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Thread: Why is this track invisible in time slider?

  1. #1
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    Default Why is this track invisible in time slider?

    I want to show a flight from Gatwick to Funchal (Madeira) in Google Earth and animate it with the timeslider.

    These are the steps I took:

    1. In GE, used Tools > Add Path to draw the flight as a straight line between two points.
    2. Saved that as a KML.
    3. Opened it in GPS Utility. (Could have done this in another map editing program like Ozi Explorer or even in my text editor.)
    4. Added arbitrary timestamps.
    5. Saved it as a new KML
    6. Opened that in GE.

    But although it animates correctly (the arrow moves), the track remains invisible.

    Anyone know why please?

    I've attached the final KML file.

    EDIT 1: I've also added a screenshot that shows how sometimes the first section of the track does get displayed. Mostly there's nothing, sometimes as in this example, and sometimes an even shorter section. Bizarre! Can anyone reproduce similar results?

    EDIT 2:
    It seems to depend on the zoom level (viewing altitude).

    EDIT 3: A key point seems to be that the track is 'drawn' by GE only when the arrow reaches the end of that section. Except that, the last section never gets drawn in the tests I've done. With many trackpoints close together this is rarely apparent, but with just a few, or the extreme case of just a start and end point, this is obviously an issue.

    My impression so far is that there are bugs in this area. And also that the visibility variation may be similar to the flaw/bug we've discussed before about road names disappearing depending on viewing altitude. It's all very frustrating!

    --
    Terry, East Grinstead, UK
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    Last edited by terrypin; 01-09-2012 at 07:50 PM.

  2. #2

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    The line is straight and is not visible when hidden by the curvature of the earth. Add more points or increase altitude.
    Matt Fox

  3. #3
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    Thanks Matt, appreciate your reply but that can't be the explanation. I get the same behaviour whether the track is 1000 feet or a 1000 miles. And changing Altitude to any of the other options, with any value, makes no difference. Did you try it with my file?

    I think the reason is either because of that behaviour I mentioned in Edit 3 (which until someone convinces me otherwise I'll assume is a bug) or some subtle reason to do with KML (in which I'm no expert).

    But meanwhile I can't make a usable 'flight' track with just a start and finish, at least not in the way I'm doing it. Making my Gatwick-Funchal track of say 50 trackpoints displays the animation correctly but is not only tedious but also loses the simple straight line. And to get a straight line with 50 points requires considerable exta external work.

    --
    Terry, East Grinstead, UK

  4. #4
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    This is a straight line flight from Gatwick to Funchal (Madeira), imported as a GPX into GE. It has just two trackpoints, so couldn't be simpler. It animates correctly with the time slider, but why is the track not shown as the arrow moves please? Its opacity is set correctly, yet it remains invisible.

  5. #5
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    Sorry, a bit off topic but I have looked at your kml and was wondering HOW you got the time slider to actually activate? I have been trying to add place marks in GE and modify their properties with time span and save it as kmz. Then go open it and I can never get the time slider to activate. When I looked at the kml, there is no time stamp or time span property at all. Sorry if it's a newbie question but would appreciate any help.

  6. #6
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    Quote Originally Posted by Stonewall View Post
    Sorry, a bit off topic but I have looked at your kml and was wondering HOW you got the time slider to actually activate? I have been trying to add place marks in GE and modify their properties with time span and save it as kmz. Then go open it and I can never get the time slider to activate. When I looked at the kml, there is no time stamp or time span property at all. Sorry if it's a newbie question but would appreciate any help.
    In Google Earth 6, if you right click a placemark and select "Snapshot View" while the timeslider is activated and on the date you want, when you close timeslider, double clicking the placemark will activate timeslider and move to the correct date.
    ٩(̾●̮̮̃̾Ľ̃̾)۶

  7. #7
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    Quote Originally Posted by Stonewall View Post
    Sorry, a bit off topic but I have looked at your kml and was wondering HOW you got the time slider to actually activate? I have been trying to add place marks in GE and modify their properties with time span and save it as kmz. Then go open it and I can never get the time slider to activate. When I looked at the kml, there is no time stamp or time span property at all. Sorry if it's a newbie question but would appreciate any help.
    Hi Stonewall,

    Placemarks by definition do not have an associated timestamp. I'm not sure exactly what you want to achieve. Do you want to see GE display an animation of a trip (real or imaginary) through a set of placemarks?

    Typically I use the Time slider to animate GPS recordings of walks/hikes, using the GPX file created by my GPS/mapping program and then imported into GE. That contains the timestamps. If I fail to get a recording (or lose the signal for sections of it) then I add them using a tool like GPS Utility, www.gpsu.co.uk

    IOW, you need a path (track) generated either automatically or manually, optionally with tools to reduce the chore of interpolating sensible times between places, at sensible speeds, depending on your objective. The KML needs to be in an acceptable format for this to work. And note that IMO GE's Time Slider is buggy in some respects, such as that discussed in this thread.

    --
    Terry, East Grinstead, UK
    Last edited by terrypin; 04-14-2012 at 09:29 AM.

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