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Garmin inReach, Spot X, etc - what is best satellite messenger?

Discussion in 'Tech Tips and Gear' started by Southern Canyoneer, Sep 13, 2018.

  1. Southern Canyoneer

    Southern Canyoneer Desert Hiker

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    I know there was a thread about satellite messengers last summer but wanted to bump this thread back up. I'm wanting to get a messenger for backcountry travel specifically backcountry skiing 7 snowboarding, canyoneering, mountain biking, off trail backpacking. I have GAIA GPS for my maps but want something in case of emergency to send a message. Curious to know what are peoples experiences with Garmin inReach, Spot X and any others devices? Pro's/Cons?
    Last edited: Sep 13, 2018
  2. Sonny Lawrence

    Sonny Lawrence

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  3. Southern Canyoneer

    Southern Canyoneer Desert Hiker

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  4. Terry LeBlanc

    Terry LeBlanc

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    We used a Garmin InReach Explorer+ last year while hiking and doing Mystery Canyon. We had the tracking feature turned on so that my wife could follow our progress, and we could send preconfigured messages and texts, which were easier to type using the phone interface. It worked. There is an SOS emergency feature, which might work, but I suspect an ACR device would be a more reliable rescue solution.
  5. townsend

    townsend

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  6. hank moon

    hank moon kinetically bulbous

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    https://www.facebook.com/groups/26638669574/permalink/10154080005089575/

    PLBS vs SENDS

    There's been a lot of discussion recently about options for emergency rescue beacons, and a lot of misinformation, misunderstanding, and confusion about the two different devices, so I thought I'd outline the crucial differences so people can make informed decisions.Whether you choose to take a PLB or a SEND or neither, or both is of course entirely up to you, but it's critical that you have the right information so you can make the right choice, and unfortunately the manufacturers of these products are not particularly forthcoming about the differences between the two.I won't be discussing the difference in performance between different models or anything like that - this isn't a review - I'll simply be discussing the technical differences between the two devices. The most critical thing to grasp is though they share some functions that on first glance may appear similar, the way the two devices function is completely different.


    But first Satellites 101, because understanding the difference between different satellite networks is critical for understanding the difference between these devices.


    Satellites orbit the earth, and communicate with devices on the surface. They require line of sight, and depending on the transmission power, signal can be disrupted by interference in the form of weather, solar activity, or even clouds of migrating insects. The more powerful the transmission, the less interference there will be.


    Not all orbits are equal. Orbital altitudes vary enormously from Low Earth Orbits (LEOs) of below 2,000km to very high orbits (the moon orbits the earth at an altitude of 384,000km).


    The lower a satellite's orbit, the shorter its orbital period will be (time taken to orbit the earth once). In addition, it's orbital speed is higher. The end result is that from the perspective of an observer on earth, the apparent time a satellite takes to cross from one horizon to another increases exponentially as the orbital height decreases. This is critical for satellite communications because this period of time represents the communication window in which a device can successfully link with a particular satellite. Satellites in LEO will cross the sky in a couple of minutes. That assumes you're in a completely flat landscape with clear views horizon to horizon. As you put yourself in steeper terrain (with a smaller and smaller view of the sky, the communication window can drop to a matter of a few seconds. In steep enough terrain, if a satellite doesn't pass directly overhead, you won't have any communication at all.


    Conversely, a satellite in sufficiently high altitude has the opposite problem; the moon for example is in such high orbit that the earth's rotation affects its apparent movement across our sky more than its own orbit does.


    Low Earth Orbit is the easiest orbit to establish and also the easiest to maintain. As a result, the vast majority of satellites operate at these low altitudes, including every manned spacecraft, and all satellite communication satellites. The problems with coverage are mitigated by having satellite constellations consisting of multiple satellites. In fairly open terrain these ensure constant coverage. However in steep terrain there can still be gaps in coverage, particularly in areas that are not directly beneath a satellite path.


    Now onto the devices...


    SEND
    A Satellite Emergency Notification Device. Popular examples include the SPOT 3 and the DeLorme InReach. These devices are essentially the texting equivalent of a Satellite Phone, and work exactly the same way. The user subscribes to a provider, and messages are sent via a commercial comsat network such as the Iridium constellation. Critically, these are COMMUNICATION devices, not an emergency beacon. An "emergency" feature is provided, that is essentially just a "template" text message that automatically sends when the designated emergency button is pressed. This includes GPS coordinates (if available). A private commercial emergency rescue facility (in effect just a call centre) receives these messages and passes them on to the appropriate Rescue Coordination Centre (RCC) to initiate a rescue in the traditional manner.There are not minimum standards for a SEND device as far as power output, battery life, durability, or environmental protection. However most devices how some degree of waterproofing and are low powered. Just how low-powered is sometimes a guess - you won't find the transmission power in the specs sheet for most SENDs. The Delorme InReach SE, however is 1.6w.

    An issue with a SEND is battery life, as they're a "dual use" device. Because they feature tracking, "check in", communication, and sometimes altimeter, barometer and other functions, depending on how the device is used it is constantly using its battery. That means when an emergency strikes, how much battery life you have is dependent on how long it has been since you last charged it, and how much you've used it. It's similar to the battery power issue you have with using a cellphone.The obvious advantage of a SEND, and indeed the function they're actually intended for, is two-way communication. They're primarily intended as a device for allowing periodic "check-in" so that friends and family can track your progress and be assured that all is well. However as mentioned, the device uses satellites in LEO, and as a result communication with satellites is not reliable. In steep terrain they simply may not be able to communicate with a satellite at all. Further, because of their low power output they need a clear view of the sky, and any transmission can be derailed by poor weather, tree cover, and so on.


    PLB
    A Personal Locator Beacon includes examples like the ACR ResQLink and McMurdo Fast Find. These are essentially small hand-held versions of the emergency beacons found on ships and aircraft and integrate with the same emergency response network used globally by world rescue agencies.Unlike a SEND, a PLB does not involve private commercial companies anywhere in its operational chain, and is not operated for profit. There is no charge for the services, and both the satellite and ground-monitoring stations are operated by government agencies.Because PLBs are a technical part of the global rescue network they must meet strict technical standards for durability, environmental protection, power output, and battery life.PLBs communicate with specialist Rescue modules on satellites in the Cospas-Sarsat Programme - an international system of distress beacon monitoring and rescue response started in 1979 and now including 26 countries. A PLB, rather than a satellite communication device, is a distress radiobeacon. While a SEND actually sends a template text message, a PLB sends out a distress radio transmission.


    A Search and Rescue payload on board seven satellites monitors and detects these distress radio transmissions, processes the signal, and then relays it to one of sixteen ground monitoring stations. From there the signal is delivered to the relevant RCC and rescue is initiated.


    The seven satellites in the Cospas-Sarsat programme are in Geostationery orbit - that is they do not "cross the sky" but remain fixed over the same exact point on the earth's surface. While the Iridium satellites (for example) are at an altitude of about 780km, the Cospas-Sarsat satellites are at an altitude of about 35,000km. The result is that for a given area of the earth, any distress radiobeacon will always communicate with the same satellite, and that satellite's position in the sky will never move (across the entire length of New Zealand the angle to the nearest satellite only moves by less than 1 degree). In addition, because the satellite is at such high altitude, no matter where on earth you are the nearest satellite always appears close to directly overhead, meaning that it is always visible even in extremely steep terrain (in NZ the nearest satellite sits about 12 degrees off vertical).Because a PLB must meet rigorous standards, and because it is a dedicated emergency device, when it is activated the remaining battery life is known and guaranteed - all PLBs must provide a minimum of 24hrs of continuous transmission at the end of the battery's 5 year shelf life. PLBs also transmit at a much higher frequency - 5W making them less susceptible to interference and able to successfully send their signal through obstructions such as a forest canopy or if beneath a pack (all attempts should still be made to give the device as clear a view of the sky as possible).


    PLBs today transmit on the 406MHz frequency which is internationally dedicated to Distress Beacons. As well as being monitored by the SAR payload on satellites, all commercial aircraft are required to monitor the 406MHz frequency and can detect and report a distress radiobeacon signal.Finally, most PLBs transmit a second low powered 121.5MHz "homing" signal simultaneously. While the GPS coordinates embedded in both a SEND text message and a PLB radio distress signal will identify the approximate area where a signal originated, GPS coordinates are seldom precise enough for a SAR team to locate someone, particularly in difficult terrain. SAR teams are equipped with 121.5MHz receivers which can detect the homing signal from a PLB and pinpoint the beacon's position to within a matter of inches. This addition alone can reduce rescue time by hours or even days.

    The major disadvantage of a PLB is that is does not allow for two-way communication. The main disadvantage in this case is mostly psychological - receiving confirmation that the cavalry is on its way can be highly reassuring, as opposed to simply trusting that your PLB worked. However there's a good chance a SEND message won't get through at all, and even if it does there's equal chance the response won't get through, so the value of two-way communication is perhaps over-stated.

    It has also been suggested that two-way communication allows you to pass crucial information to SAR teams but personally I find this doubtful. There's very little information a party in distress can actually communicate to a rescue party that will aid the rescue, other than your location. Whether anyone is injured or not is irrelevant, for a number of reasons. To begin with, no SAR team will ever take the word of a party in distress and choose to leave equipment behind because it is not needed. Whatever you might tell them, they will follow protocol, get to you as fast as they can, and then assess you. Unless the people being rescued are medical practitioners themselves any medical assessment they provide is going to be suspect anyway. The other consideration is the nature of any injury. Medical emergencies are not, contrary to popular perception, time dependent. With the exception of a few notable examples (such as cardiac arrest and stroke) medical injuries do not get worse over time, and getting to the patient sooner does not increase their chances of survival. If you sustain a fatal injury in the wilderness, you will die. It is as simple as that. No one will ever get to you in time to save your life. And if the injury is not fatal, it's irrelevant if rescue parties bring the required treatment four hours or four days after it occurs, as long as you're protected from the dangers of exposure, dehydration, etc.


    That I can think of, there is only one situation in which I can imagine 2-way communication in an emergency being useful, and that's where a large number of people require medical treatment. Such situations are likely to be rare. The only scenarios I can really think of would be a group caught in a flash flood or a bridge collapse or similar (earthquake? Rock fall?). In those scenarios the ability to notify rescuers that it is not one or two people in distress but a dozen could have significant implications.


    I hope this clarification about the difference between a PLB and a SEND is useful, and helps people make the right decision about what to carry. Personally, for my TA adventures, hopefully in a group of 3 people, it is our intention to carry both a PLB and a SEND - the SEND for providing a track of our progress and reassuring worrying parents that we are safe and well, and the PLB to summon the cavalry if things go pear shaped.
    Rapterman, Skyloaf, sbradshaw and 4 others like this.
  7. Dan Ransom

    Dan Ransom Staff Member

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    Meh, I think that post seriously mischaracterizes the value of a satellite communicator. The main advantage of two-way communication is certainly not only psychological, it allows you to coordinate the entire SAR effort without sending the cavalry just to assess the situation. Having used the InReach twice to coordinate SARs (once for myself in remote grand canyon when I fell and had a compound fracture of my left arm that left a bone fully exposed, and once for a body recovery I hiked into in the Uintas) I can say their value both for the victim and the SAR crew is incredible. In the Grand Canyon, two-way communication allowed us speak directly with park personnel, explain to them what kind of landing area was available (so they could decide if a high angle rescue was required) and confirm the site was ready before they ever take off. It also allowed them to assess the severity of the injury, and decide if they should come that night (which would require flying a different helicopter with a different crew) or if it could safely wait until the next morning. With a compound fracture, there is an element of timeliness that mattered, but risking flying at night was not necessarily the best decision. It was 4:30 pm, the sun would set within the hour, so that communication was critical.

    Honestly, the biggest advantage of a satellite communicator is simply getting help WITHOUT calling for the calvary. Last November we were on a 25 day river trip and someone suffered a serious laceration on Day 8 of 25. We had antibiotics with us, but wanted a doctor to confirm which course would be appropriate, and have a professional opinion about risk management when it came to whether we should evacuate or not. The person stayed on the trip, ran a course of antibiotics, and continued to use the communicator to relay their progress daily to a doctor to make sure a serious infection didn't set it or become dangerous, requiring an evacuation. (And yes, we had multiple people trained with WFRs on the trip, but given how long a GC trip is an how difficult an evacuation can be depending on where you are at, staying ahead of an injury like that is key.)

    Not saying a PLB isn't a great tool, it certainly is. But that post paints a very incomplete picture of the value of a satellite communicator. Kinda surprised to see it posted here as if it's gospel.
    Last edited: Jan 26, 2019
  8. Skyloaf

    Skyloaf

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    FWIW, I had some problems with my Explorer+ that I still need to contact Garmin about. I think it's a bug with their online map overlay. When I would send people my tracks, it would keep placing me in NJ, but when I would send a coordinate for where I was it would be accurate. I also find that it is very slow when sending messages sometimes, especially if you don't have a relatively wide clear view of the sky. Still love it though :)

    In hind sight, I probably would have been fine with the mini. The explorer is rather large and bulky.
    Last edited: Jan 29, 2019
    Dan Ransom likes this.
  9. Evan Christensen

    Evan Christensen Evan C

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    How is the coverage when you are in canyons? What about skinny canyons?
    Evan
  10. Skyloaf

    Skyloaf

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    Spotty. How spotty probably depends on how deep and narrow. I would be surprised if anything would go out or come back if it's very narrow and somewhat deep. To be fair, I've only tried sending messages a small handful of times while canyoneering but a bunch of times while out in the woods. It seems to take about 3-12ish minutes to send out a text depending on where I am. If I have a sliver of sky or if I'm in a very deep wooded area sometimes it fails to send or just takes longer - probably sending when I walk under a big enough patch of sky to get enough satellites.

    Oh also! Receiving a text can sometimes be annoying. That alarm doesn't seem to turn off until you open the message. Super irritating when you're mid rappel or trying to hike but put it somewhere difficult to access in your backpack by mistake. Ugh. Maybe there's a setting to change that and I just need to spend more time reading that manual I probably threw out...

    Sent from my SM-G955U using Tapatalk
    ratagonia and Evan Christensen like this.
  11. GLD

    GLD

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    Pretty good writeup Hank. I've wondered this exact question myself and have tried to analyze it. I cannot find enough publicly available information in order to make a good assessment about which system to choose if you only want to get an 'oh shit, here's my location!' message out (which is very important, details and other factors being secondary in most cases unless comms helps you avoid the oh shit moment). I previously had a ACR PLB which has bit the dust and am trying to decide what to purchase next.

    I frequently play with satellite constellation Earth coverage and space to ground accessibiltiy and you got it mostly right, enough right for the purposes of this conversation. It's not germaine to this conversation really but not all comm satellites are in LEO. Iridium and the other major US sat-phone one are (forgot it's name, but it's the non-polar one). However, there are many in GEO (Thuraya) and even a few crazy ones with Molniya orbits that are more regional specific and are fairly elliptical (shit, we're not just dealing with circles anymore, it just got more complicated! Plus that stupid Earth keeps rotating underneath our damn orbit!).

    Same thing on the transmitter side of a link budget, but you missed a few factors on the transmitter side and totally ignored the receiver side. I am not an RF engineer. If you're an RF engineer, please step in and help me! I can fake a few of the systems engineering aspects of it though and I know a few really sharp cats who are experts in this area. We could probably plead/bribe with electronics and radio components (too bad a radio shak gift card means nothing!) to get them to help or at least review an analysis if we had enough information. If we can get spec sheets on the transmitters including EIRP, transmission frequencies, and bit rate. We also need information on the satellite side of things and that's probably harder to get.

    So a few things. First of all the beacon functionality is very different I presume than the notification functionality. I know the PLBs can do both on the signal intended to be received by the spacecraft. So even if you can't successfully send your GPS position and whatever else they will try to lock onto your carrier signal and attempt to triangulate from space where you are (they can't get particularly close even with multiple passes using the technology described, our intelligence community could if they wanted to. They can find your wifi from GEO with enough accuracy to put a bomb on it, they have very directional antennas. Note I didn't say how accurate (I don't know and if I did I wouldn't have brought this up) and you can always pick a bigger bomb for the larger uncertainty cases. Though bigger bombs mean more collateral). The PLBs also transmit at another beacon frequency that terrestrial (or I suppose helicopter, fixed wing, drone...) can find and lock on to help locate you. Think how wildlife researchers put radio collars on animals and then wander around with an antenna to track the animal.

    The other portion of this is how they are modulating their signal. You can get super fancy and do all kind of modulation, but with low bit rate requirements you don't want to. In fact, for max probability of a successful transmission you want a lower bit rate to carrier frequency. Basically, you try to hhhhoooollllldddd the information for several carrier cycles. (In that example each carrier cycle is one character, so if one of the hhhh's doesn't look like an h the receiver can still figure it out. hhqhoooolllldddd). This also helps for any multi-path errors. Multi-path is when the signal is received directly and is also received off a reflected source. This is a huge problem for GPS receivers in the 'urban canyons' which basically means surrounded by high buildings. It would also be a major problem for someone trying to receive in an actual canyon (the incoming text message or if the text systems require some sort of handshake instead of a spray and pray mode-We don't know what their comm protocols are). Transmit out of a canyon is less of an issue but without line of sight to the satellite it's going to be hard.

    OK now we can start talking antennas and power. One way to compare across amps and antenna systems is EIRP (equivalent isotropic radiated power), this is important because different antenna shapes radiate can focus power in different directions, some can focus it really well (think the parabolic dishes you've got for a directTV, even though it's receiving the idea is the same) and an omnidirectional attempts to have equal power across the entire sphere. So what are the power numbers we're getting and where are they measured? IF they are measured after the amp but before the antenna that doesn't tell us much for an RF link budget cause I still don't know the attenuation between the amp and the antenna and I don't know the antenna pattern.

    OK, we've now got the same set of issues on the receiver side, in this case the spacecraft side. What are those antenna and receiver designs?

    Some people will be familiar with this at least at a gut level. Old-timers definitely remember TV before cable or direct TV was a thing. They know the difference between rabbit ears and other more directional antenna designs. They are familiar with amplifiers and filters that were required. The new schoolers who try to receive HD OTAR are also familiar with some of these problems.

    So in summary, until we see the link budget for the entire system we have no idea which is better. We also need to understand the comm protocols (do the texting systems need a handshake and confirmation or is it spray and pray? The PLBs just spray and pray.). Yes, 5W > 2W but does that help me? So getting someone in this particular industry to explain it is probably fastest or see if they've published papers. They've already done the link budget analyses and likely field tests to verify and validate their work. However, I bet most of this stuff is considered proprietary by the companies and I'm not sure how much competitor testing they are able to do. The next best thing to do is field tests and I know of no side by side comparisons...but you better warn people about what you are doing and make sure you have approval. Activating emergency systems is no joke-you wouldn't call 911 from every desk in your office just to test.

    So I'm still torn what to buy. For maximal probability you probably want a PLB and one of the texting devices as someone suggested. I just don't like carrying two things. I think for long trips though I really like the texting devices and I'll probably purchase one of those. On a climbing trip last year we were able to get weather forecasts and coordinate with our pilot. It let us get off the glacier 2 days earlier than planned and avoid a 2 week storm that would have pinned us down. I did hear they were able to fly intermittently in the storm and pick some people up, but deifnitely no one was flying out. I also know a lot of organizations use the sat phones (including the military, but they have all kinds of other comm and beacon systems) and don't use PLBs. I don't know how a phone's power and antenna compare to the text devices, but they do use the same networks.
  12. Dan Ransom

    Dan Ransom Staff Member

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    New InReach Mini is 3.5oz. Basically inconsequential when considering group gear. Less awesome to carry both if you are solo, obviously.
  13. xenonrocket

    xenonrocket

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    Here's a post suggesting ~20dB of link margin on the ACR units: https://aviation.stackexchange.com/...-epirb-carried-by-a-passenger-aid-in-locating
    And a flyer suggesting probably about ~7dB of link margin on Iridium based units: https://www.acrartex.com/download-product-attachment?id=950
    GLD likes this.
  14. Evan Christensen

    Evan Christensen Evan C

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    Woah! Maybe everyone already knows about this product, I followed your link - a dual mode device (PRB and a two-way satellite messenger). It appears that it is only available to government. It's 12.5 oz. Anyone know when or if it is available to the rest of us or can you have someone with a government title buy it for you?
    https://www.acrartex.com/products/sarlink-plb#sthash.NeacujDy.dpbs
  15. Downward Bound

    Downward Bound

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    Saw an add for this device. It works with a phone, sends text messages via satellite, and has no monthly fee. About $250 + $0.40 per message.

    https://satpaq.com




    Sent from my iPad using Tapatalk
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  16. Canyonero

    Canyonero

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    For $1100 plus a dollar a minute you can just get a satellite phone and call 911 without any of the wacky messaging issues. You can also call your partner, order pizza, make a hotel reservation etc.

    So if you want "the best" I think that's it.
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