Unclassified Quantitative Symbology for Rasters
This tutorial demonstrates the options for applying a color ramp to quantitative values in a raster dataset, by stretching the ramp across the values’ range.
Included in this tutorial:
Unclassified, by default
The Symbology Options
Changing the Color Ramp, with an example
Software version in examples: 3.4.0 Bratislava
Tutorial Data: The tutorial includes demonstration with sample data available here.
Credits: L. Meisterlin (2026)
Related Tutorials:
This tutorial begins with a quantitative distance raster dataset added to the map project. To learn how the raster was produced, see this tutorial on Creating Distance Rasters.
Unclassified, by default
For most raster datasets (depending on the values, number of bands, etc), adding a raster to your map will result in an unclassified symbology by default. This is true for non-integer, single-band datasets including the one used in this demonstration. In almost all GIS software, the default will use a black-to-white color ramp: darker shades applied to cells with lower values and lighter shades applied to cells with higher values.
the default, unclassified symbology of a raster
The Symbology Options
As with vector features, we access a raster’s symbology options through the layer properties, by right-clicking on the layer’s name in the Layers panel and choosing the Symbology tab.
We will take a moment to examine the different sections of the Symbology options.
the Symbology properties
Under Band Rendering you will find the Render Type. This default option is Singleband Gray: it renders a single raster band in the default grayscale. You can specify a particular band from a multiband raster with the Gray band option and flip the Color gradient.
If the Render Type is changed, then other options will change accordingly.
Under the Min/Max Value Settings, you can customize how the color ramp is “stretched” across the values contained in the raster dataset. This allows you to render faster or more accurately. The options also allow you to account for potential outlier values.
The Layer Rendering options offer more control over the visualization and its legibility by adjusting image contrast, brightness, and other parameters.
The Resampling method options include (as you likely guessed) the resampling methods for visualizing your values as you zoom in and out of the raster (assuming that resampling is necessary based on your map’s zoom level).
Changing the Color Ramp, with an example
As noted above, changing the Render Type will adjust some of the options within the Symbology properties. To change the color ramp, we adjust the Render Type to Singleband pseudocolor. Then, options that are familiar based on vector symbology choices will appear, including the color ramp and classification options.
For an unclassified symbology, the classification mode is set to continuous (and thus the option to change the number of classes is “greyed out”).
You can adjust the Interpolation method using the drop-down. This affects how your values are stretched across the color ramp. In the example below, we use a straightforward Linear interpolation.
adjusting the color ramp
resulting changes to the unclassified raster