Small tables work, large tables are too slow, but work. You're using GPS data, so can't jump from one end of the table to another without passing through a fair amount of it.
Sort the big data file
Find your start location & filter Lat & Long within a reasonable distance of this (how fast do you drive?).
Copy this to another table & refer to this for the immediate data.
At some distance from the boundary of the GPS data for your filtered table you delete the "wrong" side & add by using a filter the data for the same distance in the direction you are traveling.
Haven't tested this for speed with the filter process in the background & the coordinate processing in full flow.
Alternative would be to use a list & a binary sort routine with boundaries set according to the region of interest, rather than the whole table each time.
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