Database: A collection of
information, for instance, about a particular community. A
database is most useful if it is well organized and indexed.
Datum:
A point from which other things are measured. This term (in
full, geodetic datum or geocentric datum) can also refer to a
cartographical system (specifically, a reference ellipsoid, such
as WGS84) that is used to mathematically correct for
irregularities in the Earth's sphericity, such as when using the
GPS.
Declination (variation):
The angle between the magnetic north meridian and the
true north meridian at any given location. It is said to be
'east' or 'west' by a certain number of degrees according to
whether the magnetic north meridian is east or west of the true
north meridian.
Degree:
A unit (abbreviated as °) for measuring direction as if from the
centre of a circle. There are 360 degrees in a circle. Each
degree can be subdivided into 60 minutes (abbreviated as ').
Each minute can be divided into 60 seconds (abbreviated as ").
Bearings and
declination, for example,
are usually (but not always) measured in degrees.
Differential GPS:
A method of correcting for errors in
GPS coordinates
by using two receivers, one to rove and collect position data,
the other to remain stationary at a known position to collect
correction data that is transmitted to the roving receiver (or
supplied to it at a later time).
Digitize: To convert an image,
such as a
map. into a form
that a computer can store and manipulate through the use of
special software (a computer program). Digitizing is usually
done manually, with a digitizing tablet, but simply scanning the
image may be suitable for some purposes.
Displacement: A form of
generalization that involves
moving close-set
map symbols
slightly out of their correct locations so that they do not
overlap each other.
Dissolution: A form of
generalization that involves
combining two or more adjoining polygons representing
somewhat different kinds of features into one polygon.
Adapted with
permission from: Flavelle, A. 2002.
Mapping our Land
