Also, Margo Supplies are developing a GPS collar:

It was featured in a Wildlabs Variety hour:

I wish some of the experienced developers of collars would make small collars with solar panels.

Best regards,

Lars

I forgot to mention a few of the other manufacturers who has converted solar panel bird trackers into collars: 

Technosmart

Ecotone

Both of these use UHF based download. I tested a protype from Technosmart but found the download range too limited for our purpose.

Dang Lars!

You have some of the most thorough and incredibly useful answers for my questions lately! You're awesome! I will take a look all the resources after my travel here. I really appreciate this! I may have a couple extra questions from some of the links, I'll be sure to send a reply here though.

Thanks for all the help Lars!

Best,

Travis

We have some plans/ideas on doing a smaller version of our collar@Lars_Holst_Hansen. Reliability and ruggedness is key. Once we have enough long-term data to prove we've nailed that scaling it down would be fairly easy. Solar has no problem keeping the battery fully charged in sunny environments.

Sounds great, Brett! Keep up the good work! If you want someone to test under rugged and harsh arctic conditions, let me know! 

Thanks again for the links Lars, I completely agree and I'm sure, just as it was with the gradual size decrease in GPS devices, we will see decreases in solar powered trackers hopefully relatively soon. Currently, it is also quite interesting the range of longevity I see from some of some of these solar powered devices (I know I'm probably oversimplifying a lot of factors that play into this as well). For a lot of trackers running on solar power, I am seeing a battery life of ~ 6 months, sampling 1 fix a day. Then I see some other trackers, like what Dr. Craig Franklin is doing with estuarine crocodiles. GPS fixes every 30 minutes and diving profiles, and the ability to essentially track the animal inevitably. Taking into account that these animals are under water for portions of their day, if it is that efficient that seems quite incredible compared to some of the other specs I am seeing from other devices and developers.

My dilemma is considering how efficiently a solar panel will be at powering an accelerometer sampling continuously at a higher frequency (~25 Hz). I'm thinking that the added cost of the solar panels may not be worth the small increase in collected data. I'm aiming for 4 months of ACC collection and the battery can currently supply it for 2 months. Considering just adding on one more battery and calling it good instead. For added context, these collars would be deployed on some large terrestrial African wildlife.

Best,

Travis

Hi Travis! Sounds like you are about to develop your own hardware. One thing to be very attentive to is clock drift. With additional sensors like accelerometers with their own (real time clock) consider if it is crucial to keep track of the inevitable clock drift, and if so, how to do it (syncing with GPS time for instance or doing some violent shakes before and after deployment - timed with and off collar accurate GPS clock). Then you can use these time stamps to estimate the offset and drift (to get a timestamp scaling factor). 

Best regards,

Lars 

@TravisBayer For a time scale of 2-4month I think you'd likely be better off not using solar. Don't think solar adds much benefit until 6months+ in my opinion. You also need to consider if you are using solar you'll need a rechargeable battery or capacitor to utilize it. Current rechargeable batteries have significantly lower energy density and temperature tolerance than their non-rechargeable counterparts.

My guess would be the wide range in longevity you mentioned is in part an apples to oranges problem. Makes a big difference in power draw which RF technology is being used. A satellite tracking collar would use way more power then a Lora tracker that pings a base station.

That's good to know @Lars_Holst_Hansen ! We might actually take you up on that. We've been having promising results in Alaska so the Arctic could be a good next step. @MargoJack 

@Lars_Holst_Hansen This is great to think about, thank you for pointing this out! While I am not directly developing hardware, I am discussing with a tech company how to incorporate high frequency accelerometers into their existing tracking collars for my specific study. Your point is great to think about as both devices with be separate from each other, running on their own power. Just on the same collars together.

Once I take a look at the ACC signatures from the pronounced shakes before and after deployment, I should be able to determine to rate of drift, no? From there it should be able to be corrected by applying a function to the timestamps in R that corrects for the rate of drift.

@BrettMargoSupplies Great, this is the confirmation I needed. I was leaning towards, but wanted to be sure. Also, thanks for the clarification on the power draw based on method of transmitting data. That is something I will take into consideration in future studies.

Thanks for insights Brett!

Hi Travis!

I would take a close look at https://www.vectronic-aerospace.com/ and their Vertex Plus collars in particular: https://www.vectronic-aerospace.com/vertex-plus-collar/

Vectronic is generally regarded as one of the most reliable brands and they offer very flexible scheduling of fixes and data transmission via their https://www.vectronic-aerospace.com/gps-plus-x/ desktop application.

The Vertex Plus collars offer acceleration up to 32Hz and Vectronic told me that they were also going to put magnetometers in the new models. This opens up possibillities of doing so-called "dead reckoning" and thereby reconstruct more detalied tracks than what the fixes makes possible by themselves.

In the https://www.vectronic-aerospace.com/gps-plus-x/ you can play with different schedule scenarios in the lifetime calculator to get a sense of what is possible with the battery size you need.

The Vectronic ACC timestamp is supposed to get synced with GPS time but I have not yet been able to find out how and how often this happens.

Regarding the shake event method:

While making my own python scripts to investigate drift and offset in an independent audiologger which also records ACC and MAG, I stumbled upon this package: https://github.com/hpi-dhc/jointly

It seems to fit the bill very nicely but I have not tried it myself, though.

One caveat is what to do if the ACC logger has stopped before retrieval. You would then not be able to do the exact timing of a shake event after deplyment to use as the end event.

Best regards,

Lars

With a Vectronic Vertex Plus 2D collar, 32Hz 3D acceleration and 15min position fix intervals you can expect between 3-6 months of lifetime using Iridium as position transfer.

This project seem to be using both 2D and 3D sized collars on lions:

https://www.vectronic-aerospace.com/projects/#KopeLion

Lars,

As always, your insights are great! The GPS Plus X battery life calculator is great! I've downloaded it and have been toying around with it, very convenient when thinking about sampling schedules. Curious as to why more tech developers don't incorporate something similar into their own programming/analysis software. Very useful.

I've got a few meetings set up with a couple different tech developers, but may reach to Vectronic here. At first glance, their collars seem great! I appreciate the recommendations.

I must admit, I am not well versed in Python, but I am looking into something that wold be the R equivalent. If I don't have much luck, I may try and take a look at how that package was made in Python and attempt to recreate it in R.

You're the best Lars! Thanks!

Cheers,

Travis

Hi Bill,

I don't believe I will need them to be extremely accurate, but will need a good degree of accuracy for some behavioral classification and habitat use analyses. In regards to the solar, tracking the solar cycle is a great suggestion. I have also considered having some thresholds programmed in the accelerometer to power off both sensors during periods of sleep/rest in order to conserve battery life. I did this same thing in my last study for the GPS only, so there wouldn't be instances where the trackers continued to try and unsuccessfully acquire GPS fixes while the bats where inside their caves resting. After the bat's surge axis dropped into the -1 and there was 10 unsuccessful GPS fix attempts in a row, the GPS powered down.

Thanks for the suggestions and insights Bill!

Best,

Travis