scholarly journals High-Quality UAV-Based Orthophotos for Cadastral Mapping: Guidance for Optimal Flight Configurations

2020 ◽  
Vol 12 (21) ◽  
pp. 3625
Author(s):  
Claudia Stöcker ◽  
Francesco Nex ◽  
Mila Koeva ◽  
Markus Gerke
Keyword(s):  
Data Quality ◽  
Geospatial Information ◽  
Ground Control Points ◽  
Bundle Block Adjustment ◽  
High Resolution Imagery ◽  
Decision Making Processes ◽  
Combination Of Methods ◽  
Study Sites ◽  
The Impact ◽  
Base Data

During the past years, unmanned aerial vehicles (UAVs) gained importance as a tool to quickly collect high-resolution imagery as base data for cadastral mapping. However, the fact that UAV-derived geospatial information supports decision-making processes involving people’s land rights ultimately raises questions about data quality and accuracy. In this vein, this paper investigates different flight configurations to give guidance for efficient and reliable UAV data acquisition. Imagery from six study areas across Europe and Africa provide the basis for an integrated quality assessment including three main aspects: (1) the impact of land cover on the number of tie-points as an indication on how well bundle block adjustment can be performed, (2) the impact of the number of ground control points (GCPs) on the final geometric accuracy, and (3) the impact of different flight plans on the extractability of cadastral features. The results suggest that scene context, flight configuration, and GCP setup significantly impact the final data quality and subsequent automatic delineation of visual cadastral boundaries. Moreover, even though the root mean square error of checkpoint residuals as a commonly accepted error measure is within a range of few centimeters in all datasets, this study reveals large discrepancies of the accuracy and the completeness of automatically detected cadastral features for orthophotos generated from different flight plans. With its unique combination of methods and integration of various study sites, the results and recommendations presented in this paper can help land professionals and bottom-up initiatives alike to optimize existing and future UAV data collection workflows.

scholarly journals Accuracy Assessment of a UAV Block by Different Software Packages, Processing Schemes and Validation Strategies

2020 ◽  
Vol 9 (3) ◽  
pp. 164 ◽  
Author(s):  
Vittorio Casella ◽  
Filiberto Chiabrando ◽  
Marica Franzini ◽  
Ambrogio Maria Manzino
Keyword(s):  
Accuracy Assessment ◽  
Comparative Approach ◽  
Ground Control Points ◽  
Bundle Block Adjustment ◽  
Software Packages ◽  
Processing Strategies ◽  
High Resolution Imagery ◽  
Aerial Vehicle ◽  
Leave One Out ◽  
Validation Strategy

Unmanned aerial vehicle (UAV) systems are heavily adopted nowadays to collect high-resolution imagery with the purpose of documenting and mapping environment and cultural heritage. Such data are currently processed by programs based on the Structure from Motion (SfM) concept, coming from the computer vision community, rather than from classical photogrammetry. It is interesting to check whether some widely accepted rules coming from old-fashioned photogrammetry still holds: the relation between accuracy and ground sampling distance (GSD), the ratio between the vertical and horizontal accuracy, accuracy estimated on ground control points (GCPs) vs. that estimated with check points (CPs) also in relation to their ratio and distribution. To face the envisaged aspects, the paper adopts a comparative approach, as several programs are used and numerous configurations considered. The paper illustrates the dataset adopted, the carefully tuned processing strategies and bundle block adjustment (BBA) results in terms of accuracy for both GCPs and CPs. Finally, a leave-one-out (LOO) cross-validation strategy is proposed to assess the accuracy for one of the proposed configurations. Some of the reported results were previously presented in the 5th GISTAM Conference.

scholarly journals PHOTOGRAMMETRIC ACCURACY AND MODELING OF ROLLING SHUTTER CAMERAS

2016 ◽  
Vol III-3 ◽  
pp. 139-146 ◽  
Author(s):  
Jonas Vautherin ◽  
Simon Rutishauser ◽  
Klaus Schneider-Zapp ◽  
Hon Fai Choi ◽  
Venera Chovancova ◽  
...  
Keyword(s):  
Camera Model ◽  
Ground Control Points ◽  
Bundle Block Adjustment ◽  
Multiple Datasets ◽  
Site Monitoring ◽  
Typical Consumer ◽  
Competitive Pricing ◽  
The Impact ◽  
Beta Version

Unmanned aerial vehicles (UAVs) are becoming increasingly popular in professional mapping for stockpile analysis, construction site monitoring, and many other applications. Due to their robustness and competitive pricing, consumer UAVs are used more and more for these applications, but they are usually equipped with rolling shutter cameras. This is a significant obstacle when it comes to extracting high accuracy measurements using available photogrammetry software packages. In this paper, we evaluate the impact of the rolling shutter cameras of typical consumer UAVs on the accuracy of a 3D reconstruction. Hereto, we use a beta-version of the Pix4Dmapper 2.1 software to compare traditional (non rolling shutter) camera models against a newly implemented rolling shutter model with respect to both the accuracy of geo-referenced validation points and to the quality of the motion estimation. Multiple datasets have been acquired using popular quadrocopters (DJI Phantom 2 Vision+, DJI Inspire 1 and 3DR Solo) following a grid flight plan. For comparison, we acquired a dataset using a professional mapping drone (senseFly eBee) equipped with a global shutter camera. The bundle block adjustment of each dataset shows a significant accuracy improvement on validation ground control points when applying the new rolling shutter camera model for flights at higher speed (8m=s). Competitive accuracies can be obtained by using the rolling shutter model, although global shutter cameras are still superior. Furthermore, we are able to show that the speed of the drone (and its direction) can be solely estimated from the rolling shutter effect of the camera.

scholarly journals PHOTOGRAMMETRIC ACCURACY AND MODELING OF ROLLING SHUTTER CAMERAS

2016 ◽  
Vol III-3 ◽  
pp. 139-146 ◽  
Author(s):  
Jonas Vautherin ◽  
Simon Rutishauser ◽  
Klaus Schneider-Zapp ◽  
Hon Fai Choi ◽  
Venera Chovancova ◽  
...  
Keyword(s):  
Camera Model ◽  
Ground Control Points ◽  
Bundle Block Adjustment ◽  
Multiple Datasets ◽  
Site Monitoring ◽  
Typical Consumer ◽  
Competitive Pricing ◽  
The Impact ◽  
Beta Version

Unmanned aerial vehicles (UAVs) are becoming increasingly popular in professional mapping for stockpile analysis, construction site monitoring, and many other applications. Due to their robustness and competitive pricing, consumer UAVs are used more and more for these applications, but they are usually equipped with rolling shutter cameras. This is a significant obstacle when it comes to extracting high accuracy measurements using available photogrammetry software packages. In this paper, we evaluate the impact of the rolling shutter cameras of typical consumer UAVs on the accuracy of a 3D reconstruction. Hereto, we use a beta-version of the Pix4Dmapper 2.1 software to compare traditional (non rolling shutter) camera models against a newly implemented rolling shutter model with respect to both the accuracy of geo-referenced validation points and to the quality of the motion estimation. Multiple datasets have been acquired using popular quadrocopters (DJI Phantom 2 Vision+, DJI Inspire 1 and 3DR Solo) following a grid flight plan. For comparison, we acquired a dataset using a professional mapping drone (senseFly eBee) equipped with a global shutter camera. The bundle block adjustment of each dataset shows a significant accuracy improvement on validation ground control points when applying the new rolling shutter camera model for flights at higher speed (8m=s). Competitive accuracies can be obtained by using the rolling shutter model, although global shutter cameras are still superior. Furthermore, we are able to show that the speed of the drone (and its direction) can be solely estimated from the rolling shutter effect of the camera.

The impact of algorithmic decision-making processes on young people’s well-being (Preprint)

2019 ◽  
Author(s):  
Elvira Perez Vallejos ◽  
Liz Dowthwaite ◽  
Helen Creswich ◽  
Virginia Portillo ◽  
Ansgar Koene ◽  
...  
Keyword(s):  
Young People ◽  
Significant Proportion ◽  
Well Being ◽  
Early Years ◽  
Negative Experiences ◽  
Children And Young People ◽  
Online Platforms ◽  
Internet Users ◽  
Decision Making Processes ◽  
The Impact

BACKGROUND Algorithms rule the online environments and are essential for performing data processing, filtering, personalisation and other tasks. Research has shown that children and young people make up a significant proportion of Internet users, however little attention has been given to their experiences of algorithmically-mediated online platforms, or the impact of them on their mental health and well-being. The algorithms that govern online platforms are often obfuscated by a lack of transparency in their online Terms and Conditions and user agreements. This lack of transparency speaks to the need for protecting the most vulnerable users from potential online harms. OBJECTIVE To capture young people's experiences when being online and perceived impact on their well-being. METHODS In this paper, we draw on qualitative and quantitative data from a total of 260 children and young people who took part in a ‘Youth Jury’ to bring their opinions to the forefront, elicit discussion of their experiences of using online platforms, and perceived psychosocial impact on users. RESULTS The results of the study revealed the young people’s positive as well as negative experiences of using online platforms. Benefits such as being convenient and providing entertainment and personalised search results were identified. However, the data also reveals participants’ concerns for their privacy, safety and trust when online, which can have a significant impact on their well-being. CONCLUSIONS We conclude by making recommendations that online platforms acknowledge and enact on their responsibility to protect the privacy of their young users, recognising the significant developmental milestones that this group experience during these early years, and the impact that technology may have on them. We argue that governments need to incorporate policies that require technologists and others to embed the safeguarding of users’ well-being within the core of the design of Internet products and services to improve the user experiences and psychological well-being of all, but especially those of children and young people. CLINICALTRIAL N/A

Characterizing the effectiveness of COVID-19 mitigation measures: A data-centric approach (Preprint)

2020 ◽  
Author(s):  
Lukman Olagoke ◽  
Ahmet E. Topcu
Keyword(s):  
Control Measure ◽  
Control Measures ◽  
World Health ◽  
Mitigation Measures ◽  
Effective Control ◽  
The World ◽  
Decision Making Processes ◽  
And Performance ◽  
Health Organization ◽  
The Impact

BACKGROUND COVID-19 represents a serious threat to both national health and economic systems. To curb this pandemic, the World Health Organization (WHO) issued a series of COVID-19 public safety guidelines. Different countries around the world initiated different measures in line with the WHO guidelines to mitigate and investigate the spread of COVID-19 in their territories. OBJECTIVE The aim of this paper is to quantitatively evaluate the effectiveness of these control measures using a data-centric approach. METHODS We begin with a simple text analysis of coronavirus-related articles and show that reports on similar outbreaks in the past strongly proposed similar control measures. This reaffirms the fact that these control measures are in order. Subsequently, we propose a simple performance statistic that quantifies general performance and performance under the different measures that were initiated. A density based clustering of based on performance statistic was carried out to group countries based on performance. RESULTS The performance statistic helps evaluate quantitatively the impact of COVID-19 control measures. Countries tend show variability in performance under different control measures. The performance statistic has negative correlation with cases of death which is a useful characteristics for COVID-19 control measure performance analysis. A web-based time-line visualization that enables comparison of performances and cases across continents and subregions is presented. CONCLUSIONS The performance metric is relevant for the analysis of the impact of COVID-19 control measures. This can help caregivers and policymakers identify effective control measures and reduce cases of death due to COVID-19. The interactive web visualizer provides easily digested and quick feedback to augment decision-making processes in the COVID-19 response measures evaluation. CLINICALTRIAL Not Applicable

scholarly journals Ears in the Sky: Potential of Drones for the Bioacoustic Monitoring of Birds and Bats

Drones ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 9
Author(s):  
Adrien Michez ◽  
Stéphane Broset ◽  
Philippe Lejeune
Keyword(s):  
Forest Canopy ◽  
Low Cost ◽  
Population Monitoring ◽  
Biodiversity Loss ◽  
Active Species ◽  
Terrestrial Mammals ◽  
Technical Developments ◽  
High Resolution Imagery ◽  
Human Operators ◽  
The Impact

In the context of global biodiversity loss, wildlife population monitoring is a major challenge. Some innovative techniques such as the use of drones—also called unmanned aerial vehicle/system (UAV/UAS)—offer promising opportunities. The potential of UAS-based wildlife census using high-resolution imagery is now well established for terrestrial mammals or birds that can be seen on images. Nevertheless, the ability of UASs to detect non-conspicuous species, such as small birds below the forest canopy, remains an open question. This issue can be solved with bioacoustics for acoustically active species such as bats and birds. In this context, UASs represent an interesting solution that could be deployed on a larger scale, at lower risk for the operator, and over hard-to-reach locations, such as forest canopies or complex topographies, when compared with traditional protocols (fixed location recorders placed or handled by human operators). In this context, this study proposes a methodological framework to assess the potential of UASs in bioacoustic surveys for birds and bats, using low-cost audible and ultrasound recorders mounted on a low-cost quadcopter UAS (DJI Phantom 3 Pro). The proposed methodological workflow can be straightforwardly replicated in other contexts to test the impact of other UAS bioacoustic recording platforms in relation to the targeted species and the specific UAS design. This protocol allows one to evaluate the sensitivity of UAS approaches through the estimate of the effective detection radius for the different species investigated at several flight heights. The results of this study suggest a strong potential for the bioacoustic monitoring of birds but are more contrasted for bat recordings, mainly due to quadcopter noise (i.e., electronic speed controller (ESC) noise) but also, in a certain manner, to the experimental design (use of a directional speaker with limited call intensity). Technical developments, such as the use of a winch to safely extent the distance between the UAS and the recorder during UAS sound recordings or the development of an innovative platform, such as a plane–blimp hybrid UAS, should make it possible to solve these issues.

scholarly journals Analyzing Factors Affecting the Sustainability of Land Management Practices in Mecha Woreda, Northwestern Ethiopia

2021 ◽  
Vol 13 (13) ◽  
pp. 7007
Author(s):  
Habtamu Nebere ◽  
Degefa Tolossa ◽  
Amare Bantider
Keyword(s):  
Decision Making ◽  
Land Management ◽  
Land Degradation ◽  
Quantitative Data ◽  
Management Practices ◽  
Short Term ◽  
Factors Affecting ◽  
Decision Making Processes ◽  
Household Heads ◽  
The Impact

In Ethiopia, the practice of land management started three decades ago in order to address the problem of land degradation and to further boost agricultural production. However, the impact of land management practices in curbing land degradation problems and improving the productivity of the agricultural sector is insignificant. Various empirical works have previously identified the determinants of the adoption rate of land management practices. However, the sustainability of land management practices after adoption, and the various factors that control the sustainability of implemented land management practices, are not well addressed. This study analyzed the factors affecting the sustainability of land management practices after implementation in Mecha Woreda, northwestern Ethiopia. The study used 378 sample respondents, selected by a systematic random sampling technique. Binary logistic regression was used to analyze the quantitative data, while the qualitative data were qualitatively and concurrently analyzed with the quantitative data. The sustained supply of fodder from the implemented land management practices, as well as improved cattle breed, increases the sustainability of the implemented land management practices. While lack of agreement in the community, lack of enforcing community bylaws, open cattle grazing, lack of benefits of implemented land management practices, acting as barrier for farming practices, poor participation of household heads during planning and decision-making processes, as well as the lack of short-term benefits, reduce the sustainability of the implemented land management practices. Thus, it is better to allow for the full participation of household heads in planning and decision-making processes to bring practical and visible results in land management practices. In addition, recognizing short-term benefits to compensate the land lost in constructing land management structures must be the strategy in land management practices. Finally, reducing the number of cattle and practicing stall feeding is helpful both for the sustainability of land management practices and the productivity of cattle. In line with this, fast-growing fodder grass species have to be introduced for household heads to grow on land management structures and communal grazing fields for stall feeding.

scholarly journals Mapping ‘wild zones’ of globalisation: on private actors and the rule of law

2021 ◽  
Vol 17 (1) ◽  
pp. 107-113
Author(s):  
Chantal Mak
Keyword(s):  
Global Economy ◽  
Large Scale ◽  
Legal Framework ◽  
International Investments ◽  
Goods And Services ◽  
Decision Making Processes ◽  
Private Corporations ◽  
Comprehensive Framework ◽  
Private Actors ◽  
The Impact

While private corporations have become increasingly influential in the global economy, a comprehensive legal framework for their activities is missing. Although international and regional legal instruments may govern some aspects of, for instance, international investments and the supply of goods and services, there is no overarching structure for assessing the impact of large-scale private projects. In the absence of such a comprehensive framework, specific rules of private law allow profit-seeking companies to expand their activities on an economic basis, mostly without having to heed social concerns (Pistor, 2019). This is particularly problematic insofar as multinational companies have obtained power to set the rules for their engagement with states, organisations and individuals, for instance in the form of transnational investment contracts. Given the fragmented nature of the legal sphere in which such contracts are elaborated and performed, those who face the harmful consequences of such investments may not be able to participate in decision-making processes. The contracts remain in ‘wild zones’ of globalisation (Fraser, 2014, p. 150), where powerful private companies rule.

Survey Data Quality in Analyzing Harmonized Indicators of Protest Behavior: A Survey Data Recycling Approach

2021 ◽  
pp. 000276422110216
Author(s):  
Kazimierz M. Slomczynski ◽  
Irina Tomescu-Dubrow ◽  
Ilona Wysmulek
Keyword(s):  
Data Processing ◽  
Data Quality ◽  
Survey Data ◽  
A Priori ◽  
Data Sets ◽  
New Approach ◽  
Survey Quality ◽  
Survey Error ◽  
Ex Post ◽  
The Impact

This article proposes a new approach to analyze protest participation measured in surveys of uneven quality. Because single international survey projects cover only a fraction of the world’s nations in specific periods, researchers increasingly turn to ex-post harmonization of different survey data sets not a priori designed as comparable. However, very few scholars systematically examine the impact of the survey data quality on substantive results. We argue that the variation in source data, especially deviations from standards of survey documentation, data processing, and computer files—proposed by methodologists of Total Survey Error, Survey Quality Monitoring, and Fitness for Intended Use—is important for analyzing protest behavior. In particular, we apply the Survey Data Recycling framework to investigate the extent to which indicators of attending demonstrations and signing petitions in 1,184 national survey projects are associated with measures of data quality, controlling for variability in the questionnaire items. We demonstrate that the null hypothesis of no impact of measures of survey quality on indicators of protest participation must be rejected. Measures of survey documentation, data processing, and computer records, taken together, explain over 5% of the intersurvey variance in the proportions of the populations attending demonstrations or signing petitions.

Sign in / Sign up

Export Citation Format

Share Document