GPS Advice

Information, questions, and personal issues with Recreational Gear. This includes, hiking boots, GPS, backpacks, kayaks, climbing gear, etc. Can also post items you would like to sell.

Re: GPS Advice

New postby Jon » Thu Jan 17, 2013 12:17 pm

I also have a samsung galaxy and took a look at that app. Seems pretty neat.

In a semi-related story, you can't always trust a cellphone's GPS (no matter how accurate it might seem)

http://www.cbsnews.com/8301-205_162-57564153/apple-iphone-tracking-app-sends-police-to-same-las-vegas-man/
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Re: GPS Advice

New postby mike » Thu Jan 17, 2013 5:40 pm

Didn't mean to confuse the subject with "White Space" frequencies. White space frequencies will just mean that you can stay connected continuously and download stuff as needed. That would be an advantage over GPS's.
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Re: GPS Advice

New postby kennykb » Thu Jan 17, 2013 11:26 pm

Jon wrote:I also have a samsung galaxy and took a look at that app. Seems pretty neat.

In a semi-related story, you can't always trust a cellphone's GPS (no matter how accurate it might seem)

http://www.cbsnews.com/8301-205_162-57564153/apple-iphone-tracking-app-sends-police-to-same-las-vegas-man/


That's tower triangulation, not GPS. Different technology altogether.
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Re: GPS Advice

New postby Jon » Fri Jan 18, 2013 5:00 pm

well not actually. They cite how it was a GPS fault, and also the towers. It is a combination of the two, and what phones will show when they can't get a good fix. The article says it was defaulting to a general location when the GPS fix might not have been optimal. If you're lost in the woods in a valley and it just defaults to some location, however you are not aware that you didn't get a good fix. One could assume that what was being shown on the phone screen was true, when it could actually just be the center of some circle like they describe in the article.

I'm just saying that GPS app on phones might be a semi-OK solution, however there are more bugs with doing that than a dedicated GPS unit.
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Re: GPS Advice

New postby kennykb » Sat Jan 19, 2013 12:44 pm

Uhm. Yeah. Another good reason to leave the thing in airplane mode: it can't get a fix from the towers, so it's immune to that particular lie.

But for that matter, do you know what does your dedicated GPS shows when it can't get a good fix? How good a fix does it consider 'good'? Do you know how to read its accuracy indication? Garmin reports Circular Error Probable: if it is reporting an accuracy of 10 m, for instance, that means that 1 time in 100 you'll have a position that's over 25 m off. I think it can be configured to report Dilutions Of Position (VDOP, HDOP, GDOP, VDOP). Have you ever tried measuring your receiver's repeatability? (If you do, you'll learn a lot about how they behave.)

Primary navigation is map, compass, eyeball and wristwatch. For me, GPS is mostly a tool for track recording (for cyberhiking and mapmaking later!) and for cheating a bit on finding waypoints (geocaches, canisters, plane crashes, ruins, ...). Since it's generally not a safety issue if it fails, I'm content with a toy one. But I've been quite pleasantly surprised at how the latest generation of the toy performs.
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Re: GPS Advice

New postby Jon » Sat Jan 19, 2013 3:03 pm

nope nothing in the literature on my unit about those specific acronymns, and nothing in the options. It just says "high sensitivity receiver" <10m 95%. When my unit is getting a poor reception it just asks me to find satellites again, and will do that until it gets a good fix. I've never had my unit just "default" to some other random spot because it couldn't figure out where I was. If there are no satellites at all (like if you're inside) it simply asks to operate without satellites and then it doesn't know where you are. I know that it doesn't get every location exactly correct. Like when you hike up a trail in the morning and hike down the exact same trail the track might be about 10-15 feet apart from eachother, even though I know It was the same spot.

However on my garmin I can enable WAAS, which to my knowledge is a feature that almost all cellphone GPS's lack. It greatly improves the accuracy of the unit. Says with that enabled it's <3m 95% It got rid of some of the spikes in my vertical profiles, from when it mis-calculated my altitude.

Maybe I'll purchase that app, and then track a hike using my galaxy and my gps, having them in the same spot and see how they compare side-by-side? It's only $9.99 right? Also what format does it save your tracks in? Can I export them to other programs or Google Earth formats or are you only able to view it in the backcountry nav program?
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Re: GPS Advice

New postby AntLive » Sun Jan 20, 2013 11:36 am

Well that is a lot to consider for sure. I do like the idea of using the smartphone and it does seem to be something that will be used more and more. However my smartphone (iPhone) doesn't have many good hiking tools. It seems that the android phones have better outdoor activity apps. I have an app called MapMyHike. This app just doesn't have what I'm looking for. I think I have narrowed my search down to the Garmin Oregon series. The one think I would like to find out is if all of the Oregon units have the trip computer. I looked on the website but Garmin didn't seem to give that info. I am going to call them or go see a dealer. And Jon, thanks for the websites for the maps. that will come in handy in the future. You personal website was interesting too. I liked the pic/view of Phelps. I went to hike Marcy on April 29, 2012. I thought after such a warm winter I would be safe to hike it. Well it snowed the night before and most of that day and we decided to get to the dam and decide then. We met another hiker named Stephen and told us he was going to Phelps. We decided to join him. I just remember it appearing to be strait up. After viewing your website it helped me to appreciate the elevation gain of Phelps even more. (Marcy is now slated for this summer)
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Re: GPS Advice

New postby kennykb » Sun Jan 20, 2013 2:17 pm

Jon wrote:nope nothing in the literature on my unit about those specific acronymns, and nothing in the options. It just says "high sensitivity receiver" <10m 95%.


Most GPS's have the numbers on the same screen that displays the satellites in view. There will usually be an 'accuracy' or 'CEP' number, and a set of "DOP/HDOP/VDOP" numbers (or some such).

Jon wrote:However on my garmin I can enable WAAS, which to my knowledge is a feature that almost all cellphone GPS's lack. It greatly improves the accuracy of the unit.


That it does! Cell phones usually do it a different way, using 'A-GPS' (assisted GPS). WAAS uses a geostationary satellite to send correction data for the GPS signal. A-GPS downloads the correction data from the cellular network. The information it gets is wonderfully accurate for about six hours, and usable for about 24. What I've done a few times is to get up on a peak where there's a cell signal, send my wife a 'we made it' text, make sure it's got the updated data, and shut it down again.

Even with WAAS, GPS altitude determination is dodgy. The best handheld GPS units have barometric altimeters integrated in them. (Obviously, phones don't.)

Jon wrote:Maybe I'll purchase that app, and then track a hike using my galaxy and my gps, having them in the same spot and see how they compare side-by-side? It's only $9.99 right? Also what format does it save your tracks in? Can I export them to other programs or Google Earth formats or are you only able to view it in the backcountry nav program?


Yeah, it's $9.99. The track export is either KML (Google Earth's favorite) or GPX (which is fairly universal). You can also try the free version of OruxMaps, or a free app like MyTracks to record tracks - but I don't like them in the field, they're missing features that I use. None of the apps has a really good satellite display, so I use the free 'GPS Status' app for that.

It's not as good as a dedicated GPS unit. But I'm surprised at how good the phones are getting. My previous phone (a Samsung Intercept) was nearly unusable for the purpose.
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