Coordinates, Projections, Datums, and the Meaning of Life (abridged)
What’s spatial about geospatial data? Coordinates are what make geospatial data spatial. But what are coordinates, anyway? How are they related to projections and datums? And in fact what exactly are projections and datums? And isn’t the plural of datum actually data? Who came up with this stuff?
Questions, so many questions. We plunge forward uncertain, creating, manipulating, analyzing, displaying geospatial data, because there is work to do, bills to pay, deadlines. Yet on some level we understand that one of the most fundamental functions of a GIS is the ability to correctly overlay spatial datasets. And we know, deep within our souls, that it cannot be done correctly without a solid understanding of coordinates, projections, and datums. Well, maybe not us, but somebody has to understand those things. Right?
Actually, it is us, or should be us. This presentation seeks to provide an explanation of coordinates, projections, and datums, in an unrealistically short time. Particular emphasis is on the unsettling topic of datum (aka geographic) transformations, leading to the even more disturbing idea that modern transformations change with time. With the exploding interest in 3D data, a brief foray into the vertical component of spatial data will be made to address that gnawing question, which way is up? And finally, if anyone is left in the room and time allows, the meaning of life will be revealed. In color.