2,801 research outputs found
Introducing GEOBIA to landscape imageability assessment: a multi-temporal case study of the nature reserve “Kózki”, Poland
Geographic object-based image analysis (GEOBIA) is a primary remote sensing tool utilized in land-cover mapping and change detection. Land-cover patches are the primary data source for landscape metrics and ecological indicator calculations; however, their application to visual landscape character (VLC) indicators was little investigated to date. To bridge the knowledge gap between GEOBIA and VLC, this paper puts forward the theoretical concept of using viewpoint as a landscape imageability indicator into the practice of a multi-temporal land-cover case study and explains how to interpret the indicator. The study extends the application of GEOBIA to visual landscape indicator calculations. In doing so, eight different remote sensing imageries are the object of GEOBIA, starting from a historical aerial photograph (1957) and CORONA declassified scene (1965) to contemporary (2018) UAV-delivered imagery. The multi-temporal GEOBIA-delivered land-cover patches are utilized to find the minimal isovist set of viewpoints and to calculate three imageability indicators: the number, density, and spacing of viewpoints. The calculated indicator values, viewpoint rank, and spatial arrangements allow us to describe the scale, direction, rate, and reasons for VLC changes over the analyzed 60 years of landscape evolution. We found that the case study nature reserve (“Kózki”, Poland) landscape imageability transformed from visually impressive openness to imageability due to the impression of several landscape rooms enclosed by forest walls. Our results provide proof that the number, rank, and spatial arrangement of viewpoints constitute landscape imageability measured with the proposed indicators. Discussing the method’s technical limitations, we believe that our findings contribute to a better understanding of land-cover change impact on visual landscape structure dynamics and further VLC indicator development
Empirical Evaluation of Route-Based Landscape Experiences
This thesis explores a method of visual analysis that aims to create a more in-depth understanding of how individuals see and visually perceive their environment. Here we explore a geospatial tool, called Visual Magnitude, to assess road-based experiences. We aimed to provide evidence of a relationship between the tool and scenic rating preferences from a survey. The content of this thesis is split between two articles. The first article, contained in Chapter 2, focuses on optimizing the selection of viewpoints along route-based envrionments. In this study we ask the question is there an optimal sampling rate of viewpoints along a route that can increase efficency in running a visual magnitude analysis and still represent accurately represent the envrionment. We found that for visually sensitive areas, a 30-meter sampling distance produced optimal results. For other landscapes a 50-meter sampling distance poduced resonable results in both sampling points and retained raster area.
The second article, contained in Chapter 3, is an applied visual magnitude study where we use the optimal sampling distance of 30-meters to extract visual magnitude values for 15 different envrionments. These values are then compared to scenic rating values that we collected though a survey where participants saw videos of the same 15 envrionments and rated their scenic quailty. By doing this we were able to provide emperical evidence that the visual magnitude tool can be a way to predict best visual experiences within Utah.
With the results from these studies we can make suggestions to professionals on how they can better use this GIS tool. These suggestions include sampling distances for multiple envrionments and the potential for this tool to be used as a poxy when attempting to interpret how landscapes observers feel about them. This additional infromation will help planners in understanding and making decisions more informed planning decisions along roadways and surrounding areas that have the highest potential impact on observers. By using this tool planners can assess where those areas are and the amount of impact that positive or negitive planning decisions will have on observers
Quantifying spatial uncertainties in structure from motion snow depth mapping with drones in an alpine environment
Due to the heterogeneous nature of alpine snow distribution, advances in hydrological monitoring and forecasting for water resource management require an increase in the frequency, spatial resolution and coverage of field observations. Such detailed snow information is also needed to foster advances in our understanding of how snowpack affects local ecology and geomorphology. Although recent use of structure-from-motion multi-view stereo (SFM-MVS) 3D reconstruction techniques combined with aerial image collection using drones has shown promising potential to provide higher spatial and temporal resolution snow depth data for snowpack monitoring, there still remain challenges to produce high-quality data with this approach. These challenges, which include differentiating observations from noise and overcoming biases in the elevation data, are inherent in digital elevation model (DEM) differencing. A key issue to address these challenges is our ability to quantify measurement uncertainties in the SFM-MVS snow depths which can vary in space and time. The purpose of this thesis was to develop data-driven approaches for spatially quantifying, characterizing and reducing uncertainties in SFM-MVS snow depth mapping in alpine areas. Overall, this thesis provides a general framework for performing a detailed analysis of the spatial pattern of SFM-MVS snow depth uncertainties, as well as provides an approach for correction of snow depth errors due to changes in the sub-snow topography occurring between survey acquisition dates. It also contributes to the growing support of SFM-MVS combined with imagery acquired from drones as a suitable surveying technique for local scale snow distribution monitoring in alpine areas
LiDAR, UAV or compass-clinometer? Accuracy, coverage and the effects on structural models
This study was carried out as part of a University of Aberdeen provided PhD supported by The NERC Centre for Doctoral Training in Oil & Gas, (grant reference: NE/M00578X/1). Thanks to Magda Chmielewska for her training and help with LiDAR processing, without which this study could not have been undertaken. Midland Valley Exploration is thanked for academic use of Move 2016 software. We gratefully acknowledge the detailed and constructive reviews by Mike James and an anonymous reviewer, and thanks to Bill Dunne for careful and thorough editorial comments, all of which greatly improved the manuscript.Peer reviewedPublisher PD
Linking Spatial Video and GIS
Spatial Video is any form of geographically referenced videographic data. The forms in which it is acquired, stored and used vary enormously; as does the standard of accuracy in the spatial data and the quality of the video footage. This research deals with a specific form of Spatial Video where these data have been captured from a moving road-network survey vehicle. The spatial data are GPS sentences while the video orientation is approximately orthogonal and coincident with the direction of travel.
GIS that use these data are usually bespoke standalone systems or third party extensions to existing platforms. They specialise in using the video as a visual enhancement with limited spatial functionality and interoperability. While enormous amounts of these data exist, they do not have a generalised, cross-platform spatial data structure that is suitable for use within a GIS. The objectives of this research have been to define, develop and implement a novel Spatial Video data structure and demonstrate how this can achieve a spatial approach to the study of video.
This data structure is called a Viewpoint and represents the capture location and geographical extent of each video frame. It is generalised to represent any form or format of Spatial Video. It is shown how a Viewpoint improves on existing data structure methodologies and how it can be theoretically defined in 3D space. A 2D implementation is then developed where Viewpoints are constructed from the spatial and camera parameters of each survey in the study area. A number of problems are defined and solutions provided towards the implementation of a post-processing system to calculate, index and store each video frame Viewpoint in a centralised spatial database.
From this spatial database a number of geospatial analysis approaches are demonstrated that represent novel ways of using and studying Spatial Video based on the Viewpoint data structure. Also, a unique application is developed where the Viewpoints are used as a spatial control to dynamically access and play video in a location aware system.
While video has been to date largely ignored as a GIS spatial data source; it is shown through this novel Viewpoint implementation and the geospatial analysis demonstrations that this need not be the case anymore
Three decades of volume change of a small greenlandic glacier using ground penetrating radar, structure from motion, and aerial photogrammetry
Glaciers in the Arctic are losing mass at an increasing rate. Here we use surface topography derived from Structure from Motion (SfM) and ice volume from ground penetrating radar (GPR) to describe the 2014 state of Aqqutikitsoq glacier (2.85 km2) on Greenland's west coast. A photogrammetrically derived 1985 digital elevation model (DEM) was subtracted from a 2014 DEM obtained using land-based SfM to calculate geodetic glacier mass balance. Furthermore, a detailed 2014 ground penetrating radar survey was performed to assess ice volume. From 1985 to 2014, the glacier has lost 49.8 ± 9.4 106 m3 of ice, corresponding to roughly a quarter of its 1985 volume (148.6 ± 47.6 106 m3) and a thinning rate of 0.60 ± 0.11 m a-1. The computations are challenged by a relatively large fraction of the 1985 DEM (∼50% of the glacier surface) being deemed unreliable owing to low contrast (snow cover) in the 1985 aerial photography. To address this issue, surface elevation in low contrast areas was measured manually at point locations and interpolated using a universal kriging approach. We conclude that ground-based SfM is well suited to establish high-quality DEMs of smaller glaciers. Provided favorable topography, the approach constitutes a viable alternative where the use of drones is not possible. Our investigations constitute the first glacier on Greenland's west coast where ice volume was determined and volume change calculated. The glacier's thinning rate is comparable to, for example, the Swiss Alps and underlines that arctic glaciers are subject to fast changes
Visual Descriptors: A Design Tool for Visual Impact Analysis
This study is concerned with the development of a practical and effective
form of computer-aided analysis of the visual impact of building
development in rural areas. Its contribution is fourfold. Firstly, a
conceptual model has been developed for the process of seeing in the
context of visual impact analysis. Secondly, a mathematical model for a
consistent series of visual descriptors has been devised. Thirdly, a
suitable design tool has been devised to make use of visual descriptors
in visual impact analysis. Fourthly, visual descriptors have actually been
implemented as computer software.
The concept of visual impact analysis is defined and placed within the
wider context of landscape research. The problems faced by a designer in
the context of visual impact analysis are identified and the concept of a
'design tool' is introduced and defined. A number of existing computer
software packages, intended or used for visual impact analysis, are
reviewed critically. The concept of 'visual descriptors' as measures to be
used by designers is introduced and examined critically. A conceptual
model is presented for the process of seeing in the context of visual
impact analysis. A range of possible measures for use as visual
descriptors is presented and developed further into a series of precise
definitions. A method of implementing visual descriptors is presented
together with formal algorithms for the derivation of eight visual
descriptors. A software package incorporating these descriptors is
presented and verification and case studies of its use carried out. Visual
descriptors, as implemented, are assessed for their effectiveness as a
design tool for visual impact analysis.Strathclyde University
Dept. of Architecture and
Building Scienc
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