|
Since The Natural Area Coding System has generated simple NACs for all areas
on the earth and three-dimensional regions in the universe and short coordinates
for all geodetic points, the system can significantly improve the structure of
a geographic or geospatial database and reduce its storage size more than 80%.
One of the structures of the system for managing a geographic database is
described in the following:
A NAC geographic information database for the whole earth surface stored in
a computer contains two main directories. The first main directory is called
the main NAC directory under which all geographic information is saved
according to the NAC structure. The second main directory is called the main
index directory under which all the information about geographic identities
are linked to the NAC areas and the information about
these identities can be retrieved from the NAC directories through the linkage.
The main NAC directory contains several files and first level NAC directories.
The files are the information of the global geographic identities such as
continent borders, ocean borders, country borders, global transportation
networks, etc. The first NAC level directories contain the information of the
first level NAC areas and named by the NAC of the first level NAC areas with
a lower case hypen to link the two parts of a NAC such as N_K for NAC: N K.
There are 900 first level NAC areas on the earth, so there will be 900 first
level directories under the main NAC directory.
A first level NAC directory contains several files and second level NAC
directories. The files are the information of the geographic identities
of the size suitable to be shown on the first level NAC area map such as
country borders, rivers, province borders, forests, deserts, etc. The
geodetic coordinates of the geographic identities will be saved in relative
NACs of the first level NAC area such as the absolute NAC of a geodetic point
at NAC: NJKL KGDF will be saved as "JKL GDF" under the first NAC directory named
by N_K. This arrangement can save lots of required memory. A second level
NAC directory containes the geographic information of the second level NAC
area and named by the relative NAC of the second level NAC area such as the
second level NAC directory for the second level NAC area of NAC: NJ KG will
be named as J_G under the first level NAC directory named by N_K. There
are 900 second level NAC directories in total.
A second level NAC directory contains several files and third level NAC
directories. The files are the geographic information suitable to be shown
on the second level NAC area map. All the geodetic coordinates of the
geographic information will be saved in relative NACs such as a geodetic
point at NAC: NJKL KGDF will be saved as "KL DF" under the second level NAC
directory named by J_G under the first level NAC directory named by N_K.
A third level NAC directory will be named by its relative NAC such as the
third level NAC directory for the third level NAC area of NAC: NJK KGD will
be named as K_D under the second NAC directory named by J_G under the first
level NAC directory named by N_K.
A third level NAC directory will be created in the same way as the second level
NAC directory, so do a fourth or fifth level NAC directory.
The geographic identities such as a straight line section of any length
parallel to the lines of constant longitude or constant latitude or an area
of any size and any side ratio bounded by lines of constant longitude and
constant latitude can be simply represented by a single NAC such as
NAC: HJKL KG and NAC: HJKL KG--K are straight line sections while
NAC: HJK KGD and NAC: HJK KGD-F are areas. These notations can save a lot
of memory to represent these geographic identities. Many state and county
boundaries in the United States are straight line sections parallel to the
lines of constant longitude and constant latitude.
The second main directory is the main index directory which containes an index
file and first level index directories for global geographic identities such as
oceans, countries, etc. The index file lists all the names and their variations
of the global geographic identities with their sequence indexes alphabetically.
The sequence index of a global identity is a 30-based number expressed by 30
NAC characters. The index file contains the names of global geographic
identities and their indexes with one line for one geographic identity. For
example, a line for the United States in the file may look like:
United States of America; US; USA; United States; 23B
where the first one is the official name, and others are its variations, and
the last one is the index. The index uses only NAC characters to make it
shorter than only numerals. Excluding vowels is to eliminate combinations
to be words. The indexes will be used as file names in NAC directories.
A first level index directory for a geographic identity will be named by its
sequence index.
A first level index directory contains one index file and second level index
directories for its second level geographic identities such as provinces, states,
etc. The index file lists the NACs of the NAC areas covering the
geographic identity on the first line and lists the names and their variations
of second level geographic
identities with their sequence indexes alphabetically. The second level index
directories are named by their indexes listed in the index file.
A second level index directory has the same structure as the first level index
directory, so does a third or fourth level index directory.
The name of a file in a NAC directory will be the absolute index of its
corresponding geographic identity defined in an index directory plus an extension.
The index will function as the key between NAC directories and index directories.
The indexes in the index file in the main index directory will be directly
used as the file names in the NAC directories because they are already
absolute indexes, while indexes in the index files in sub index directories will
be prefixed by its directory name, parent directory name, or even its grand parent
directory name because these indexes are relative indexes and the names of index
directories under the main index directory are named by their relative indexes.
For example, an geographic identity with index of 583 listed in an index file at
Main Index Directory/23B/4H7/Q8R/index.txt
Its detail description files in a NAC directory will be named as:
23B_4H7_Q8R_583.ext
where ext can be any extension you want to distinguish different files about
the geographic identity.
When you try to find this object, you can first look up it in the index directories
and find its index and the NAC it resides in. Then go to this NAC directory to
find all files about this geographic identity.
A user interface for the database may allow the user to input either a NAC of
an area or a name of a geographic identity to retrieve the geographic data.
If a NAC of an area is input, the computer will directly go to the NAC directory
to retrieve the data. If a name of a geographic identity is input, the computer
will go to the index directory to find out the NACs of the NAC areas covering
the geographic identity, and then go to the NAC directories to retrieve the
corresponding data.
There are many significant advantages of the NAC system over other databases:
- Using absolute NACs to represent geodetic points
can save about 50% of memory compared with using other systems;
- Using absolute NACs to represent straight line sections parallel to the lines of
constant longitude or constant latitude can save more then 75% of memory;
- Using absolute NACs to represent rectangular areas with the sides of constant
longitude and constant latitude can save 87% of memory;
- Using relative NACs to represent geodetic point, straight line sections or
rectangular areas can save even more meomory.
- If a 5-bit integer is introduced to represent a NAC character in the computer
program, there will be another 40 percent of required memory to be saved when the
geographic data are stored as binary files.
- Using NACs to name the geographic database instead of direct using names
of geographic identities can easily link the geographic information between
neighboring geographic identities without the overlaps of geographic data;
- Using NACs to name the geographic databases allows users to retrieve their
interesting areas directly by typing in very few character NACs;
- The system can also help users to store their own
geographic data into the database efficiently if it
includes a function for users to view and edit the
database since the database structure is so systematic
that any geographic data can be saved as a feature file
under the directory named by the NAC of the area.
Therefore, a NAC geographic information management system
is a progressive system which can be updated by users all
the time.
A NAC geodetic information management system for a
three-dimensional database can be constructed in a way
similar to a NAC geographic information management system
for the earth surface, using the NACs of three-dimensional
NAC geodetic blocks instead of two-dimensional NAC geographic
cells as the directory names.
The three-dimensional system will be even more efficient than
the two-dimensional NAC geographic information management system
because of the higher efficiency of the NACs in representing
three-dimensional regions.
With so many significant advantages, the NAC
geographic and geodetic information management system
will be the most economic, efficient and user friendly
geographic and geodetic information system.
| 