Map Projections, la deuxième partie

I seem to recall saying something last week about finally truly understanding the various concepts of map projection, and how projections and coordinate systems are handled in a GIS.  This week I learned I was wrong.  The bravado caused by my hubris was a preemptive celebration, and, though I came to a much, much better understanding of projections and coordinate systems with this week's work, I now know that I've only seen the tip of the iceberg.  I also had the opportunity this week to search for and download some public GIS data, in the form of shapfiles and aerial photos, which was something I'd only ever dabbled in before.

This map is comprised of 2 ortho quads (each made with 4 quarter sections), created by the USGS, and 3 different vector datasets- Florida county boundaries, major roads, and USGS quad boundaries.  The vector line data was in a different coordinate system than the aerial photos, and had to be reprojected in ArcMap to the State Plane Florida North system.  The files would have appeared correctly together in the map document if added together in different coordinate systems, but there would be a loss of functionality- which is something I have personally encountered in ArcMap, and never knew how to "fix" it.  It isn't enough to merely describe the coordinate system in the metadata, ArcMap has to actually change and export the file in a different projection.  The process itself is easy enough, but the theory behind it was a definite challenge for me.  I did, after many hours of work, finally get a decent grasp on the general concepts and theory that exist, and run in the background, to accurately display the 3 dimensional earth on a 2 dimensional surface.  Additionally, I gained some experience in adding x,y data coordinates from a tabular source to create features on a map- which are the storage tank contamination monitoring sites of Escambia county in the map above.  Another procedure that may seem simple and intuitive, but is, in reality, a bit of a complicated process.