Dušan Petrovič

Automated building extraction from IKONOS images in suburban areas

The article addresses automatic building extraction from IKONOS images in suburban areas. In the proposed approach, we used a stereo pair of IKONOS images. Automatic photogrammetric methods of image matching were used to generate a digital surface model (DSM) and a digital elevation model. In further processing, single-image methods were used. The orthophotos of individual bands were created. The initial building mask was generated from the calculated normalized DSM (nDSM). The calculated normalized difference vegetation index and the road data extracted from the existing topographical database were used to remove vegetation and traffic surfaces. The mask was further improved with our own combination of methods based on non-linear diffusion filtering, unsupervised classification, colour segmentation and region growing. The final mask was vectorized using the Hough transform. Compared with a reference building database, 83.2% of the buildings in the test area were detected using the proposed approach with a quality percentage (how likely a building pixel produced by an automatic approach is correct) of 49.46.

A Polynomial Equation for the Natural Earth Projection

The Natural Earth projection is a new projection for representing the entire Earth on small-scale maps. It was designed in Flex Projector, a specialized software application that offers a graphical approach for the creation of new projections. The original Natural Earth projection defines the length and spacing of parallels in tabular form for every five degrees of increasing latitude. It is a pseudocylindrical projection, and is neither conformal nor equal-area. In the original definition, piece-wise cubic spline interpolation is used to project intermediate values that do not align with the five-degree grid. This paper introduces alternative polynomial equations that closely approximate the original projection. The polynomial equations are considerably simpler to compute and program, and require fewer parameters, which should facilitate the implementation of the Natural Earth projection in geospatial software. The polynomial expression also improves the smoothness of the rounded corners where the meridians meet the horizontal pole lines, a distinguishing trait of the Natural Earth projection that suggests to readers that the Earth is spherical in shape. Details on the least squares adjustment for obtaining the polynomial formulas are provided, including constraints for preserving the geometry of the graticule. This technique is applicable to similar projections that are defined by tabular parameters. For inverting the polynomial projection the Newton-Raphson root finding algorithm is suggested.

Spatio-temporal evaluation matrices for geospatial data

Abstract The global geospatial community is investing substantial effort in providing tools for geospatial data-quality information analysis and systematizing the criteria for geospatial data quality. The importance of these activities is increasing, especially in the last decade, which has witnessed an enormous expansion of geospatial data use in general and especially among mass users. Although geospatial data producers are striving to define and present data-quality standards to users and users increasingly need to assess the fitness for use of the data, the success of these activities is still far from what is expected or required. As a consequence, neglect or misunderstanding of data quality among users results in misuse or risks. This paper presents an aid in spatio-temporal quality evaluation through the use of spatio-temporal evaluation matrices (STEM) and the index of spatio-temporal anticipations (INSTANT) matrices. With the help of these two simple tools, geospatial data producers can systematically categorize and visualize the granularity of their spatio-temporal data, and users can present their requirements in the same way using business intelligence principles and a Web 2.0 approach. The basic principles and some examples are presented in the paper, and potential further applied research activities are briefly described.

Determination of Large Wood Accumulation in a Steep Forested Torrent Using Laser Scanning

In order to estimate large wood (LW) recruitment potential in torrential watersheds, and to describe the interactions of wood and torrential sediments in a cascading forested torrential channel, we performed a field survey of the lower reach of the Kuzlovec Torrent in the Gradascica watershed, using a terrestrial laser scanner (TLS). The point cloud consisted of several million points. The points were coloured with images made with digital camera to support visual interpretation of the captured objects. Data were used to create digital terrain model (DTM) (0.05 m grid cell) of the torrential channel area to be used for modelling of torrential flows. Furthermore, the point cloud was used for recognition of fallen trees and dead wood (574 LW pieces were recognised), and the results were compared with manual dead wood survey. Approximately 20 % of the LW was not recognised using TLS if compared to the manual survey. The amount of LW was estimated to be ~0.1 m3 per running meter of the torrential channel, and dead tree volume (~30 m3/ha) was compared to the average forest stand for the area (346 m3/ha)–LW found close to the torrential channel represents ~8 % of the wooden biomass. The time consumed for the LW volume calculation stressed the need for the further automation of the procedures.

Effective Online Mapping and Map Viewer Design for the Senior Population

Abstract Geographical information is connected to everyday life in many ways. Web cartography has made geospatial data more available to the public. In the next few years, the average age of the population will be over 51 years, with more than 15% of the population over the age of 65 years. The fact that the senior population is increasing suggests that online mapping and map viewer design should be aware of the senior population’s visual restrictions, as well as restrictions of other potential map users, including colour-vision-impaired users. This paper describes the senior population’s visual restrictions that can be compared with colour-vision-impaired users and provides guidelines with regard to online mapping and map viewer design for this growing segment of the elderly population.

Different visualizations and used data sources of the mountain battlefield on the Soča/Isonzo front line

ABSTRACT The Soča/Isonzo front line was about 90 km long battlefield area along the Soča (ital. Isonzo) river valley and the surrounding mountain tops and ridges, running from the Julian Alps (Slovenia) in the north to the Gulf of Trieste in the south. Using available historical data, sketches, rare photographs and written documents, supplemented with contemporary aerial photographs, orthophotos and airborne lidar data, we interpreted the exact position of fire trenches, supply tracks, barracks, cable lifts and other objects for selected areas. A variety of visualizations and presentations, such as changes of the front line during some battles, space-time cubes, augmented reality visualisations, and animated flyovers, were prepared from various computational environment and background image datasets.

Spatio-temporal analysis of the state of sports facilities in Slovenia from 1975 to 2012

Sports facilities are built objects and outdoor surfaces in the built environment, with significant impacts and effects on society, economy and environment. High-quality sports facilities, their proper spatial distribution and accessibility are important factors in the development of sport and sports-related activities and influence the quality of life. Data on sports facilities and their spatial distribution are a measure for the quality of sports areas. They represent the basis for strategies for the development of sports facilities on local and national levels, their placement in the built environment, and support the development of other sports-related activities. This article highlights the definition of a sports facility and its importance to the built environment and society. The survey includes an analysis of spatial and other databases on sports facilities in Slovenia and an assessment of their quality. A variety of methods and procedures was used to merge and complement the existing databases of sports facilities. The article presents spatial and other analyses and thematic maps of sports facilities by municipalities and statistical regions. It also presents a correlation between the funds Slovenia invested in sports facilities, and the development coefficient of municipalities. Indoor and outdoor sports facilities in individual municipalities are also presented.

Positioning under Adverse Conditions Using High Sensitivity GPS

Positioning is a key component of location-based services (LBS). An LBS user wants to acquire the current location in any possible environment. GNSS positioning, the fundamental component of a positioning system, is limited to open areas with unobstructed reception of GNSS satellites signals. In order to assure a ubiquitous positioning, other sensors have to be included in the positioning system. Inertial sensors are the most commonly used to compliment the GNSS sensors. However, the inertial sensors are very susceptible to drifts and other errors. Recently, other sensors have been considered for use in the positioning systems, e.g. UWB, Wi-Fi, pseudolites and high sensitivity GPS. High sensitivity GPS receivers have extended the use of GNSS navigation to environments which were previously believed unsuitable for satellite signal reception. However, extra care has to be considered when using high sensitivity GPS because autonomous solutions can cause major errors in the estimated position in the challenging environments. A careful and consistent treatment of the observation data can yield adequate results even under adverse conditions for signal reception.

What about topography? Status and quality of topographic data in Slovenia

Topographic data, an important part of the National Spatial Data Infrastructure, have been given serious attention since Slovenias independence. It has become publicly available, updated and harmonised. Financing of topographic data in Slovenia has significantly decreased over the previous decade. As a result, the present status is far from acceptable or expected. The current status of the topographic data, as well as its quality and usability for potential users is discussed in this article. The overview starts with basic source data, aerial surveys, photographs and orthophotos. The quality of orthophotos largely depends on the DTM quality. Topographic data is nowadays organised in thematic datasets (geographical names, building cadastre, etc.) or joined in datasets of different levels of accuracy and details. The status in Slovenia is compared to those in some neighbouring and other comparable countries.