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A combined non-contact measurement system comprising attitude angle sensor, angle encoder, laser rangefinder, and total station is adopted to measure the spatial coordinate of the hidden zones in large-scale space. The laser from the total station is aimed at the optical system of the attitude angle sensor to obtain the spatial coordinate and the spatial attitude angles. Then, the angle encoder driven by a stepping motor is rotated to drive the laser rangefinder to direct at the measured point. This approach is used to obtain the distance from the rangefinder to the measured point and the angle of the angle encoder. Finally, the spatial coordinates of the measured point can be calculated by using these measured parameters. For the measurement system, we propose a weighted least squares (WLS) calibration method, in which weights are determined for the angular distribution density. Experimental results show that the measurement system could expand the scale and achieve reliable precision during combined measurement and the measurement error of the weighted least squares method is less than that of the ordinary least square (OLS) method. [ABSTRACT FROM AUTHOR]

The compass measurement is one of the customary surveying methods that is used almost from the beginning of systematic geodesy and cartography. After the periods of the decreased use of this method, it was partially renewed by the ascension of the Field-Map technology that connects the compass measurement with the software tools for the environment mapping. It is currently mostly used for the forestry under-canopy mapping and other special tasks, where the current progressive technologies, especially photogrammetry and GNSS, can be used only with complication. The Field-Map set can include either the laser rangefinder Impulse LR 200 with MapStar Compass Module II compass, or TruPulse laser rangefinder that allows also the azimuth measurement. The research was aimed on the accuracy of mentioned devices. The measured lengths and azimuth were evaluated primarily. The evaluation of the field condition results showed the mean length error 0.07–0.09 m for Impulse rangefinder, while 0.25–0.29 m for TruPulse rangefinder. The mean azimuth error was around 0.5 degree for MapStar compass and above 3 degrees for TruPulse. After this basic evaluation the data were used for the computation of four compass traverses using various measurement and computation methods. The results showed, that the compass measurement, especially using the Impulse + MapStar set, can be still a suitable method for lower accuracy surveying, although effective only in specific conditions. [ABSTRACT FROM PUBLISHER]

The effects of gamma radiation on common sensors used in robots intended for nuclear remediation scenarios are examined. Commercial rangefinders are chosen as an exemplar of the impact of gamma radiation on sensors and systems. This paper illustrates sensor radiation degradation not only in operational failure, but also in changes in the sensor transfer function. Three types of commercial range-finding sensors are considered [infrared (IR) triangulation using a position sensitive detector, sonar using time of flight, and laser rangefinder using triangulation and a CMOS camera]. Experimental results show significant changes in the IR sensor's static sensitivity with dose, abrupt failure of the laser range finder at low dose, and degradation and abrupt failure for the sonar detector. The input-output relationship of the IR sensor showed further variation after a period of room-temperature annealing. Significant part-to-part variation in radiation response is shown for both the sonar and IR sensor. System level impacts due to sensor input-output relationship degradation and a technique to diagnose the degradation extendable to more complex sensor assemblies are presented. [ABSTRACT FROM PUBLISHER]

This paper presents the design and construction of a laser autocollimator-based optical sensor for measurement of the tilt angles of a reflector mounted on the guideways or the moving table of a precision linear slide in the production process of the slide, where the measurement is repeatedly carried out together with a hand scraping operation for correction of the form errors of the slide guideways. Differing from a conventional autocollimator, a laser rangefinder unit is integrated with the autocollimation unit for detection of the positions of the reflector, which is necessary for the efficient error correction of the slide guideways. The autocollimation unit and the rangefinder unit share the same light source for a compact optical design. The optical power of the laser beam is first set to be constant for tilt angles measurement. Then the optical power is modulated with a frequency of 66.7 MHz for measuring the position/distance based on the phase shift method. The resolution of the laser autocollimator is confirmed to be 0.2 arc-second over a range of ±50 arc-seconds while the measurement positions can be detected with a resolution of 1 mm by the rangefinder, which satisfies the requirements from production of the slide. [ABSTRACT FROM AUTHOR]

The Kalman filter is a valued method of signals filtration having the possibility of a sensors fusion, which is commonly applied in aerospace technology. Mainly, it eliminates random noises, improves the accuracy of a measurement system and their resistance to unexpected faults. Small unmanned aerial vehicles (UAV) are a challengeable area for various applications of the Kalman filter, because their high dynamics makes them highly sensitive to external disturbances acting on the on-board sensors. The paper discusses an application idea of the Kalman filter, whose purpose is to reduce the quantity of accidental incorrect measurements reported by a miniature laser rangefinder fixed to the UAV's wing. To verify the filtration effectiveness, real distance measurements recorded during real flights were applied. The results compare two approaches: an optimization using a reference signal from the second sensor mounted to the same UAV, and an adaptation of the covariance matrix R based on innovation. We can observe that the measurements of the laser rangefinder are corrected significantly, especially for the adaptation method, what is visible as the reduced amount of the incorrect distance measurements. Hence, the reliable detection and localization of an obstacle can be achieved by the usage of the miniature laser rangefinder. [ABSTRACT FROM AUTHOR]

Various types of military lasers are discussed, especially laser rangefinders for air defense applications. The paper gives a more detailed description of Nd-YAG laser rangefinder with Raman cell that increases the wavelength of radiation and makes a laser eye-safe. A review of contemporary high frequency laser rangefinders is given too. Some procedures to enhance the of range measurement are proposed.

Electronic devices consisting of field computer, laser rangefinder, electronic compass and global positioning system unit were used for data collection in the tropical rainforest of the Peruvian Amazon with the objective of comparing forest inventory methods. Forest stand was studied by mapping trees to obtain spatial dimensions and basic tree characteristics. The inventory conducted on 200 ha of forest in the Loreto Department were compared with inventory conducted using the common method (tapes and mechanical compasses). A map of the study site was created. Attributes of all trees with diameter at breast height (dbh) ≥ 400 mm were recorded: position, species, total height, trunk height and dbh. The study showed that the method using electronic devices was more exact and faster. The difference in timber stock measured by both inventories was 24.5 m3 ha-1. Our results may play an important economic role in forest planning and management in the region. Mitigation of the inaccuracies in inventories may weaken illegal logging in the Peruvian Amazon. [ABSTRACT FROM AUTHOR]

A noncontacting combined measuring system comprising a nondiffracting beam attitude angle sensor, laser rangefinder, and total station is proposed for the coordinate measurement of hidden parts in large-scale spaces. The laser from the total station is aimed at the retro-reflector of the attitude angle sensor to obtain the spatial coordinates. Moreover, parts of the laser pass through the retro-reflector and generate a nondiffracting beam spot on the charge-coupled diode through an axicon lens. The horizontal angle of the attitude angle sensor can be obtained by using center fitting of the nondiffracting beam spot. An inclinometer can be used to obtain the rolling angle and the pitching angle. The laser from the rangefinder is directed at the measured point to measure the distance from the attitude angle sensor to the measured point. Finally, the spatial coordinates of the measured point can be calculated by using the measured spatial coordinates, the three attitude angles, and the distance. The experimental results of the combined measuring system are compared with those of the total station. The two results show good agreement. [ABSTRACT FROM AUTHOR]

Laser rangefinder performance (i.e., maximum range) is strongly affected by environment due to visibility-dependent laser attenuation in the atmosphere and target reflectivity variations induced by surface condition changes (dry vs. wet). Both factors have their unique spectral features which means that rangefinders operating at different wavelengths are affected by specific environmental changes in a different way. Current state of the art TOF (time of flight) semiconductor laser rangefinders are based mainly on two wavelengths: 905 nm and 1550 nm, which results from atmospheric transmission windows and availability of high power pulsed sources. The paper discusses the scope of maximum range degradation of hypothetical 0.9 μm and 1.5 μm rangefinders due to selected water-related environmental effects. Atmospheric extinction spectra were adapted from Standard Atmosphere Model and reflectance fingerprints of various materials have been measured. It is not the aim of the paper to determine in general which wavelength is superior for laser range finding, since a number of criteria could be considered, but to verify their susceptibility to adverse environmental conditions. [ABSTRACT FROM AUTHOR]

Miniature rangefinding modules based on pulsed semiconductor laser technology are becoming more and more popular components of a variety of modern optoelectronics devices where precise, fast and eye-safe range estimation is needed. Current trends associated with minimization of both physical dimensions and cost of such modules lead to the design approach relying on exact meeting the requirements of a given application, concerning the spatial resolution and especially the maximum range. Optical components of a rangefinder cover a substantial part of its cost and determine its overall dimensions, but primarily - the indigenous parameters of the transmitter and receiver trains are crucial for the maximum measurable range. The quantitative analysis of transmitter optics aberrational characteristics impact on signal-to-noise ratio range dependence and thus the maximum range of a laser rangefinder is presented in the paper. Modern optical fabrication technology offers a huge range of solutions, changing in imaging/projecting characteristics which implies the price level as well. Rangefinder optics has a very specific task which sometimes makes it unreasonable to fight for the diffraction limited performance. The article provides the approach how to determine the acceptable level of optical aberrations which still does not degrade the measurable range significantly. [ABSTRACT FROM AUTHOR]

Abstract: New modifications of VFH+ and V FH∗ (Vector Field Histogram) methods are presented in the paper. The features of the histogramic algorithms are generally improved and also using a potential of advanced sensors such as laser scanners is enabled. The main focus of the work is an introduction of modifications that provides collision-free navigation in environments with moving obstacles. For this purpose, a new approach in creating a look-ahead tree is proposed. All new modifications are analyzed and experimentally verified. The results obtained using conventional and modified methods have been compared. Experiments have demonstrated the validity and the technical feasibility of the proposed methods. [Copyright &y& Elsevier]

The Brazilian deep space mission ASTER, as temporarily named, plans to send a small spacecraft to encounter and investigate the triple asteroid 2001-SN263. The launch is scheduled (initially) to occur in 2015, arriving in 2018. The main motivation of the mission is the development of technology and expertise to leverage the national space sector. Within the scientific goals, the investigation of the still unknown asteroid 2001-SN263. The main project guideline is to aggregate the widest possible Brazilian involvement in the platform, the development and operation of subsystems, integration, payload, as well as in the tracking, navigation, guidance and control of the probe. To meet this guideline, among others, the decision for the development of a laser altimeter in Brazil to fly in the mission was taken. This effort is currently coordinated by a group of researchers from the aerospace engineering personnel of UFABC. This article presents the preliminary development plan for the design of this instrument, which was called ALR (ASTER Laser Rangefinder).

Highlights: [•] It only needs a LRF and a planar object. [•] It is well suited for on-site calibration in large spatial environments. [•] The relative distance error is 0.3‰ when the distance between cameras is 4m. [ABSTRACT FROM AUTHOR]

A reactive obstacle avoidance strategy based on local virtual target following is proposed in this paper with reference to obstacle avoidance problems for a unicycle mobile robot in an unknown environment. The strategy took a laser rangefinder as the main environment detecting sensor. A polar co-ordinate vector map (PMap) was utilized to store environmental information and a cluster ideology was used to describe obstacle features. The local virtual target comprised environment features and target information together and so it was used as a temporary target to guide the robot to track the real goal while accomplishing obstacle avoidance. This method could be applied to obstacles with arbitrary shapes and could reduce the environment memory amount dramatically. It improved the dynamic response performance of the robot and fulfilled real time obstacle avoidance when the robot was following a target. A great deal of robot experiments showed that the propounded strategy was very effective. [ABSTRACT FROM AUTHOR]

This study examined the appropriateness of self-report (predicted) data obtained from high-level golfers in tournament play. Twenty-one high-level golfers (mean ± s, handicap = +2.8 ± 1.8) completed one round of 18 holes. For approach-shots to the green on par 4 and 5 holes, three measurements were predicted by each player: a) Distance to Hole, b) Approach Shot Distance and c) Ball to Hole Distance, for on and around the green. A fourth variable, Percent Error Index (PEI) was also determined. Actual distances were measured using a combination of a laser rangefinder and tape measure. A series of accuracy, precision and agreement statistics were calculated. Despite between-distance differences being evident for some measures of precision, both low error and good between-method agreement was found for the four variables examined. Results from this study suggest that high-level golfers can utilise self-report data relating to approach-iron shots in golf. [ABSTRACT FROM AUTHOR]

Highlights: [•] We provided an error offset item to compensate the errors induced by lens distortion so that the accuracy of distance computation can be increased. [•] Applying the curve fitting technology to obtain the equation of the error offset item. [•] Low cost scheme on the sensor base structure improvements which enhance the mechanical strength for mobile robots application. [Copyright &y& Elsevier]

The paper describes practical application of pulsed microchip laser generating at 1535-nm wavelength to a laser rangefinder. The complete prototype of a laser rangefinder was built and investigated in real environmental conditions. The measured performance of the device is discussed. To build the prototype of a laser rangefinder at a reasonable price and shape a number of basic considerations had to be done. These include the mechanical and optical design of a microchip laser and the opto-mechanical construction of the rangefinder. [ABSTRACT FROM AUTHOR]

We address a tracking system of 360^\circ field of view using Light Detection And Ranging (LiDAR) sensors, which are a key module for detecting surrounding traffic and infrastructure for vehicular safety applications. We propose a joint algorithm for estimating motion and a nonparametric contour model whose complexity is O(N), with N being the number of scan points. Particularly, the proposed nonparametric model has the potential to track objects with arbitrary shape (e.g., car, pedestrian, and bicycle). A comparison of the proposed approach with other methods using parametric models shows the robustness and the quality of the proposed system. Quantitative performance evaluation against ground truth is presented in tracking a car, a pedestrian, and a bicycle. Experiments demonstrate that the proposed system substantially improves performance. Road test results show the effectiveness and efficiency of the implemented system. A lane-change alert (LCA) demonstration system is built based on the detection system, and the LCA performance is analyzed using ground truth. [ABSTRACT FROM PUBLISHER]

This paper presents the design and construction of an experimental prototype that performs metalworking sizing from digitized three-dimensional models, in order to advance quality control of them. The data provided by the 3D laser, are transformed into a point cloud platform through ROS (Robotic Operating System) and processed with the library PCL (Point Cloud Library). Also shown are the results obtained by measuring a sample of gas cylinders manufactured under the 5th 522-1 NTC update, which were provided by the company Electrigas city of Pereira, Risaralda, noticing that in no case the error in the measurement exceeds 5%. [ABSTRACT FROM AUTHOR]

A novel scheme of calibrating the laser rangefinder using optical fiber baseline is proposed. Coupling between laser beam and optical fiber is studied for the optical components design. By establishing the coupling system between laser diode and optical fiber, the outdoor baseline is successfully replaced by the indoor optical fiber. Optical path length measurement experiments are conducted on three kinds of fibers. Effects of wavelength, temperature and material dispersion on the experiment results are discussed. Stable data are derived in the experiments, the deviation is proved to be within 2 mm, indicating that the proposed calibration method is feasible. [ABSTRACT FROM AUTHOR]

Abstract: This paper discussed an information sharing system for multiple mobile robots using IC tags. In our system, the multiple mobile robots share the environmental information using IC tags. It is necessary for intelligent mobile robot to recognize the environmental information around the robot. The IC tag is very useful device for getting the environmental information around the robot. We developed the mobile robot which is equipped an IC tag reader/writer with an antenna, a laser rangefinder and a PC. We use the laser rangefinder in order to detect the collision-free space around the robot. The mobile robots write and read the information to the IC tag and share the environmental information each other. This mobile robot moves according to the information from the IC tags. The effectiveness of our system is demonstrated by several experimental results. [Copyright &y& Elsevier]

In recent years, laser rangefinder sensors have been introduced to the practice and research of agricultural engineering. In research, laser rangefinders have been investigated in horticulture and agriculture. For vehicle-based determination of crop biomass, commercially available laser rangefinders have been analysed and tested to measure aboveground biomass in oilseed rape, winter rye, winter wheat, oats and grassland. Resulting from limited measuring range and fixed beam types, the laser rangefinder models that were investigated only partially met the specific demands for agricultural field and crop conditions. Therefore, a new laser rangefinder scanner (ibeo-ALASCA XT) was chosen. This sensor was specifically developed for driver assistance and autonomous guiding of road vehicles. The scanner was tested in 2008 focusing on the measurement of crop stand parameters in winter wheat under field conditions. The sensor achieved good results with reproducible measurements. Measuring from a stationary vehicle, the standard deviation for the measurements of crop height to characterise the crop stand was less than 3 mm in low, medium, and high biomass areas. The ground speed of the vehicle, ranging from 6 to 24 km h, did not significantly influence the readings. For measurements in front of tractors and self-propelled machines (field sprayers, combines and forage harvesters), the sensor has to scan the crop stands at different inclination angles. It was shown that the inclination angle of the laser beam, which varied from 10° to 80°, significantly influenced the readings. Higher inclination angles resulted in apparent increased heights of the crop stand. For the functional relationship between reflection height levels (95th, 75th, 50th and 25th percentiles, and mean values) and crop biomass density, the coefficient of determination (R) was greater than 0.9. [ABSTRACT FROM AUTHOR]

Person following with mobile robots has traditionally been an important research topic. It has been solved, in most cases, by the use of machine vision or laser rangefinders. In some special circumstances, such as a smoky environment, the use of optical sensors is not a good solution. This paper proposes and compares alternative sensors and methods to perform a person following in low visibility conditions, such as smoky environments in firefighting scenarios. The use of laser rangefinder and sonar sensors is proposed in combination with a vision system that can determine the amount of smoke in the environment. The smoke detection algorithm provides the robot with the ability to use a different combination of sensors to perform robot navigation and person following depending on the visibility in the environment. [ABSTRACT FROM AUTHOR]

In this paper, a silicon photomultiplier (SiPM) array module is evaluated and implemented as the receiver of laser rangefinding experiments to simultaneously measure the range of multiple targets. The array consists of 4 \times 4 SiPMs on a single chip. Each SiPM is followed by a transimpedance amplifier to have an adequate output signal voltage. The 4 \times 4 array is capable of measuring the range of 16 targets. A SiPM is an avalanche photodiode that operates in Geiger mode, where a huge multiplication factor, as high as 1 000 000, is obtainable. Thus, it can achieve high sensitivity. Our performance evaluation results show that the sensitivity of the measured SiPMs actually approaches the quantum limit. The SiPM can detect one single photoelectron in the depletion region. Each SiPM has a large active area, i.e., 8 \mm^2, and can collect much more returned light compared with typical silicon avalanche photodiodes (Si-APDs). The rise time of output voltage waveforms from SiPMs varies from 6 to 300 ns, depending on incident light power. The rising edges of output waveforms are compared for time measurement. Using a digital oscilloscope, the time of flight can be measured with 1-ns accuracy. This corresponds to a range resolution of 15 cm. [ABSTRACT FROM PUBLISHER]

We describe a system that uses laser rangefinders to track the positions of people in typical environments and then builds predictive models of the observed movement patterns and interactions between persons. We represent all human activity as detected by the laser rangefinder system as a probability distribution over the space of possible displacements. The assumption is that different activities will map to distinct probability distributions. Position tracks are first segmented and clustered into short sequences representing different activities. The sequence of activity clusters is then used to build a stochastic model of the observed movement patterns and the typical frequency of occurrence. Interactions are assumed to occur between persons whose corresponding probability distributions exhibit a high degree of similarity. We describe the performance of the system on data recorded from unscripted activities that occurred in different environments: open layout laboratory, corridor, and an outdoor courtyard. In the laboratory environment, the system was able to detect interactions between people (ping-pong players) without utilizing a pre-defined model of specific interactions. In the courtyard environment, the system was able to flag a sudden increase in the number of people in the courtyard as an anomalous occurrence without any pre-defined concept of occupancy of the environment. [ABSTRACT FROM AUTHOR]

Laser rangefinders and laser scanners are widely used for industrial purposes and for remote sensing. In agriculture information about crop parameters like volume, height, and density can support the optimisation of production processes. In scientific papers the measurement of these parameters by low cost laser rangefinders with one echo has been presented for short ranges. Because the cross section area of the beam increases with the measuring range, it can be expected that laser rangefinders will have a reduced measuring accuracy in small sized crops and when measuring far distances. These problems are caused by target areas smaller than the beam and by the beam striking the edges of crop objects. Lab tests under defined conditions and a real field test were performed to assess the measuring properties under such difficult conditions of a chosen low cost sensor. Based on lab tests it was shown that the accuracy was reduced, but the successful use of the sensor under field conditions demonstrated the potential to meet the demands for agricultural applications. Insights resulting from investigations made in the paper contribute to facilitating the choice or the development of laser rangefinder sensors for vehicle based measurement of crop parameters for optimisation of production processes. [ABSTRACT FROM AUTHOR]