7 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
PARALLEL VISIBILITY AND FRESNEL-ZONES CALCULATION USING GRAPHICS PROCESSING UNITS
Delo opisuje inovativno metodo izračuna vidnosti [61, 62] in Fresnelovih con na digitalnih
zemljevidih z uporabo grafično procesnih kartic CUDA NVIDIA. Izdelani so trije
vzporedni algoritmi:
• modificiran vzporedni algoritem R2 za računanje vidnosti (R2-P),
• algoritem za izračun zakrivanj Fresnelovih con (FZC),
• algoritem za izračun prečnega preseka Fresnelovih con med oddajnikom in sprejemnikom
(FZTI).
Na osnovi uveljavljenega sekvenčnega algoritma R2 za računanje vidnosti je razvit modificiran
vzporedni algoritem R2-P, ki za pohitritev izračuna poleg večnitenja izkorišča še
druge uporabne lastnosti grafične procesne enote. Združen dostop do globalnega pomnilnika
pripomore k hitrejšemu pretoku podatkov in s tem k hitrejšemu izračunu. Izmenjava
informacij med nitmi v času računanja igra ključno vlogo pri pohitritvi. Izračun vidnosti
na poljubno velikih podatkih je omogočeno s segmentacijo digitalnega zemljevida.
Modificiran vzporedni algoritem R2 je primerjan z že implementiranimi algoritmi za
izračun vidnosti v smislu točnosti izračuna in časa izračuna. Izkaže se, da je novi algoritem
enako točen kot že uveljavljeni sekvenčni algoritem R2, hkrati pa omogoča bistveno
pohitritev izračuna. Čas izračuna je skrajšan iz reda nekaj minut na red nekaj sekund.
To pa v praksi pomeni možnost interaktivnega dela.
Pri načrtovanju radijskega pokrivanja je poleg vidnosti zelo uporaben podatek o zakrivanju
Fresnelovih con. Pri algoritmu za izračun zakrivanj Fresnelovih con se izbere
lokacijo radijskega oddajnika, višino oddajnika, opazovano višino sprejemnika nad terenom
in valovno dolžino radijskega valovanja. Algoritem za vsako točko terena izračuna,
katera Fresnelova cona je zakrita. Rezultat je digitalni zemljevid z izrisanimi območji
zakrivanj Fresnelovih con, kar o radijskem signalu na terenu pove precej več kot izračun
vidnosti. Predvsem na področjih, kjer je prva Fresnelova cona povsem zakrita, se v primerjavi
z izračunom vidnosti pridobi v praksi zelo uporabna informacija. Algoritem ima
tudi možnost upoštevanja rabe tal, kjer se višina terena poveča v odvisnosti od rabe tal
(npr. za gozdno površino reda 15 m). Z modifikacijami, kot sta vpeljava Friisove enačbe in upoštevanje smernega diagrama
anten, postane algoritem enostaven propagacijski model in tako primeren za izračun radijskega
pokrivanja. Izračun radijskega signala se primerja z izmerjenimi vrednostmi na
terenu za frekvence 90 Mhz (FM), 800 MHz (LTE) in 1800 MHz (LTE). Za različne
vhodne parametre enostavnega propagacijskega modela se izračuna standardna deviacija
sprememb med izmerjenimi in izračunanimi vrednostmi in se jih prikaže na grafih. Tako se
pridobijo najbolj optimalne vrednosti vhodnih parametrov za vsako frekvenčno področje
posebej.
Algoritem za izračun prečnega preseka Fresnelovih con med oddajnikom in sprejemnikom
izračuna sliko Fresnelovih con, ki predstavlja matematični presek vseh skaliranih
prečnih presekov Fresnelovih con vzdolž radijske poti. Rezultat je vizualna slika, ki pokaže
lastnosti radijske (linkovske) zveze v smislu zakritja posameznih Fresnelovih con. V
praksi bi algoritem najbolj koristil pri načrtovanju radijskih linkov, kjer bi lahko preverili,
koliko in kateri del Fresnelovih con manjka zaradi ovir (terena).
Vsi trije algoritmi so implementirani kot moduli GRASS GIS in se lahko uporabljajo
na vsakem osebnem računalniku, ki ima vgrajeno grafično procesno enoto CUDA NVIDIA
in naloženo ustrezno prosto dostopno programsko opremo.The work describes an innovative method with which to calculate the visibility [61, 62]
and Fresnel zones on digital maps using graphics processing NVIDIA CUDA cards. Three
parallel algorithms were formulated:
• modified R2 parallel algorithm for calculating visibility (R2-P),
• algorithm for calculating Fresnel zone clearance (FZC),
• algorithm for calculating Fresnel zone transverse intersection between the transmitter
and the receiver (FZTI).
The R2 parallel algorithm was developed based on the established R2 sequential algorithm
for computing visibility. Aside from threading, other useful features of the graphics
processing unit were used to speed up calculation time. Coalesced access to the global
memory helps speed up the flow of information and thus also speeds up the calculation.
Exchange of information between threads during computation plays a key role in the
speedup. The segmentation of the digital map enables the calculation of visibility for
huge data sets.
The modified parallel R2 algorithm was compared with the already implemented algorithms
for the viewshed calculation in term of accuracy and duration of the calculation.
It turned out that the new algorithm R2-P had the same accuracy as the already established
sequential algorithm R2, although the former also makes it possible to significantly
speed up the calculation. Calculation time is reduced from the order of a few minutes to
the order of a couple of seconds. This, in practice, means that there is a possibility of
interactive work.
In addition to the viewshed, Fresnel zone clearance is very useful for planning the radio
coverage. Algorithm FZC starts with the location of the radio transmitter, the height of
the transmitter, the receiver observation height above terrain, and the wavelength of
the radio waves. The algorithm for each point of the terrain calculates the first clear
Fresnel zone. The result is a digital map with the plotted areas of Fresnel zone clearance.
This map provides better information about the radio signal than just a calculation of the
viewshed. Indeed areas where the first Fresnel zone is completely obscured are particularly
good for providing very useful information. The algorithm also has the ability to take
into account land use, where the height of the terrain is raised as a function of land use
(eg. For the forest area, raising can be 15 m).
With modifications, such as the introduction of the Friis transmission equation and
consideration of the radiation pattern, the algorithm becomes a simple radio propagation
model and thus is suitable for the calculation of radio coverage. Calculation of the radio
propagation is compared with the measured values on a field for frequencies of 90 MHz
(FM), 800 MHz (LTE) and 1800 MHz (LTE). For a variety of input parameters, the
standard deviation of changes between the field measurements and calculated propagation
is presented in graphs. In this way, the optimal values of the input parameters for each
frequency band can be obtained.
The algorithm for calculating Fresnel zone transverse intersection between the transmitter
and the receiver produces an image of Fresnel zones, which represents the mathematical
section of all scale cross-sectional Fresnel zones along the transmission path. The
result is a visual image that shows the characteristics of the radio link in terms of masking
individual Fresnel zones. In practice, the algorithm is most useful in the design of radio
links, where man can check how much and which part of the Fresnel zone is missing due
to terrain obstacles.
All three algorithms were implemented as GRASS GIS modules and can be used on any
PC with an integrated GPU NVIDIA CUDA and loaded with the appropriate free-access
software
Analyse de visibilité et géolocalisation en milieu urbain avec un modèle numérique 3D
L'analyse de visibilité est une question importante de la recherche qui peut trouver des applications dans de nombreux domaines: sécurité, conception de réseau sans fil, gestion du paysage, mise en oeuvre d'accès piétonniers .... La prise en compte de la troisième dimension dans le calcul de visibilité est un réel défi. Seules quelques solutions peuvent détecter les obstacles 3D qui limitent l'isovist. Dans cette communication, nous présentons un nouvel algorithme qui peut détecter tous les objets qui bloquent la vue dans un environnement 30 reconstitué numériquement intégrant le relief. Une démonstration avec des données SIG est également effectuée.La reconnaissance automatique des bâtiments est une étape essentielle pour la réalité augmentée et un outil possible pour la géolocalisation d'une prise de vue. Les recherches dans ce domaine n'utilisent pas la localisation par contenu de l'image. Cet article présente une méthodologie pour l'enrichissement d'une base de données urbaine SIG grâce à un descripteur de texture de façade calculé sur des images de référence. Cet indicateur est ensuite utilisé pour retrouver ce bâtiment dans une nouvelle image et le localiser dans une base de données SIG 3D afin d'estimer sa position et son orientation dans le repère de l'appareil photographique qui a pris le cliché. La qualité des résultats obtenus fait l'objet d'une discussion.The isovist or vision field is an interesting topic with many applications in different fields: security, wireless networkdesign, landscape management and analysis, pedestrian access .... Taking in account 3D environment is a verychallenging task. Only a few solutions can detect 3D obstacles that limit the vision field. We present in this paper a newalgorithm that can detect all the objects which block the sight in a 3D environment including the ground surface. A demonstration with GIS data is also given.Building recognition is the first step for augmented reality and the geolocation of the camera. Research in this field usually does not use the content of the image to locate it. This paper presents a methodology for enhancing and complementing a GIS database of buildings with a texture descriptor of the facades by using information extracted from reference images. This descriptor is used to locate any other image by searching similar texture in the image and locate it through the 3D GIS data base. The absolute position and orientation of the camera of the new image can then be computed if camera parameters (i.e. focal length) are known. The quality of the results is presented and discussed.ST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF
Geographic Information Science (GIScience) and Geospatial Approaches for the Analysis of Historical Visual Sources and Cartographic Material
This book focuses on the use of GIScience in conjunction with historical visual sources to resolve past scenarios. The themes, knowledge gained and methodologies conducted might be of interest to a variety of scholars from the social science and humanities disciplines
Across Space and Time. Papers from the 41st Conference on Computer Applications and Quantitative Methods in Archaeology, Perth, 25-28 March 2013
This volume presents a selection of the best papers presented at the forty-first annual Conference on Computer Applications and Quantitative Methods in Archaeology. The theme for the conference was "Across Space and Time", and the papers explore a multitude of topics related to that concept, including databases, the semantic Web, geographical information systems, data collection and management, and more
Across Space and Time Papers from the 41st Conference on Computer Applications and Quantitative Methods in Archaeology, Perth, 25-28 March 2013
The present volume includes 50 selected peer-reviewed papers presented at the 41st Computer Applications and Quantitative Methods in Archaeology Across Space and Time (CAA2013) conference held in Perth (Western Australia) in March 2013 at the University Club of Western Australia and hosted by the recently established CAA Australia National Chapter. It also hosts a paper presented at the 40th Computer Applications and Quantitative Methods in Archaeology (CAA2012) conference held in Southampton