A hierarchical approach for refining point cloud quality of a low cost UAV LiDAR system in the urban environment

2022 ◽  
Vol 183 ◽  
pp. 403-421
Author(s):  
Bisheng Yang ◽  
Jianping Li
Keyword(s):  
Urban Environment ◽  
Point Cloud ◽  
Low Cost ◽  
Hierarchical Approach ◽  
Lidar System

scholarly journals EVALUATION OF LOW-COST TERRESTRIAL PHOTOGRAMMETRY FOR 3D RECONSTRUCTION OF COMPLEX BUILDINGS

2017 ◽  
Vol IV-2/W4 ◽  
pp. 199-206 ◽  
Author(s):  
S. Altman ◽  
W. Xiao ◽  
B. Grayson
Keyword(s):  
Natural Disaster ◽  
Point Cloud ◽  
Low Cost ◽  
Point Clouds ◽  
3D Modelling ◽  
Negative Effects ◽  
Accessible Method ◽  
Digital Modelling ◽  
Terrestrial Photogrammetry

Terrestrial photogrammetry is an accessible method of 3D digital modelling, and can be done with low-cost consumer grade equipment. Globally there are many undocumented buildings, particularly in the developing world, that could benefit from 3D modelling for documentation, redesign or restoration. Areas with buildings at risk of destruction by natural disaster or war could especially benefit. This study considers a range of variables that affect the quality of photogrammetric results. Different point clouds of the same building are produced with different variables, and they are systematically tested to see how the output was affected. This is done by geometrically comparing them to a laser scanned point cloud of the same building. It finally considers how best results can be achieved for different applications, how to mitigate negative effects, and the limits of this technique.

scholarly journals TECHNICAL CONSIDERATIONS IN LOW-COST HERITAGE DOCUMENTATION

2019 ◽  
Vol XLII-2/W17 ◽  
pp. 225-232
Author(s):  
A. Murtiyoso ◽  
P. Grussenmeyer ◽  
D. Suwardhi
Keyword(s):  
Point Cloud ◽  
Low Cost ◽  
Bundle Adjustment ◽  
Ease Of Use ◽  
Cloud Data ◽  
Heritage Sites ◽  
Common Reference ◽  
Trade Offs ◽  
Dense Point

Abstract. The use of photogrammetry in 3D heritage documentation has matured over the recent years. In the same time, many types of sensors have also been developed in the field of imaging. While photogrammetry is considered as a low-cost alternative to TLS, several options exist in terms of sensor type with trade-offs between price, ease of use, and quality of resolution. Nevertheless, a proper knowledge on the acquisition and processing is still required to generate acceptable results. This paper aims to compare three photogrammetric sensors, namely a classical DSLR camera, a drone, and a spherical 360° camera in documenting heritage sites. Main comparison points include quality of the bundle adjustment and quality of the dense point cloud. However, an important point of the paper is also to determine whether a sensor at a given cost and effort is enough for documentation purposes. A TLS point cloud data was used as a common reference, as well as control and check points issued from geodetic surveying. In the aftermath of the comparison, several technical suggestions and recommendations were proposed as regards to the use of each sensor.

scholarly journals Improvement of 3D Power Line Extraction from Multiple Low-Cost UAV Imagery Using Wavelet Analysis

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 700 ◽  
Author(s):  
Anna Fryskowska
Keyword(s):  
Point Cloud ◽  
Accuracy Assessment ◽  
Low Cost ◽  
Three Dimensional ◽  
Point Clouds ◽  
Power Line ◽  
Power Lines ◽  
Remotely Sensed Data ◽  
Processing Algorithms

Three-dimensional (3D) mapping of power lines is very important for power line inspection. Many remotely-sensed data products like light detection and ranging (LiDAR) have been already studied for power line surveys. More and more data are being obtained via photogrammetric measurements. This increases the need for the implementation of advanced processing techniques. In recent years, there have been several developments in visualisation techniques using UAV (unmanned aerial vehicle) platform photography. The most modern of such imaging systems have the ability to generate dense point clouds. However, image-based point cloud accuracy is very often various (unstable) and dependent on the radiometric quality of images and the efficiency of image processing algorithms. The main factor influencing the point cloud quality is noise. Such problems usually arise with data obtained via low-cost UAV platforms. Therefore, generated point clouds representing power lines are usually incomplete and noisy. To obtain a complete and accurate 3D model of power lines and towers, it is necessary to develop improved data processing algorithms. The experiment tested the algorithms on power lines with different voltages. This paper presents the wavelet-based method of processing data acquired with a low-cost UAV camera. The proposed, original method involves the application of algorithms for coarse filtration and precise filtering. In addition, a new way of calculating the recommended flight height was proposed. At the end, the accuracy assessment of this two-stage filtration process was examined. For this, point quality indices were proposed. The experimental results show that the proposed algorithm improves the quality of low-cost point clouds. The proposed methods improve the accuracy of determining the parameters of the lines by more than twice. About 10% of noise is reduced by using the wavelet-based approach.

scholarly journals Dense point cloud acquisition with a low-cost Velodyne VLP-16

2020 ◽  
Author(s):  
Jason Bula ◽  
Marc-Henri Derron ◽  
Grégoire Mariéthoz
Keyword(s):  
Point Cloud ◽  
Low Cost ◽  
Point Clouds ◽  
Abandoned Mines ◽  
Lidar System ◽  
Gnss Positioning ◽  
Dense Point ◽  
Slam Algorithm ◽  
Calibration Step ◽  
Cloud Density

Abstract. This study develops a method to acquire dense point clouds with a low-cost Velodyne VLP-16 lidar system, without using expensive GNSS positioning or IMU. Our setting consists in mounting the lidar on a motor to continuously change the scan direction, which leads to a significant increase in the point cloud density. A post-treatment reconstructs the position of each point accounting for the motor angle at the time of acquisition, and a calibration step accounts for inaccuracies in the hardware assemblage. The system is tested in indoors settings such as buildings and abandoned mines, but is also expected to give good results outdoors. It is also compared with a more expensive system based on IMU registration and a SLAM algorithm. The alignment between acquisitions with those two systems is within a distance of 2 cm.

scholarly journals FIRST ASSESSMENTS INTO THE USE OF COMMERCIAL-GRADE SOLID STATE LIDAR FOR LOW COST HERITAGE DOCUMENTATION

2021 ◽  
Vol XLIII-B2-2021 ◽  
pp. 599-604
Author(s):  
A. Murtiyoso ◽  
P. Grussenmeyer ◽  
T. Landes ◽  
H. Macher
Keyword(s):  
Solid State ◽  
Point Cloud ◽  
Laser Scanning ◽  
Low Cost ◽  
Sensor Technology ◽  
The Past ◽  
Geometric Quality ◽  
The Moment ◽  
Near Future

Abstract. Heritage documentation has benefitted greatly from significant developments in sensor technology during the past two decades. Miniaturisation of sensors is also an important aspect in the development of low cost sensors, always interesting in heritage projects where budgetary constraints are often present. Among these sensors, the solid-state lidar has begun to attract attention, partly due to its integration in Apple Inc.’s latest version of the iPhone and iPad series. We hypothesise that this type of sensor will see a lot of use in the near future; however, the question remains whether they are sufficient for heritage documentation purposes. In this paper, results from the 2020 iPad Pro SSL point cloud will be assessed and compared to more traditional techniques for 3D scanning (photogrammetry and terrestrial laser scanning). While understandably the geometric quality of benchmark-level techniques such as these remain undeniably better, at least for the moment, the paper concludes that SSL sensors may nevertheless be sufficient for some lower-precision applications.

scholarly journals INVESTIGATION INTO THE USE OF ACTION CAMERAS IN THE DOCUMENTATION OF ARCHITECTURAL DETAILS – THE CASE STUDY OF A BAROQUE CHAMBER

2018 ◽  
Vol XLII-2 ◽  
pp. 667-674 ◽  
Author(s):  
J. Markiewicz ◽  
S. Łapiński ◽  
M. Pilarska ◽  
R. Bieńkowski ◽  
A. Kaliszewska
Keyword(s):  
Point Cloud ◽  
Low Cost ◽  
Point Clouds ◽  
Distortion Correction ◽  
Ground Control ◽  
Architectural Elements ◽  
Ground Control Points ◽  
Analysis Quality

In this paper the possibility of using the Xiaomi 4K action cameras as a low-cost sensor for the generation of high resolution documentation of architecture and architectural elements in the field of Cultural Heritage was analysed. For that purpose a series of images was acquired together with tachometric measurements to determine the ground control points. Additionally TLS data was collected, which was treated as a reference. For the purpose of point cloud generation the Structure-from-motion (SfM) and Multi- View Stereo (MVS) approaches were used. The following parameters of the collected data and the resulting documentation were tested: the interior orientation parameters analysis, quality of the Xiaomi built-in Lenses Distortion Correction; the accuracy of the orientation on ground control and check points, the point cloud density; the flatness of the walls; the discrepancies between point clouds derived from the low-cost cameras and TLS data, shape of the architectural details based on cross-section analysis. After the analysis of the obtained results it can be concluded that the Xiaomi 4K low-cost sensors are well suited for the purpose of documentation of architecture and architectural details. All the data for the presented investigation were acquired at the baroque residence of the Bieliński Palace in Otwock Wielki in Poland.

Effect of Computerized Auditory Training on Speech Perception of Adults With Hearing Impairment

2013 ◽  
Vol 20 (3) ◽  
pp. 91-106 ◽  
Author(s):  
Rachel Pizarek ◽  
Valeriy Shafiro ◽  
Patricia McCarthy
Keyword(s):  
Hearing Loss ◽  
Speech Perception ◽  
Literature Review ◽  
Low Cost ◽  
Experimental Designs ◽  
Auditory Training ◽  
Hearing Impairments ◽  
Communicative Disorders ◽  
And Training

Computerized auditory training (CAT) is a convenient, low-cost approach to improving communication of individuals with hearing loss or other communicative disorders. A number of CAT programs are being marketed to patients and audiologists. The present literature review is an examination of evidence for the effectiveness of CAT in improving speech perception in adults with hearing impairments. Six current CAT programs, used in 9 published studies, were reviewed. In all 9 studies, some benefit of CAT for speech perception was demonstrated. Although these results are encouraging, the overall quality of available evidence remains low, and many programs currently on the market have not yet been evaluated. Thus, caution is needed when selecting CAT programs for specific patients. It is hoped that future researchers will (a) examine a greater number of CAT programs using more rigorous experimental designs, (b) determine which program features and training regimens are most effective, and (c) indicate which patients may benefit from CAT the most.

Registration and Fusion of UAV LiDAR System Sequence Images and Laser Point Clouds

2020 ◽  
Author(s):  
Jiayong Yu ◽  
Longchen Ma ◽  
Maoyi Tian, ◽  
Xiushan Lu
Keyword(s):  
Point Cloud ◽  
Image Data ◽  
Point Clouds ◽  
Optical Image ◽  
Point Cloud Data ◽  
Feature Points ◽  
Lidar System ◽  
Registration Accuracy ◽  
Cloud Data ◽  
Intensity Image

The unmanned aerial vehicle (UAV)-mounted mobile LiDAR system (ULS) is widely used for geomatics owing to its efficient data acquisition and convenient operation. However, due to limited carrying capacity of a UAV, sensors integrated in the ULS should be small and lightweight, which results in decrease in the density of the collected scanning points. This affects registration between image data and point cloud data. To address this issue, the authors propose a method for registering and fusing ULS sequence images and laser point clouds, wherein they convert the problem of registering point cloud data and image data into a problem of matching feature points between the two images. First, a point cloud is selected to produce an intensity image. Subsequently, the corresponding feature points of the intensity image and the optical image are matched, and exterior orientation parameters are solved using a collinear equation based on image position and orientation. Finally, the sequence images are fused with the laser point cloud, based on the Global Navigation Satellite System (GNSS) time index of the optical image, to generate a true color point cloud. The experimental results show the higher registration accuracy and fusion speed of the proposed method, thereby demonstrating its accuracy and effectiveness.

VALORIZATION OF THE URBAN ENVIRONMENT OF SOUTH SERBIA FROM THE AIR QUALITY ASPECT

2018 ◽  
Vol 28 (4) ◽  
pp. 1329-1333
Author(s):  
Miodrag Šmelcerović
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Urban Environment ◽  
Pollution Sources ◽  
Anthropogenic Sources ◽  
Anthropogenic Factors ◽  
Limit Values ◽  
Cause And Effect ◽  
Sources Of Pollution

The protection of the environment and people’s health from negative influences of the pollution of air as a medium of the environment requires constant observing of the air quality in accordance with international standards, the analysis of emission and imission of polluting matters in the air, and their connection with the sources of pollution. Having in mind the series of laws and delegated legislations which define the field of air pollution, it is necessary to closely observe these long-term processes, discovering cause-and-effect relationships between the activities of anthropogenic sources of emission of polluting matters and the level of air degradation. The relevant evaluation of the air quality of a certain area can be conducted if the level of concentration of polluting matters characteristic for the pollution sources of this area is observed in a longer period of time. The data obtained by the observation of the air pollution are the basis for creation of the recovery program of a certain area. Vranje is a town in South Serbia where there is a bigger number of anthropogenic pollution sources that can significantly diminish the air quality. The cause-and-effect relationship of the anthropogenic sources of pollution is conducted related to the analysis of systematized data which are in the relevant data base of the authorized institution The Institute of Public Health Vranje, for the time period between the year of 2012. and 2017. By the analysis of data of imission concentrations of typical polluting matters, the dominant polluting matters were determined on the territory of the town of Vranje, the ones that are the causers of the biggest air pollution and the risk for people’s health. Analysis of the concentration of soot, sulfur dioxide and nitrogen oxides indicates their presence in the air of Vranje town area in concentrations that do not exceed the permitted limit values annually. The greatest pollution is caused by the soot content in the air, especially in the winter period when the highest number of days with the values above the limit was registered. By perceiving the influence of natural and anthropogenic factors, it is clear that the concentration of polluting matters can be decreased only by establishing control over anthropogenic sources of pollution, and thus it can be contributed to the improvement of the air quality of this urban environment.

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