Locosys
Locosys was the benchmark for many years but they no longer make these devices.
- GT-11 - originally the benchmark for quality 1 Hz logging at an affordable price!
- GT-31 - still 1 Hz logging but with more accuracy and the addition of SDOP
- GW-52 - smaller unit with 1 Hz and 5 Hz logging
- GW-60 - wristwatch with 1 Hz and 5 Hz logging