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I do not have any reference data to talk about the accuracy, but in my experience with this method and a PA6C module (manufacturer's accuracy ±3m) in widely open space like golf courses, I would say it's pretty well matches within a few yards to many of those golf gps apps (these also have some tolerance ranges) for smartphones.

I'm glad you made it. Yours looks a lot prettier than mine. Enjoy it.Thanks for sharing the pictures.

Hi Johan,That's quite interesting project. My concern is how fast the GPS data need to be updated. Recently I have posted another GPS related project (https://jeonlab.wordpress.com/2018/03/10/golf-gps/) using PA6C GPS module. Its datasheet says its update rate is 10Hz, but due to other calculations on the microcontroller, actual update is much slower than that. I guess your project needs pretty fast update to measure the time difference between two positions. How far is the distance between those two gates and what resolution of time measurement do you need?

Did you mean the PCB? You can buy one from me.

Great Instructable! Thank you for sharing this. I was looking for a simple solution to upload sketches to ESP-01 without those two annoying switches for RST and GPIO0 which is not always successful. With your solution, I could always successfully upload sketches. Thanks again.

Those spray paint you can buy from a hardware store are normally non-conductive, so it won't affect on the antenna. But somehow, if the spray paint you want to use is conductive, just be careful not to spray on the connector.