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When to reclassify a raster layer in QGIS?
When you create a categorical data from a continuous value data (e.g. categorical raster based on a slope, elevation etc.) or managing a category, reclassify function is key. This process is very important to create a potential map (suitable map, probability map, etc.).
When to use reclassification of a slope raster?
The slope raster in percentage generated from the previous MOU presents values from 0 to 238, a reclassification is applied in ranges that allow a better interpretation of the relief: 0 – 25% Flat to inclined terrain To do this, enter the expression in the Raster Calculator:
How is the NDVI multiplied in a raster calculator?
The NDVI values are Float type with 14 decimals, the Raster Calculator has the limitation that it does not make transformations to integers. Before performing the reclassification, the NDVI is multiplied by a constant, in this case 1000 was used:
How do you convert a raster to an integer?
Then select Raster menu > Conversion > Translate (Convert Format), to convert the generated raster to integer. In the dialog box in Input Layer select ndvi1000, configure the SRC, in Advanced Parameters > Output Data Type select Int32, execute. A raster called Converted is generated with values ranging from 0 to 874.
What is the purpose of reclassification of a raster?
Reclassification allows you to group together the current values of a raster. These operations can be useful in the analysis of the different types of raster, Digital Elevation Models, discrete raster, satellite images.
Why is it important to reclassify a satellite image?
The reclassification of an NDVI can help the process of interpretation of a satellite image, it can also be useful to evaluate the result of a classification. NDVI values are related to the presence or absence of vegetation, low values generally coincide with bare soils or water bodies.
How is the slope of a raster layer colored?
This process is very important to create a potential map (suitable map, probability map, etc.). In this tutorial, we are going to use the below slope map. The map is colored by slope categories (e.g. 15 < slope <= 30).
How to add a raster to a calculator?
To add a raster to the raster calculator expression field, double click its name in the Fields list. You can then use the operators to construct calculation expressions, or you can just type them into the box. In the Result layer section, you will need to define an output layer.
How to redefine nodata value into zero in QGIS?
With this calculation, if the cell value is -32768 you will get a 0 in that cell and if it is different from -32768 the cell will keep the value it had. The simplest one-step and, IMO, most consistently reliable solution to reclassifying NoData to zero is to use the Reclassify Grid Values tool (SAGA) in the processing toolbox.
Where do I find the raster bands in QGIS?
The Raster bands list contains all loaded raster layers that can be used. To add a raster to the raster calculator expression field, double click its name in the Fields list. You can then use the operators to construct calculation expressions, or you can just type them into the box.