Ido Ran

In the code I've published each record is 10 bytes (SERIALIZED_LENGTH) made up of long-lat-time. I'm "squizing" time into 2 bytes, you can see write_time function.The memory is 32k byte which means we have 3276 / 10 = 3,276 entries.You can calcualte the time by 3276 * interval_in_seconds / 60 / 60 = hours-to-run - in my code 3276 * 3 / 60 / 60 = 2.73 hours.One relatively easy way to extend this is to check the last two entries and update the last entries (instead of adding new one) if the diff between the one before last and the current location does not exceed say 5 meters.Also, remove the time field will of course leave more room for entries.

Thanks for the code update, you are welcome to create a PR in github if you fells like it :)About the need to run it for 8 hours, there are two main factors to consider: battery and memory.I aim for 2 hours max so the battrey was not an issue, even though I didn't do any real testing of how long battaries will last. I was more concerned with having enough memory to keep the locations.If you aim for 8 hours then batteries do become an issue and that's outside my knowledge but I do know you should put both the Arduino and the GPS module in some kind of sleep mode, from what I read there are multiple modes of sleep.Than again, if you put 4 AA battaries it might be just enough as it is.Thank you again for sharing the updates.

Hi,Thanks for the picture and also for the fix to use 4 battaries!I also notice that when the battaries low the GPS doesn't always works.You should have a blinking LED on the GPS module when the GPS has good connection and is able to read the location, if the LED on the GPS does not blink it will not record locations.

I'm happy to see the project helps you.I have some set back with the online version :\ but I do hope to get around to it.

Hi,I've reworked on my offline GPS instructables, adding a video of my dog wearing the GPS as well as fixing links and adding whole new step of mounting it on the dog.I'll appreciate if you can please take a look and give me feedback about it.https://www.instructables.com/Finding-Lychee-Dog...Thank you,Ido.

Hi,I've wrote my first Instructables and will be really happy for tips on how to improve it.https://www.instructables.com/Finding-Lychee-Dog-GPS-Offline-Tracker/