Mobile Mapping System Do it yourself!

Mobile laser scanning is an essential part of todays 3D documentation technologies. It is already widely used in generating 3D city models, as well as in registration of roadway damage and in the CGI (Computer Generated Images) sector. Through interaction of an inertial measurement unit, with a GPS system and a laser scanner it is possible to get a 3D point cloud. New developments in IMU sensor technology (MEMS based) opens up new markets and can be seen with a promising future.

In todays market such systems are still really cost intensive and only available for some projects. Due to the need for high investments mobile LIDAR is only used by a small number of companies as compared to the surveyor market.

There are also some issues to be considered when using a mobile laser scanning system on a car. In the future a lot of cities will be car-free. You wont be able to drive through the city without special permission, which takes time and as we all know, Time is Money. And what about paths with barriers which cant be navigated by car?

As part of my master thesis which was done in cooperation with Faro, Applanix and Tobias Moehlihs, a colleague from my university I thought about all these facts and developed a solution: A mobile mapping system which is completely flexible and easy to set up. The principle follows the concept: Do it yourself.

At the moment it is still a prototype, but in the near future it will be further developed. We will also integrate cameras into the system. With the Focus3D laser scanner Faro offers a cost-effective component for such a system, because of its small size and low weight. After testing several Inertial Measurement Units with a focus on the results and the possibilities of synchronization I decided to use the POS LV220 from Applanix as the inertial navigation component.

This system delivers robust data even in cities with high buildings. Additionally with the two antenna system of the POS LV the heading is improved by the GAMS (GPS Azimuth Measurement Subsystem) Solution developed by Applanix. To adhere to the principle of simplicity I use the trigger signal from the Faro Focu3D to synchronize the components. This means every time a new mirror rotation of the laser scanner starts, a trigger signal is sent to the IMU and this saves the position and orientation.

So if you have a laser scanner, an IMU and a vehicle of your choice you can start set up your own system. In the picture the necessary components of my mobile mapping system are shown.

The POS LV220 contains the IMU, two GPS Antennas, the DMI and the processor. The laser scanner Faro Focus3D with the Helical-Kit, a laptop, a battery and a bike trailer make up the rest of the system.

The fact that this is not a complete system makes it easy to set it up on every vehicle you need for your task. During my master thesis I set it up on a van and also on the bike trailer.

The advantage of the bike trailer is, it is a green solution and you can use it in all places the car cannot pass. I scanned for example an old church in Stuttgart within a couple of minutes, which would take a minimum of an hour if you scan it statically. But if you have bigger project like corridor mapping you can easily take the components and put them on your car. For the van I used two aluminum plates to mount the components on. These plates with the components were put on the roof rack and screwed in tightly.

For transformation of the laser scan data I wrote a program using Matlab, for pointcloud editing Faro SCENE is used and for postprocessing of the GPS data POSPac from Applanix. If you want to have more information about the postprocessing in Matlab feel free to contact me. The result of this mobile mapping system is shown in the following picture.

To sum it up I can say with this self-built compatible system you can scan fast and easily in almost every environment. The software is easy to use, you get precise positions with post processing in POSPac and easy point cloud editing with SCENE.

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