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Caches Offset With Google Earth/kml Linking


ibycus

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Anyone else notice a slight 'shift' in caches between where they should show up relative to ground and where they do show up when viewing through the KML linking with google earth? I've heard from some folks in Edmonton seeing the same thing as I see in Calgary (Calgary has some other data alignment issues in the west side, which is what I assumed it was originally, but they see it up in Edmonton too.)

 

I'll see if I can find some specific caches to check it on...

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The tiled images in Google Earth are off. This puts the image of the actual location in a different spot. You can see this at the edges of the tiles where roads don't line up.

 

So, no, you can't use it for geocaching in the sense that you can tell yourself it's next the third tree from the fountain, because it could actually be in the fountain!

 

The reason the tiles are off is, I thinking anyway, is because the images are from different sources and it would be a monumental task to straighten everything out. If you are looking for more accurate aerial maps PhotomapUSA is a better bet.

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The tiled images in Google Earth are off. This puts the image of the actual location in a different spot. You can see this at the edges of the tiles where roads don't line up.

Yes and no. Yes in the sense that there are errors in the Google Earth data set (just take a look at the west side of Calgary, around 51N 114W). No, in that this isn't the problem in this case:

 

1. GPX overlayed with the same data shows the cache in the right place (and the KML linked one in the 'wrong' place.

2. Google Maps (which I'm guessing uses the same dataset) shows the cache in the right place.

3. At high zooms, caches seem to jump around.

4. Jeremy said so (see above). My guess is its to avoid data scrapers.

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1. GPX overlayed with the same data shows the cache in the right place (and the KML linked one in the 'wrong' place.

Well, that was my take considering my own observations show the GCkml and my own home-grown kml show one my caches in approximately the same spot and about 100' from the actual location.

 

When I get home I'll do a direct overlay to see. Maybe I was just "lucky" in the GCkml wasn't very far off that time and looked like it was in the same spot.

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If you are looking for more accurate aerial maps PhotomapUSA is a better bet.

USAPhotomap isn't perfect either (Terraserver actually) as I've discovered caching along the southern Oregon coast.

 

Check out the image misalignment near Port Orford, OR

 

There are caches along this area of high bluffs that show up out in the Pacific!

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Things are much clearer now. I too had noticed that not only were the caches off in the KML files but that when using the network KML file caches would jump around when zoomed in close. I also noticed that a reason for making a bookmark list selection the default for further bookmark adds was "This is great for the Google Earth feature and/or reduces the time to add bookmarks." Now I understand, the intent is to use the networked KML file to browse for caches in an area. Click the bookmark link in Google Earth to add the caches you're interested in to a bookmark list, then run a pocket query on that bookmark list to generate a GPX file. This file can be loaded into Google Earth to see an accurate view of the caches and can be loaded in your GPS and you're ready to go. Cool B) . Another reason for being a Premium member.

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Yep. It is intentional. Google Maps are for viewing caches, not using the KML files for caching. That's what the bookmark list link is there for.

Excuse my ignorance, but what good does the "Download Google Earth KLM" link on the bookmarks? Now I have to start putting all the cache I want to view in Google Earth in a bookmark? ;) No thanks! I'd rather use GSAK and export as GPX for importing into Google Earth!

 

I would love to be able to use the Google Earth Network Link feature to help me figure out where a new cache is before I head out the door. I need to know on which side of the creek it is, not just ballpark where it is! When a new cache comes out, I'll have to keep doing what I used to do, which is download the single GPX file to GSAK and export it to GPX for Google Earth viewing!

 

So in a sense, while the new feature is COOL :P (thanks for adding it), it is almost useless for practical use. :lol:

 

B) On a different note, I'd like to make a more general comment about the site: The site is very technical (uses lots of technical terms) and layout is not always intuitive or easy to figure out. I haveno problem with it because I am a software engineer and all this stuff is second nature to me, but I introduced and trained a lot of people to geocaching and they are confused and have difficulty remembering how to do things or where things are. B)

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So a random number of feet is added by Groundpseak to the cache location to generate the network KML file?

 

edit: Never mind, I think i see the difference..Maps is just more "accurate" than Earth which suffers from bounce.

Edited by maingray
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The reason why this was done was because in essence the KML file is a "look" into our entire database. So instead of someone scripting something that just moved along a route and capturing all that data we "obfuscated" the lat/lon so you get a general idea of where the cache is. I think that the KML viewer is excellent for just looking in area and determining where you want to go and bookmarking the caches. Then you can run a pocket query and have the exact cordss that you need.

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Looks to me like the coods are randomized within a certain radius every time the view is changed (zoom/pan), even if only slightly. I just measured one of my caches and the deviation was .2 miles from 400 feet up. That's quite a lot.

 

Otherwise this new feature is most excellent. Great work guys.

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When I get home I'll do a direct overlay to see.

Not that I have to confirm what you guys are saying, but I see it now. I turned on my home-grown list and called up a GCkml and sure 'nough, they didn't match.

 

I like it. Hopefully because of the randomization this feature with stay available to regular members.

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If there's any way to refresh this "jumping" such that you can ask to see the location and it pinpoints a random location *near* the right answer but still within a certain range, then if you sample this spatial jumping a given number of times, the samples will all average to be the origin of the circle used to randomize the location.

 

Your randomization is handcuffed by the fact that the KML file you're generating needs to still be *somewhat* accurate, so the radius of jumpiness can't get out of hand. This lessens the number of samples necessary before the average finally hones in on the center of the circle.

 

Essentially, you can do what some GPSrs did before SA was turned off, but instead using the network KML file(s) to undo your randomization obfuscation.

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If there's any way to refresh this "jumping" such that you can ask to see the location and it pinpoints a random location *near* the right answer but still within a certain range, then if you sample this spatial jumping a given number of times, the samples will all average to be the origin of the circle used to randomize the location.

Heh. No. That isn't correct. Because of obfuscation I can't explain further.

Edited by Jeremy
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You can refresh all day long to try and figure out the "right" cords if you like.. but you'll hit your 200 views pretty quick then you'll just have to sit and be bored till the next day.

And in the time you spent messing with GE you could've gone out and physically found the cache already! B)

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How about premium members get un-obfuscated coords in their Google Earth maps? That would be a nice premium feature, huh?

You can use a GPX for that same effect.

 

If the were unobscufated in a KLM file, then it would be like getting a file of core GPX (or LOC) info for free.

 

Personally, for what I use this for it works just fine as is. Appreciate it!

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You can use a GPX for that same effect.

Oh. Never mind. I only downloaded Google Earth today, and I didn't realize that.

 

So premium members really don't need the "live" KML link; in fact, since it shows all the caches (including the ones you've found) it's actually less useful...

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Thanks Moose, that's pretty much why we randomize the coords.. max of 150 caches at once times 200 views a day would basically give you access to 30,000 caches with "perfect" coords.

 

outshines a PQ with its max of 500 B)

My answer to that is "so?"

 

He said it could be a PM feature. I can imagine the "obfuscating" adds a bit to the server load. By allowing a PM to use a different SQL query you could actually use that to your benefit. You're already commited to the server load and bandwidth, what not allow PM's to get perfect coords? They're gonna get them anyway.

 

Additionally, don't count on folks not being able to figure out your obfuscation scheme. I'm already seeing a pattern because I'm comparing the results to known locations. Not saying that I've got a solution or even if there is a solution as I've detailed a method completely hide the true location a while back and I'm not certain you guys aren't using it. My point is, there are plenty of folks that really like puzzles. This might be something worth solving.

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It was all interesting for the first 10 views... but I'm finding Google Earth to be a bit of a pig. Don't take that as a slam on Groundspeak... it's Google's fault. I just don't see myself using this new feature very much since the application required to use it less than great. Maybe I just had very high expectations since a lot of people talk of GE like its the best thing since sliced bread. Was the interface designed by Fisher-Price?

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I like it for an easy way to find a spot where there is access to several caches. For instance, on Monday after work, I had to go to a place to pick up trophies for a disc golf league I run. I looked on Google Earth for a park nearby the location that had a couple of cache's which I then booked marked in cachemate on my palm.

 

I'm not all that interested in Google Earth getting me within 5' of a cache. For me its an easy way to get a visual on a specific area and the cache's it contains.

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I like that I can easily and rapidly pan around and look for clusters of caches. With the geocaching.com maps, you'd wait for the server to create the map, then wait for it to redraw every time you panned or zoomed. Very time consuming. In GE, you just pan and go. Much more dynamic. The feature I'm waiting for, with this networked KML, is the ability to view maps without caches I have already found. I thought Jeremy or Raine said this was on the way, and they were starting out simple to see how the feature works and what kind of load the servers are getting. About the geocaching.com maps, any plans to match the panning ability of Google Maps? Would that require using AJAX?

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As with any software release (except for Microsoft maybe) We plan on adding more features and more filtering to the Network KML. If you have suggestions for feature you would like to see, let us have it! As far as integrating with Google Maps I'll defer that conversation to Jeremy :(

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As someone who finds caches with maps and aerial photos, I can tell you that Google's products have a degree of randomness anyway. Some areas in WGS-84, others in NAD-27, areas where the various layers don't match, areas where the layers are fudged together because they saw something was wrong but not what was wrong, and areas where they don't offer the resolution needed to be useful. So Google is only good for general observations anyway. Putting the coords off by a decimal place or two doesn't hurt anything because Google is off by the same anyway.

 

I sometimes wonder if Google is intentionally obfuscating its data at their end.

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If you have suggestions for feature you would like to see, let us have it!

I'd like to see a preview of a PQ so I know what I'm getting before I commit running that PQ for the day.

A little off topic but you can preview a PQ.

...umm...as a KML file in Google Earth.

ohhhh.. I misunderstood. sorry. :(

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The tiled images in Google Earth are off. This puts the image of the actual location in a different spot. You can see this at the edges of the tiles where roads don't line up.

 

No, the maps are right in GE, it's the cache locations that are off, and intentionally, apparently. If I enter the coordinates of some of my caches, they're dead on. In fact, I can identify the particular fencepole that one of them is in from GE, if I manually enter coordinates. When possible, before I post a new cache, I run its coordinates through GE to see if where I think I put it is where it really is.

 

So premium members really don't need the "live" KML link; in fact, since it shows all the caches (including the ones you've found) it's actually less useful...

 

I wouldn't go that far. I turn on the GC KML, and the "Parks" layer, and I can now zoom around Jacksonville, FL, finding places to take my 3 and 1.5 year old caching. Not to mention the already requested "Follow your driving route, tag the caches into a Bookmark list, and run PQ against it" ability. It's useless for going to caches, not useless for finding cache areas.

 

If you have suggestions for feature you would like to see, let us have it!

 

Do you have the ability to add items to the right-click menus through the application? I'd much rather rightclick > bookmark then click, move, bookmark, close balloon...but that's just me :(

 

I'd like to see a preview of a PQ so I know what I'm getting before I commit running that PQ for the day.

 

If you mean, what the GPX file gives you, you can download a single cache as a GPX entry and see what it tells you about a cache. If you mean, what caches will be returned by a given set of PQ parameters, I'd recommend the "Preview" link next to the PQ entry on the left ;)

Edited by PetsAllOver
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Do you have the ability to add items to the right-click menus through the application? I'd much rather rightclick > bookmark then click, move, bookmark, close balloon...but that's just me :(

So would I, but I don't think Google Earth exposes the right click option to developers. You should submit that to them though (great idea!)

 

As for preview in KML, it is a good idea. We are, however, trying to keep the querying of the KML server down while we determine the impact of the new feature. Since it will take folks a while to ramp up and use it more we won't have a good idea for a while. However we'll keep a feature list available for when we start making new features for Google Earth.

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As far as previews...is there a way to generate the .LOC for an entire PQ? As near as I can tell, you can only generate it per screen.

No. There is no way to do massive queries on the fly. The reason why we have Pocket Queries in the first place is to allow batching of queries so there isn't a huge strain on the databases.

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As someone who uses aerial photos to find caches (the high res aerials in GE are superb and very accurate in MA) would it be possible to add a "download KML" from the the cache page (like .loc and .gpx)? This way its only for a single cache (I'm assuming this would get away from the scraping issues since you are doing essenitally the same thing on a bug page) but it would provide accurate coordinates, actually useful for finding a cache. I'm aware of other solutions (.gpx->GE and GreaseMonkey extensions) but a direct and accurate KML cache link blessed by TPTB would be helpful for those of use who are lazy!

 

GO$Rs

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