RADIS system development
Several software sub-systems are integrated into RADIS to obtain the required functionality. The design architecture for each sub-system is explained as follows:
Sub-system 1: Camera video imaging and GPS coordinate capture, display and record A number of threads, namely the capture thread, graphic canvas thread( per camera), display thread, and recording thread, are designed to fulfil the required video image capture, display and recording functions of the sub-system. The sequential diagram representing the operation of each thread is shown in Figure 1 [ 3, 4 ].
Plate 1: Video image recording system
Figure 1: Sequential diagram( video image capturing, displaying and recording)
Using a similar concept, a number of threads were developed for the GPS capture( client), display and recording( see Figure 2).
Sub-system 2: Client and server based GPS coordinates streaming system With the lack of GPS software on the Lenovo 4500U Laptop and the requirement to use a single device to record both the camera video image and GPS coordinates to avoid time synchronization issues, an HTC One X smartphone with a built-in GPS module was used. Using the configured Wi-Fi link between the Lenovo 4500U Laptop and the HTC smartphone, the GPS client programme( TCP / IP socket) running inside the smartphone sends the result of GPS coordinate calculation to the connected server( laptop). At the same time, the smartphone also displays the current GPS location on a rendered map.
Sub-system 3: Camera calibration for horizontal( lane width) measurement The image produced by a pin-hole camera can be modelled as the projection of an object in the 3D world into a 2D image plane. For example, the projection of a planar object( e. g. road surface) in the 3D world into the 2D image plane can be described by a planar homography H( matrix with dimension 3x3) as
[ 1.0 ]
Figure 2: Sequential diagram( GPS capture, display and recording) where m is the pixel coordinate on the camera image plane and M is the grid coordinate of the 3D planar object [ 5 ].
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