How to create Greyscale versions of Colour Rasters in QGIS

The raster basemap layers from Digimap are all colour products, some are faded but are still colour.  It can be very useful to remove all colour when you have transparent coloured polygons overlying the basemap, or if you want to really emphasise a point dataset.

The following instructions show you how to make your data greyscale in QGIS 2.14 though they will work for earlier versions of the software:

Step 1: Download Basemap Data

There are many different raster basemaps available form the Ordnance Survey Collection's Data Download, these instructions will work equally well on the Hydroview Charts form Marine Download.

Step 2: Add the Colour Raster Data to QGIS

Use the Add Raster Button to load the data into a map:

Step 3: Change the Properties

• Right-click on the raster layer that you want to change and select Properties.
• On the Style tab go to the Color Rendering section
• Change Grayscale from Off to one of the other options.

We prefer doing this by lightness but either of the other options will work.

Optional: Adding a Colour Tint

QGIS has many great cartography options, if you want to give your map a certain look you can use the Colorize option to give tint the grey to a certain colour.  In this example we used brow to give a sepia look to the lower raster data tile.