A LiDAR-based 3-D point cloud measuring system includes a base, a housing, a plurality of photon transmitters and photon detectors contained within the housing, a rotary motor that rotates the housing about the base, and a communication component that allows transmission of signals generated by the photon detectors to external components. In several versions of the invention, the system includes a vertically oriented motherboard, thin circuit boards such as ceramic hybrids for selectively mounting emitters and detectors, a conjoined D-shaped lens array, and preferred firing sequences.

High definition lidar system

Road safety inspection is currently carried out by time-consuming visual inspection. The latest mobile mapping systems provide an efficient technique for acquiring very dense point clouds along road corridors, so that automated procedures for recognizing and extracting structures can be developed. This paper presents a framework for structure recognition from mobile laser scanned point clouds. It starts with an initial rough classification into three larger categories: ground surface, objects on ground, and objects off ground. Based on a collection of characteristics of point cloud segments like size, shape, orientation and topological relationships, the objects on ground are assigned to more detailed classes such as traffic signs, trees, building walls and barriers. Two mobile laser scanning data sets acquired by different systems are tested with the recognition methods. Performance analyses of the test results are provided to demonstrate the applicability and limits of the methods. While poles are recognized for up to 86%, classification into further categories requires further work and integration with imagery.

Recognizing basic structures from mobile laser scanning data for road inventory studies

This paper presents a novel low-cost mini-UAV-based laser scanning system, which is also capable of performing car-based mobile mapping. The quality of the system and its feasibility for tree measurements was tested using the system’s laser scanner. The system was constructed as a modular measurement system consisting of a number of measurement instruments: a GPS/IMU positioning system, two laser scanners, a CCD camera, a spectrometer and a thermal camera. An Ibeo Lux and a Sick LMS151 profile laser were integrated into the system to provide dense point clouds; intensities of the reflected echoes can also be obtained with the Sick LMS. In our tests, when using a car as a platform, the pole-type object extraction algorithm which was developed resulted in 90% completeness and 86% correctness. The heights of pole-type objects were obtained with a bias of −1.6 cm and standard deviation of 5.4 cm. Using a mini-UAV as the platform, the standard deviation of individual tree heights was about 30 cm. Also, a digital elevation model extraction was tested with the UAV data, resulting in a height offset of about 3.1 cm and a standard deviation of 9.2 cm. With a multitemporal point cloud, we demonstrated a method to derive the biomass change of a coniferous tree with an R 2 value of 0.92. The proposed system is capable of not only recording point cloud data giving the geometry of the objects, but also simultaneously collecting image data, including overlapping images and the intensity of laser backscatter, as well as hyperspectral and thermal data. Therefore we believe that the system is feasible for new algorithm and concept development and for basic research, especially when data is recorded multitemporally.

A low-cost multi-sensoral mobile mapping system and its feasibility for tree measurements

Accurate road environment information is needed in applications such as road maintenance and virtual 3D city modelling. Vehicle-based laser scanning (VLS) can produce dense point clouds from large areas efficiently from which the road and its environment can be modelled in detail. Pole-like objects such as traffic signs, lamp posts and tree trunks are an important part of road environments. An automatic method was developed for the extraction of pole-like objects from VLS data. The method was able to find 77.7% of the poles which were found by a manual investigation of the data. Correctness of the detection was 81.0%.

Detection of Vertical Pole-Like Objects in a Road Environment Using Vehicle-Based Laser Scanning Data

This paper outlines a study, carried out on behalf of a national mapping agency, to validate laser scanned point cloud data collected by a ground-based mobile mapping system. As the need for detailed three-dimensional data about our environment continues to grow, ground-based mobile systems are likely to find an increasingly important niche in national mapping agency applications. For example, such systems potentially provide the most efficient data capture for numerical modelling and/or visualisation in support of decision making, filling a void between static terrestrial and mobile airborne laser scanning. This study sought to assess the precision and accuracy of data collected using the StreetMapper system across two test sites: a peri-urban residential housing estate with low density housing and wide streets, and a former industrial area consisting of narrow streets and tall warehouses. An estimate of system precision in both test sites was made using repeated data collection passes, indicating a measurement precision (95%) of between 0.029 m and 0.031 m had been achieved in elevation. Elevation measurement accuracy was assessed against check points collected using conventional surveying techniques at the same time as the laser scanning survey, finding RMS errors in elevation in the order of 0.03 m. Planimetric accuracy was also assessed, with results indicating an accuracy of approximately 0.10 m, although difficulties in reliably assessing planimetric accuracy were encountered. The results of this validation were compared against a theoretical error pre-analysis which was also used to show the relative components of error within the system. Finally, recommendations for future validation methodologies are outlined and possible applications of the system are briefly discussed.

Geometric validation of a ground-based mobile laser scanning system

Laser mapping has become quite popular in recent days due to its capability of providing information directly in three dimensions These days, we observe the emergence of new demands for ‘along-street’ 3-D data ‘Along-street’ 3-D data provide a real or true visualization of the environment that is different from virtual reality However, there still lacks a reliable and quick method of acquiring 3-D ‘along-street’ data of the urban area at higher resolution Most of the vehicle-borne systems developed so far are based on stereo photographs as the main source of data In order to overcome the problem of acquiring 3-D data in urban area reliably, quickly and at high resolution, we have developed a vehicle-borne laser mapping system (VLMS) The system is equipped with laser scanners and line cameras for data acquisition The system will assist in building 3-D GIS database of urban areas In this paper we focus our discussions on auto-extraction of building faces from the laser data captured by VLMS In an urban area we encounter many different types of features like buildings, roads, utility facilities, vehicles, trees and others Geo-referenced raw laser data were used for extraction of urban features The raw laser data were simply point cloud data in 3-D space without any other information like intensity value We have classified the laser data into various classes like building faces, road surfaces, tunnels, utility poles, vehicles and trees Our discussions will be basically limited to the extraction of building faces with some explanation on extraction of road surfaces, trees and tunnels

/pdf/auto-extraction-of-urban-features-from-vehicle-borne-laser-4gd08lcsne.pdf

Auto-extraction of urban features from vehicle-borne laser data

Our research goal is developing and deploying indoor and outdoor seamless Location-Based Service (LBS) that covers indoor and outdoor locations. The prime concern for GPS-based positioning systems such as car navigation are that they are not allowed to use ins ide building nor underground, where GPS signals are out of range. To increase flexibility for providing such se rvices, both indoor and outdoor seamlessly, we have developed a novel seamless positioning system with the followin g three steps. First, IMES (Indoor Messaging System), an innovative technology for seamless positioning that uses GPS chipset receiver was applied to realize indoor positioning. Any device that has a GPS chipset in t he receiver can detect IMES signal for positioning. Sec ond, the firmware on GPS chipset was modified in order to smoothly provide seamless location information both indoor and outdoor in accordance with the movement of the user. Third, Network-Assist GPS/IMES was developed to improve time to first fix and vertical positioning accuracy. The system will meet the needs of emergency where quick and accurate personal location information dramatically makes difference. The application may be extended to commercial activity as well for personal store navi gation. A prototype of system has been implemented and a shopping application has been investigated.

/pdf/indoor-and-outdoor-seamless-positioning-using-indoor-3lmw6vgn73.pdf

Indoor and Outdoor Seamless Positioning using Indoor Messaging System and GPS

We have developed a vehicle-borne laser mapping system (VLMS), which consists of Laser Scanners, Line Cameras, GPS and INS. The system uses range data, scanned by the laser scanners as the main source of 3D data. In this paper, we present about the development of VLMS, which includes the system architecture, calibration and geo-referencing of sensors and positioning devices. Next, we present the extraction of some basic features like building surfaces, road surfaces (man made features) and trees (natural features). Finally, we will show how these features can be used to build 3D urban GIS database, which will assist in various applications as mentioned above. Besides, we will also discuss about the capabilities and difficulties of such a system.

Vehicle-borne laser mapping system (VLMS) for 3-D GIS

Software-based GPS (SGR) Receiver helps us processing the GPS signal at the lowest level of GPS raw signal data from the antenna. A software-based GPS receiver consists of a front-end device that converts the radio frequency signal from the antenna to an intermediate frequency in digital format. The signal thus converted is processed by high level programming language to compute position and velocity. In SGR, it is possible to do acquisition and tracking using different parameters and threshold values, which give a user total flexibility of operation. This helps in processing weaker signal, multipath mitigation and simulate “what-if” scenarios. In this paper, we will discuss about GPS signal acquisition and tracking that will form a base for the development of SGR. Keyword Software GPS, Acquisition, Tracking, DLL, PLL

GPS Signal Acquisition and Tracking An Approach towards Development of Software-based GPS Receiver

Laser mapping has become quite popular in recent days due to its capability of providing information directly in three dimensions. Three dimension data are used in many applications, like navigation, urban planning and management, utilities planning, virtual reality, computer games etc. However, there still lacks a reliable and quick method of acquiring three dimension data of the urban area at higher resolution. Most of the vehicle -borne systems developed so far are based on stereo photographs as the main source of da ta. In order to overcome the problem of acquiring three dimension data in urban area reliably, quickly and at high resolution, we have developed a vehicle borne laser mapping system (VLMS). The system is equipped with laser scanners and line cameras for da ta acquisition. The system will assist in building 3 -D GIS database of urban areas. In this paper we focus our discuss on feature extraction of such a system including it’s capabilities and limitations. In an urban area we encounter many different types o f features like buildings, roads, utility facilities, trees and many others. Our discussions will be basically limited to the extraction of road surface, building faces, poles, trees, tunnel and some other features on the ground. We believe that this type of mobile mapping system will provide complimentary data to the existing photogrammetry method for the generation of more accurate 3 -D data of urban environment.

Dinesh Manandhar

Papers

Auto-extraction of urban features from vehicle-borne laser data

Indoor and Outdoor Seamless Positioning using Indoor Messaging System and GPS

Vehicle-borne laser mapping system (VLMS) for 3-D GIS

GPS Signal Acquisition and Tracking An Approach towards Development of Software-based GPS Receiver

Feature extraction from range data