Pioneering Single Photon LiDAR in Europe

Author: Renata Barradas Gutiérrez

The first maps were painted in parchment and were very limited in accuracy, quality and distribution. Technological changes have revolutionised cartography drastically, changing the way we capture, communicate and distribute spatial information. Today, detailed maps with geographic information can be viewed from any device with a browser.

If you are visiting Pamplona, capital of Navarre province in northern Spain, famous worldwide for the running of the bulls, and you are planning an excursion, maps with all the topographic information of this multifaceted region are accessible through the comfort of your mobile phone.

Navarre’s Department of Economic Development has opened its doors to give access, in a single interface, to multiple base maps, including cadastre, hydrography, culture, infrastructure, cartography orthophotos and more. Beyond the level of detail and information available, these maps are the first information capture in Europe taken with single-photon LiDAR.

Quantum leaps

Navarre has historically been a pioneer region introducing new technologies to obtain cutting-edge geographic information. In 1929, a pilot flew the region of Navarre to photograph and produce a cadastre of the region. In 1967, Navarre’s government prepared the first cartographic plan, which required the construction of a remarkable geodesic infrastructure, leading in its time.

Navarre’s surface was captured with LiDAR 44 years later. Between 2011 and 2012, Tracasa, a firm developing major projects in cadastre, cartography and territorial information systems in the Spanish market, covered Navarre’s territory with high point density LiDAR. Using the Leica ALS60 airborne sensors, Tracasa captured 1.2 points per square metre of this heterogenous region from the sky.

In 2017, the management of cartography in Navarre decided to update the LiDAR data of the region, increasing the point density of the previous LiDAR flight by 10 – the technology provided by the Leica SPL100 LiDAR sensor made a quantum leap, increasing the density of the previous LiDAR flight by to 14 points per m2.

Choosing the right technology to try something completely new in Europe

With no other companies in Europe having experience with this sensor, how to decide the first commercially available single-photon LiDAR airborne sensor was the right technology?

Tracasa, following the assignment of the government of Navarre and in collaboration with the Spanish National Geographic Institute (IGN), set up a demanding tender that included a very high point density of 10 points per square metre – very few sensors could comply with these high specifications with the efficiency needed for such a vast area.

Geared with a SPL100 LiDAR sensor and the medium format Leica RCD30 camera in a B200 aircraft, Tracasa entrusted the flight and capture of information to Grup-Air-Med and COWI. With 100 output beams and a total of 6 million measurements per second provided by the SPL100, the team mapped the entire vast area in just a couple of months.

“The novelty of this coverage is the increase in point cloud density that will allow us to obtain a wide range of applications. We obtained an average point density of 14 points per metre squared with an accuracy better than 20 centimetres in planimetry and 15 centimetres in altimetry. The joint capture of RGBN images with a medium-format photogrammetric camera, made also possible to obtain simultaneous images of the LiDAR data used to colourise the point cloud. “We are happy with the data – we have the point density, zone specification and accuracy we desired. In 2011 we had 1 point per metres squared and now we have 14 points per metres squared,” said Víctor García Morales, project manager at Tracasa.

Ain’t no mountain high enough

Bordering with France, between the Pyrenees and the Ebro River, the region of Navarre covers a surface of 10,391 square kilometres. Despite its relatively small size, Navarre is quite a diverse region dominated by the Pyrenean mountain range, with altitudes above 2,400 m, contrasting with the flat alluvial plains of the Ebro valley.

“Navarre is the perfect area to pilot any airborne sensor. If this sensor ran here, in this heterogenous area were vegetation, flight planning and execution can be very challenging, it can run everywhere,” said Moisés Zalba Almándoz, director at Tracasa.

Before flying, many aspects needed to be considered. The flight plan to cover Navarre initially offered 200 flight lines. The SPL100 created high-density point clouds penetrating Navarre’s vegetation, ground fog and thin clouds while the 80 MP camera captured RGBN colour information.

“It took us approximately 270 hours to fly with the previous technology; with the SPL100, time was reduced to 170 hours and point clouds are 14 times denser. With enhanced planning this can even be further reduced,” said García Morales.

When decision making affects wide areas, requires detailed and consistent data, and demands frequent updates at manageable costs, companies should be driven by cost per data point. Single-photon LiDAR systems capture 1 million measurements per second with 2 km swath width. The SPL100 is ideal to acquire large areas, lowering the cost per acquired data point.

Multiple applications, multiple business

This project, framed within IGN’s National Orthophotography Area Plan (PNOA), aims to update LiDAR information with high density throughout Spain every six years. Enabling cartographic data at everyone’s fingertips is an arduous process where LiDAR data collection is one piece of the puzzle. A workflow would not be completed without data processing and visualisation.

The SPL100 LiDAR data of Navarre was postprocessed with HxMap, while Leica MissionPro flight planning software enabled a 3D virtual globe planning environment and traditional 2D map planning view. HxMap was the main post-processing platform used in this project to generate all LiDAR data products within one single interface. Combining single-photon LiDAR and HxMap into one workflow allowed experts to generate airborne data for varied applications including:

• Produce a digital terrain model and a digital surface model
• Update cartography
• Prepare a forest management plan
• Mapping flood zones and other hydrological applications
• Support emergency management plans
• Map powerlines
• Deliver information to the public