The map below shows robbery patterns across the London Borough of Croydon thematically shaded by using grid cells of 250m in size. A custom range has been used to present the distribution of this crime type. The custom range follows in a logical and easy to understand sequence. The map more accurately identifies areas of high robbery concentration than the example for geographic boundary thematic maps. The map also makes use of natural colours that help to distinguish areas that are hot and not so hot.

Problems with this technique relate to,

• defining when ‘hot’ is ‘hot’
• spatial detail can be lost as hotspots are not naturally formed as grid blocks
• the size and orientation of the grids can lead to different interpretations of where the hotspots are.