Travel Advice - How to use the map index and the grid reference to
Good quality maps contain an index that lists the names of places
located on the map, as well as a notation describing their position on
- It is a little known fact that many cartographic publishers may have
more places named on the map than they have room for in the index and,
often, delete names from the index in the interest of space.
- If a place that you want to visit is not in the index, look on the
map in the general location (if you know it) and you may find it
sitting there in all its glory.
Street or place names listed in the index are associated with a grid
reference number that identifies these locations on the map. The grid
reference number points to a grid cell on the map or in the case of a
road atlas to a page and then a grid cell on that page.
The number of grid cells varies based on the size and scale of the map,
as well as the density of the information symbolized on the map (see
What does scale mean and how to use it?).
- Large sized cells make it easy for the cartographer to create the
index but make it very hard for users to find locations, since each grid
cell may contain a large number of town or street names.
- Conversely, small sized grids make it easy to find places, since
there are usually few names in each cell, but the grids may be hard to
work with due to the great number of cells symbolized.
- In addition, when the grid cells are numerous the cell notation
scheme can become quite complex.
Normally, grid reference is given in the form of a pair of coordinates
(e.g. 1, 5, or B, 2). Cartographic convention dictates that the first
grid reference should be found along the bottom or top of the map and
the second along the side of the map.
- Most map publishers have converted to a form of indexing known in
the mapping industry as “Bingo Referencing”.
- "BINGOing" makes finding the location on the map just like playing
- You find the column and, then, the row identifying the cell and
"Bingo" your town will be somewhere within that cell (this is the
reason that most maps are indexed with a combination of alphabetic
and numeric coordinates).
One trick of the cartographer’s trade is to show towns too small to be
portrayed at the scale of the main map on "inset maps" (small maps set
off from the main map and usually placed around the edges of the map
- Inset maps are shown in a larger scale to present greater detail
than is possible on the main map.
- Another one of the relatively unknown rules of map making is that
cartographers index the streets and towns shown on their maps at the
most detailed scale possible.
- Even if a town is shown on both the main map and in an inset, the
town will frequently be indexed to refer to the inset rather than
the main map, since the inset is a more detailed representation.
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