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Bridges to GIS software
Published in Robin Lovelace, Jakub Nowosad, Jannes Muenchow, Geocomputation with R, 2019
Robin Lovelace, Jakub Nowosad, Jannes Muenchow
This subsection is only a brief introduction to PostgreSQL/PostGIS. Nevertheless, we would like to encourage the practice of storing geographic and non-geographic data in a spatial DBMS while only attaching those subsets to R’s global environment which are needed for further (geo-)statistical analysis. Please refer to Obe and Hsu (2015) for a more detailed description of the SQL queries presented and a more comprehensive introduction to PostgreSQL/PostGIS in general. PostgreSQL/PostGIS is a formidable choice as an open-source spatial database. But the same is true for the lightweight SQLite/SpatiaLite database engine and GRASS which uses SQLite in the background (see Section 9.4).
CityGML goes mobile: application of large 3D CityGML models on smartphones
Published in International Journal of Digital Earth, 2019
Christoph Blut, Timothy Blut, Jörg Blankenbach
In this paper we presented our platform-independent offline CityGML viewer for use in mobile AR environments. Possible solutions for processing CityGML data from a file to an in-memory model were presented and evaluated. Due to the high use of RAM of these methods, we proposed a solution based on a mobile spatial database (SpatiaLite). We use the XMLPullParser, which is included in Android™, to read CityGML files. The data are saved to a SpatiaLite database that allows us to store spatial data and perform position-dependent queries to load selective data, thereby, keeping the object count low and improve performance on mobile devices. The necessary polygon triangulation is performed by an extended Ear-clipping algorithm. When rendering, we combine meshes to reduce the number of draw calls to the OpenGL™ API which has a significant impact on the frame rate during visualization. The benchmarks showed that the performance is sufficient for a good usability and renders an appropriate solution for utilization in mobile real-time AR applications. Web-based solutions such as Cesium are not applicable in our case due to the lack of network connectivity and required low-level access to the smartphone’s hardware for AR. The 3D Tiles specification presents efficient methods for displaying large-scale city scenes. Our use case though is focused on smaller more specific objects and the semantics of the objects, so a custom solution is required.