scholarly journals Quality Assessment of Photogrammetric Methods—A Workflow for Reproducible UAS Orthomosaics

2020 ◽  
Vol 12 (22) ◽  
pp. 3831
Author(s):  
Marvin Ludwig ◽  
Christian M. Runge ◽  
Nicolas Friess ◽  
Tiziana L. Koch ◽  
Sebastian Richter ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Spatial Data ◽  
Forest Canopy ◽  
Cost Effective ◽  
Temporal Analysis ◽  
Unmanned Aerial Systems ◽  
Wide Range ◽  
Very High Spatial Resolution ◽  
Multi Temporal ◽  
Aerial Systems

Unmanned aerial systems (UAS) are cost-effective, flexible and offer a wide range of applications. If equipped with optical sensors, orthophotos with very high spatial resolution can be retrieved using photogrammetric processing. The use of these images in multi-temporal analysis and the combination with spatial data imposes high demands on their spatial accuracy. This georeferencing accuracy of UAS orthomosaics is generally expressed as the checkpoint error. However, the checkpoint error alone gives no information about the reproducibility of the photogrammetrical compilation of orthomosaics. This study optimizes the geolocation of UAS orthomosaics time series and evaluates their reproducibility. A correlation analysis of repeatedly computed orthomosaics with identical parameters revealed a reproducibility of 99% in a grassland and 75% in a forest area. Between time steps, the corresponding positional errors of digitized objects lie between 0.07 m in the grassland and 0.3 m in the forest canopy. The novel methods were integrated into a processing workflow to enhance the traceability and increase the quality of UAS remote sensing.

scholarly journals Evaluation of the Apple iPhone 12 Pro LiDAR for an Application in Geosciences

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gregor Luetzenburg ◽  
Aart Kroon ◽  
Anders A. Bjørk
Keyword(s):  
High Resolution ◽  
Optical Sensors ◽  
Cost Effective ◽  
Point Clouds ◽  
3D Models ◽  
Absolute Accuracy ◽  
Wide Range ◽  
Financial Investments ◽  
Coastal Cliff ◽  
High Resolution Models

AbstractTraditionally, topographic surveying in earth sciences requires high financial investments, elaborate logistics, complicated training of staff and extensive data processing. Recently, off-the-shelf drones with optical sensors already reduced the costs for obtaining a high-resolution dataset of an Earth surface considerably. Nevertheless, costs and complexity associated with topographic surveying are still high. In 2020, Apple Inc. released the iPad Pro 2020 and the iPhone 12 Pro with novel build-in LiDAR sensors. Here we investigate the basic technical capabilities of the LiDAR sensors and we test the application at a coastal cliff in Denmark. The results are compared to state-of-the-art Structure from Motion Multi-View Stereo (SfM MVS) point clouds. The LiDAR sensors create accurate high-resolution models of small objects with a side length > 10 cm with an absolute accuracy of ± 1 cm. 3D models with the dimensions of up to 130 × 15 × 10 m of a coastal cliff with an absolute accuracy of ± 10 cm are compiled. Overall, the versatility in handling outweighs the range limitations, making the Apple LiDAR devices cost-effective alternatives to established techniques in remote sensing with possible fields of application for a wide range of geo-scientific areas and teaching.

scholarly journals UAS for Wetland Mapping and Hydrological Modeling

2019 ◽  
Vol 11 (17) ◽  
pp. 1997 ◽  
Author(s):  
Justyna Jeziorska
Keyword(s):  
Spatial Data ◽  
Hydrological Modeling ◽  
High Spatial Resolution ◽  
Spatial Scales ◽  
Regulatory Environment ◽  
Unmanned Aerial Systems ◽  
Wetland Mapping ◽  
Monitoring Strategies ◽  
Sensing Technology ◽  
Aerial Systems

The miniaturization and affordable production of integrated microelectronics have improved in recent years, making unmanned aerial systems (UAS) accessible to consumers and igniting their interest. Researchers have proposed UAS-based solutions for almost any conceivable problem, but the greatest impact will likely be in applications that exploit the unique advantages of the technology: work in dangerous or difficult-to-access areas, high spatial resolution and/or frequent measurements of environmental phenomena, and deployment of novel sensing technology over small to moderate spatial scales. Examples of such applications may be the identification of wetland areas and use of high-resolution spatial data for hydrological modeling. However, because of the large—and growing—assortment of aircraft and sensors available on the market, an evolving regulatory environment, and limited practical guidance or examples of wetland mapping with UAS, it has been difficult to confidently devise or recommend UAS-based monitoring strategies for these applications. This paper provides a comprehensive review of UAS hardware, software, regulations, scientific applications, and data collection/post-processing procedures that are relevant for wetland monitoring and hydrological modeling.

scholarly journals Design and Evaluation of Sensor Housing for Boundary Layer Profiling Using Multirotors

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2481 ◽  
Author(s):  
Ashraful Islam ◽  
Adam L. Houston ◽  
Ajay Shankar ◽  
Carrick Detweiler
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Ground Level ◽  
Radiation Shielding ◽  
Unmanned Aerial Systems ◽  
Heat Sources ◽  
Wide Range ◽  
Artificial Heat ◽  
Aerial Systems ◽  
Airborne Sensors

Traditional configurations for mounting Temperature–Humidity (TH) sensors on multirotor Unmanned Aerial Systems (UASs) often suffer from insufficient radiation shielding, exposure to mixed and turbulent air from propellers, and inconsistent aspiration while situated in the wake of the UAS. Descent profiles using traditional methods are unreliable (when compared to an ascent profile) due to the turbulent mixing of air by the UAS while descending into that flow field. Consequently, atmospheric boundary layer profiles that rely on such configurations are bias-prone and unreliable in certain flight patterns (such as descent). This article describes and evaluates a novel sensor housing designed to shield airborne sensors from artificial heat sources and artificial wet-bulbing while pulling air from outside the rotor wash influence. The housing is mounted above the propellers to exploit the rotor-induced pressure deficits that passively induce a high-speed laminar airflow to aspirate the sensor consistently. Our design is modular, accommodates a variety of other sensors, and would be compatible with a wide range of commercially available multirotors. Extensive flight tests conducted at altitudes up to 500 m Above Ground Level (AGL) show that the housing facilitates reliable measurements of the boundary layer phenomena and is invariant in orientation to the ambient wind, even at high vertical/horizontal speeds (up to 5 m/s) for the UAS. A low standard deviation of errors shows a good agreement between the ascent and descent profiles and proves our unique design is reliable for various UAS missions.

scholarly journals Surrogate Safety Analysis of Pedestrian-Vehicle Conflict at Intersections Using Unmanned Aerial Vehicle Videos

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Peng Chen ◽  
Weiliang Zeng ◽  
Guizhen Yu ◽  
Yunpeng Wang
Keyword(s):  
Data Extraction ◽  
Cost Effective ◽  
Safety Analysis ◽  
Conflict Analysis ◽  
Unmanned Aerial Systems ◽  
Trajectory Data ◽  
High Exposure ◽  
Safety Issues ◽  
Traffic Conflict ◽  
Aerial Systems

Conflict analysis using surrogate safety measures (SSMs) has become an efficient approach to investigate safety issues. The state-of-the-art studies largely resort to video images taken from high buildings. However, it suffers from heavy labor work, high cost of maintenance, and even security restrictions. Data collection and processing remains a common challenge to traffic conflict analysis. Unmanned Aerial Systems (UASs) or Unmanned Aerial Vehicles (UAVs), known for easy maneuvering, outstanding flexibility, and low costs, are considered to be a novel aerial sensor. By taking full advantage of the bird’s eye view offered by UAV, this study, as a pioneer work, applied UAV videos for surrogate safety analysis of pedestrian-vehicle conflicts at one urban intersection in Beijing, China. Aerial video sequences for a period of one hour were analyzed. The detection and tracking systems for vehicle and pedestrian trajectory data extraction were developed, respectively. Two SSMs, that is, Postencroachment Time (PET) and Relative Time to Collision (RTTC), were employed to represent how spatially and temporally close the pedestrian-vehicle conflict is to a collision. The results of analysis showed a high exposure of pedestrians to traffic conflict both inside and outside the crosswalk and relatively risking behavior of right-turn vehicles around the corner. The findings demonstrate that UAV can support intersection safety analysis in an accurate and cost-effective way.

scholarly journals Laws and Trends of the Evolution of Traditional Villages in Plane Pattern

2020 ◽  
Vol 12 (7) ◽  
pp. 3005
Author(s):  
Xi Yang ◽  
Ke Song ◽  
Fuan Pu
Keyword(s):  
Spatial Data ◽  
Nearest Neighbor ◽  
Morphological Evolution ◽  
Temporal Analysis ◽  
Mean Value ◽  
Significant Shift ◽  
Spatial Processes ◽  
Common Mean ◽  
Multi Temporal ◽  
The Stability

This study collected and analyzed dynamic spatial data of eight traditional villages scattered in different regions of China. A multi-temporal analysis of morphological metrics of spatial patterns and a regression analysis of the morphological evolution were used to analyze and contrast the historical spatial processes of different villages. These were then compared using patch texture and rural macro-morphology perspectives. This led to an assessment of the general laws and trends associated with rural spatial processes. (1) There has been a significant shift in the stability of rural spatial development since the founding of the People’s Republic of China (PRC). (2) Most small and medium-sized villages have maintained a relatively stable spatial texture, while large villages have changed significantly. (3) The mean and variance of the patch area, and the Euclidean nearest-neighbor distance, are correlated in some cases. (4) The mode of rural expansion may be relevant to limitations in the total area of growth. (5) The fractal dimension of the rural macro-morphology may follow a morphological order of oscillation around the equilibrium level. (6) The common mean value of the projected area of rural building patches is expected to be 100 m2.

scholarly journals Unmanned Aerial System Imagery, Land Data and User Needs: A Socio-Technical Assessment in Rwanda

2019 ◽  
Vol 11 (9) ◽  
pp. 1035 ◽  
Author(s):  
Claudia Stöcker ◽  
Serene Ho ◽  
Placide Nkerabigwi ◽  
Cornelia Schmidt ◽  
Mila Koeva ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Land Tenure ◽  
Spatial Data ◽  
Information Needs ◽  
Institutional Environment ◽  
Social Study ◽  
Unmanned Aerial Systems ◽  
Quality Of Data ◽  
Priority List ◽  
Aerial Systems

Unmanned Aerial Systems (UAS) are emerging as a tool for alternative land tenure data acquisition. Even though UAS appear to represent a promising technology, it remains unclear to what extent they match the needs of communities and governments in the land sector. This paper responds to this question by undertaking a socio-technical study in Rwanda, aiming to determine the match between stakeholders’ needs and the characteristics of the UAS data acquisition workflow and its final products as valuable spatial data for land administration and spatial planning. A needs assessment enabled the expression of a range of land information needs across multiple levels and stakeholder sectors. Next to the social study, three different UAS were flown to test not only the quality of data but the possibilities of the use of this technology within the current institutional environment. A priority list of needs for cadastral and non-cadastral information as well as insights into operational challenges and data quality measures of UAS-based data products are presented. It can be concluded that UAS can have a significant contribution to match most of the prioritized needs in Rwanda. However, the results also reveal that structural and capacity conditions currently undermine this potential.

scholarly journals Measuring Transverse Displacements Using Unmanned Aerial Systems Laser Doppler Vibrometer (UAS-LDV): Development and Field Validation

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6051
Author(s):  
Piyush Garg ◽  
Roya Nasimi ◽  
Ali Ozdagli ◽  
Su Zhang ◽  
David Dennis Lee Mascarenas ◽  
...  
Keyword(s):  
Laser Doppler Vibrometer ◽  
Field Tests ◽  
Field Measurements ◽  
Cost Effective ◽  
Laser Doppler ◽  
Unmanned Aerial Systems ◽  
Dynamic Displacement ◽  
Railway Bridges ◽  
Industrial Adoption ◽  
Aerial Systems

Measurement of bridge displacements is important for ensuring the safe operation of railway bridges. Traditionally, contact sensors such as Linear Variable Displacement Transducers (LVDT) and accelerometers have been used to measure the displacement of the railway bridges. However, these sensors need significant effort in installation and maintenance. Therefore, railroad management agencies are interested in new means to measure bridge displacements. This research focuses on mounting Laser Doppler Vibrometer (LDV) on an Unmanned Aerial System (UAS) to enable contact-free transverse dynamic displacement of railroad bridges. Researchers conducted three field tests by flying the Unmanned Aerial Systems Laser Doppler Vibrometer (UAS-LDV) 1.5 m away from the ground and measured the displacement of a moving target at various distances. The accuracy of the UAS-LDV measurements was compared to the Linear Variable Differential Transducer (LVDT) measurements. The results of the three field tests showed that the proposed system could measure non-contact, reference-free dynamic displacement with an average peak and root mean square (RMS) error for the three experiments of 10% and 8% compared to LVDT, respectively. Such errors are acceptable for field measurements in railroads, as the interest prior to bridge monitoring implementation of a new approach is to demonstrate similar success for different flights, as reported in the three results. This study also identified barriers for industrial adoption of this technology and proposed operational development practices for both technical and cost-effective implementation.

scholarly journals Illumination Geometry and Flying Height Influence Surface Reflectance and NDVI Derived from Multispectral UAS Imagery

Drones ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 55 ◽  
Author(s):  
Daniel Stow ◽  
Caroline J. Nichol ◽  
Tom Wade ◽  
Jakob J. Assmann ◽  
Gillian Simpson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vegetation Indices ◽  
Flying Height ◽  
Unmanned Aerial Systems ◽  
Radiometric Calibration ◽  
Very High Spatial Resolution ◽  
Vegetation Surveys ◽  
Solar Noon ◽  
Aerial Systems ◽  
Reflectance Measurements

Small unmanned aerial systems (UAS) have allowed the mapping of vegetation at very high spatial resolution, but a lack of standardisation has led to uncertainties regarding data quality. For reflectance measurements and vegetation indices (Vis) to be comparable between sites and over time, careful flight planning and robust radiometric calibration procedures are required. Two sources of uncertainty that have received little attention until recently are illumination geometry and the effect of flying height. This study developed methods to quantify and visualise these effects in imagery from the Parrot Sequoia, a UAV-mounted multispectral sensor. Change in illumination geometry over one day (14 May 2018) had visible effects on both individual images and orthomosaics. Average near-infrared (NIR) reflectance and NDVI in regions of interest were slightly lower around solar noon, and the contrast between shadowed and well-illuminated areas increased over the day in all multispectral bands. Per-pixel differences in NDVI maps were spatially variable, and much larger than average differences in some areas. Results relating to flying height were inconclusive, though small increases in NIR reflectance with height were observed over a black sailcloth tarp. These results underline the need to consider illumination geometry when carrying out UAS vegetation surveys.

Bioinspired optical sensors for unmanned aerial systems

2011 ◽  
Author(s):  
Javaan Chahl ◽  
Kent Rosser ◽  
Akiko Mizutani
Keyword(s):  
Optical Sensors ◽  
Unmanned Aerial Systems ◽  
Aerial Systems
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