Development of free and open source software for flow mapping integrated to geographic information systems

---

Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: NAİM CEM GÜLLÜOĞLU

Danışman: NURKAN KARAHANOĞLU

Özet:

Mapping of spatial interaction data is an ongoing challenge for cartographers. In many Geographic Information Systems (GIS) software there is no off-the-shelf functionality for processing and visualizing spatial interactions or geographical flows. Considering the development efforts that have been made in the last few decades to discover the potential of GIS almost in every aspect, handling and visualization of spatial interaction data under GIS remain underutilized. The main objective of this study is to develop a general purpose free and open source software for flow mapping that is fully integrated to a desktop GIS application. Identified as the most fundamental form of geographical flows, the scope of this study focuses on exploration and visualization of interactions taking place between geographic locations where the actual flow routes are unknown or negligible. The flow mapping software, FlowMapper, is designed as a plugin to the popular, free and open source Geographic Information Systems software Quantum GIS (QGIS). Development environment tools utilized in this study consists of Python programming language, PyQGIS Python bindings for QGIS API, PyQt Python bindings for Qt framework, Qt Designer tool and OGR Simple Feature Library. Designed as a fully menu driven and user friendly plugin, users of FlowMapper are capable of generating flow maps easily by supplying node coordinates and interaction matrix. Besides, flow related attributes such as net, gross magnitude calculations are automatically performed and flow gaining, flow losing nodes are automatically identified. In order to increase cartographic quality, advanced symbology options and flow filtering capabilities are also offered in FlowMapper as spatially non-distorting visual clutter reduction techniques. Capabilities of developed plugin are successfully tested with different scenarios and by using several flow datasets consisting of four to two hundred nodes. Comprising of more than 6.500 lines of code, FlowMapper plugin received more than ten thousand downloads during two years of development period. Besides, plugin website received visitors from more than eighty countries. These indicators prove the need for integration of flow mapping tools to popular, open source desktop GIS applications. The main contribution of this study is the free and open source, general purpose flow mapping application FlowMapper which is integrated to QGIS in plugin form that aids exploration of spatial interaction data and creation of flows maps with symbology and filtering options.