Mapping the way to success

TopGis is a Czech company operating mainly within Europe, with a focus on aerial imaging, photogrammetry, mobile mapping, and various other geographic information systems (GIS). Operating in a competitive market, the company needs to deliver the highest quality data quickly, efficiently and at the lowest possible cost. In order to do this, TopGis selected cameras from international vision company, JAI.

Within the Czech Republic, one of TopGis’ largest partners is Seznam.cz, a company that operates a range of services, including a web portal, search engine and web mapping portal similar to those of Google. One aspect of TopGis’ role in the partnership is to handle all the geographic data gathering and processing for Seznam, and essentially participate in the commercialisation of geomatics to its full potential. In addition to providing standard aerial imaging for use in photo maps, TopGis extended its services to oblique aerial imaging of cities, and decided to build a mobile mapping car in order to generate data from the ground. In principle, these cars are similar to the ones used in the creation of Google Street View.

‘There are many companies and state agencies within the Czech Republic that offer the same imaging services we do, so the key to success in the market is quality,’ explained Vladimir Plšek, technology manager at TopGis. ‘There’s a broad range of panoramic cameras available to choose from, but we found the resolution of the images many of them produced just wasn’t competitive compared to the standard of Google Street View, for example. We therefore decided we not only needed to build our own system, but that it would have to use the highest quality cameras.’

In 2013, TopGis designed its first system using a variety of the latest cameras available on the market at that time. According to Plšek, the cameras all used CCD (charge-coupled device) chips, which proved slightly insufficient when producing images in high levels of light – images taken in the direction of the sun, for example. The limits of the technology represented a real challenge for the company, as Plšek explained: ‘The parameters we’re dealing with are very complex. On the one hand there are systems that combine panoramic cameras with laser scanners in order to provide accurate and precise positioning data for geographic information systems. This is specifically for mapping purposes and although effective, the quality and resolution of the panoramas being produced by those systems is very low. The other factor is cost as not only is laser scanning quite expensive, but the cost of processing that data is higher than many of our customers would be willing to pay.

‘Then there are mobile units like the car/camera set-up used for Google Street View, and that’s a completely different world,’ he continued. ‘Google has its own system and despite the position and orientation information being gathered via global positioning systems (GPS) and inertial measurement units (IMU), the main focus is the generation of images for viewing purposes only. A high level of detail is gathered but it’s mainly used for positioning within a scene.

‘The challenge we faced was how to combine those two types of systems so that we have very precise information about the orientation of space, together with high resolution photographic images. It’s about utilising the benefits of both systems in order to deliver accurate and detailed panoramic images that can be used for both mapping and viewing,’ added Plšek.

TopGis is currently finalising the second version of its mobile mapping system, which comprises a car containing 18 separate cameras. In order to create competitive and accurate panoramas, navigation, positioning and image triggering were all important factors that needed consideration, but the most critical was image resolution. For this reason, TopGis began looking for cameras with 1-inch CMOS chips.

‘The mobile mapping car runs for about eight hours per day and during that time the light conditions will be naturally changing,’ Plšek explained. ‘In addition to that, the car travels in urban areas at around 50kph, and so when it passes between buildings the light levels can suddenly change very rapidly. We experienced some issues with the CCD chips as they weren’t able to sufficiently adjust to those unpredictable and fluctuating levels of light. CMOS chips, however, react very well to these types of conditions and are especially effective when taking photos towards the sun.’

It was determined that 18 cameras would be needed to produce panoramas with the required level of detail, and after testing a variety of different camera models, TopGis ultimately settled on the five-megapixel JAI SP-5000C-GE2. ‘We had a strict list of parameters that the camera had to satisfy,’ commented Plšek, ‘including the size of the chip, the use of a global shutter, a high rate of frames per second, the ability to quickly and easily download data to a computer, and also the ability to trigger the camera by a TTL (transistor-transistor logic) pulse coming from the positioning system. We needed to fulfil all these criteria and JAI made that possible.’

Plšek added that the high resolution afforded by the cameras was the determining factor because the better the image quality, the happier their customers. The decision to use JAI’s cameras also has economic benefits for TopGis as the legibility of details such as the names on street signs and the numbers on building plates has a significant impact when addresses are being mapped from images. If the mobile mapping car were to use low resolution cameras and then journey down a wide street, for example, it would most likely need to pass the buildings twice; once in one direction and then again in the opposite direction. With higher resolution cameras the cost of mapping decreases as the car only needs to travel once down a street.

‘In the future, we plan to build three additional systems in order to cover the entire road network in the Czech Republic within the next two years,’ said Plšek. ‘That represents about 350,000km of landscape that needs to be mapped. A panorama shot is taken every three metres, so you can imagine the amount of data and images being generated. Once you aim to commercialise that level of data, you have to ensure you’re using the latest technology. JAI cameras satisfy all these needs and provide us with a competitive advantage, which is why we plan to use them in all our future systems.’