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GPS Location on an Iphone


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I have found 50+ geocaches to date and want to start hiding a few myself but I am a bit confused on how I work out my GPS location


I'm using an Iphone with the official Geocaching app


could anyone please explain the best way to get an accurate reading and where i find this on my iphone please?


understand everything else just a bit confused about this and want to make sure i get it right for my first cache?


Many thanks



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Well, first off, expect to get a bunch of replies from the "You should never hide a cache with a smartphone, only a real GPS" crowd. And I agree with them to an extent, if you have access to a handheld GPS unit, you will get better accuracy. But that doesn't mean you can't hide one with an iPhone. I've done it and have gotten no complaints about my coordinates.


To start with, what version of the iPhone do you have? The iPhone 4 is reportedly much more accurate than the older versions, so if you have a 4 you're in good shape.


Next, you don't want to base your coordinates on a single reading. You should average several different readings for maximum accuracy. Furthermore, if you can possibly obtain readings on a few different days and at different times if the day, and average them, that would increase your accuracy even more.


I've used a free app called Perfect Mark for obtaining my coordinates. It will automatically average a group of readings for you. You might also look into an app called Motion X. There's a free or "lite" version and a full version with more features. The free version works just fine, though, and it's an excellent general purpose GPS app.

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I think I can help you. I asked around and did searches a bit. I placed my first one with an iphone and now I am placing my second one this weekend with my Garmin Oregon. Checking the coordinates for a cache involves a little more work than you'd think - especially with an iphone. First off, finding the coordinates on the Groundspeak app: You will need a notepad. On the very first page it says... "Device's Current Location" - write the coordinates whilst basically standing over your cache (or under - you get my meaning). Next, walk away about 50 feet in a northern direction... then come back to the cache. Do this for each direction, writing down the coordinates (they'll be different). Note the time of day. Come back two different times during the same day - the satellites will be in different positions. Do the same procedure again both of those times. Note all the coordinates. Then, come back the following day and do the same procedure three DIFFERENT times than the day before. After all of this you should have 24 coordinates. Add all of these numbers together, then divide by 24. That will give you your average number. THEN... and this is the most important part - I did this. Write a friend or a nearby cacher with a real gps and ask them if they wouldn't mind coming to check your coordinates - beta test if you will. There is an error of +/- a few feet... very few cache coordinates have placed me ON TOP of a cache (only one actually). Hope this helps. I'm sure there are more qualified individuals to give you advice, but sadly there are also some that don't feel iphone-ers should be caching at all :/ OH I almost forgot... then check your coordinates on Google Earth.




Edited by Hilltop Homeschooler
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I agree with some of the other replies... to get any kind of accurate reading with the iPhone 4, you'd have to return to the locations several times and then average the readings. If you have the iPhone 3, I wouldn't try hiding a cache with it if I were you.


I have the Garmin eTrex Venture HC and it has an outstanding feature for measuring coordinates. When you are marking a waypoint, you can press an average (Avg) button and it starts taking readings over and over, automatically averaging the results. There is a readout for the estimated accuracy. Generally, the more readings you wait for it to take, the lower the accuracy. I usually try to let it get inside of 8 foot accuracy and call it good... but anything under 10 is usable in my mind. Here is a couple of early comments from one of my recent hides: "The coords are right on even in the trees." and "Coords were spot on and I made a quick find."


I do 90% of my caching with my iPhone, but there is no substitute for my GPSr for hiding a cache, and for a particularly pesky hide in a tough satellite location or when there are a LOT of places it could be within a 10 foot radius (like a nano on a bridge, for example). In these cases, a real GPSr is a big plus. Looks like the eTrex Venture HC pretty easy to come by on eBay for about $75 used. Just my $.02 ...

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My experience with my Android phones is that they're about as accurate as my old yellow eTrex (from before there were multiple models of eTrex). With my old yellow eTrex, I verify my coordinates before I publish them. To do that, I get coordinates as described above. Then I enter the coordinates into my device and tell it to go to the coordinates. I approach the cache location from about 100' away, from multiple directions. No matter which way I approach the cache, the arrow should point to the cache as I approach it. If it doesn't, then I fix the coordinates and try again.


For bonus points, you can repeat the test later, when the satellites are in a different configuration.


I would expect the same technique to work for Android phones or iPhone 4 phones, which have a GPS receiver of similar accuracy.

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If you don't know anyone else with a good GPS, or simply want some additional help from someone with experience, you could try contacting a cache owner in your area through the website and see if they would be willing to assist you in placing your first cache. I personally would not use smartphone coordinates alone to place a cache. Even if you have an app that can do GPS averaging. That is especially true if there is any sort of cover between the phone/GPS and the satellites. (aka woods) Checking the coordinates multiple times in multiple weather conditions sounds like a very good idea to me.


Don't forget, there are other considerations then just getting the coordinates. Like getting permission to place a Geocache in that area in the first place. (I know I wouldn't place a Geocache anywhere without explicit permission. And the main candidate I have in mind for an eventual Geocache location is a location that I'm sure a reviewer would want explicit permission. I don't expect I would have much if any trouble getting permission at that particular site though.)

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