After the feature extraction is completed, a standard 
output file is created containing all feature 
information about the collected data. The re 
formatting software, included with Feature 
Extraction Software, can process the standardized 
output files to create input files for a targeted 
AM/FM or GIS system 
The stereo vision system of the GPSVision collects 
huge amount digital data. Automated feature 
extraction is very important to the mobile mapping 
system, but it is still in the research step. One test 
has been done with automatic extraction of the 
road edge lines, it works with the well-painted road 
edges, but it still can’t be used in the production. 
The automated relative orientation and 
triangulation could be implemented for the mobile 
mapping system, but they are not so critical, because 
these procedures do not require to much effort to be 
performed by a person. How to more efficiently 
extract the information from stereo images will be 
the next focus of our new development. 
4. Data fusion of terrestrial image 
and aerial image 
To better serve the user’s needs, a study was 
conducted to combine the GPSVision data and the 
digital aerial photographies. The main idea is to use 
the GPSVision to measure feature along the road 
and then use them as controls to rectified the digital 
aerial images. The aerial image are then serve as the 
background images and also used to digital the 
features off the road. Software were developed to 
measure the control point from terrestrial image and 
to rectify the aerial image. All of the rectified aerial 
images are mosaiced and tiled in small images for 
easy display and handling [Fig.5]. 
The digital aerial imaging was taken using a 
panchromatic 2k x 2k digital camera system. To 
identify ground features with a dimension of 0.5m x 
0.5m, the aerial images will be collected with the 
ground resolution of 0.25 meters. An aerial image 
will cover 500m x 500m of ground area. Between 
each image there will be a 60% overlap. Only every 
other image (ie: image number 1,3,5... ) was used 
for rectification, with the remaining images as fail 
safe material. 
All features extracted from the terrestrial 
GPSVision images are overlaid on the rectified 
aerial photography. This gives user not only very 
detailed view of vector map, but also enable them 
to view interested features with the views both 
from the ground and in the air [Fig.6]. With the 
digital imagery in hand, engineers and technicians 
avoided the costly effort of having to drive to the 
field to view a particular track condition or 
potential problem. 
5. Roadway Application 
Lambda Tech was contracted to map 400 miles of 
railroad between the Detroit and Chicago, USA 
The GPSVision mobile mapping system mounted 
on a high rail vehicle was used for this project. Data 
was collected in 3.5 days. All man made features 
like rail road signals, road crossing, traffic signals, 
parallel tracks, utility poles are extracted from 
stereo images. Attributes are also tagged to each 
features. Completely detailed electronic maps were 
delivered to the project engineer five weeks later. 
During construction, as built fiber locations were 
captured with sub-meter accuracy using Trimble 
GPS equipment. 
After the digital imagery data was collected in the 
field and the GPS data differentially corrected and 
processed. Approximately 25 miles of imagery on 
each CD was then ready for feature extraction. 
Using a PC and Feature Extraction software in the 
office, technicians produced data files containing 
the locations of rail assets and related features such 
as poles, trees, road crossings and bridges. Each 
feature was positioned with a horizontal accuracy 
of one meter or less. The mapping production rate 
was approximately one mile per hour. After the 
feature extraction process was completed, a file in 
DXF format contained the track centerlines, the 
positions, names and attribute tags of required 
assets and features as well as the stationing from a 
known point were delivered to user. 
Image data allows users to map visible features, 
such as rail road signals, utility poles, traffic signs, 
buildings, trees, and even potholes and more. 
Anything you can see with the cameras can be 
mapped with the GPSvision system, most 
important, it is faster and more accurately (sub 
meter horizontally) than in the past. Additionally, 
the digital stereo images used to create the maps 
could be used over and over again for maintenance, 
trouble analysis and inventory. 
5A-3-5