An empirical study of algorithms for point feature label placement

A major factor affecting the clarity of graphical displays that include text labels is the degree to which labels obscure display features (including other labels) as a result of spatial overlap. Point-feature label placement (PFLP) is the problem of placing text labels adjacent to point features on a map or diagram so as to maximize legibility. This problem occurs frequently in the production of many types of informational graphics, though it arises most often in automated cartography. In this paper we present a comprehensive treatment of the PFLP problem, viewed as a type of combinatorial optimization problem. Complexity analysis reveals that the basic PFLP problem and most interesting variants of it are NP-hard. These negative results help inform a survey of previously reported algorithms for PFLP; not surprisingly, all such algorithms either have exponential time complexity or are incomplete. To solve the PFLP problem in practice, then, we must rely on good heuristic methods. We propose two new methods, one based on a discrete form of gradient descent, the other on simulated annealing, and report on a series of empirical tests comparing these and the other known algorithms for the problem. Based on this study, the first to be conducted, we identify the best approaches as a function of available computation time.Engineering and Applied Science

Deconstructing U.S. Army Maps of Korea: A Case Study for Rethinking Historical Environmental Data

At a time when the natural world and global climate are experiencing extreme changes at unprecedented speeds, understanding these environmental changes over time is more important than ever. With advances in remote sensing technology, large amounts of information about the natural world are becoming more accessible than ever before; however, satellite-collected data are only available from 1984 onwards. To understand how land use has changed on longer timescales, researchers have turned towards archival maps as a data source. Archival maps are a rich source of environmental information; however, they are often saturated with complicated colonial histories. Maps, more so than other historical materials, can hide behind the veneer of objectivity and thus escape important interrogation. As methods that utilize archival maps become more popular, the need to critically analyze the historical and social contexts of the maps becomes even stronger. This thesis argues for a rethinking of historical environmental data through a case study of U.S. Military Maps of Korea from 1945-1954. By providing appropriate historical and social context, three maps of Seoul are deconstructed, thereby illuminating their fallibility as objective environmental sources. This case study ultimately encourages scholars to engage with environmental history more critically and think beyond the analogues dictated by current technology

An Evolutionary Approach to Adaptive Image Analysis for Retrieving and Long-term Monitoring Historical Land Use from Spatiotemporally Heterogeneous Map Sources

Land use changes have become a major contributor to the anthropogenic global change. The ongoing dispersion and concentration of the human species, being at their orders unprecedented, have indisputably altered Earth’s surface and atmosphere. The effects are so salient and irreversible that a new geological epoch, following the interglacial Holocene, has been announced: the Anthropocene. While its onset is by some scholars dated back to the Neolithic revolution, it is commonly referred to the late 18th century. The rapid development since the industrial revolution and its implications gave rise to an increasing awareness of the extensive anthropogenic land change and led to an urgent need for sustainable strategies for land use and land management. By preserving of landscape and settlement patterns at discrete points in time, archival geospatial data sources such as remote sensing imagery and historical geotopographic maps, in particular, could give evidence of the dynamic land use change during this crucial period. In this context, this thesis set out to explore the potentials of retrospective geoinformation for monitoring, communicating, modeling and eventually understanding the complex and gradually evolving processes of land cover and land use change. Currently, large amounts of geospatial data sources such as archival maps are being worldwide made online accessible by libraries and national mapping agencies. Despite their abundance and relevance, the usage of historical land use and land cover information in research is still often hindered by the laborious visual interpretation, limiting the temporal and spatial coverage of studies. Thus, the core of the thesis is dedicated to the computational acquisition of geoinformation from archival map sources by means of digital image analysis. Based on a comprehensive review of literature as well as the data and proposed algorithms, two major challenges for long-term retrospective information acquisition and change detection were identified: first, the diversity of geographical entity representations over space and time, and second, the uncertainty inherent to both the data source itself and its utilization for land change detection. To address the former challenge, image segmentation is considered a global non-linear optimization problem. The segmentation methods and parameters are adjusted using a metaheuristic, evolutionary approach. For preserving adaptability in high level image analysis, a hybrid model- and data-driven strategy, combining a knowledge-based and a neural net classifier, is recommended. To address the second challenge, a probabilistic object- and field-based change detection approach for modeling the positional, thematic, and temporal uncertainty adherent to both data and processing, is developed. Experimental results indicate the suitability of the methodology in support of land change monitoring. In conclusion, potentials of application and directions for further research are given

A computer system for a cadastral mapping application

In 1973, the New Zealand Government instituted a metric measurement system and the New Zealand Department of Lands and Survey (NZLS) implemented a new mapping grid and projection system that permits the accurate representation of the whole country on a uniform basis. These two related decisions required the mapping division of the NZLS to assume responsibility for the conversion of both topographical and cadastral maps in the former imperial mapping grid system to the new metric mapping grid system. This thesis deals with the design of an automated mapping system and identifies the techniques necessary to automate the conversion of cadastral maps from the imperial mapping system to the new metric system. The research undertaken encompasses the following three major areas: (a) the design of an efficient system to automate the conversion from one mapping series to another, (b) the identification and testing of techniques necessary to generate computer produced maps to cartographic standards, (c) to design a data structure for graphical data and its corresponding descriptive data in a format suitable for use by a land information processing system. Although this research deals with a specific problem, the problems discussed in this thesis are of relevance to any general mapping application

Proceedings of the meeting on: Research based on Ordnance Survey small-scales digital data

Special issue (CISRG - Cartographic Information Systems Research Group) ;

Validation Protocol for Emergency Response Geo-information Products

Europe is making a significant effort to develop (geo)information services for crisis management as part of the Global Monitoring for Environment and Security GMES) programme. Recognising the importance of coordinated European response to crises and the potential contribution of GMES, the Commission launched a number of preparatory activities in coordination with relevant stakeholders for the establishment of an Emergency Response GMES Core Service (ERCS). GMES Emergency Response Services will rely on information provided by advanced technical and operational capabilities making full use of space earth observation and supporting their integration with other sources of data and information. Data and information generated by these services can be used to enhance emergency preparedness and early reaction to foreseeable or imminent crises and disasters. From a technical point of view, the use of geo-information for emergency response poses significant challenges for spatial data collection, data management, information extraction and communication. The need for an independent formal assessment of crisis products to provide operational services with homogeneous and reliable standards has recently become recognized as an integral component of service development. Validation is intended to help end-users decide how much to trust geo-information products (maps, spatial dataset). The focus, in this document, is on geo-information products, in particular those derived from Earth Observation data. Validation principles have been implemented into a protocol, as a tool to check whether the products meet standards and user needs. The validation principles, methods, rules and guidelines provided in this document aim to give a structure that guarantees an overall documented and continuous quality of ERCS products.JRC.DG.G.2-Global security and crisis managemen

Geomatics and Virtual tourism

The most recent technological revolution, concerning web and “ICT”, not only changed individual and collective behaviors, but also allowed experiences no possible before: a real time communication, regardless of the distances; an extended access to disjointed data and sources; the shift in different realities – missing or entirely imaginary. Nowadays, we can think about a new concept of museum, much more inclusive than “objects container”: now the museum involves entire countries, entire ecosystems, entire regions. We can speak of “museum outside of the museum”, to extend museum “storytelling” to a regional scale, beyond the walls of the traditional museum. On a regional scale experiments entirely convincing have not yet been carried out, but from this point of view cultural lands can be visited as great open air museums, to find objects, artworks or signs: the whole land is a “collection” to be preserved, to be presented and to be interpreted. Thus the visit allows to elicit outstanding objects, to read into landscapes with different filters. Both the physical and virtual visit seem to be a “tour” (Minucciani and Garnero, 2013). To create a virtual tourism prototypal station, we need several and unconventional geometrical data (shared geographic databases, DTMs, digital orthoimages and angle shots, modeling with spherical cameras, ...), thematic data (related to cultural content) and no conventional input units to move and to observe how and where the observer prefers. Authors report here their experience to carry out a prototypal station, able to relate geomatics references to cultural content and to offer a whole experience, involving users also from the sensory point of view. That’s nowadays a specific purpose of new technologies applied to cultural heritage