London, like most other major cities, has extensive underground infrastructure for fresh water supply and sewer networks. From 1861, Victorian engineers built miles of underground tunnels large enough to walk through, to run gas, electricity, water, and hydraulic pipes. London Underground was also the first subway in the world, and remains one of the most extensive. As someone could imagine though, it’s not easy to set up conventional surveying equipment thousands of times inside these complex structures without it taking a very long time.
These GNSS-denied underground networks with poor lighting and very tight working conditions present a problem for consise and efficient 3D data capturing. Engineers and surveyors need a 3D documentation tool that has the capacity to operate in these dark areas and move around in limited spaces.
With the Pegasus:Backpack those tasked with documenting underground networks and utilities can walk, climb, kneel or crawl if needed to collect the data. Armed with a powerful flash light module, even in absolute darkness, the Pegasus:Backpack can augment the collected LiDAR data with clear images of the underground environments helping to create comprehensive 3D maps.
To elaborate the possibilities this technology offers we will examine three distinctive cases.
Infrastructure mapping – Hydroelectric Dam
Aging infrastructures are now expanding their designed lifespan. It’s essential though to examine how these existing structures operate in order to maintain them. The dam is drained for maintenance works every 10 years and engineers need to ensure that everything is still working and at the right place. The Leica Pegasus:Backpack was recently used to monitor an infrastructure dam in Italy. This technology enabled operators to walk around the dam and collect high detail imagery and LiDAR data to document the dam’s current condition.
Infrastructure mapping – sewer mapping
For sewer mapping the images are critical. The camera and the flash light module fire at the same time, this means that the capture of detailed imagery is possible in the dark for the collection of data such as, spray marks on sewer walls which can be reference points.
The Leica Pegasus:Backpack flash light module extends the application space into the darkness.
Urban planning – Mapping Densely Populated Areas
Underground infrastructures are not the only dark and inaccessible places that benefit from flashlight photography. A look at the world’s densest megacities demonstrates the need to map their 
heavily populated areas . The Pegasus:Backpack was used in Asia to map the dwellings and allow a connection between the buildings and the actual occupants. This validation process gave the dwellers an identity by enabling the local authorities to locate their buildings.
Accessibility was only possible by foot. During the data collection high-resolution imagery was vital as individual dwellings had painted house numbers outside on the walls. Simply walking between these buildings with the Pegasus:Backpack no assets were left behind.
The solution
Imagine not having clear images with the LiDAR data, you would not be able to capture details such as marks on walls, historic signs and cracks in underground structures. With the lighting feature, the Pegasus:Backpack is aimed at all those involved in commissioning, planning, maintenance, managing and carrying out work on or near underground utilities and dark GNSS denied areas.
The Leica Pegasus: Backpack enables engineers to combine underground information with above ground assets to provide georeferenced data, faster and more efficiently than traditional methods using control points.