Thematic maps emphasize upon a certain theme or topic. They discard all the information available except that which is immediate and relevant, this being one of the main features why they differ from conventional mapping approaches. As a general rule they don’t include natural features such as rivers, cities or political boundaries unless these details are essential to the maps formation, for example for the user to orientate themselves to the data or to highlight certain aspects. An English astronomer called Edmund Halley created the first thematic map during the 17th Century. He produced a star chart that was a lot more accurate than the current examples at the time due to the advancement of the cartography era.
Considerations when creating thematic maps today are to keep the intended audience in mind so that the information included is as minimal and relevant as possible.
John Snow, 1854
For me one of the most notable approaches for thematic mapping was the work by John Snow in 1854. Through the use of this medical cartography technique, patterns regarding the cholera epidemic in relation to the water pumps in the local area were made clear leading to revolutionary breakthroughs in the medicinal world which helped saved the lives of thousands. Due to this breakthrough Snow is now considered one of the founding fathers of Epidemiology – the science of the study of patterns, causes and effects of healthy organisms and diseased in defined populations.
His research took route from his refusal to believe the theory that Cholera was a disease bred through airborne means. He argued that the bacteria in fact entered the body through the mouth and published his ideas in an essay ‘On The Mode Of Communication of Cholera’ in 1849. He proved his theory after careful investigation of where the diseased areas fell on the map. Snow was then able to identify a water pump in the area as a source of the disease. He had the handle removed and soon after the cases of cholera began to diminish
I think this is an amazing discovery that was found through such a unique and imaginative method.