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Master Thesis Vector Tiles Als Datenbasis Für Master Thesis im Rahmen des Universitätslehrganges „Geographical Information Science & Systems“ (UNIGIS MSc) am Interfakultären Fachbereich für GeoInformatik (Z_GIS) der Paris Lodron-Universität Salzburg zum Thema Vector Tiles als Datenbasis für OGC- Darstellungsdienste WMS und WMTS vorgelegt von Dipl. Ing. (FH) Gerd Jünger 104577, UNIGIS MSc Jahrgang 2016 Zur Erlangung des Grades „Master of Science (Geographical Information Science & Systems) – MSc(GIS)” Halle (Saale), 21.11.2018 Eigenständigkeitserklärung Ich versichere hiermit, dass ich diese Master Thesis eigenständig, ohne fremde Hilfe und nur unter Nutzung der angegebenen Quellen erstellt habe. Diese Arbeit hat in gleicher oder ähnlicher Form keiner anderen Prüfungsbehörde vorgelegen. Alle Ausführungen, die aus anderen Quellen wörtlich oder sinngemäß übernommen wurden, sind entsprechend gekennzeichnet. Halle (Saale), 21.11.2018 Ort, Datum Unterschrift I Kurzfassung Mit der Zunahme des Erfordernisses Geodaten mit einer hohen clientseitigen Flexibilität performant über das Internet zugänglich zu machen, wächst das Interesse an effizienten und vielseitig nutzbaren Datenaustauschformaten. Rasterdaten, die zur Darstellung von Geodaten weit verbreitet sind, erfordern einen hohen Speicherbedarf sowie einen höheren Datendurchsatz und sind in ihrer Flexibilität eingeschränkt. Originäre Vektordaten, z. B. über WFS bereitgestellt, bieten eine hohe clientseitige Flexibilität, die entsprechenden Dienste sind jedoch oft sehr langsam. An dieser Stelle bieten sich Vector Tiles zur Verteilung von Geodaten an, da sie die Vorteile von Raster- und Vektordaten verbinden können. Da Vector Tiles in den verbreiteten Desktop Clients bisher nicht oder nur unzureichend implementiert sind, entstand die Idee zu untersuchen ob es möglich und sinnvoll ist, Geodaten in Vector Tiles zur direkten Nutzung anzubieten und parallel eine Beschleunigung von OGC Darstellungsdiensten zu erreichen, indem diese Vector Tiles als deren Datenquelle eingesetzt werden. Im Rahmen der detaillierten Recherchen zur Verwirklichung dieser Idee wurde eine umfassende, strukturierte Grundlagendarstellung zu Vector Tiles erarbeitet und aktuelle Software zu ihrer Verwendung ermittelt. Basierend auf den daraus gewonnenen Erkenntnissen erfolgte die Umsetzung von zwei Szenarien eines WMS basierend auf Vector Tiles. Ein Szenario nimmt den Umweg über mit TileServer GL gerenderte Raster Tiles und wird über Mapproxy bereitgestellt. Die zweite Lösung nutzt die direkte Einbindung von Vector Tiles in MapServer über die GDAL-Bibliothek. Diese ist aktuell jedoch nur sehr eingeschränkt umgesetzt. Die Performance der beiden Szenarien wurde in Lasttests mit der von zwei herkömmlichen WMS basierend auf Shape-Dateien verglichen. Im Ergebnis wurde festgestellt, dass die Performance der WMS mit der untersuchten Software nicht eindeutig verbessert werden konnte. Beim der Verwendung von TileServer GL und Mapproxy entscheidet die Schwerpunktsetzung bei der Interpretation der Ergebnisse über die Beantwortung der Frage. Bei dem Szenario mit MapServer verhinderten die aktuell noch unzureichende Einbindung der GDAL-Bibliothek und deren eingeschränkte Funktionalität einen effektiven Zugriff auf die Daten. Darüber hinaus ergeben sich beim ersten Szenario entscheidende Nachteile, wie der Wegfall von Attributinformationen. Mit Blick auf die aufgetretenen Probleme und festgestellten Einschränkungen, verbunden mit der aktuell stark voranschreitenden Entwicklung bei Vector Tiles ist ein produktiver Einsatz der untersuchten Lösungsansätze nicht empfehlenswert. Es ist davon auszugehen, dass nach Entwicklung eines offenen Standards für Vector Tiles mittelfristig praktikablere und performantere Lösungen zu deren Einbindung als Datengrundlage in einen Darstellungsdienst möglich werden. Diese Richtung ist in einem ersten Schritt anhand der direkten Einbindung von Vector Tiles in MapServer abzulesen. II Abstract With the increase in the need to make geodata accessible via internet with a high client-side flexibility, interest in efficient and versatile data exchange formats is growing. Raster data, which are widely used for the representation of geodata, requires a high storage capacity and a higher data throughput and are limited in their flexibility. Original vector data, e.g. provided via WFS, offering a high client-side flexibility. The services are, however, often very slow. At this point, Vector Tiles can be used to distribute geodata because they can combine the advantages of raster and vector data. Since Vector Tiles are not or only insufficiently implemented in popular desktop clients, the idea was born to investigate whether it is possible and reasonable to offer geodata in Vector Tiles for direct use and to achieve an acceleration of OGC display services in parallel by using these Vector Tiles as data source. As part of the detailed research for the realization of this idea, a comprehensive, structured basic presentation of Vector Tiles was developed and current software for their use was determined. Based on the lessons learnt two scenarios of a WMS based on Vector Tiles were implemented. One scenario takes the detour via raster tiles rendered with TileServer GL and is provided via Mapproxy. The second solution uses direct integration of Vector Tiles into MapServer via GDAL library. However, this is currently only implemented to a very limited extent. The performance of the two scenarios was compared in load tests with two conventional WMS based on shape files. As a result, it was determined that the performance of WMS could not be clearly increased with the examined software. When using TileServer GL and Mapproxy the focus of the interpretation of the results decides on the answer to the question. In the scenario with MapServer the currently insufficient integration of GDAL library and its limited functionality prevented an effective access to the data. In addition, the first scenario has decisive disadvantages, such as the omission of attribute information. With regard to the problems that have occurred and the limitations that have been established, combined with the current strong progress in the development of Vector Tiles, a productive use of the investigated solution approaches is not recommendable. It can be assumed that after the development of an open standard for Vector Tiles, more practicable and better performing solutions will be published. This will serve as a data basis for a presentation service in the medium term. The direct integration of Vector Tiles into MapServer can be seen as first step in this direction. III Inhalt 1 Einleitung.................................................................................................................................................................1 1.1 Forschungsziel.....................................................................................................................................................2 1.2 Vorgehensweise...................................................................................................................................................3 1.3 Nicht behandelte Themen und unberücksichtigte Inhalte...................................................................................3 2 Stand von Forschung und Technik........................................................................................................................5 2.1 Forschungsarbeiten..............................................................................................................................................5 2.2 Stand der Technik................................................................................................................................................6 3 Grundlagen..............................................................................................................................................................8 3.1 OGC Darstellungsdienste....................................................................................................................................8 3.1.1 Web Map Service (WMS)........................................................................................................................8 3.1.2 Web Map Tile Service (WMTS)..............................................................................................................8 3.2 Beispieldaten.......................................................................................................................................................9 3.3 Softwarelizenzen...............................................................................................................................................10 4 Vector Tiles.............................................................................................................................................................11 4.1 Allgemeine Beschreibung..................................................................................................................................11 4.2 Begrifflichkeiten................................................................................................................................................12 4.2.1 Ansätze...................................................................................................................................................12 4.2.2 Konzepte.................................................................................................................................................13 4.2.3 Schemata................................................................................................................................................13
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