Bottom line – like many things get the equipment for the intended use. If you want to send messages to family, friends, & facebook – go with a Spot. If you are looking for a last line in an emergency go with an ACR. The article below, along with a lot of other research is what helped me make up my mind – hope it helps you as well.

Below is a comment posted at the following url:
http://desertexplorer.wordpress.com/2009/11/10/the-spot-messenger-and-personal-locator-beacons/

There are a few more critical emergency signaling differences between the SPOT and ACR SARLink:

Power and Frequency Differences:
Power and Frequency are two key areas to consider when researching a life saving device. Satellites are thousands of miles away from earth, so your beacon’s signal needs to have enough power to travel that far and be able to go through anything between you and the satellite (trees, weather, out of slot canyons, etc.).

POWER: SPOT is powered by 400 milliWatts while ACR 406 MHz PLBs and EPIRBs use 5 Watts. You would need 12.5 SPOT units to equal the POWER of one ACR PLB or EPIRB! When your signal has to travel 22,000 miles to reach a satellite, you want to make sure you have more than enough power to get it there!

FREQUENCY: The basic principles of frequency are that the lower the frequency, the easier it can penetrate buildings, trees and meteorological activity that appear between the transmitting device (PLB, EPIRB or SPOT) and the receiving device (the satellites). FM radios and TV channels work on a lower frequency which is why they can penetrate buildings and the environment pretty easily. Now think about radar which uses a really high frequency. Radar works by hitting an object and bouncing off, that’s how radar knows where to place an airplane on the radar screen. So the higher the frequency, the less likely it can penetrate things in between, the lower the frequency, the easier it can penetrate. 406 MHz PLBs and EPIRBs use a dedicated frequency set up by the search and rescue community that is in the same range as UHF TV stations. SPOT uses the 1.6GHz frequency which is four times higher in the frequency spectrum. This means SPOT’s frequency is four times less likely to go through an object or weather than the lower 406 MHz frequency.

Considering power, combined with frequency, ACR’s 406 MHz beacon stands head and shoulders above satellite messenger systems like SPOT. ACR has 12.5 times more power and is four times more likely to penetrate objects in between the beacon and the satellite than SPOT.

Redundancies: PLBs and EPIRBs have multiple ways to contact SAR in order to get you rescued. SPOT has one single transmission method. PLBs and EPIRBs can contact SAR via 406 MHz, which locates your beacon using Doppler Shift, it can contact SAR using GPS data and it also has a 121.5 MHz homing frequency so when SAR forces get a few miles away from you, they can home in directly on your beacon and find you faster. SPOT uses GPS only to send its location. If you cannot download GPS, SAR will have no idea where you are!

Coverage: EPIRBs and PLBs use the Cospas-Sarsat satellite system which contains 2 different satellite systems (LEOSAR – Low earth orbiting and GEOSAR – Geostationary). These two systems cover every inch of the planet. SPOT tracker is part of Globalstar and uses the Globalstar (Nasdaq: GSAT) satellite system which only covers a certain percentage of the earth, but has quite a few locations that are undetectable.

The SPOT is an excellent tool for personal tracking and checking in with friends and family to say “I’m OK”. In fact, I own a SPOT myself and carried one on a remote 6 week kayaking expedition in the Pacific North West last summer – I was able to check in every few days and send my friends GPS coordinates so they can track the progress of the expedition. However, the SPOT was brought purely for those tasks, not for emergency use – for emergency use I wanted to ensure that I had a device that was certified to the highest standards, was fast, and provided more than just GPS signaling – for these reasons I carried an ACR SARLink GPS equipped PLB.

More info:
- The SPOT unit will still send out a distress message even if it doesn’t have any GPS data. However this distress transmission will be a simple “help me” without any geo-location, hence not very useful for SAR. In comparison, a 406MHz PLB distress signal (also without any GPS data) still identifies your location to within 5km using Doppler triangulation (LUTs detecting the non-geostationary satellites of the Cospas-Sarsat system interpret the Doppler frequency shift heard by LEOSAR and MEOSAR satellites as they pass over a beacon transmitting at a fixed frequency. The interpretation determines both bearing and range). Of course if the PLB is able to get a GPS-lock then your location is even more accurate. The reason I feel this distinction is important is because the GPS-lock is the least reliable part of the distress system – the upper limit of a GPS cold-lock is around 20min (regardless of whether you’re using a SPOT or a PLB, they both rely on the same GPS satellite network). Furthermore, a GPS-lock under canopy or in a slot canyon is very unreliable, because the GPS unit requires a minimum of four visible satellites). SPOT relies entirely on this GPS system to acquire coordinates. With PLBs, as soon as you press the distress button, you will be able to immediately send out your location to within 5km using a powerful 5 Watt blast of the 406MHz signal, then if a GPS lock is possible the following transmissions (every 50 seconds) will include the GPS coordinates.

- As I mentioned previously, the SPOT unit uses the Globalstar communications satellite network, which is not designed for SAR and does not have dedicated channels listening for SAR distress signals. This means that your SPOT, similar to a Sat Phone, needs to first listen in order to find a free slot before it can transmit your distress signal to a Globalstar satellite (acquisition time). This introduces extra delay into the system. Comparatively, the PLBs Cospas-Sarsat system is dedicated to 406MHz distress signals, so a PLB can begin transmitting distress signals immediately, and they will be picked up by the satellites immediately as well. In short what I’m trying to convey is that the Cospas-Sarsat system has been designed for the ground up specifically for just SAR distress signaling. The SPOT unit uses a commercial communications satellite network which is not dedicated for SAR nor specifically optimized to handle SAR distress calls.

On the subject of battery life, the much shorter (35hr) transmission time of the ACR PLB is because the ACR unit transmits at a much much higher power (minimum 5 watts, typically 6.3 watts), hence drains its batteries quicker compared to the weaker 400 milliWatts SPOT signal. PLB’s transmit every 50 seconds during that 35hr period, while the SPOT unit does not guarantee any transmission rate (only that most likely something will be sent within 20 minutes). The 35hr time window is definitely more than enough to relay the message to the satellite. Plus, I’d much rather have a shorter transmission time of a powerful signal rather than a longer transmission time of a weak signal that has a lower chance of actually reaching the satellites.

Another thing to consider when comparing battery life is to look at the different testing and certification requirements between the two units: Personal Locator Beacons, like EPIRBs, must be submitted to an independent test lab that verifies the frequency, operating life, testing in extreme temperatures, environmental testing, etc. From there, the product must go to Cospas-Sarsat, USCG and finally the FCC (or other comparable agencies in each country) for approval to certify that the EPIRB/PLB meets the standards for Radio Technical Commission for Maritime Services (RTCM) and that it exceeds required operating and mechanical conditions that will appear in the marine environment. PLBs and EPIRBs are rigorously tested by governing agencies to confirm they will work properly in the environment. This is a big difference from SPOT which only has to self-test and self certify that it meets Part 15 FCC. So the “up to 7 days” that SPOT reports in its spec sheet might not be a very well grounded statistic…

One note on the GPS coordinates for the SPOT and GPS equipped PLBs such as the ACR SARLink: I’m not sure about the exact GPS chipset used in either of the units, but on average autonomous civilian GPS horizontal position fixes are typically accurate to about 15 meters (45ft). From my experience the SPOT unit is consistent with these figure. HOWEVER, any PLB or EPIRB is only accurate to 100m – a much bigger error range! The reason is actually not the inferiority of the unit’s GPS chipset itself but because the space in the hex message protocol (set by Cospas-Sarsat) for position information is limited, so transmitted accuracy is approximately +/- 125 meters. In my opinion 100m range accuracy is plenty enough for SAR purposes, however might not be accurate enough if you wish to use the device for non-emergency use (to plot trail heads, etc). The SPOT is by design a great GPS tracker, accurate to 15m on average, however I still feel that for emergency signaling use PLBs are far superior by design.

Jerry Amendola
303-638-1568

First, SPOTS, PLBs, whatever won’t do you much good if you need help yesterday. If you’re planning on a massive heart attack, leave the device at home and bring a good shovel.

Second, make sure you know how to use the device. The SPOT can be somewhat confusing to use at first; played with it a lot before leaving. Some of the buttons have to be pressed for a few seconds, for example.

Third, (RE arguments about whether to get a SPOT or PLB); one benefit in my case to the SPOT was that even if my 911 call couldn’t get out, LOTS of people had been tracking me on a regular basis via the SPOT tracking feature, and someone would have noticed that I hadn’t moved in awhile… Don’t know how much time I had in the middle of the wilderness with no place to go, but having a lot of people in the know might have helped (NOTE: they also would have known my coordinates when they last saw me moving).

Fourth, I was under heavy tree cover in a small canyon (was worried about satellite reception). Not knowing whether my signal was getting out or not, I restarted the SPOT a few times to resend the 911 signal (I also understood that I should have it out in the open with the face pointed towards the sky). I later learned that all were received.

Fifth, the Grant county SAR teams have only worked two SPOT rescues, including mine. They were impressed with both.

Sixth, to reiterate…let lots of people know where and what you are doing.

Seventh, I think there are great arguments for BOTH the SPOT and PLBs. Take some time to understand the benefits, drawbacks of both, then decide which on works best for your circumstances. Probably makes a LOT of sense to have both now that I think about it.

I’m sure I’ll think of something alse as soon as I submit, but that’s all I can think of for now.

Cheers,

Dan

SPOT uses a global communications satellite network to transmit location-based messages. This is a proven simplex data network that is also supporting tens of thousands of commercial and industrial data modems sending millions of messages each month for asset tracking and remote management applications, aviation flight monitoring and emergency asset tracking. SPOT satellite coverage includes about 80 percent of the land mass of the earth and areas offshore. A complete coverage map is available at http://findmespot.com/en/index.php?cid=109.

When researching safety devices such as PLB vs SPOT there are some feature benefits which should be considered:

• SPOT will notify the GEOS International Emergency Response Coordination Center of your location and need for help. SPOT also allows for multiple messaging options including Track progress which provides a last known location every 10 minutes. This is valuable especially if you’re unable to activate the SOS feature.
• The global commercial satellites used by SPOT are only 870 miles above earth compared to the GEOSAT satellites 22,000 miles above earth. Less power is needed to get your message out which results in faster transmission. Because the satellite constellation is in constant motion orbiting the earth, different angles of detection and overlapping coverage helps pick up and transmit SPOT messages.
• In SOS mode, SPOT sends alerts to GEOS every 5 minutes for the life of the battery (between 3 days and 7 days depending on model.) Frequent alerts with updated location data is invaluable for prompt rescue response when floating in a current or having to be on-the-move for some reason and needing help.
• The GEOS Rescue Center works with both public service agencies and private rescue contractors around the world. This is important in countries where public service agencies like the USCG are not available.
• SPOT offers a higher accuracy in GPS location data than most EPIRBs and PLBS. (5 meters compared to 100 meters.)
• SPOT distress alerts are directed to GEOS with or without GPS location and GEOS has access to all previous button depressions for the past 24 hours to help determine what actions have been taken.

Again, any safety device is a step in the right direction and PLB units have evolved in lower costs and new functionality. My intent is to provide some information regarding SPOT which hopefully readers find helpful when exploring options.

Regarding the Little Bear accident, we have had conversations with the involved parties discussing in detail functionality, messaging cycles, steep typography of Hour Glass, positioning, etc. I can’t comment on the customer’s knowledge awareness of their devices. Both climbers have used SPOT on numerous occasions before.

SPOT will not send a Track Progress or OK message if it can’t acquire a GPS location at the time of sending the message. This could be due to SPOT positioning on the body or blocked sky. Both Help and SOS are designed to transmit the message every 5 minutes with or without GPS location for redundancy and will continue trying to acquire a GPS fix each time. For best results in an emergency it is important to engage SOS on SPOT and leave the unit in one place if possible. This allows the unit time to quickly acquire a GPS fix and continuously transmit its message every 5 minutes.

Derek

Also, since the SPOT satellites are in low orbit, their field of view is much more limited than the higher U.S. government satellites. The PLBs put out a much stronger signal to reach those satellites and for getting through tree canopy.

Thanks for bringing up this topic, Frank.

“At 7:41, my SPOT sent it’s last message. My device sends out a message every ten minutes whether or not i push the button, Kevin’s has to be manually sent. He sent his last message at 8:42, which means for whatever reason his lasted longer than mine. The incident happened at 10:15, so for a good hour and a half – 2 hours, our devices both had no satellite signal. When Kevin fell, i pulled out my device and mashed on the SOS and HELP button, the sending light would not come on, but power WAS on. I decided mine was not working, so I downclimbed to Kevin hoping his still worked. But, as i tried to put mine away, it fell out of its pocket and slid a long way out of my vision down the mountain. When i got to Kevin, his was nowhere to be found.

We talked extensively with SPOT, and the common belief is that during that long pitch, the signal was somehow obstructed. No one knows how, but thats our best idea.”

Would you like to comment at all on the performance of SPOTs vs. PLBs? Benners makes some interesting comments above and I’m sure we’d all like to know where SPOT stands on their performance vs similar devices. As you said, doing some research first is an important step when considering a purchase like this.

Additionally, if you are ever at liberty to discuss specifics regarding the Little Bear accident, especially as it may pertain to customer knowledge awareness of their devices, I hope you can pass that information along.