lecture: Nobody cares about your datum: or the Kleinstaaterei of spatial reference systems
What is the difference between people that make maps and GIS people: GIS people waste much of their time dealing with spatial reference systems while people making maps just avoid them like the plague and instead focus on the projections they need to use to represent their data with.
Most discussions on the topics of projections and spatial reference systems is mainly on the large number of small spatial reference systems each used by a limited number of groups. Work for the state of Massachusetts, use EPSG 2805, work for the Boston police? then you use EPSG 2249.
This talk will focus on the gap between how projections work in theory vs how people constantly waste their time dealing with projections. Most of the mental energy spent on projections and spatial reference systems is spent on incompatible local systems used for storage of data, which are also known as internal details nobody should care about with disproportionate time spent converting between datums whose differences are smaller then the precision of the data.