  Geospatial joins are a core building block of connected mobility
applications. An especially challenging problem are joins between streaming
points and static polygons. Since points are not known beforehand, they cannot
be indexed. Nevertheless, points need to be mapped to polygons with low
latencies to enable real-time feedback.
  We present an adaptive geospatial join that uses true hit filtering to avoid
expensive geometric computations in most cases. Our technique uses a
quadtree-based hierarchical grid to approximate polygons and stores these
approximations in a specialized radix tree. We emphasize on an approximate
version of our algorithm that guarantees a user-defined precision. The exact
version of our algorithm can adapt to the expected point distribution by
refining the index. We optimized our implementation for modern hardware
architectures with wide SIMD vector processing units, including Intel's brand
new Knights Landing. Overall, our approach can perform up to two orders of
magnitude faster than existing techniques.
