Map Calculus in GIS: a proposal and demonstration

This paper provides a new representation for fields (continuous surfaces) in Geographical Information Systems (GIS), based on the notion of spatial functions and their combinations. Following Tomlin's (1990) Map Algebra, the term 'Map Calculus' is used for this new representation. In Map Calculus, GIS layers are stored as functions, and new layers can be created by combinations of other functions. This paper explains the principles of Map Calculus and demonstrates the creation of function-based layers and their supporting management mechanism. The proposal is based on Church's (1941) Lambda Calculus and elements of functional computer languages (such as Lisp or Scheme)

MSUO Information Technology and Geographical Information Systems: Common Protocols & Procedures. Report to the Marine Safety Umbrella Operation

The Marine Safety Umbrella Operation (MSUO) facilitates the cooperation between Interreg funded Marine Safety Projects and maritime stakeholders. The main aim of MSUO is to permit efficient operation of new projects through Project Cooperation Initiatives, these include the review of the common protocols and procedures for Information Technology (IT) and Geographical Information Systems (GIS). This study carried out by CSA Group and the National Centre for Geocomputation (NCG) reviews current spatial information standards in Europe and the data management methodologies associated with different marine safety projects. International best practice was reviewed based on the combined experience of spatial data research at NCG and initiatives in the US, Canada and the UK relating to marine security service information and acquisition and integration of large marine datasets for ocean management purposes. This report identifies the most appropriate international data management practices that could be adopted for future MSUO projects

Shingle 2.0: generalising self-consistent and automated domain discretisation for multi-scale geophysical models

The approaches taken to describe and develop spatial discretisations of the domains required for geophysical simulation models are commonly ad hoc, model or application specific and under-documented. This is particularly acute for simulation models that are flexible in their use of multi-scale, anisotropic, fully unstructured meshes where a relatively large number of heterogeneous parameters are required to constrain their full description. As a consequence, it can be difficult to reproduce simulations, ensure a provenance in model data handling and initialisation, and a challenge to conduct model intercomparisons rigorously. This paper takes a novel approach to spatial discretisation, considering it much like a numerical simulation model problem of its own. It introduces a generalised, extensible, self-documenting approach to carefully describe, and necessarily fully, the constraints over the heterogeneous parameter space that determine how a domain is spatially discretised. This additionally provides a method to accurately record these constraints, using high-level natural language based abstractions, that enables full accounts of provenance, sharing and distribution. Together with this description, a generalised consistent approach to unstructured mesh generation for geophysical models is developed, that is automated, robust and repeatable, quick-to-draft, rigorously verified and consistent to the source data throughout. This interprets the description above to execute a self-consistent spatial discretisation process, which is automatically validated to expected discrete characteristics and metrics.Comment: 18 pages, 10 figures, 1 table. Submitted for publication and under revie

Towards a compact representation of temporal rasters

Big research efforts have been devoted to efficiently manage spatio-temporal data. However, most works focused on vectorial data, and much less, on raster data. This work presents a new representation for raster data that evolve along time named Temporal k^2 raster. It faces the two main issues that arise when dealing with spatio-temporal data: the space consumption and the query response times. It extends a compact data structure for raster data in order to manage time and thus, it is possible to query it directly in compressed form, instead of the classical approach that requires a complete decompression before any manipulation. In addition, in the same compressed space, the new data structure includes two indexes: a spatial index and an index on the values of the cells, thus becoming a self-index for raster data.Comment: This research has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Actions H2020-MSCA-RISE-2015 BIRDS GA No. 690941. Published in SPIRE 201

Locating Mineral Exploration Targets using a Geographical Information System

This paper outlines the research and development of a complete open source geographic information system (GIS) that offers real-time geoprocessing over the Internet. The premise of the geoprocessing is to locate mineral exploration targets that have high potential for success based on parameters chosen by the end-user of the system. Components integrated in the system include a spatial database PostGIS, a GIS processing engine GRASS, a GIS server GeoServer, a web server Apache, and front-end technologies OpenLayers and GeoExt. Appropriate data was sourced from the Geological Survey of Ireland to be used for the geoprocessing. With all the components of the GIS integrated, an individual not specialised in the use of a GIS can interact with and interrogate the data through a web browser. The GIS then provides a vital role as a decision support system for locating mineral exploration targets

Interactive topographic web mapping using scalable vector graphics

Large scale topographic maps portray detailed information about the landscape. They are used for a wide variety o f purposes. USGS large scale topographic maps at 1:24,000 have been traditionally distributed in paper form. With the advent of the Internet, these maps can now be distributed electronically. Instead of common raster format presentation, the solution presented here is based on a vector approach. The vector format provides many advantages compared to the use of a raster-based presentation. This research shows that Scalable Vector Graphics (SVG) is a promising technology for delivering high quality interactive topographic maps via the Internet, both in terms o f graphic quality and interactivity. A possible structure for the SVG map document is proposed. Interactive features such as toggling thematic layers on and off, UTM coordinate readout for x, y, and z (elevation) were developed as well. Adding this type of interactivity can help to better extract information from a topographic map. A focus group analysis with the online SVG topographic map shows a high-level of user acceptance

Map Services Management

About 20 years ago, Google and other companies introduced the tiled maps, and nowadays, it is possible to produce similar work using open data and open source software. Web Map Service and Tile Map Service are a set of open standards to provide ways for users to access and visualize maps by interacting with geospacial data, over the internet. Most of the solutions to provide maps, make use of geospacial databases like PostgreSQL/PostGIS or MBTiles/PMTiles. Dedicated servers follows the standards specified by organizations such as Open Geospatial Consortium. The main goal of this work is to create a centralized and scalable solution that publish basemaps for a predefined set of geographic regions. These basemaps are displayed as part of a desktop or mobile applications with internet access. In order to fulfill this purpose, the best approach is, for each geographic region, to generate a MBTile database using raw data extract of the OpenStreetMap packed by Geofabrik. The raw data are also combined with a second data source, Natural Earth, to complete the map information at smaller scales. The final result goes through a process of cartographic generalization to be able to access only the relevant geospatial data at a given map scale or zoom level. The data are published as vector tiles, using a tile server, and for legacy applications there’s also the possibility to display the basemaps as raster tiles. Another available option is to use PMTiles files, which are similar to MBTiles but cloud optimized and suitable for serverless solutions. In the interest of ensuring good performance and stability, it is possible to keep everything together behind a reverse proxy, using as an example a Nginx server. Taking advantage of HTTP range requests functionality, also available in Nginx, it is possible to consider the serverless option of PMTiles and the standard tile server under the same umbrella. Finally, two points were considered and explored as opportunities for improvement, however not fully implemented. The first is the ability to cache vector/raster tiles requests, and the second is the ability to deploy the solution supported by a Content Delivery Network.Google e outros serviços introduziram o tiled maps há cerca de 20 anos. Atualmente, é possível produzir trabalhos semelhantes usando dados e software de código abertos. Web Map Service e Tile Map Service são um conjunto de protocolos padrão abertos que fornecem aos utilizadores uma forma de acederem e visualizarem mapas interagindo com dados geoespaciais, através da Internet. A maioria das soluções que fornecem mapas fazem uso de bases de dados geoespaciais PostgreSQL/PostGIS ou MBTiles/PMTiles. Os servi dores são dedicados conforme normas padrão especificadas por instituições como a Open Geospatial Consortium. O principal objetivo deste trabalho é criar uma solução centralizada e escalável que publique mapas de base para um conjunto predefinido de regiões geográficas. Estes mapas de base devem ser mostrados numa aplicação desktop ou mobile com acesso à internet. De forma a atingir este propósito, a melhor abordagem é, para cada região geográfica, gerar uma base de dados MBTile, usando extratos de dados em bruto do OpenStreetMap disponibilizados pela Geofabrik. Os dados em bruto são também combinados com uma segunda fonte de dados, o Natural Earth, para completar a informação do mapa nas escalas menores. O resultado final passa por um processo de generalização cartográfica de forma a disponibilizar os dados geoespaciais relevantes para uma determinada escala ou um determinado nível de zoom do mapa. Os dados são publicados como vector tiles, usando um tile server, e para aplicações legacy também existe a possibilidade de disponibilizar os mapas em formato raster. Existe uma outra opção que consiste na utilização de ficheiros PMTile, que são ficheiros similares aos MBTiles mas otimizados para a cloud e disponibilizados num princípio serverless. De forma a garantir um bom desempenho e estabilidade, é possível agregar toda a solução atrás de uma reverse proxy usando por exemplo um servidor Nginx. Tirando partido da funcionalidade HTTP range requests, disponível também no Nginx, torna-se possível servir PMTiles (serverless) e Tile servers sob a mesma infraestrutura. Por fim, mais dois pontos foram considerados e explorados como oportunidades de melhoria, mas não foram totalmente implementados. O primeiro é a capacidade de armazenar em cache pedidos de Tiles vector/raster e o segundo é a capacidade de disponibilizar a solução apoiada num Content Delivery Network