OpenStreetMap is a very exciting and vibrant project aiming to make accessing geographic data easier. Our research group at the Department of Computer Science NUI Maynooth Ireland is carrying out research into a broad range of topics including: map data generalisation, geographic shape complexity, web map services, map-based interface for pedestrian navigation. One of the common themes across this research is the use of OpenStreetMap as the principal source of geospatial data. In this paper we describe how our research productivity, research collaboration, and general data interoperability have been greatly enhanced from our early adoption of a fully open source GIS approach to working with OpenStreetMap. While one can work successfully with OpenStreetMap in non-Open Source environments the flexibility offered by an open source approach is a major advantage. This flexibility is delivered in many flavours including: a wide choice of software, inter-connectability of software packages and components, a wide network of support through documentation, message boards, and free and open exchange of ideas

Ciepłuch, Błażej

Corcoran, Padraig

Jacob, Ricky

Mooney, Peter

Winstanley, Adam C.

English

NUI Maynooth Eprint Archive

Using a fully open source approach to working with OpenStreetMap

Maynooth EPrints and ETheses Archive

Maynooth University ePrints and eTheses Archive

MURAL - Maynooth University Research Archive Library

USING A FULLY OPEN SOURCE APPROACH TOWORKING WITH OPENSTREETMAPBLAZEJ CIEPLUCH, RICKY JACOB, PETER MOONEY, PADRAIG CORCORAN,AND ADAM C. WINSTANLEYAbstract. OpenStreetMap is a very exciting and vibrant project aim-ing to make accessing geographic data easier. Our research group at theDepartment of Computer Science NUI Maynooth Ireland is carrying outresearch into a broad range of topics including: map data generalisation,geographic shape complexity, web map services, map-based interfacefor pedestrian navigation. One of the common themes across this re-search is the use of OpenStreetMap as the principal source of geospatialdata. In this paper we describe how our research productivity, researchcollaboration, and general data interoperability have been greatly en-hanced from our early adoption of a fully open source GIS approach toworking with OpenStreetMap. While one can work successfully withOpenStreetMap in non-Open Source environments the flexibility offeredby an open source approach is a major advantage. This flexibility isdelivered in many flavours including: a wide choice of software, inter-connectability of software packages and components, a wide networkof support through documentation, message boards, and free and openexchange of ideas.1. IntroductionThe advantages for organisations and individuals in using open sourcesoftware are well publicised and documented. Anderson and Moreno-Sanchez(2003) find that using open source software has a number of advantages fororganisations with scarce resources: no software costs, software tools areeasily learned by personnel with general IT background, small software foot-prints, no need to commit to proprietary software, freedom to extend thesoftware with functionality not present in commercial software and compat-ibility with existing IT infrastructure. OpenStreetMap (OSM) is a collab-orative project to create a free editable map of the world. The maps arecreated using data from portable GPS devices, aerial photography, otherfree sources or simply from local knowledge. The data collected for theOpenStreetMap project is freely available for download in OpenStreetMapXML (OSM XML) data for all countries and continents directly from theOpenStreetMap servers. On a weekly basis the most current fully QA/QCversion of OpenStreetmap is made available as an OSM XML file. This XMLfile is in .osm format and conforms to the OpenStreetMap XML schema.12 CIEPLUCH ET. ALThe OpenStreetMap software tool chain provides a “healthy software ecosys-tem” for building the basemap and developing applications based on Open-StreetMap data (Ciepluch et al., 2009). The full chain stretches from theraw data editors (JOSM, Merkator), spatial database (PostGIS), renderers(Mapnik, Osmarender), tile servers (tilecache, Map Server), viewers (uDIG,QGIS, web browser, etc), applications (bliin.com, cloudmade.com), androuting applications (openrouteservice.org). Due to space constraints in theabstract we now provide summary details on two OpenStreetMap relatedprojects currently ongoing in our research group. Each example attemptsto highlight the advantages of using a fully open source GIS approach toour research. We begin with a description of a web-based application toexplore an OpenStreetMap database. This is followed by the descriptionof the application of map generalisation techniques to geographic featuresstored in OpenStreetMap databases.1.1. Development of an OpenStreetMap database explorer. One ofthe most popular ways for those interested in OpenStreetMap to access thespatial data on their local machines is to load OpenStreetMap XML (OSMXML) into a PostGIS database. Once the spatial data is stored in PostGISit can be used in any number of ways. However for users without significantOpenStreetMap experience exploring the database can be a little confusing.OpenStreetMap data can be explored online from www.openstreetmap.org.This interface requires users to have some knowledge of how OpenStreetMapdata is organised before they can take maximum benefit from the interface.To address these issues we are developed an OpenStreetMap database ex-plorer application. The application is written in PHP. OpenLayers is usedas the Javascript map container. AJAX technology is used to ensure thatquery results are returned in response to user actions on the map with-out the need for page refresh or movement of the map from the currentuser context. The MAPNIK tool has been used to generate our own cus-tom OpenStreetMap tiles. We have access to a collection of data from theIrish Environmental Protection Agency for research purposes. This data ismostly point and polygon based spatial data. Using a set of PHP scriptswe take this data (from CSV files and Shapefiles) and insert into the localcopy of OpenStreetMap in PostGIS on our server. We configure the mapstyle file for the Mapnik tool to ensure that the newly generated set of maptiles for Ireland contains the newly added features. The user can also ex-plore these newly added local features through the map explorer interface.The query fields on the map explorer interface are generated dynamically.If a new column is added to the PostGIS database for a new feature - forexample chimney stack for a factory then this option is available automat-ically for query from the interface. In this way we can easily explore otherOpenStreetMap databases in a seamless way without the need to change theinterface when a new PostGIS database is loaded.USING A FULLY OPEN SOURCE APPROACH TO WORKING WITH OPENSTREETMAP3Figure 1. A screenshot of the OpenStreetMap database ex-plorer application. A user has searched for places of worshipwithin a 500 meter radius of their mouse click on the mapIn Figure 1 we show a screenshot of one particular use case of the Open-StreetMap database explorer. The user has clicked on the map and chosento run a query which will return all places of worship within a 500 meterradius of the mouse click. All polygons which match these criteria are re-turned and are highlighted on the map. The query results are displayed ina dynamically created HTML table underneath the map. From here theuser can further explore the results for example: retrieve all tags associatedwith a specific polygon from the search results, links to view the polygonon the OpenStreetMap website explorer at www.openstreetmap.org, down-load KML version of the polygon(s) and other features to view in other wayssuch as Google Earth. Figure 2 shows another example this time with anadministrative boundary (Kildare county) shown.Unlike the traditional proprietary paradigm of software development,users of open source software have free access to the source code in opensource environment which can be modified to fit with changing problemspecifications and user needs. One excellent example of this occurs with theosm2pgsql tool. This tool takes raw OpenStreetMap XML data and auto-matically inserts this data into a PostGIS database. By default osm2pgsqlimports a set number of spatial attributes for each geographic feature. Thisset is only a subset of the total number of spatial attributes which couldpotentially be imported. However one can easily edit some of the configura-tion files of osm2pgsql to alter the number of spatial attributes imported andto specify the import of additional attributes. This is particularly useful inthe case of users how maintain their own local copy of OpenStreetMap andhave either (1) integrated their own data into the PostGIS database withOpenStreetMap or (2) added additional localised spatial attributes.4 CIEPLUCH ET. ALFigure 2. A screenshot of the OpenStreetMap database ex-plorer application. A user has searched for all polygons andhas choosen an administrative boundary - County KildareTo summarise the following software products and tools have been utilisedin this project:• The PostGIS database• The GDAL (Geospatial Data Abstraction Library) library allowingus to export data from PostGIS from a command line interface.• PHP and the Apache Webserver• phpMyAdmin and pgAdmin for backend administration of the Post-GIS database• Mapnik: for the generation of custom sets of web map tiles• Tilecache: to provide a web-map service to serve out locally gener-ated and stored map tiles.1.2. Map Generalisation. OpenStreetMap contains spatial data on poly-gons for almost every geographic feature class. In some cases, depending onthe characteristics of the real world object, these polygons are sampled ata very high resolution. It is not uncommon for polygons representing lakesor ponds less than 0.5km2 in area to have over 300 nodes or sample points.To transfer such polygons, in vector format, to a mobile device accessing alocation-based service (LBS) this amount of data can possibility be: slow todownload to the device, or slow to load and provide a visualisation to theuser. Our group is investigating a map generalisation approach, by simplifi-cation, for OpenStreetMap data. Software has been developed in Java andC++ to investigate if a polygon, or group of polygons and other featuressuch as roads, should be simplified. The shape characteristics of the poly-gons are analysed and the results of this are used to quantitatively decideif the set of features should be simplified. Simplification is recommended ifUSING A FULLY OPEN SOURCE APPROACH TO WORKING WITH OPENSTREETMAP5the feature can have a significant number of nodes removed without alter-ing the shape characteristics of the feature to a point where the simplifiedversion is unrecognisable from the original feature. We now provide an ex-ample. In Figure 3 the polygon on the left is a large lake in Ireland. Theoriginal polygon is represented by 647 nodes. The simplified version of thispolygon is shown on the right of Figure 3 and is represented by 39 nodes.For transfer of this polygon, in vector format, to mobile devices accessinglocation-based services this is a very significant reduction in data transfersize. The polygon is simplified to the extent that it is very suitable for view-ing at scales where high resolution representations are not required. Thesimplification algorithms are developed such that all topological relation-ships are maintained. This simplification process and associated work shallbe explained in greater detail in the full paper. The researchers involvedin the development of both the Java and C++ code both cite the openavailability of powerful code libraries as a major advantage. Rather thanexpending resources into writing ones own code for well known problems itmakes more sense to reuse libraries such as: the standard template library,CGAL for computational geometry, PLPLOT for plotting in C++, and theJava Topology Suite (JTS) in Java. The focus shifts away from the tediousjob of re-inventing the wheel to developing new research ideas. Steiniger andBocher (2009) agree with this conclusion when they remark that “free andopen source software (FOSS) preserves the researcher from ’re-inventing thewheel”’. In a perfect resonance for our work here the authors make a spe-cific example of map generalisation research by stating that “one can avoidre-implementing generalisation algorithms previously developed by otherson other platforms” (Steiniger and Bocher, 2009).2. Concluding RemarksOpen Source GIS software have proven to be able to provide robust capa-bilities for geospatial database creation, spatial analysis and geospatial webapplications. The growing trend of the adoption of open source technolo-gies for GIS is largely due to the fact that many successful OSS projectshave proven to perform at acceptable and sometimes exceptional levels ascompared to proprietary products (Serra˜o et al., 2003; Raghunathan et al.,2005). Our experience in working in GIS with a fully open source softwareapproach has, so far, proven this correct. At this point in time we canconfidently speculate that even as yet unknown future research needs anddirections will not provide reason for our research group to stray outsidethe open source GIS paradigm. Steiniger (2009) strongly advocates a freeand open source GIS approach because such an approach will help to miti-gate against issues of “current proprietary software licenses and pricing anddevelopment models which limit access to broader community growth andimplementation”. One of the more tangible advantages of this approach6 CIEPLUCH ET. ALFigure 3. An example of the generalisation, by simplifica-tion, of a polygon from OpenStreetMap. The original poly-gon is on the left while the simplified polygon is on the rightfrom a research collaboration point of view is that researchers using pro-prietary computing environments have never found issues or problems withour use of an open source approach. Our software choices such as PostGIS,GDAL, uDIG (User Friendly Desktop and Internet GIS), etc means that wecan consume spatial data and services from other computing environmentseasily. Alternatively we can exchange spatial data and services in an inter-operable fashion meaning that software choice is encapsulated away fromthose outside our own research group. We close with remarks from Steinigerand Bocher (2009) who closes his paper with the statement that “while opensource software may not be suited for everyone if the price tag argument isset aside. But it is the best choice for research in GIS”.ReferencesGeoffrey Anderson and Rafael Moreno-Sanchez. Building web-based spatialinformation solutions around open specifications and open source soft-ware. Transactions in GIS, 7(4):447–466, 2003. URL http://dx.doi.org/10.1111/1467-9671.00158.Blazej Ciepluch, Peter Mooney, Ricky Jacob, and Adam C. Winstanley.Using openstreetmap to deliver location-based environmental informationin ireland. SIGSPATIAL Special, 1(3):17–22, 2009.USING A FULLY OPEN SOURCE APPROACH TO WORKING WITH OPENSTREETMAP7S. Raghunathan, A. Prasad, B. K. Mishra, and Hsihui Chang. Open sourceversus closed source: software quality in monopoly and competitive mar-kets. IEEE Transactions on Systems, Man, and Cybernetics, Part A,35(6):903–918, 2005. URL http://dx.doi.org/10.1109/TSMCA.2005.853493.Carlos Serra˜o, Daniel Neves, and Paulo Trezentos. Open source securityanalysis - evaluating security of open source vs. closed source operatingsystems. In International Conference on Enterprise Information Systems,pages 433–440, 2003.Stefan Steiniger. Free and open source geographic information tools forlandscape ecology. Ecological Informatics, 4(4):183 – 195, 2009. ISSN1574-9541.Stefan Steiniger and Erwan Bocher. An overview on current free and opensource desktop gis developments. International Journal of GeographicalInformation Science, 23(10):1345 – 1370, 2009.

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Using a fully open source approach to working with OpenStreetMap

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