Data storage on SD card - file organisation, library search.

Robin2:
Can you give an example of 3 or 4 records showing the range of sizes that you need to deal with.

Ok. I try.

File named WAY.TXT - This is data for reading in Arduino and have record:

1 56.3331239 41.3052903
2 56.333281 41.3052708
3 56.334128 41.3042505
etc up to record with index 1000
Can be less that 1000 but no more.

this file exist in SD card before running.

FILE named PATH_1.TXT - This is data for writing - real path storage. Looks like

1 56.331239 41.3052903
2 56.331252 41.30530
3 56.331305 41.3053205
etc up to record with index
1000
Can be less that 1000 but no more.
If index overrun 1000 - it start from 1, but new file must be open for storage with name PATH_2.TXT