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Thread: New Datum and Map Scales on QTopo

  1. #1
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    New Datum and Map Scales on QTopo

    I recently downloaded a few (lots) of PDF maps from Qtopo to calibrate and add to the collection I use on my tablet with OziExplorer. On closer inspection during the calibration process I noticed the datum set was GDA2020. As this was not an option in the calibration screen of Ozi, I contacted their support via email and got this response from Des .......

    Quote
    For the use in OziExplorer the new datum GDA2020 is the same as WGS 84 which is the same as GDA94, the difference is extremely small and not noticeable.

    Just use GDA94 - it will not affect new maps or the old maps in any way.

    Unquote

    So away I went and got my calibrations done, reformat for tablet, upload and all is good.

    I went back into Qtopo last night and noticed (pretty sure it wasn't there the day before) that you can now get maps down to 1:10000. All numbered as per their standard within the 1:25000. There appears to be much greater detail, even on the computer screen with this new scale. Should be good for hikers and hunters.

    They are limited in the areas that they cover though, not over the whole state.

    Hope that helps someone.
    There is no eraser on the pencil of life.

    Now - 2008 D3 SE 4.0l V6
    Was - 2000 D2 TD5 with much fruit.

    Ray

  2. #2
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    Hi

    Quote Originally Posted by ChookD2 View Post
    I contacted their support via email and got this response from Des .......
    Quote
    For the use in OziExplorer the new datum GDA2020 is the same as WGS 84 which is the same as GDA94, the difference is extremely small and not noticeable.

    Just use GDA94 - it will not affect new maps or the old maps in any way.

    Unquote
    Rubbish. They are different datums. They are certainly a few metres different. If you are using a electronic theodolite to survey where your property boundary or house will be sited then assuming GDA94 = GDA2020 will get people into a lot of legal and technical problems and expense. The new datum brings Aust into line with the rest of the world and accounts for the fact that we have drifted closer to Asia (literally!).

    Mike
    Our car: Fuji White MY13 D4 SDV6 SE 3.0 Litre, 8 spd auto.
    My car: Series 2a Workshop, 109 inch WB, ex mil., 1971. To be restored.
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  3. #3
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    Well, I'm no surveyor so that is why I asked the question of the software developer. He did qualify his answer at the beginging with "For the use in OziExplorer......." whether that has any bearing (no pun intented) on the output I don't know that either. If it shows me on the right track and not off it, I'll be happy.
    There is no eraser on the pencil of life.

    Now - 2008 D3 SE 4.0l V6
    Was - 2000 D2 TD5 with much fruit.

    Ray

  4. #4
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    Hi

    Quote Originally Posted by ChookD2 View Post
    Well, I'm no surveyor so that is why I asked the question of the software developer. He did qualify his answer at the beginging with "For the use in OziExplorer......." whether that has any bearing (no pun intented) on the output I don't know that either. If it shows me on the right track and not off it, I'll be happy.
    Well it won't be the software developer, it will be the technically illiterate sales and support person. Though to tell the truth datums can get bloody complex. It would have been much easier for us all if the world was flat instead of being very slightly ellipsoid with bulges with drifting continents.

    Yes you will be on the right track though :-)

    Mike
    Our car: Fuji White MY13 D4 SDV6 SE 3.0 Litre, 8 spd auto.
    My car: Series 2a Workshop, 109 inch WB, ex mil., 1971. To be restored.
    Wife's car: Series 2a FFT, LWB, ex. mil., 1966. To be restored.

  5. #5
    Saitch's Avatar
    Saitch is offline ForumSage Silver Subscriber
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    Quote Originally Posted by ChookD2 View Post
    Well, I'm no surveyor so that is why I asked the question of the software developer. He did qualify his answer at the beginging with "For the use in OziExplorer......." whether that has any bearing (no pun intented) on the output I don't know that either. If it shows me on the right track and not off it, I'll be happy.
    C'mon, Ray. The difference between GDA94 and 2020 is 1.8 metres. Now, with some on this forum being able to bear testament to your 'Geographical Skill Sets', one would have to say that, in your case, +/- 1.8 metres is extremely accurate.

    Mind you though, the difference will increase over time. We can test it out tomorrow, perhaps?
    Infinity: A measureless measurement of a timeless time.


  6. #6
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    And letís not forget that the accuracy of a consumer grade gps in a smartphone/tablet is in the order of 5m, so the small datum change really doesnít matter unless you are working with sub metre survey equipment.

    Cheers
    Steve
    12 - 1994 Jaguar XJ12 "Lady Penelope"
    6 - 1986 Alfa Romeo GTV6 Grand Prix
    5 - 2003 Discovery 2 S Td5 "Charlie"


  7. #7
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    if the world was flat ....

    it isnt?

    your kidding me aren't you?

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