Airborne photogrammetry and LIDAR for DSM extraction and 3D change detection over an urban area : a comparative study

A digital surface model (DSM) extracted from stereoscopic aerial images, acquired in March 2000, is compared with a DSM derived from airborne light detection and ranging (lidar) data collected in July 2009. Three densely built-up study areas in the city centre of Ghent, Belgium, are selected, each covering approximately 0.4 km(2). The surface models, generated from the two different 3D acquisition methods, are compared qualitatively and quantitatively as to what extent they are suitable in modelling an urban environment, in particular for the 3D reconstruction of buildings. Then the data sets, which are acquired at two different epochs t(1) and t(2), are investigated as to what extent 3D (building) changes can be detected and modelled over the time interval. A difference model, generated by pixel-wise subtracting of both DSMs, indicates changes in elevation. Filters are proposed to differentiate 'real' building changes from false alarms provoked by model noise, outliers, vegetation, etc. A final 3D building change model maps all destructed and newly constructed buildings within the time interval t(2) - t(1). Based on the change model, the surface and volume of the building changes can be quantified

Characterizations of rectangular (para)-unitary rational Functions

We here present three characterizations of not necessarily causal, rational functions which are (co)-isometric on the unit circle: (i) Through the realization matrix of Schur stable systems. (ii) The Blaschke-Potapov product, which is then employed to introduce an easy-to-use description of all these functions with dimensions and McMillan degree as parameters. (iii) Through the (not necessarily reducible) Matrix Fraction Description (MFD). In cases (ii) and (iii) the poles of the rational functions involved may be anywhere in the complex plane, but the unit circle (including both zero and infinity). A special attention is devoted to exploring the gap between the square and rectangular cases.Comment: Improved versio

Characterizations of Families of Rectangular, Finite Impulse Response, Para-Unitary Systems

We here study Finite Impulse Response (FIR) rectangular, not necessarily causal, systems which are (para)-unitary on the unit circle (=the class U). First, we offer three characterizations of these systems. Then, introduce a description of all FIRs in U, as copies of a real polytope, parametrized by the dimensions and the McMillan degree of the FIRs. Finally, we present six simple ways (along with their combinations) to construct, from any FIR, a large family of FIRs, of various dimensions and McMillan degrees, so that whenever the original system is in U, so is the whole family. A key role is played by Hankel matrices

Wireless Networks In-the-Loop: Software Radio as the Enabler

A software architecture to rapidly develop and test radio networks in real and physical environments is proposed. Radio network terminals are developed in software and run on generic hardware to maximize reconfigurability. Due to the software nature of the radio terminals, radio networks can be simulated in a virtual environment, where physical channels are emulated by software entities. Without any changes to the code base, the same waveform can also be run in a real, physical environment. This feature is used to rapidly switch between real and virtual networks, thus bridging the gap between simulation and physical reality. Aspects of the proposed system are implemented and demonstrated with the GNU Software Radio framework

Fast Inverse Nonlinear Fourier Transform For Generating Multi-Solitons In Optical Fiber

The achievable data rates of current fiber-optic wavelength-division-multiplexing (WDM) systems are limited by nonlinear interactions between different subchannels. Recently, it was thus proposed to replace the conventional Fourier transform in WDM systems with an appropriately defined nonlinear Fourier transform (NFT). The computational complexity of NFTs is a topic of current research. In this paper, a fast inverse NFT algorithm for the important special case of multi-solitonic signals is presented. The algorithm requires only $\mathcal{O}(D\log^{2}D)$ floating point operations to compute $D$ samples of a multi-soliton. To the best of our knowledge, this is the first algorithm for this problem with $\log^{2}$-linear complexity. The paper also includes a many samples analysis of the generated nonlinear Fourier spectra.Comment: Submitted to IEEE ISIT 2015 (fixed a few typos

Development of a method for mapping the highest coastline in Sweden using breaklines extracted from high resolution digital elevation models

[b]Utveckling av en metod för att kartera högsta kustlinjen i Sverige med hjälp av brytlinjer extraherade från högupplösta höjdmodeller[/b] Högsta kustlinjens (HK) geografiska läge i landskapet markerar gränsen mellan subakvatiskt och supraakvatiskt avsatta sediment. Idag varierar HKs höjd över havet från några få m.ö.h. i Skåne till omkring 289 m.ö.h. i Ångermanland på grund av den glacialisostatiska landhöjningen. Högkvalitativ HK-data är av intresse bland annat vid markanvändnings- och samhällsplanering och vid rekonstruktion av historiska havsnivåer och händelser i Östersjöns havsbassäng. Den här studien har undersökt möjligheten att använda brytlinjer i terrängen, extraherade från så kallade ”land surface parameters” (LSPs) som genererats ur högupplöst höjddata, för att automatisera karteringen av HK i svallade områden i Sverige. För att uppskatta lämpliga skaldimensioner som framhäver terrängbrytlinjer av intresse för studien testades ett intervall av fönsterstorlekar för terrängparameterberäkningarna. Fyra stycken semi-automatiserade metoder för att extrahera brytlinjer baserade på markytans krökning utvecklades i ESRIs ArcGIS 10.2.2 for Desktop och tillämpades på två pilotområden i Sverige. Metoderna är uppbyggda av ett gemensamt steg där brytlinjerna extraheras och ett individuellt steg där brytlinjerna klassificeras med olika grad av automation. För att jämföra HK-kartorna genererade från de utvecklade metoderna med HK-kartor som manuellt karterats från högupplösta terrängskuggningskartor och med HK-data som idag finns tillgänglig hos Sveriges geologiska undersökning (SGU) beräknades klassificeringsnoggrannhet och höjdfel för samtliga kartor i förhållande till referensdata. Studien fann att en 22x22m fönsterstorlek var framgångsrik för att extrahera brytlinjer av markytans krökning relaterad till strandvallar och glaciala lineationer som används för att kartera HK i pilotområdena. Noggrannhetsutvärderingen indikerar att tre av de utvecklade metoderna genererar HK-kartor med högre noggrannhet än SGUs HK-data, och liknande till högre noggrannhet än HK-kartor baserade på HK-punkter manuellt karterade från högupplösta terrängskuggningskartor. Metoderna som använder en manuell klassificering av brytlinjerna visade en högre noggrannhet än metoderna som använder en automatiserad klassificering av brytlinjerna. Denna studie visar att brytlinjer av markytans krökning genererade från högupplösta höjdmodeller kan användas för att göra kartering av HK i svallade områden mer automatiserad, strukturerad och reproducerbar samtidigt som man uppnår liknande noggrannhet som vid manuell kartering baserad på terrängskuggningskartor.[b]Development of a method for mapping the highest coastline in Sweden using breaklines extracted from high resolution digital elevation models[/b] The geospatial position of the highest coastline (HCL) defines the boundary between subaquatic and supra-aquatic deposited sediments. Today the HCL is located at different elevations throughout Sweden, a few m.a.s.l. in southern Scania to around 289 m.a.s.l. at the coast of Ångermanland, due to the glacio-isostatic rebound. High quality data of the HCL is of interest e.g. in land-use and spatial planning and when reconstructing historical sea levels and events within the Baltic Sea Basin. In this study the use of land surface parameter (LSP) breakline extraction methods applied on high resolution DEMs for automating mapping of the HCL in wave washed areas in Sweden was investigated. Appropriate scale dimensions for enhancing breaklines of interest was estimated by testing a range of moving window sizes for the LSP computations. Four semi-automated mapping methods based on curvature breakline extraction was developed in ESRI’s ArcGIS 10.2.2 for Desktop and applied on two pilot areas in Sweden. The methods consist of a common breakline extraction step and individual breakline classification steps with differing grade of automation. To compare the HCL maps generated by the developed methods with HCL maps manually mapped from high resolution hillshade maps and with the current HCL data supplied by the Geological Survey of Sweden (SGU) classification accuracies and elevation errors were computed using a reference data set. A 22x22m moving window size was found successful for the extraction of curvature breaklines related to wave washed features and glacial flow lineation features used to map the HCL within the pilot areas under investigation. The accuracy assessment indicates that three of the developed methods generate HCL maps with accuracies above the current HCL data provided by SGU and accuracies similar to or above HCL maps based on manually mapped HCL data points. Higher accuracies were found for the methods using a manual classification of the extracted breaklines than for the methods using an automated classification of the extracted breaklines. This study found that, by applying curvature breakline extraction methods on high resolution DEMs, HCL mapping in wave washed areas can be made more automated, structured and reproducible while still reaching similar accuracies as manual hillshade mapping methods.[b]Mapping the highest coastline using high resolution elevation data[/b] The highest position the coastline had after the last ice age is called the highest coastline (HCL). Today the HCL is located at different elevations throughout Sweden, a few m.a.s.l. in southern Scania to around 289 m.a.s.l. at the coast of Ångermanland, due to the glacio-isostatic rebound. The glacio-isostatic rebound occurs at different rates in Sweden, depending on to what extent the ground at a location was depressed by the weight of the ice-sheet. Today the HCL can be mapped by determining the elevation of relict landforms connected to the HCL e.g. the highest beach ridge formed by wave washing action of a historical sea. High quality data of the HCL is of interest e.g. in land-use and spatial planning and when reconstructing historical sea levels and events within the Baltic Sea Basin. Using a high resolution digital elevation model (DEM), landforms connected to the HCL can be identified with high precision. Manual digital mapping using a detailed DEM can be time-demanding and therefore partly automated mapping methods using Geographical Information Systems (GIS) are of interest when working with large areas. This study investigates the possibilities to automate the mapping of the HCL by extracting information of landforms connected to the HCL from Sweden’s national high resolution DEM. The main aim of this study was to develop a structured and reproducible method for mapping the HCL while reaching similar accuracies as manual digital mapping methods and higher accuracies than the current HCL data available at the Geological Survey of Sweden (SGU). Four mapping methods with differing automation were developed using GIS. The methods consists of two main parts: part 1 where maximum and minimum curvature information of the topography is extracted from the DEM, generating curvature breaklines which describe concave and convex surfaces of landforms, and part 2 where the breaklines are classified into landforms connected to the HCL. HCL maps produced by the developed methods were compared with manually mapped HCL maps and the HCL data supplied by the SGU. Three of the developed methods were found to generate HCL maps with the desired accuracies aimed for. Higher accuracies were found for the developed methods using a manual classification of the extracted breaklines in part 2 than for the methods using an automated classification of the breaklines. This study shows that HCL mapping, in areas where wave washed landforms are dominant, can be made more automated while still reaching similar accuracies as manual digital mapping methods