Distance and scale can be indicated in a variety of ways on a map in verbal, numeric, or graphic form.
Remember, scale varies significantly across the area of some maps. If this is true of yours, be sure to note the adjustments required.
DirectionThe question of what is north can be an issue on some maps. On the earth, true north (the direction to the North Pole) differs from magnetic north, and the magnetic north pole moves due to changing geophysical conditions of the earth's crust and core. Many reference maps indicate both. Most maps we compose are oriented to true north, even though compass readings in the field are angled to the magnetic pole. Adjustments for these compass deviations are made routinely.
Legend
Unless it is absolutely clear from the context in which a map appears, readers will need to know about the sources from which the map was derived. You must identify your sources so that the reader could, if needed, track them down to check your information and interpretation. Often the age, accuracy, and reliability of sources is critical to the interpretation of a map and should be noted. Sometimes it is also important to indicate how the data was processed, grouped, generalized, or categorized.
The title of a map is usually one of it's most essential features. As such, it should receive very careful attention so as to match the needs of the theme and audience. A short title might suffice if readers can be assumed to be familiar with the theme being presented, more information is needed for less experienced readers. The content of the title should also be measured against other lettering applied to the map, for example in the legend or annotations. Sometimes, legends and annotations supplant much of the content of a title. Also, be aware that captions usually take the place of titles for maps appearing in publications such as books and journals.
The projection used to create a map influences the representation of area, distance, direction, and shape. It should be noted when these characteristics are of prime importance to the interpretation of the map. Some widely used locational reference systems such as the U.S. State Plane Coordinate system and Universal Transverse Mercator system are based on predefined projective geometries that are implicit in the use of the coordinate systems themselves.
The authority lying behind the composition of a map can be of prime importance in some situations. Most maps note the name, initials, or corporate identity of the cartographer(s).
The meaning and value of some maps--such as those relating to current affairs or weather--are time sensitive. The reader must know when they were produced to gauge whether to trust them. An out-of- date road atlas or city map can cause tremendous frustration. Other maps are less sensitive to the passage of time, but the date of production can still be important if, for example, better information becomes available in the period after publication. Be sure to indicate the date of production for your map, or make sure that it can be inferred from the context in which it is to appear (maps that appear in newspapers, magazines, and journals can be dated in this way). The detail with which you specify the date of production will depend again on the nature of your theme and audience.
Diagram of selectively-used elements
Neatlines or clipping lines are used to frame a map and to indicate exactly where the area of a map begins and ends. The outer neatline of a map--its border--helps to frame the entire map composition to draw the reader's attention to the various elements of information. Neatlines are also used to "clip" the area of the body of the map and of locator, inset, and index maps. Neatlines are not always needed to trim the body of the map. Examples. Some geographic areas can, so to speak, be suspended in space without a neatline. In other cases, the areal extent of a map can be made apparent in other ways.
Some maps portray areas whose locations may be unfamiliar to readers. In such cases, the cartographer adds a "helper" or locator map that places the body of the map within a larger geographical context with which the reader can be expected to be familiar. A detailed map of troop movements on the first day of the Battle of Gettysburg may require, for example, a locator map indicating Gettysburg's position within the road network of south central Pennsylvania and northern Maryland in 1863.
Sometimes observations and data are so densely clustered in small sections of a larger map that the cartographer must provide the reader with additional close-up, "zoomed-in" maps of these smaller areas. Otherwise the data will obscure itself. These close-up detailed maps are called insets.
There are limits to the amount of information that can be placed effectively in the body of a map, even though this information is useful to readers. Sometimes labels and other information have to be moved to an index map.
The maps move from a rather large scale down to a very precise representation of Nagasaki. Because the three maps are shown together, it is not necessary to include a locator map in the map of Nagasaki. If, however, a map of Nagasaki is intended to stand alone, a locator map is absolutely necessary. Click on any of the frames to see alternate layouts for these maps. (inactive 5/17)
