Detecting Spatial and Temporal Route Information of GPS Traces - Geoinformatics for Intelligent Transportation - page 63

(a) (b)

Node

Node

d 2 d 2

d 1

d 0

d 0 d 1

Road segment Road segment

Fig. 1 Distance between the a node to a road segment. a Direct perpendicular distance. b Indirect
perpendicular distance

2.1 Control Variables

2.1.1 Distance to Road

The distance between two geographical objects represents the correlation between
spatial locations. The road segment, which is mostly closed to the referenced node,
has a high probability to be the correct road. However, the distances from a GPS
point to a speci

c road segment vary in terms of the spatial correlation between the
two geographical objects. As shown in Fig. 1 , there could be three types of dis-
tances between a node to a line, which are the perpendicular distance (d 0 ) and the
distances from the node to the end nodes (d 1 and d 2 ) of the link.
In most of cases, the perpendicular distance was considered as an ef

cient
measurement. Other distances might be used to calculate angle information of the
virtual triangular to provide further location information. In our case, we take the
closest distance between the node and the road. In another words, it is the per-
pendicular distance (d 0 ) as in the case of Fig. 1 a and d 1 as in the case of Fig. 1 b. In
this way, every road segment in the candidate set can be differentiated through the
shortest distance from a node to a road.

2.1.2 Direction Difference

Despite that the distance measures the reference information for a single node it
does not say anything about the sequence information. The integral consideration of
two or more adjacent nodes can provide information in both time and direction
dimensions. Basically, the direction between the line connecting two adjacent nodes
should be consistent in some extent with the direction of the matched link.
Moreover, it can also bene cation of whether there happens a turning

action which mostly indicates a cross section closed to the node (Fig. 2 a).
To further identify the correlation between the line of two nodes and the road
segment, we use the angle information by incorporating the direction of the lines, as
shown in Fig. 2 b. In order to determine the degree of the angle consistently between
a location and multiple road candidates, the direction of the road and two nodes are
pre-set in advance. As shown in Fig. 2 b, to ensure that Road 1 and the link

it to the identi