MEOS is the underlying C library driving MobilityDB.
https://libmeos.org/
MEOS corresponds to the C library GEOS for trajectory management.
https://libgeos.org/

Currently, MEOS support R-Tree in-memory indexes.
https://github.com/MobilityDB/MobilityDB/blob/master/meos/src/temporal/temporal_rtree.c

We are looking for contributors that can help us to develop Quad-tree and K-d tree in-memory indexes for MEOS, which would correspond to the SP-GiST indexes in MobilityDB.