Leica Mobile Mapping Day 2016 - Mobile Mapping Chez Leica - 20/01/2017
Leica Geosystems mobile mapping day featured the UK release of two new pieces of equipment and a refresh of two others. The day at Milton Keynes was a mix of indoor presentations and outdoor demonstrations, reports Richard Groom.
Leica ProScan is a new threewheeled trolley-based scanning system with a P40 scanner, which can be used indoors or outdoors. Position fixing is by total station tracking and IMU both indoors and outdoors. For outdoor work there is in addition a GNSS receiver. What makes this system special is that, when controlled using total-station tracking, it can achieve a pointcloud accuracy of 5mm, which means that it can compete with static scanning and is potentially much more productive in certain situations. Example applications include measurement of asphalt courses during road construction and survey of large relatively open areas without steps – like factories.
SiTrack:One is a rail trolley system. It carries a P40 scanner, 1000Hz IMU, spheres for self calibration, an optional GNSS and two laser odometers, which measure distance along the track. The system can also be fitted with pairs of lasers (DMI’s) for each rail that measure the rail shape, and therefore rail wear, precisely. The system comes with a suite of software for field operation, data processing and analysis. Alan Barrow has been given the task of assessing SiTrack:One with the intention of getting it approved for use on Network Rail. This is work in progress, but he was able to give an insight into the tests. He has chosen a length of London Overground between Gospel Oak and Barking, which has recently been surveyed by ABA Surveying. The test involved surveying the same length of track as surveyed using the SiTrack trolley with two Amberg trolleys and a rail shoe observation at all 10m markers. He is making use of observations to permanent survey control, installed at 200m intervals, to assess the control needs for a SiTrack workflow. The hope is that the DMIs will improve the accuracy of chainage – a problem with mechanical odometers, which slip on the track. Because it is possible to reverse engineer the trajectory of the trolley, it could encourage rail engineers to order asbuilt surveys – a key aspect of BIM. Will this be a second generation trolley? We wait to see.
The Pegasus:Two and Pegasus Backpack systems have both been refreshed. Leica has sold three Pegasus:Two systems in the UK and claims that it is still the most accurate on the market when used with the Z+F scanner. Users who already have a P40 scanner can mount it on Pegasus and there is a version that uses Velodyne scanners. And for those who just want to take imagery, there is a camera-only version. The Pegasus:Two only carries one scanner but the reasoning for this seems logical: the roads are now so congested that you need more than one pass to survey a motorway and, by observing using different scanner configurations and in different directions you achieve denser point clouds and data redundancy and greater chance of avoiding obstructions. The point cloud can also be constrained using ground control points, which can control in plan, height or 3D. For the future, Leica is looking at adding external sensors and a second Z+F scanner – for rail applications only. Pegasus:Stream is a Pegasus:Two combined with a ground penetrating radar array towed behind the vehicle. It collects GPR data as well as observing point clouds. Utilities up to 4m deep can be surveyed, depending on ground conditions. There’s also a pavement camera, for collecting data on pavement defects.
Scanning on the hoof
The Leica Pegasus:Backpack carries two Velodyne scanners: one for point cloud data collection and a second for position-fixing using SLAM, the simultaneous localization and mapping algorithm, when working indoors. There is a GNSS receiver for position-fixing outside and both inside and outside position fixing is aided by an IMU. The quoted accuracy of outdoor point clouds is 35mm (2.5 σ) and for indoor point clouds is 50mm (2.5 σ). The cameras can be used for photogrammetric observations. It is possible to include control points in the post processing of the data.
This article was first published in Geomatics World January/February 2017.Last updated: 25/04/2017