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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
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* Mover Entrance/Exit points
Lifls are bi-directional but escalators are uni-directional
(up or down) in the moving direction.
» Split points
An open space that leads to many directions of travel is
represented as a split point.
» Turning points
A winding path with an abrupt bend in the route
direction needs a turning point at the juncture.
Link
A link is an edge connecting two nodes and along which
pedestrians walk. Four kinds of paths are possible in view of
the slope angle: horizontal, vertical, diagonal, and staircase.
Most people would prefer walking on horizontal surfaces.
When they get into a lift, the movement becomes vertical.
Walking on steps or taking an escalator would entail a diagonal
movement. Staircases are differentiated from escalator services
because of differences in efforts.
Landmark
Landmarks are selected based upon criteria identified by Lynch
(1960): singularity, prominence of spatial location, distant,
accessibility, content, meaning, use or cultural significance, and
prototypicality.
The following examples from the HKU campus are listed by
geometrical categories:
* Point landmarks — Sun Yat-Sun statue
= Line landmark — the June Fourth Memorial Words on
the Swire Bridge, Zhong Shan staircase
* Polygon landmarks — Lily pond, Main Library
Optimal path
The computation for an optimal path must consider user
preferences. Some possible solutions are:
# Shortest route by distance measured
* Quickest route by time spent
= Simplest route by minimal turns
« Easiest route by least effort devoted
" Scenic route by significant landmarks
Psychological factors also play an important role in the choice
ofa route. For instance, visitors might be willing to walk up
one or two flights of stairs, but would prefer to take a lift when
available for longer distances. The decision variables for
computing the optimal path are critical factors to consider.
Data acquisition of terrain/landscape
The Survey and Mapping Office of the Land Information
Center of Hong Kong offers for sale digital topographic map
data and digital land boundary data. The 1:1,000 maps with
building outlines, roads, spot heights and contours are used to
construct a base map for the HKU campus (Figure 2).
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Figure 2: A digital map of the University of Hong Kong
Data on the man-made features must be weed out in the
preparation of a digital elevation model (DEM) for the
landscape. For instance, there exist spot height values for
overpasses, bridges, and podiums or rooftops. Distinction
among spot height, relief, and contour data must be made clear
to enable integration and the creation of a 3D perspective view
ofthe campus. The data modeling procedure was accomplished
with the 3D Analyst extension of ArcView GIS software and as
outlined in Figure 3.
/ Be 7 / Spot Heights ^
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Figure 3: Data modeling for DEM
3.4 Route directions
We indicated earlier that the landmark-based format of
instruction is chosen to provide route guidance in our research.
Following is one example of route directions within the HKU
campus.
L] Route directions from the West Entrance to the Hui Oi
Chow Science Building:
€ Start from the West Entrance
© Walk by steps to the front of lifts at the Haking Wong
Building
© Take lift up to the fifth floor
< Go by the left corridor until the end
€ Turn right and should see James Hsioung Lee Building
straight ahead
€ Turm left and the Hui Oi Chow Science Building is on your
left.
The series of guiding instructions is close to the human's
natural language. With the exception of the beginning and
