Not so simple! Maps come in all shapes, sizes, and media types...and some don't even look like maps. But they all have a geographical base in common: to navigate by land, sea, or air; to explore for oil, gas, and other mineral resources; to relate information such as a customer base in an geographical information system; or for some other scientific or industrial use such as climate and meteorological studies.
No electronic media has been able to duplicate the photographic resolution and large breadth of vision provided by a finely printed map. Resolution of photographic film is magnitudes greater than any high resolution screen.
As the geographical base changes either politically or geologically, the maps themselves must reflect the current state. Ships and aircraft require maps showing the current location of hazards and authorized pathways. Subscription map services update subscribers as the maps are revised and published.
Mapping services exist to supply unique maps for real estate ventures, construction projects in unmapped regions of the globe, and other uses for which published sources do not exist.
Land Maps: Whether used with compass or GPS, paper maps continue to be an effective way to navigate on the ground. US Coast and Geodetic survey maps cover almost the entire United States and provide political and geographical information in two dimensions, and via contours a semblance of three dimensions to the expert map reader.
Maps convey three dimensions via color and elevation-marked contours. Political boundaries and other designations not visible on the ground, as well as man-made features such as roads, railroads, parks, and buildings add richness to the normal two dimensions of a flat map.
The Sanborn Fire Insurance Maps are no longer published for US cities, but are available in archives and libraries. Some have been digitized and can be found online, either in institutional libraries or for sale. They detail, building by building, aspects of use and construction that might affect the insurance risk, including adjacent structures, roads, and other features.
Nautical Charts: Useful and often beautiful - one of the highest forms of the printer's art - charts used to navigate the world's oceans and waterways may be the oldest form of map. Modern navigational charts show what can't be seen: depth and unseen hazards; the outline of dredged seaways; and the location of other navigational aids such as radio frequencies of coastal and harbor authorities.
Ships usually need the resolution and breadth of printed paper maps - maps for every place on the ship's itinerary, lots of paper. Changes to mapped conditions are frequent enough to require active users of nautical charts to subscribe to an update service.
Aeronautical Maps: While ships are dependent on the underwater information supplied by their charts, pilots require radio information for basic navigation and to connect to air traffic controllers for guidance. Maps tell the pilot or navigator approximate location, and when lost, landmarks that can be identified from the air. However, commercial aircraft usually fly too high to make what's passing 37,000 feet below useful.
Maps show air traffic control protocols within range of major airports. Here, digital display is more effective, and most pilots have traded in those heavy satchels full of paper maps for an iPad.
Oil, Gas, and Resource Maps: The representation of oil reserves, geologic formation, and other information underground are highly proprietary efforts. Oil companies may produce their own maps, which they hold close to the vest. Those available commercially cover larger, more generic areas which are not much use to drillers. But, they have value as economic, planning documents.
A variety of resources such as mineral deposits within an array of rock formations are usefully depicted on a flat map. In depleted oil fields in certain soil conditions fault maps show sinkings and splits which affect detrimentally any surface structures built over them.
Geographical Information Systems: The map plotting Napolean's march from Kovno to Moscow and back from the summer of 1812 to the early winter of 1813 shows 1) a scaled width of the line of march from 422,000 at start diminishing to 10,000 at the end, 2) the date and temperature are shown at bottom showing the speed of movement and effect (in the width of the line) of the extreme winter temperatures. It is triumpth of information and of the cartographer's art and intelligence.
GIS seeks to combine disparate information that has a geographic base: location of customers or resources; certain phenomena for which geography plays some critical part; and other kinds of information which when related to the underlying geography, illuminates aspects of the information otherwise invisible or unknown.
Scientific Maps: We are all used to seeing meteorological information plotted on a physical map at varying scales. Information about climate, resources, the distribution of all kinds of effects and materials are represented on a wide variety of maps common to many scientific disciplines.
Historical Maps: Any map whose information has been superceded by a later issue should qualify as "historical." The comparison of what is with what was is in itself an aspect information not otherwise present in the current map. Maps far older, if not ancient, display the limits of knowledge or technology at the time of their making.
Subscription and Mapping Services: Maps have a shelf life: areas without much growth or change - a long time; areas undergoing rapid and significant changes - quite short. Subscription map services update customers who require it the latest published of a particular type or area.
When the latest published version is not soon enough, mapping services provide any kind of map tailored to use and need. These can impose future improvements, and record changes as quickly as the customer requires.