https://gis.stackexchange.com/questions/8650/measuring-accuracy-of-latitude-and-longitude
https://gis.stackexchange.com/questions/664/difference-between-projection-and-datum
https://gis.stackexchange.com/questions/5701/differences-between-dem-dsm-and-dtm
https://gis.stackexchange.com/questions/3083/seeking-examples-of-beautiful-maps