I believe the formula just implements the interleaving of the X and Y coordinates used in the QuadTiles[1] indexing schema in an efficient way by using some clever bit operations.
[1] https://wiki.openstreetmap.org/wiki/QuadTiles#Quadtile_implementation On Tue, Jan 14, 2020 at 11:11 AM Lorenzo Stucchi <lorenzostucch...@outlook.it> wrote: > > Hi all, > > I have almost complete the explanation of the schema regarding the element > (node, way and relation) I have just one last element to be understood. > > The “tile” in the node table. I found in the code a function called > “public.tile_for_point” [1] and seems that should be the one that do this > process. But I’m not able to understood which is the output of the function, > in particular what this part of code does: > > x := (x | (x << 8)) & 16711935; — 0x00FF00FF > > Thanks for all the reply. > > Best, > Lorenzo > > [1] > https://github.com/openstreetmap/openstreetmap-website/blob/751e8ad32c864f50eae9e9359d74a11dc44de007/db/structure.sql#L160 > > Il giorno 10 gen 2020, alle ore 15:51, Lorenzo Stucchi > <lorenzostucch...@outlook.it> ha scritto: > > Thanks for the reply. > > Is this the formula [1] ? > > Best, > Lorenzo > > [1] > https://github.com/openstreetmap/openstreetmap-website/blob/751e8ad32c864f50eae9e9359d74a11dc44de007/db/structure.sql#L160 > > Il giorno 10 gen 2020, alle ore 15:22, Frederik Ramm <frede...@remote.org> ha > scritto: > > Hi, > > On 10.01.20 15:08, Lorenzo Stucchi wrote: > > What does it mean the “timestamp” present in the table (“node", “way" and > “relation")? > > > When the object was last changed. > > What does it mean the “tile” element present in the “node" table? > > > An integer derived from the lat/lon of the node using a mathematical > formula. > > What does it mean the “sequence_id” in the “way_nodes” table and > “relation_member” table? > > > An integer used to store the ordering of the nodes/members (which node > is the first, the second, ... in the way). > > Bye > Frederik > > -- > Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33" > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > https://lists.openstreetmap.org/listinfo/dev > > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > https://lists.openstreetmap.org/listinfo/dev > > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > https://lists.openstreetmap.org/listinfo/dev _______________________________________________ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
