C+S August 2021 Vol. 7 Issue 8 (web)

calibrate it to provide the functionality and data quality they require. By mid-2019, the Center had initiated its first major mobile-mapping proj - ect: imaging and scanning the emirate’s roads and urban infrastructure. Dubai in 3D To begin, teams first focused on Dubai’s roughly 12,000 kilometers of roads, targeting major routes and landmarks such as the Global Vil - lage festival and amusement park, the Old Souk markets, and Dubai’s downtown. The aim was to capture every existing feature on and along the road to create 360-degree street views, point clouds, and 2D and 3D base maps of the 60- by 60-kilometer Emirate. To provide geospatial referencing to the MX9 system, the Dubai Mu - nicipality Survey Department has a network of roughly 12,000 existing ground control points (GCPs) to provide centimeter-accuracy control for the mobile mapping. The department also has a network of Virtual Reference Stations (VRSs) to support RINEX post-processing for the MX9’s GNSS. With the MX9 mounted on top of their SUV, a two-person crew drove the roadway in two directions. Traveling at 80 kilometers/hour, the system scanned road furniture such as road signs, light poles, stop lights, markings and medians––any feature within 400 meters of the road––and captured nine images (panoramic and multi-angle) every 5 seconds. Simultaneous to the image capture, the system collected a point cloud of the AOI at 2 million points per second. On average, it took the team two to three hours to acquire 100 kilometers of data per day on both sides of the roads. “A notable benefit of the MX9 is not only that it has two scanners, but also their positioning angle, which allows us to capture features that could potentially be blocked if we only had one scanner,” says El Mustafa. “Dubai, for example, has heavy traffic, so it would be easy to miss a feature because a car passes you. Two scanners ensure that if one is momentarily blocked, the other will scan those points. In ad- dition, the MX9’s overhead reach is up to 400 meters high, so we can capture nearly all of Dubai’s tallest buildings to create an accurate and true 3D model of the city.” The luxurious five star hotel, Burj Al Arab, lights up the night. Standing at 328-meters tall, it is one of the tallest hotels in the world.

The GIS Center completed its first project phase of capturing all of Dubai’s major roadways, landmarks and buildings in 3D in April 2020. For the remainder of 2020, teams were focusing on collecting the rest of the road network, landscapes, and infrastructure to complete the 3D mapping of the entire emirate. “We wouldn’t have been able to finish this major achievement this quickly without the MX9,” says El Mustafa. “A surveyor using con - ventional technology would likely need nearly two months to cover the same amount of distance we collect in one day. And they’ll maybe acquire about 200 points a day. We get 360-degree panoramas every five seconds and two million 3D points per second of everything that’s there. There’s no comparison.” No Need To Explain After each data acquisition, a team used a suite of Trimble software tools to process the data. When the MX9’s GNSS and inertial data were processed with POSPac, Trimble Business Center software integrated the trajectory information and control-point measurements to georefer- ence the data collected from the MX9 cameras and scanners. They also processed and colorized each point cloud. And from the 3D view, they Thanks to the MX9’s overhead reach of up to 400 m high, crews can capture nearly all of Dubai’s tallest buildings.



july 2021

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