- 3.1
Introduction
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- This
study considers the features available in the web-based VRML environment and
applies some of them to create a demographic mapping environment.
First, this research focuses on the ability to use 3D representation
of maps. Next this study
considers dynamic capabilities of VRML which allow for the inclusion of
animation. Finally, there is a
focus on user interaction and navigation within a VRML world.
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- 3.2
Setting
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-
This experiment was conducted on the
University of Hawai`i at Manoa campus in the Geography Department
Cartography computer lab. The
facility was chosen due to access to a computer with a Pentium® II 450
Megahertz processor with 256K memory, running Microsoft Windows NT® with a
17 inch (43 cm) monitor. This
computer, while not among the most powerful desktop computers available
today, was the fastest one available and the most practical.
Furthermore, it was located in a corner attracting little attention
during the experiment.
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The participant group included a variety
of people of different backgrounds, thirty in all, selected mostly because
they were willing to participate and able to come to the facility.
Just over half the participants were related to the University of
Hawai`i at Manoa Geography Department as either undergraduate or graduate
majors, or else non-major students of Geography classes.
About one quarter of the participants were acquaintances of the
researcher through the University of Hawai`i at Manoa Music Department.
The remaining participants had other backgrounds.
Personal details were not requested from the participants, whose ages
ranged from about 20 to 60. All
participants who began the experiment completed it in one sitting.
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- 3.3
Experimental Base Map
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- This
study involves a series of 3D scenes, also known as worlds, modeled with
VRML. Central to each world is
a contour map showing topographic lines of a region (Emerald Bay and
surrounding area at Lake Tahoe, California) with varied terrain including
flat land, hills and water bodies. Figure
3.1 shows the map. The map was
taken from a website (http://www.microtopo.com/, [accessed
September 13, 2000]) sponsored by Visualization Software LLC.
Note that graphics taken from Netscape Navigator® are restricted to
a resolution of 72 dots per inch. Due to the smaller size on paper, images do not show up as
clearly in print as on the computer screen.
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The software used to view the worlds is Netscape Navigator 4.7® using VRML
plug-in Cortona VRML Client version 3.1.
Cortona VRML Client shows the image in the main portion of the screen
with optional navigation controls on narrow strips at the left and bottom of
the screen. The maps are
presented from a viewpoint in front of the map, looking out across the
landscape. As a background to the maps, a basic sky color has been
chosen to give the map a seemingly natural setting.
The light blue background gradually gets darker, higher on the
screen. On each of the four
corners of the map is a legend in the form of rectangular gray boxes labeled
with “(100)” on top to represent the height of the boxes.
In front of each of the four sides of the map is a worded direction,
with the word “South” in front and “North” in back.
-
- Figure
3.1. Picture of map used in
experiment
-
- This
same map is presented in two forms - as a flat map and as a 3D image draped
over elevated terrain. Figure
3.2 shows the map along with the navigation toolbars.
The flat map is shown on top. Below
that is the 3D terrain map which has the image of the map draped over a VRML
Elevation Grid. The VRML
Elevation Grid used to show this map topographically
was created from United States Geological Survey Digital Elevation Model and
Digital Raster Graphic.
-
-
Figure
3.2. Map as presented in VRML
with toolbars on left and bottom of screen;
- flat
map on top, 3D terrain map on bottom
- 3.4
Experimental Symbols
-
- Placed
atop each map are 3D cylinders which represent population data for the
locations where they are placed. These
cylinders have a series of basic and dynamic characteristics.
Basic characteristics include height, diameter, color, location (x,
y), and elevation (z). The
dynamic characteristics include rate and direction of rotation which is
parallel to the base map. Figure
3.3 shows a world with a flat map, and with the cylinders included, as used
in the experiment.
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- Figure
3.3. VRML world as used in
the experiment showing cylinders placed atop the map
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-
- The cylinders are
divided into two groups: those
being used as targets in the experiment, and those which are not, also known
as distractors. Distractors are
used because a map may contain additional information besides that which is
of focus. To provide a constant
in the experimental test, the target cylinders are all assigned the same
color. The distractors are
assigned a variety of other colors. The
target cylinders all have the same diameter.
The distractors have a variety of diameters, some the same as the
target cylinders. The target
cylinders are further split into two groups:
those that are rotating and those that are stationary.
The rotating target cylinders all rotate at the same rate in the same
direction. Height, location,
and elevation are discussed along with all specific characteristics being
used in the experimental design.
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- 3.5
Experimental Design
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-
This is a within subjects, four factor, complete factorial design,
with replication within the experimental conditions.
As indicated in Table 3.1, there are two levels of maps: flat and 3D terrain. There
are also three different levels of user interaction which participants
encounter: static,
pre-programmed fly-by, and participant controlled. As a result, there are six experimental conditions possible.
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