The essence of geospatial analysis is discovering the relationships of objects on Earth. Items that are closer together tend to have a stronger relationship than those that are farther apart. This concept is known as Tobler's First Law of Geography. Therefore, measuring distance is a critical function of geospatial analysis.
As we have learned, every map is a model of the Earth and they are all wrong to some degree. For this reason, measuring the accurate distance between two points on the Earth while sitting in front of a computer is impossible. Even professional land surveyors (who go out in the field with both traditional sighting equipment and very precise GPS equipment) fail to account for every anomaly in the Earth's surface between point A and point B. So, to measure distance, we must look at the following questions:
- What are we measuring...