and use the suggested alternatives when needed.

Both these notes are taken from this course: https://www.udemy.com/course/fundamentals-of-geographic-information-systems-gis-in-qgis/learn/lecture/30566860#questions/20586730

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