|
The NAC map grid system uses specifically selected
constant longitude lines and constant latitude lines to
form grid cells. There are a series of grid levels in the
NAC grid system. The first level grid lines in the
south-north direction are the lines on which their
constant longitude equals to Longitude West 180, 168,
156, 144, 132, 120, 108, 96, 84, 72, 60, 48, 36,
24, 12, 0 degrees, and Longitude East 12, 24, 36, 48, 60,
72, 84, 96, 108, 120, 132, 144, 156, 168 degrees,
respectively. The first level grid lines in the east-west
direction are the lines on which their constant latitude
equals to Latitude South 90, 84, 78, 72, 66, 60, 54,
48, 42, 36, 30, 24, 18, 12, 6, 0 degrees, Latitude North 6,
12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78,
84 degrees, respectively. Each resulting cell is assigned one
character from the Table of the NAC Character and Integer
Correspondences both in the east-west direction and the
south-north direction in the order as appeared in the
table, that is, NAC: 0 0 is the NAC grid index of the
first cell bounded by lines of constant longitude:
Longitude West 180 degrees, Longitude West 168 degrees, and constant
latitude: Latitude South 90 degrees and Latitude South 84 degrees. The
first 0 in the NAC grid coordinates represents its
longitude coordinate and the second 0 represents its
latitude coordinate. The second level of the NAC grid is
formed by dividing the cell of a first level grid
uniformly into 30 subdivisions in both longitudinal and
latitudinal directions, each of which is assigned one NAC
character as the relative coordinate in both directions
respectively, so is the third and other NAC grid levels.
This definition of the NAC map grid system is equivalent
to the algorithm in the definition of the Natural Area
Coding System.
These grids can be applied to all maps such as a
world map, country map, province map, city map and local
community map, or maps for specific purposes. The
resultant grid coordinates are of universal meaning,
simplicity (an eight-character NAC specifically for a
less than 25 by 50 meter area anywhere in the world) and
multiple use. So, the NAC grid coordinates can become an
important part of an address and everybody will like to
keep them together with an address.
With this grid system, a map can be efficiently used
to pinpoint any addresses with NACs and people do not
need to look up the street from an street name alphabetic
list and search for the street number along the street.
All information obtained from different maps can be
easily correlated by the NAC grid coordinates and people
will not have problems to link two maps of neighboring
cities.
The NACs of two addresses anywhere in the world can
be used to calculate their distance and their natural
time difference and determine their relative locations.
Maps of the NAC cells can be named by their Natural
Area Codes and stored systematically in a map library
according to the NAC character order, which may give
people much convenience to use the maps.
Tourist maps may include the list of hotels,
restaurants, railway stations, airports, tourist
information centers, parks, historic sites, shopping
malls, and museums with their NACs, which will be very
useful to tourists.
|
