[OSM-dev] VECTOR TILING in applications
sandors39 at gmail.com
Mon Apr 2 06:41:42 UTC 2018
Tiling strategies and models are very well known and developed today. Especially uniform raster and vector tiling models in services where the tiles are pre-generated for efficient transmission and rendering. However, vector tiling is much, mush more than that. It is a powerful tool in many application. Let us mention some of the applications where a special vector tiling radically increases the efficiency. The examples are selected based requests/interest on OSM forums.
1. Detecting objects being inside a large polygon from a large set of objects. The issue is illustrated by OSM buildings and the polygon of Africa. If a usual “objects in polygon” algorithm manages the task, it will probably use very long time. Using an efficient vector tiling based algorithm the task can be accomplished just in several seconds.
2. When we do visual inspection of the result in 1. we can see that many buildings are partly in the sea. Whether these cases are mapping errors or not is irrelevant here but the issue triggers a task to detect buildings in Africa being partly in the sea for further actions. By using the usual filtering models it is almost impossible to solve this task or it will last even longer than in 1. The progressive vector tiling, the multitiling procedure helps to solve this task in seconds.
3. When RW area estimates are needed for large areas in a projection (e.g. Mercator) we inevitably meet the accuracy problem. We need to create area fragments and apply known position based correction factors. Here, again, a progressive tiling helps us to solve the issue on-the-fly.
4. Sometimes, when using Polygon Algebra based operations with area arguments the results might be so complex and complicated that we could never be sure that what we see is really what we wanted. For instance, if we need the intersection, the common area of several highly complex areas. In similar cases we need a reliable, simple and fast verification model. Vector tiling might provide an excellent validation model for these cases.
The mentioned applications are described in details here https://goo.gl/tuR5Wr. In the paper there are many supporting illustrations, examples and explanations as well. There are many hints for interested that they could repeat the experiments in an arbitrary programming language. The progressive tiling, the multitiling is also described and illustrated. Its comparison to the usual vector tiling shows its pre-dominance and the reality of the on-the-fly tiling in vector based GIS systems and vector map making.
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