SFR: What are the current good options for a hiking/fishing GPS?

Discussion in 'Fly Fishing Forum' started by Josh, Jul 9, 2013.

  1. Kent Lufkin

    Kent Lufkin Remember when you could remember everything?

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    I still have the notes from a fascinating presentation on GPS technology dating from right after the military de-scrambled GPS satellite signals for public use.

    GPS satellites are in so-called geosynchronous orbits - their position about 24,000 miles above us is stationary relative to the earth. There are 24 US GPS satellites, one for each time zone. So on flat, unobstructed land, at least several are in 'view' at any given time. Mountains and trees can block receivers from getting the signals sent by satellites, especially from those further towards the horizon in either direction. Most receivers require signals from at least 3 satellites in order to triangulate position. Fewer than 3 sets of signals means no triangulation, thus the receiver isn't able to indicate its position.

    That's why receivers with more-sensitive and powerful antennas are more accurate. Some receivers like the Garmin 60 and 62 series actually have jacks that allow separate antennas to be attached, vastly improving their accuracy.

    BTW, GPS-calculated distances can be pretty accurate in X and Y axes (down to as fine as 2-3 meters). But the Z axis or elevation, is much less accurate which is why most units still rely on a barometer to calculate altitude.

    My notes don't indicate how flocks of birds might influence signal accuracy!

    K
     
  2. KerryS

    KerryS Ignored Member

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    I see a new twist added to the remake of The Birds which is due out within the next couple of years.
     
  3. Nicolas Eckhardt

    Nicolas Eckhardt Member

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    If you want to have accurate Z elevations you need to use a differential GPS unit which is either connected to a real-time GNSS network, such as Washington State Reference Network (WSRN), or you post process the collected GPS information using the same reference system through data files. In many cases, depending on how and when the data was collected, you can elevation down to about +/- 6 in to 1 ft and XY to less than that. Then again you would need to have a GPS unit such as the Trimble XH coupled with an external antenna or some kind of Real-Time Kinetics (RTK) unit. Neither of which are cheap.
     
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  4. David Loy

    David Loy Senior Moment

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    I bought a Garmin GPS76 a few years ago, and have uploaded topography for most of the state (all except some of the desert regions). It is a very handy tool and has the compass and altimeter. I expect there are better units out there now. But, I am a map and compass guy first, so the GPS generally stays in the pack, as backup I suppose. I have it so I bring it (& extra batts).
    Nicolas, I can tell you're in the survey business too. I still think the handheld GPS altimeter is a good tool. Even 20 or 50 feet of elevation accuracy is helpful when you're finding your position on a map. I've used the compass in my Garmin enough to appreciate my Silva Ranger. I've used the Silva to locate our position in a whiteout (observing the bearing of a shear wall) and then plotted our route to the summit of Mt Olympus. I'll never hike without it. I've also used it (& hipchain) to survey creek routes (between two knowns, fun to see how well you close), and for preliminary timber inventory on projects. The GPS could do much of that (& no doubt better) but I'm old school. Old something anyway.
     
  5. Josh

    Josh dead in the water

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    Excellent advice from everyone.

    It should be noted that this is more of a "fishing hole tracker" for me than a "how do I not get lost" tool. But all the comments about not relying solely on GPS are spot on for anyone who finds this thread via google.

    In that vein, I'm not sure that touchscreen is a killer for me. The amount of times that I would want to use it and wouldn't be able to take off gloves or dry my hands are almost zero. Still, a point worth noting.
     
  6. Nicolas Eckhardt

    Nicolas Eckhardt Member

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    I am actually a GIS Analyst but part of my duties include doing topographic surveys using a total station, most of the time along creek routes, and I have used differential GPS unit to obtain positional data. I agree with you on the GPS altimeter. For hiking and fishing purposes +/- 20 - 50 feet overall is pretty good and enough information. Sometimes we expected more from these units than it is possible to obtain. The Silva Ranger is a good compass and definitely good to have as a backup for the GPS compass. I have one as well. It is amazing how accurate those old timber surveys and PLSS surveys are given the type of equipment used. Nothing wrong with the old school way.
     
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  7. David Loy

    David Loy Senior Moment

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    Oh no. A GIS analyst? (The dark side!) We have issues.;) The world is flat.
     
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  8. Nicolas Eckhardt

    Nicolas Eckhardt Member

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    Haha. Good one. Someone has to make sense of all the data collected on the flat world. ;)
     
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  9. Richard Torres

    Richard Torres Active Member

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    LOL!

    I guess I should have been more descriptive. That's what I say when talking about satellites at our office.
     
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  10. Richard Torres

    Richard Torres Active Member

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    You are right Nicolas. Or we just run a level traverse between known USGS benchmarks within the area we are working with conventional equipment.
     
  11. Richard Torres

    Richard Torres Active Member

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    I agree Josh, IMHO a touch screen works for dry applications. Myself being hard on electronics (2 phones toasted by moisture) I prefer something I can get dirty or wet without worrying about it.

    The collectors we use at work are moisture resistant but not water proof. We still have to air them out at the end of the day and with the weather we have here sometimes the touch screens get fogged up, making them temperamental.
     
  12. Richard Torres

    Richard Torres Active Member

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    I've done my share of sidewalk collection (keeping up with Gov't ADA requirements) in this area. Although it's been a while, collecting data in a creek bed or body of water is more to my liking!
     
  13. Nicolas Eckhardt

    Nicolas Eckhardt Member

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    A lot of the areas where I have done work are not close to any easily obtained benchmarks that could easily be done by a level traverse. In most cases I have to set my own benchmarks and assign my own starting X,Y, Z values. But you are right running a level traverse is another way to do it with known points.
     
  14. Nicolas Eckhardt

    Nicolas Eckhardt Member

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    There were a couple of intersections in my neighbourhood that were just redone to comply with ADA rules. I do remember seeing them survey it and thinking it was interesting. I've never done it. Collecting data along a creek bed is fun but definitely presents its own unique set of challenges. I look kind of strange using a total station in waders.
     
  15. Brian Miller

    Brian Miller Be vewy vewy qwiet, I'm hunting Cutthwoat Twout

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    I won't say I disagree with Kent because I don't have a dedicated GPS to compare it to but I've had great results with two Android phones (LG Dare, now Moto RAZR Maxx) running the Orux Maps GPS app. I use another app to create custom maps from a USGS master and upload them to the phone for offline use. Orux shows and records the route I have travelled, plus gives voice distance and speed hacks every mile. I usually travel to and fish water in dense forests and deep ravines and I have yet to not get a satellite lock. If I shut down my BT and cell sync functions my 3200 mAh battery lasts all day, and I carry either a 1600 mAh charger on all trips plus a solar charger on overnighters. If I am going off trail for any distance I'll carry map, compass, and barometric altimeter that is periodically calibrated at every known landmark elevation.