chem10beaker Posted January 4, 2012 Share Posted January 4, 2012 I have tried using Google Earth coordinates (rolling the cursor over a location) with my Garmin eTrek H. I changed the settings on Google Earth to match what I thought would match the coordinate system of the Garmin. Well, at least the number of digits matched. I wrote down the lat/lon and then entered them into the Garmin following the instructions in the owner's manual (an online resource). Once out hiking I tried "Go To" one of the coordinates. I knew I was within a mile of the location. The Garmin said I was 21.5 miles away. Any suggestions? Quote Link to comment
+BBWolf+3Pigs Posted January 4, 2012 Share Posted January 4, 2012 I have tried using Google Earth coordinates (rolling the cursor over a location) with my Garmin eTrek H. I changed the settings on Google Earth to match what I thought would match the coordinate system of the Garmin. Well, at least the number of digits matched. I wrote down the lat/lon and then entered them into the Garmin following the instructions in the owner's manual (an online resource). Once out hiking I tried "Go To" one of the coordinates. I knew I was within a mile of the location. The Garmin said I was 21.5 miles away. Any suggestions? Make sure Google Earth is set to the same coordinate format as your eTrex. GC uses DD MM.mmm format (Degrees Minutes.Decimal Minutes). Your GPSr and GE can be set to DD.dddd (degrees.decimal degrees), DD MM SS (degrees minutes seconds) among others. Quote Link to comment
+PFF Posted January 4, 2012 Share Posted January 4, 2012 GoogleEarth coordinates should be accurate to within a few feet. As mentioned above, make sure you are using the same coordinate format. The best accuracy is achieved when using decimal degrees (DDD.DDDDDD) in GoogleEarth and in your GPS unit. (See "Settings" to change the GPS readout.) Zooming in increases the accuracy in GoogleEarth, as does putting the target in the center of the screen. I have been using GoogleEarth to load my GPS units for several years, with excellent success. It's not perfect, but I promise that it will do better than 21.5 miles. [Grin.] Coordinates from GoogleEarth are great for programming your auto GPS to a street address, or for taking you to the entrance to a cemetery, or finding an abandoned rail line. But this disclaimer: Use your GPS unit when setting a geocache. -Paul- Quote Link to comment
+Lil Devil Posted January 5, 2012 Share Posted January 5, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? Quote Link to comment
+The A-Team Posted January 5, 2012 Share Posted January 5, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? Absolutely agreed. I just did a test with the cache that used to be across the street. I plugged the coordinates into GE, and measured to where GZ actually is in the image. It was a difference of 24 feet. And before anyone asks, yes, the provided coordinates are bang on. I remember running into scenarios in the past where the GE difference was up to 50 feet. I'm sure the area around the Googleplex in California is perfectly acccurate, but other than that, I never trust GE. Quote Link to comment
+phlatlander Posted January 5, 2012 Share Posted January 5, 2012 "few" as in several. GoogleEarth can generally be used to confirm a location within a "few" feet but be aware that if the map tiles do not align, a few feet rapidly becomes more than, say 20 feet. BTW there doesn't appear to be an easy way to recognize when the map tiles are not aligned. As others have said, make sure both GoogleEarth and your GPS are using the same coordinate format. Quote Link to comment
+dfx Posted January 5, 2012 Share Posted January 5, 2012 "few" as in several. GoogleEarth can generally be used to confirm a location within a "few" feet but be aware that if the map tiles do not align, a few feet rapidly becomes more than, say 20 feet. BTW there doesn't appear to be an easy way to recognize when the map tiles are not aligned. Sometimes it is, at boundaries: http://g.co/maps/y8md8 http://g.co/maps/99fzt And sometimes the (lack of) alignment with road map data speaks volumes: http://g.co/maps/q5jb8 Quote Link to comment
+The A-Team Posted January 5, 2012 Share Posted January 5, 2012 And sometimes the (lack of) alignment with road map data speaks volumes: http://g.co/maps/q5jb8 Yeah, about a year ago the imagery in my area became mis-aligned, and it's still out: http://g.co/maps/qnr33 I just did a rough measurement, and it's misaligned by about 30-40 feet. Quote Link to comment
+edscott Posted January 5, 2012 Share Posted January 5, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? OK... call it "several" feet, but in areas where I've cached in the US they are not off enough to prevent finding a cache. About the same error as the normal GPS has. Quote Link to comment
+edscott Posted January 5, 2012 Share Posted January 5, 2012 (edited) And sometimes the (lack of) alignment with road map data speaks volumes: http://g.co/maps/q5jb8 Yeah, about a year ago the imagery in my area became mis-aligned, and it's still out: http://g.co/maps/qnr33 I just did a rough measurement, and it's misaligned by about 30-40 feet. Yes I see the street version is not aligned with the photo, but i've found in most areas when this happens the cache and photo agree and so the street map should be ignored. One area where the caches are aligned with the street version and thus off on the satellite image was in the area of Christchurch New Zealand where if my memory is accurate my correction number was almost 100 meters. Either way once this correction is established and applied, the maps are totally usable for caching. Since the street overlay is much more likely to be wrong, I usually don't look at that layer. Edited January 5, 2012 by edscott Quote Link to comment
+W4G_SOTAGoat Posted January 5, 2012 Share Posted January 5, 2012 Yes I see the street version is not aligned with the photo, but i've found in most areas when this happens the cache and photo agree and so the street map should be ignored. One area where the caches are aligned with the street version and thus off on the satellite image was in the area of Christchurch New Zealand where if my memory is accurate my correction number was almost 100 meters. Either way once this correction is established and applied, the maps are totally usable for caching. Since the street overlay is much more likely to be wrong, I usually don't look at that layer. I've found that the road maps are generally georeferenced correctly and that it's the image overlays that are shifted. A good example is Amicalola Falls state park. A cache there shows about 80m West of the actual location in relation to the sat image, but is correct based on the road map. Quote Link to comment
+edscott Posted January 5, 2012 Share Posted January 5, 2012 I've found that the road maps are generally georeferenced correctly and that it's the image overlays that are shifted. A good example is Amicalola Falls state park. A cache there shows about 80m West of the actual location in relation to the sat image, but is correct based on the road map. Yes it varies from one area to another. I've only done one cache in Georgia.. at some motel along I95. I don't remember it being much of a challenge, so the map there must have been close enough. Quote Link to comment
+trampyjoe Posted January 5, 2012 Share Posted January 5, 2012 For the purposes of the OP, also check your map datum is WGS84 on both. Quote Link to comment
+Ladybug Kids Posted January 5, 2012 Share Posted January 5, 2012 One area where the caches are aligned with the street version and thus off on the satellite image was in the area of Christchurch New Zealand where if my memory is accurate my correction number was almost 100 meters. Alaska's Turnagain Pass and Seward Highway passing through that area have been about 100 meters off for several years. I placed a geocache (Turnagain Path)near a rest area, averaged coordinates, went home and pulled up GoogleEarth to verify. Imagine my surprise when the coordinates put the cache inside the restroom! I had found a geocache on a trail bridge (Turnagain Pass Micro Cache)on the other side of the Seward Highway, checked its placement on GoogleEarth, and found the same offset. GoogleEarth and Garmin maps are similarly off in Valdez and Cordova, Alaska, but will put you on the exact spruce tree in the Anchorage bowl. So, use GoogleEarth maps and imagery with caution... Quote Link to comment
+NYPaddleCacher Posted January 5, 2012 Share Posted January 5, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? Absolutely agreed. I just did a test with the cache that used to be across the street. I plugged the coordinates into GE, and measured to where GZ actually is in the image. It was a difference of 24 feet. And before anyone asks, yes, the provided coordinates are bang on. I remember running into scenarios in the past where the GE difference was up to 50 feet. I'm sure the area around the Googleplex in California is perfectly acccurate, but other than that, I never trust GE. I found a cache at the Googleplex in Mountain View a few years ago prior to an all day meeting I had there. For some reason my GPS was sending me all over the place and it never occurred to me to go inside, fire up my laptop, and look up the location on Google Earth. Quote Link to comment
+power69 Posted January 6, 2012 Share Posted January 6, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? OK... call it "several" feet, but in areas where I've cached in the US they are not off enough to prevent finding a cache. About the same error as the normal GPS has. google earth is waaaay more accurate than iphones. Quote Link to comment
+edscott Posted January 6, 2012 Share Posted January 6, 2012 ... remember the coordinates on Google Earth are only as "good" as the GPS or iphone used by the CO. Quote Link to comment
+NYPaddleCacher Posted January 6, 2012 Share Posted January 6, 2012 GoogleEarth coordinates should be accurate to within a few feet. What have you been smoking? OK... call it "several" feet, but in areas where I've cached in the US they are not off enough to prevent finding a cache. About the same error as the normal GPS has. google earth is waaaay more accurate than iphones. Coordinate accuracy is only one part of the equation. It's the inconsistency in the satellite imagery that, to me, leads me to the opinion that Google Earth should not be relied upon to provide navigation data. I've posted images of a few examples in the past, so won't do it again but there a lot of places in the world where the resolution of the imagery is just not good enough to identify a feature that can be associated with a set of lat/long coordinates. Because the imagery is just a photograph, anything that gets in the way between the camera and the ground is going to significantly impair ones ability to associate a specific location with lat/long coordinates. Just take a look at Google Earth images for Costa Rica and you'll find large portions of real estate entirely obscured by clouds (a common occurrence in a rain forest). Since Geocaching is a worldwide game a method of obtaining and navigating to a set of coordinates that is reliable almost anywhere in the world is necessary. Quote Link to comment
+edscott Posted January 7, 2012 Share Posted January 7, 2012 I agree that all Google photos are not uniformly accurate or easy to use due to misalignment or poor visibility. They are becoming more difficult to use now that they are posting many photos in full foliage which lessens the detail that can be used for navigation. In spite of these inconsistencies, the photos I've seen in the areas where I cache will still allow me to get as close to the cache as I could get using a GPS. Quote Link to comment
+BBWolf+3Pigs Posted January 7, 2012 Share Posted January 7, 2012 I agree that all Google photos are not uniformly accurate or easy to use due to misalignment or poor visibility. They are becoming more difficult to use now that they are posting many photos in full foliage which lessens the detail that can be used for navigation. In spite of these inconsistencies, the photos I've seen in the areas where I cache will still allow me to get as close to the cache as I could get using a GPS. I'm relying more on Bing Maps' Birds Eye View. In my area they get in pretty darn close, and most of the imagery is in the fall, so less tree cover! Quote Link to comment
diggingest_dogg616 Posted January 8, 2012 Share Posted January 8, 2012 So I tried this today. Someone pointed out some stuff that isn't marked on Google Earth and then my dad read the coords off to me. Today, I went on a hike and had those coords in my GPS and everything was close enough that I could find it (petroglyphs and pictographs). I even transferred my route or track log or whatever it is to my computer and the spots I punched in before hand matched up perfectly with where I'd veer off to find something (someone else had different coords, so I was following them). I'd loose my signal because I was in a canyon and if I got up on a wall then it'd just crap out, but when I had a clear view and good accuracy then I'd check my GPS. Overall, I was rather pleased I think if you zoom in and are very specific about where you want to end up, then you should get close enough. There are issues with map tiles and so on, so I'm not going to say it's perfect by any means, but I think if you're just needing to be in a general sort of area then some of the time it should be okay. Quote Link to comment
+phlatlander Posted January 11, 2012 Share Posted January 11, 2012 Today I went out to verify the precision of my week-old Oregon 550. I also brought along my trusty Nuvi 1350 which I have been using for paperless geocaching. I know where there is a Geodetic Survey point and so my terrier and I went out for a morning walk to: Name: PIER A Zone: 14 E 609386.573 N 5523535.96 Zone 14 This translates to : 49.854247 / 97.478251 The Oregon 550 read: 49.854250 / 97.478250 The Nuvi 1350 read: 49.854250 / 97.478267 Just for information here is a GoogleEarth view of the survey point. The red arrow points to the exact physical location while RefPt is the kml (gps) location. Given all the possibilities for error (photographic errors, mathematical rounding errors, and likely a host of others) the accuracy is pretty good. All this to say that GoogleEarth is a good reference but the only sure things in life are still death and taxes... (I did several recalculations and the answer varied between 45.71' and 52.63' (GoogleEarth ruler) Quote Link to comment
diggingest_dogg616 Posted January 11, 2012 Share Posted January 11, 2012 That's very interesting! Thank you for doing that! Quote Link to comment
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