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US Patent 6,005,504
1. Latitude(-90 to 90 degree)?Integer Steps (0.1sec unit, from 0 to 6480000) ?23 bit Binary
2. Longitude(-180 to180 degree)?Integer Steps (0.1sec unit, from 0 to 12960000) ?24 bit Binary
3. Concatenate 23 bit latitude binary as a upper digit, with 24 bit longitude binary as lower. ?47bit.
4. Use 0-9,A-Z,and “=”, total 37 characters, express 47 bit binary value by 37th radix notation. Code is 9-digit length.
Sony proposes that make this code length into 10-digit length, by adding one more letter as an error-correcting code. Sony’s code looks random to human, so error correction code is a good idea to detect human error that may cause trouble.
SJ=E8JN32E(With Check Digit)