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  1. #1
    Senior Member himespau's Avatar
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    GPS for multiple purposes

    My wife and I are research scientists (microbiologists). We're starting a project for some undergraduates at our university that will involve them going out and taking samples at various sites. We were both kind of thinking that it'd be good for them to use a GPS to record the location of the samples in case we want to go back and do a longitudinal study at one of the sites or go back to that exact location for any reason at a later time.

    Since this project is going to be funded by a grant we have, the first thought was to buy a GPS of some sort with the grant. The thing is, they're going to be using it for sampling for about 3 weeks and then it might not ever be used again (there might be others in our department who have one they've bought used a few times and then put in a drawer and I'm going to ask them first to see if there's one laying around). We might do this every year if it's a successful training project, or it might be a one time deal. So I was thinking that this might be a good time for me to get a moderately inexpensive GPS for my bike out of my own pocket and just let the kids use it for those 2-3 weeks (ethically and legally I couldn't use one bought on the grant on my bike for personal use).

    If I decide to go the buy one for my own use and let the kids use it for their 3 week sampling exercise, can anyone point me in the direction I need to look? It needs to have precise location tagging (obviously), and beyond that I don't really need a lot. Would like a mapping feature for rides so I could design a route beforehand and it'd tell me when to turn. Speed and distance, obviously. If it could hook into a cadence transmitter, that'd be great, but not essential. Same for altitude and/or slope. Mountable on bars would be essential, of course, but I'm assuming there's a mount for just about everything these days. I'm not a powertap kind of person, so I don't need that sort of functionality. Since I'd be having undergrads use it, it'd need to be fairly rugged and not too outrageously expensive that I'd be out too much if it got broken/lost (I'd love turn by turn directions after input of new address on an edge 800, but that fails this price requirement). Anybody have any suggestions?

    I'm in no way shape or form a brand snob that needs something from garmin and would be perfectly willing to go with one of those deal extreme models if they meet my requirements and are reliable enough.
    Punctuation is important. It's the difference between "I helped my uncle, Jack, off a horse" and "I helped my uncle Jack off a horse"


  2. #2
    The Recumbent Quant cplager's Avatar
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    If you already have a smart phone, it probably has GPS and there are several free apps you can get to do exactly what you want. Do keep in mind that there is a resolution to GPS (~ 10m or 30ish feet) and that may or may not limit the usefulness of what you're trying to do (you can play some tricks by using a known easily found benchmark location and also keeping the relative position to said benchmark).
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  3. #3
    Senior Member himespau's Avatar
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    No smart phone, but that is a good point as most of my students probably do (and maybe I can get those who don't to pair with someone who does), and there's nothing really wrong with my wired computer that I have now.
    Punctuation is important. It's the difference between "I helped my uncle, Jack, off a horse" and "I helped my uncle Jack off a horse"


  4. #4
    Senior Member dougmc's Avatar
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    I've found a GPS to be very useful in geotagging pictures, such as these pictures I've taken of the Austin area while on a bike over the years.

    The GPS is keeping track of my path and has the time saved with each data point, and my camera stamps each picture with the time, so it was just a matter of some perl to calculate the coordinates of each picture and add it to the map. I was even able to go back to old pictures and geotag them because I had GPS data for my older rides before I started doing this.

    Really, the biggest problem is the clock drifting on the camera -- the GPS clock is always right on, but the camera clock isn't always right. But if I take a picture of the GPS's clock during each ride, then I can adjust the time stamps on the pictures appropriately and then tag each picture accurately.

    If you take a picture of each sample's source and have the GPS recording at the time, you should be able to work out the locations later. The stuff I wrote to do this is probably a whole lot more complex than is needed, but there is software out there that will do this for you.

    As for what GPS to use for all of this, I used an Edge 305 and 705, and I've also used the tracks recorded by my car's Nuvi GPS to do exactly the same thing with my family vacations. I imagine any GPS that keeps your track ought to work.

  5. #5
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    I'd personally recommend the Garmin etrex 10, 20 or 30. It has all the functionality you say you desire and can be found fairly cheaply on eBay (used). The 10 is the base model while the 30 can use a cadence sensor.

    It might be possible to use a car-style GPS BUT battery life might be an issue (most won't last more than 4hours no matter what). That's part of why I like the etrex 10/20/30. Takes AA batteries and lasts 16-20 hours.

    My recommendation is based purely on functionality and personal in-use reliability, not manufacturer snobbery. Also, I got a great deal on a refurbished etrex 20 which has more than met my needs and expectations.
    Last edited by 20_700c; 10-23-13 at 08:08 PM.

  6. #6
    Senior Member Looigi's Avatar
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    Smart phones have GPS, records tracks, stores POIs, logs pix as a function of coordinates, etc. No data plan, cell plan or cell reception is needed to perform these functions. Apps and maps can be download while connected via WIFI and tracks, POIs, pix can be uploaded via WIFI.

    OSMand is an app that allows downloading OS maps and I believe has all the functionality you'll need.

  7. #7
    Senior Member dougmc's Avatar
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    Quote Originally Posted by Looigi View Post
    Smart phones have GPS, records tracks, stores POIs, logs pix as a function of coordinates, etc. No data plan, cell plan or cell reception is needed to perform these functions. Apps and maps can be download while connected via WIFI and tracks, POIs, pix can be uploaded via WIFI.
    Note that I've found this to be quite unreliable.

    They generally have the capability, yes, but they leave the GPS turned off to save battery when possible, so when you do take a picture it has to turn the GPS on real quick and use it to try and get a fix, and it seems that if it can't do so quickly enough it'll use coordinates from cell phone or wifi location instead, and that is much less accurate. The cell phone tower triangulation is especially bad and can be like a quarter mile off. Which may or may not be acceptable.

    And looking at the location EXIF data from my iPhone 5's pictures, some of it's really wonky -- like in other cities, dozens of miles away. No idea why. At least in some of those cases, the coordinates were truncated -- like a latitude of 30 N rather than 30.2513 N, but not all.

    I've found similar problems with the two cameras I've got that have built in GPSs -- they're "lazy" about getting GPS data and will update it it infrequently, and if the camera shuts off (often just due to inactivity) it forgets all the GPS lock information it had before so it takes a while to find out where it is again. One camera will just keep using the old location for a while in that situation, and the other just won't record any location data.

    I've done a lot of this, and I've found nothing that works as well as 1) having a GPS keep track of your path data, and 2) either keeping the camera clock exactly right or knowing exactly how far it is off so that you can correlate the two. Now, perhaps the professional camera equipment works better than the point and shoots with gpses that I've used, but I haven't tried it. (For example, I'd hope the Canon GP-E1 would work well.)

  8. #8
    Senior Member Roosterbird's Avatar
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    Garmin Dakota 20 and use it with ridewithgps or garminconnect with your bike. https://buy.garmin.com/en-US/US/on-t...prod30926.html

  9. #9
    Formerly Known as Newbie Juha's Avatar
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    dougmc nailed it IMO. Dedicated GPS devices are better at what they do. If exact positioning is a priority - as seems to be the case here - I would take any GPS with mapping capabilities. Possibly something that works with AA batteries so you don't have to replace proprietory built-in batteries after a few years of sporadic use and shelf storage.

    --J
    To err is human. To moo is bovine.

    Who is this General Failure anyway, and why is he reading my drive?


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  10. #10
    The Recumbent Quant cplager's Avatar
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    Quote Originally Posted by dougmc View Post
    Note that I've found this to be quite unreliable.

    They generally have the capability, yes, but they leave the GPS turned off to save battery when possible, so when you do take a picture it has to turn the GPS on real quick and use it to try and get a fix
    With android phones you have more control. But even with an iPhone, if you turn on a tracking app that actively uses the GPS, then you're golden.
    http://Charles.Plager.net
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