This is a guest blog from Liam Mason, a spatial analyst with Marine Scotland. Some of his other data visualisations can be seen on his @marinemaps Twitter account or the Marine Scotland Maps portal maps.marine.gov.scot
[Edit: the tutorial was modified to use the GDAL-based DEM (Terrain Analysis) tools instead of Raster Terrain Analysis]
I love mapping bathymetric data in 3D. It’s almost magical, the ability to draw back the veil of the sea and reveal the mysterious landscapes below.
Yet, it’s remarkably simple to do using QGIS 2.8 or higher.
These maps display the density and distribution of a phenomena over a geographic area. The markers, usually a dot or cross, represent the occurrence or an aggregation of occurrences which are then randomly distributed across distinct regions of the map. Colours can be used to represent different classifications to add an extra dimension to the map.
Creating proportional symbol maps in QGIS is made very easy in QGIS with two main methods for making them. You can use basic Single Symbol style with the Size Assistant in the Data Defined Override, or you can use the Graduated style and choose Size as the method of gradation. Below is a set of instructions on how to use either method to create proportional point symbols for your map. Continue reading “Creating a Proportional Symbol map in QGIS 2.18”