BONUS BASMATI State of the Art Report on Multi-Channel Map Applications. Deliverable 5.2

Abstract

<p>This document describes basic building stones for developing state of the art multi-channel map applications, such as the Baltic Explorer. By multi-channel we describe the system as being able to communicate information through multiple different devices, including personal computers, large touch screen devices, and smartphones. The Baltic Explorer that is to be developed in the BONUS BASMATI project, is a highly interactive, web-based spatial decision support system (SDSS), with functionality that includes geospatial data exploration, real-time cumulative impact assessment, co-location, and suitability analysis. By SDSS we mean a system designed for facilitating decision making processes based on complex spatial problems, and it provides an integrating framework for database management, geospatial analysis, visualisation, and the expert knowledge of decision makers.</p><p>Web mapping libraries provide frameworks for developing the client-side web map applications. The Baltic Explorer will feature a highly intuitive map-based interface, making web mapping libraries and application programming interfaces (APIs) ideal development tools for it. This report presents the results of two tests that were carried out for five different web mapping libraries (OpenLayers, Leaflet, ArcGIS API for JavaScript 3, ArcGIS API for JavaScript 4, Cesium). The tests provided insight on how the client-side of the Baltic Explorer could be constructed and highlighted some of the differences between the libraries. In the first test, the libraries were tested for integration with HELCOM ArcGIS REST API, a primary data source for the BONUS BASMATI project. In the second test, the APIs were tested for how their content adapts to smartphone screens. Modern web pages and applications use responsive web design (RWD) to make their content adapt to different sized screens. If RWD rules are included in a library, it can speed up the development of the Baltic Explorer and leaves more time for the development to focus on other issues.</p><p>The result of the two tests revealed that all five libraries were able to complete both tests, and as such, the tests were unable to exclude any of the libraries from consideration for the Baltic Explorer. However, some smaller differences were revealed in the tests. For example, unlike the other three libraries, OpenLayers and ArcGIS API for JavaScript 3 require extensions to become responsive to different screen sizes. RWD and web mapping libraries will be useful in developing the client-side of the Baltic Explorer. The chosen web mapping library will provide the backbone of the Baltic Explorers client-side and RWD will enable map interfaces to adapt to screens of different size, including computer monitors and large touch screens, both planned to be platforms for the Baltic Explorer. For smaller touch screen devices such as smartphones, additional design elements like larger buttons that are easy to use with fingers, might need to be implemented.</p><p>The next step in the development of the Baltic Explorer is to build the first prototype of the SDSS. In the upcoming months, more complex tests for the client-side web mapping libraries are needed in order to decide which library provides the best features for the Baltic Explorer. The Baltic Explorer is envisioned to be used in participatory settings with non-expert users, which emphasizes the need for good performance, and a user interface that is intuitive, interactive, and easy-to-use. Further testing of the mapping libraries will focus on these requirements. It is not yet decided if the Baltic Explorer needs to be capable of 3D visualisation, such as provided by ArcGIS API for JavaScript 4 and Cesium. If there is no need for a 3D map environment, these libraries might prove to be excessively big. Finally, while ArcGIS API for JavaScript 3 and 4 are free to use, they are not open source. Developers are thus not able see the source code, which to a degree limits the transparency of the system.</p>