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Elevation accuracy in google earth

Discussion in 'Bob's Track Builder' started by TOFFEE, Aug 23, 2011.

  1. I`ve been making Toronto street circuit,but the main thing which discourages me big time is Google Earth height data;basically is very unaccurate. The end result is terrain as flat as a pancake even in those places where you can easily notice a slope while switching to Google Earth Street View or looking at the photos(for instance the north of the Lake Shore Boulevard,there`s the noticable slope,I reckon it must be at least 3m height difference when I look at the fencing).
    What`s the best method of creating the terrain in the BTB ?Should I make more paths where the terrain exists,update them in 3D Route Builder and then in the BTB add the terrain to those paths and delete the paths afterwards?
    In this case I would have at least more believable heights in these places where they should be,or am I barking up the wrong tree?
  2. This is what Ive done for myself, someone out there may have a better way of making it more accurate.....
    1st off, go into GE's Tool>Options & turn the elevation exaggeration figure up slightly (either 1.5 or 2 should be plenty but go back out to view changes to be sure....)
    2nd of all, Open 3dRB & change Altitude Adjust Intervals(meters)[It's the second of the 2 white windows] to 0.5 instead of the standard number of 1.5.
    This means it'll read the heights at half meter instead of 1.5 meter intervals.
    Now try your route data again.....
    Did you get your route data by drawing the route out in GE or by importing a URL from Google Maps?
    The first method gives more data points & therefore better working height data, the second method is rather sparing with it's data points making a track seem to be a bit flat & throws in extras(Those little thumbtacks that tell you where to turn)that cause doubled-up nodes in BTB causing Export failure if not removed, but, if your working with Isle of Man sized tracks this method makes track building significantly easier.
    I hope this is of some assistance, although someone out there may have a better idea to improve those elevations you need....
  3. Thanks a lot Lee Knight for your reply.I`ll definitely try your method.
    What about changing Altitude Adjust Intervals in 3d Route Builder even higher,let`s say to 0.1m (10cm);GeoTool will update the heights at 10cm intervals or is it the overkill?
    Which brings me to another topic which is drawing the route out in GE.The more points you make the more heights you get and this equals to more accurate height data,but you`ll end up with a very jagged line instead of the straight one(which can be easily fixed in 3ds Max by creating a new spline and conforming the spline to the jagged one made in GE).Is it a way to create as many points as I want and keep the line (route) straight in GE?The problem is,if you have a long straight (or any distance for that matter) and you created only 2 points to keep the route as straight as possible,in between these 2 points might be some elevation changes in real life and you`ll get exactly the same heights in between these 2 points which is again not accurate at all.This is the reason why I think that making more points in GE is more beneficial than creating less.

    So is it possible to make as many points as I need in GE and keep the line (route) straight?It would save me a lot of time in 3ds Max.
  4. It all depends on the data available. Some areas are down to the meter (usually main cities, look at Tokyo in google earth for example), other areas are like 30m, 90m and so on. Check out USGS to get an idea on how the data is collected http://www.usgs.gov/

    [ED] It is also possible to find LIDAR data if it's available.
  5. Gday TOFFEE,
    As mianiak says it mainly depends on how well the area has been mapped.
    Ive found a high population area has more accurate height data available than a low population area, say central Australia, where it can be fairly poor....
    As for your second question regarding long straights, if you feel there's enough data there to be gathered then go for it & if the line isn't straight enough you can always go & move the data points in 3dRB before exporting to BTB-just remember that if you do to always go back & redo the heights after you've finished moving the data points about.
    Ive compared tracks built with the two methods & the 'drawn' method does definitely feel better on closed road type circuits & you can actually see the slight up & down like a real road, where as the URL method seems more incline to change elevations in quick sudden jumps.
    The URL method though does make 30+km tracks a lot quicker & easier to throw a route together for.....
    @ mianiak, where would I be best off looking for LiDAR data?
    Whenever Ive tried entering the term into a search engine I get a link to the BTB home page.....
  6. @ Lee Knight,sorry about a noob question,but how to move the data points in 3d Route Builder to get the route straight enough?

    As for your question about LIDAR data this is the best place you can head off to:

  7. Thanks for the link TOFFEE, Ive looked several times (although a while ago) & never seen a link to that site!
    Now to just work out how I can use this information....

    As for those tools & moving data points....

    http://s1217.photobucket.com/albums/dd387/BLeeK_Bitz/3D RB Tools/

    The Red circle is (from left to right) How much data point will be moved by each click, move towards- left, top, bottom, right.
    The Blue circle is the elevation tools of which Ive only used those in the Green circle.
    When the cursor rests on these buttons it'll give a brief description of what they're for which is how I learnt to use it.
    Don't worry, Im a Noob too, I 've only gotten to know 3dRB through all the troubles I had to finally get working route data for an 80km track that I'm attempting to build & the (at the time) sole reason I got into track building.
    I just had a strange thought, are you embeding GE so that you can see the route overlayed on the map?
    If so, just use the Red circled tools to align the data points with the roads on the map.
    If need be check out these 2 tutorials Ive uploaded to here:- http://www.mediafire.com/file/l7iwcg7whlid4ba/Tutorials.flv
    & http://www.mediafire.com/file/fexszmi767at6ii/Tutorials_1.flv
    Good luck,

    PS. Just thought of this thread, not sure if you've seen it yet...... http://www.racedepartment.com/bobs-track-builder/45130-google-earth-confusion.html
  8. @ Lee Knight,I`ve got the tutorials already,but thanks anyway.

    Do you have any issues regarding to viewing the LIDAR dataset on the lidardata site? If I click the green pin or overlay which represents available LIDAR data to view details, after a while GE plugin crashes and I`m unable to see them.Someone from this board was kind enough and sent me a link to the Toronto LIDAR data page,so I could order the data ( yes,you need to pay for it ) by filling out a short form.I filled the form out and then it took me to the main RaceDepartment page which is very irritating.I`ve tried a couple of times,but the same case scenario repeats every time I finish filling out the form.
    Did you manage to actually get the LIDAR data and how much does it cost?
  9. Ive gotten the GE add-on but there's no LIDAR for Australia that I could see so haven't tried it much beyond the point of looking at the green stuff....
  10. Kyle Puttifer

    Kyle Puttifer
    @ Simberia @Simberia

    Well I'm not ordering it for you toffee. :)
    I can't work out why the link isn't working for you though.
  11. Yep,only Sydney and Melbourne are covered so far .
  12. Shame on you!:)
    Maybe you could get me a baby kangaroo ( a joey,right?) instead please! They`re so cute and soft, the LIDAR data is a nasty piece of point cloud c...;for starters you need to filter out all the unnecessary rubbish contained in the LIDAR mess and trust me on that one,this is no fun at all!
  13. Ive been having another look at it & 'I think' it depends on how your internet is at the time (Im on wireless....)
    I went back later on & found that the whole Great Dividing Range has been done apparently....
    I havent yet tried gathering any data due to time constraints but if I do I'll let you know how I get on with it.....
    Unfortunately, the size of land I was looking at to get a scan of is 1458996.38 Square Kilometers!
    I'd be interested to see how much THAT would cost!
    The GEplug-in did mention a couple of free sites it can get it's updates from, so it'll be interesting to find out....

    I dont know if we have any joey's left now sorry TOFFEE, I think we've sold them all off to the Koala Keyring factory....:wink:
  14. For some reason it works now.

    I`ve got a reply from Mr Josh McBrayer,a business development manager of the AIRBORNE 1 CORPORATION which laser scans,the company which has the headquarters in El Segundo,California,USA.He`s written this:

    Thanks for the inquiry. I will be glad to help if you can provide some
    additional information. Can you tell me the specific area that you are
    interested in? The data set for SPDB is rather large, and I want to make
    sure we do not quote more area than you are interested in.


    As you can see,you just let them know what`s your area of interest is and they`ll provide you with the laser scanned data of the particular region you specified.I think if you send them for example,simply coordinates of the specific region you`re interested in,they return LIDAR data only that area marked by coordinates.
    And I`m more than sure, that they do custom laser scanning.

    This is a link to the AIRBORNE 1 CORPORATION just in case you would want to find out more details on this subject: