Dan62
Tourist
Reged: 08/23/05
Posts: 4
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I'm trying to use GE+ to extract coordinates (lat, lon, altitude) for points along a road that shows in a GE image. When I make a path of a series of points, and save it as a .kml file, in notepad I can see the latitude and longitude for each point, but the altitude is always 0. I've tried all the different settings for altitude on a path (absolute, relative to ground, and clamped to ground) and they all give the same result--0, for altitude. When the terrain is switched on, the altitude of each point shows at the bottom of the screen--how do I get this altitude value to be saved for each point along the path. Any ideas???
Dan
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simon_a
Master Guide
Reged: 08/21/05
Posts: 1773
Loc: London, UK
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Hello Dan,
As you've found, the path tool does not generate altitude information in its output; by default, a path is clamped to the ground.
You have to manually edit the KML to add elevation information and tell the client how to use the data.
Having said that, one of the best things about the GE Community as that people come up with interesting and clever ideas for solving problems like these; take a look at the following post, which may solve your problem:
http://bbs.keyhole.com/ubb/showthreaded.php/Cat/0/Number/422117
Simon.
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Terry_Pinnell
Tourist
Reged: 08/24/05
Posts: 374
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Simon: Prompted by your post I've just been experimenting with the tool you mentioned, Barry Hunter's neat 'KML Altitude Filler' tool at
this page.
But have you found any practical use for these 'filled' files in GE itself please? I gather from Barry that they are really intended only for use in other applications.
Playing a filled (3 co-ordinate) path here gives exactly the same experience as playing the original (2 co-ordinate) path. And that's true whether I use Clamped or Relative. GE apparently ignores the altitude co-ordinate.
So I'm puzzled as to what you meant by "You have to manually edit the KML to add elevation information and tell the client how to use the data."
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Terry, West Sussex, UK
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tekgergedan
Master Guide
Reged: 09/25/05
Posts: 8051
Loc: Turkey GMT+2
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Hi Terry
We have two alternatives.
Either to enter the values in Notepad or use Barry's tool. I think, Barry's tool is useful as it edits the path in accordance to the earth surface.  I used it several times and it works well in GE too.
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Terry_Pinnell
Tourist
Reged: 08/24/05
Posts: 374
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Thanks tekgergedan. But I don't see how that answers my questions! As I said, I know how to make the filled files using Barry's tool. But how do you use them in GE? Perhaps if you could publish an example of Test.kml and Test-filled.kml and tell us what different uses can be made of them?
Maybe I'm still missing something very fundamental here?
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Terry, West Sussex, UK
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simon_a
Master Guide
Reged: 08/21/05
Posts: 1773
Loc: London, UK
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Hello Terry,
You have to use the <altitudeMode> tag to see any difference.
If you don't, the path gets clamped to the ground by default and the altitude values are simply ignored.
Using that tag, you get a choice between using absolute values or values relative to the ground (take a look at the kML documentation for more info).
Simon.
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Terry_Pinnell
Tourist
Reged: 08/24/05
Posts: 374
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Ah! Thanks a bunch, Simon, that looks like the crucial breakthrough I need
Will experiment tomorrow if I can.
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Terry, West Sussex, UK
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Terry_Pinnell
Tourist
Reged: 08/24/05
Posts: 374
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Still no success! Perhaps someone could provide a simple example please?
Before I tried amending my own KML path files I thought I'd search for an existing one somewhere. I found a file 33194-Flight Path.kml which I've attached.
That contains altitude co-ordinates, together with the <altitudeMode> tag as per Simon's advice.
Even when I use Edit to change that to Relative, when I play the path I can detect no difference. It does not follow the altitudes set (50,000 m etc), but simply views the path from the fixed height set in GE.
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Terry, West Sussex, UK
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simon_a
Master Guide
Reged: 08/21/05
Posts: 1773
Loc: London, UK
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Hello Terry,
I've no access to GE at the moment but I know the placemark in this post has altitude values set (the path actually hovers over the ground).
http://bbs.keyhole.com/ubb/showthreaded.php/Cat/0/Number/553542
Simon.
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Terry_Pinnell
Tourist
Reged: 08/24/05
Posts: 374
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Thanks Simon. But that example too behaves the same here. (And it's not a very good example in the current context. The altitudes are all very similar, around 180 m, so there would be little difference anyway. The example I gave has altitudes ranging from 0 to 75,000 m.)
I suspect a misunderstanding. As per my original post up-thread, "Playing a filled (3 co-ordinate) path here gives exactly the same experience as playing the original (2 co-ordinate) path." I thought you had identified the reason: include the <altitudeMode> tag. But that appears to make no difference to the playing experience.
--
Terry, West Sussex, UK
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