Now that everyone with an internet connection has access to Google Earth and Google Maps, we all have access to some fairly high quality air photo imagery. This might seem to be a good thing, but there are problems with air photos. They are not maps.
A map is a representation, or an interpretation of reality (most often derived from air photos), with information added to it from land survey data, elevation data, etc. For example, while an air photo can show you what the ground cover is, and where the roads are, the map shows you the contours (indicating elevation), road names, the scale, what what the land use it (industrial, residential, park etc). While some may argue that Google Earth “Satellite” view is a map because it overlays the roads and such, it still suffers from too much information, and not enough of the correct kind of detail that can be offered by a well designed map.
A topical example is provided below. The recent explosion and sinking of the Deepwater Horizon oil rig in the Gulf Coast.
The Satellite image shows the oil slick in relation to the coastline.
The status map, on the other hand, shows scale and geographic grid. It shows the extent of surface oil and the quality of the slick as observed by survey flights. It shows specific distances from points on the slick’s front to points on the coast for reference. It shows the exact position of the incident, including a reference latitude and longitude, it shows staging areas, it includes the date and time of the data, etc.
It’s not that the map provides more data, it’s that it provides more useful data, provided and interpreted by experts, and data that is not available on the air photo. It provides context and it tells a story. It’s easier to read and get a sense of what is going on.
All of this may seem to be obvious, but I still come across people who do not understand that a map as an interpretation of reality is in most cases more useful than an air photo.