measured by it’s size and computed from the number it
correspond to.
We propose the CONTRACT to describe when a object
decreasing it’s space that occupied in the geo-spatial way, as a
result of CONTRACT process, geometrical area or volume
reduced in a computable way, CONTRACT is a original
process.
Rotation plays an important role in the geometric
transformation, change the direction of the object by adding or
decreasing the angle from the axis, a lot of geographical
phenomena related the changing of orientation can be displayed
by ROTATE.
We propose MOVE a basic process for the independent change,
the object change it’s position from one place(often marked in
certain coordination) to a different place, MOVE process
provides a broad range of phenomena such as changing address.
Regardless of the identity and the related change happened to
other objects, EXPAND, CONTRACT, ROTATE and MOVE
comprise of the independent change, which created a basis for
basic spatio-temporal process. We deem independent change as
a original level of spatio-temporal process, and dependent
change a higher one, in many cases, independent process
happened as a result through the dependent process. The
classification of STP do benefit for the following section, and
built a fundamental basis for the visualization of STP, in the
following paragraph, numerous variables will be utilized for the
displaying of the STP, with respect to each process under the
framework proposed here.
3. DYNAMIC VARIABLES AND TEMPORAL
MAPPING
It has become clear that the traditional visual variables, which
we will call the static visual variables from here on, do not
suffice in describing the added means of expression we have in
dynamic visualization of spatio-temporal processed through
cartographic animations. To this end six "new" visual variables
including moment, duration, frequency, order, rate of change,
synchronization have been introduced by DiBiase et al. (1992 )
and MacEachren (1994) . These will be called the dynamic
visual variables from here on.
Research by DiBiase et al. (1992) and Koussoulakou & Kraak
(1992) has shown that visual variables can indeed be used on
the individual frames of an animation in such a way that these
images effectively communicate the cartographic message to
the user, while the movement of the animation gives the
message an extra dimension and "new energy". Furthermore,
the findings of Koussoulakou & Kraak (1992) showed that
using animated maps helped users grasp the contents of a
message in a more effective manner compared to using
traditional static maps or map series.
3.1 Four Implementai Dynamic Variables
In this paragraph, in order to get an implementai framework of
dynamic visualization for the STP, we chose Moment, Duration,
Order and Frequency for the representation of temporal aspect
of objects, there are the reasons for the choice:
3.1.1 Moment
In most time, we look process time as a continuous variable,
however, each process can be divided into discrete time pieces,
we call it MOMENT, The moment that an element in the map
changes during a STP can be used for temporal as well as non
temporal animations, e.g. every procedure has a begin time and
end time, some key remarkable MOMENT are often record in
spatio-temporal database.
3.1.2 Duration
From the Start to the end, the time span that between two
different MOMENT is named DURATION, we can also name
it after from one specific state to another state of objects or
phenomena, The last time always is an important item in the
geographic information, e.g. how long will be typhoon last.
3.1.3 Order
Order is used to differentiate change sequence among several
spatio-temporal changes, sometimes we use a frame according
to a specified spatio-temporal process, The order of change is
similar to the topological relationship or spatial neighborhood,
in one hand ,the sequence of the frame can be represented by
ORDER, in the other hand, order also refers to the order of
phases in a series of changes in the spatial domain.
3.1.4 Frequency
Frequency refers to the number of times that a phase is repeated
in a series of changes in the spatial domain. It is also used to
determine how the frame for representing the STP to be
repeated, since a lot of phenomena reoccurs according to a
regular time, here the frequency can conceptualize this
phenomena very well.
Altogether, the variable mentioned above may not sufficient to
describe all the STP representing the objects and phenomena,
however it can build a implementai framework for a practical
implementation.
3.2 Temporal Mapping
There are at least three kind of time for the spatio-temporal
object, Real World Time, Database Time and Display Time,
when dealing with a temporal process a direct relation between
display time and world time exists. World Time is the time
scale of reality, the moment an event takes place in the real
world. Examples of these processes are those of the Dutch
coastline from Roman times until today, boundary changes in
Africa since the Second World War, or the changes of
yesterday's weather. Time units can be seconds, weeks, or years.
In order to represent the spatio-temporal process in a dynamic
(animated) way, the mapping from Real World Time to Display
Time is necessary, because it is impossible to display a time
sequence change according to actual time. Figure2 show a
relation between Real World Time to Display Time, T1 and T2
are world time, Display time Tl’ and T2’ are derived through a
mapping. All this time are recorded in the Database time, that
means that Database Time is a complete record temporal
variable aggregation. Not only the transactional time but also
the Real World Time and Display Time are derived from it.
