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Auto corrections did not use my location as the EPSG code

  • 1.  Auto corrections did not use my location as the EPSG code

    Posted 01-16-2020 03:36

    I recently did a job in Hamilton, New Zealand. Corrections, in the Mobile Manager App, is set to automatic. On getting back to the office, and looking at the excel file, I discovered that it had used the EPSG code 1165, which I believe is Eritrea, Africa.

     

    Now that I've done the job, how can I go about converting the EPSG from 1165 to 4326? I tried epsg.io but it doesn't have the 1165 code listed to be able to do a conversion.

     

    Also, if the Mobile Manager isn't managing to set my EPSG to 4326, using Auto location, I'll need to set it manually. However, going to the manual setting I see that the one listed as 'current' is WGS84(1762), so does this mean that something's not working correctly or some other issue going on?

     

    Something that might've been an issue, in the chain of events, is that I used 'UAV Ground Control' app to collect the points. Going into settings, in this app, there doesn't seem to be an option to set the corrections source so I'm guessing it doesn't have any control over the code being used...

     

    Thanks for all your help



  • 2.  Re: Auto corrections did not use my location as the EPSG code
    Best Answer

    Posted 01-16-2020 05:07

    Hi,

     

    I'm starting at the end - assuming you wanted positions in WGS84 all is good.

    If you want positions in the NZ local geodetic frame (NZGD2000) a transformation is missing (at least if I understand everything correctly).

    What type of positions did you expect - and what correction source did you use? And is there any reason (aka shift) which triggers you suspicion something is wrong?

     

    Details:

    I'm answering in steps so I hope I don't miss too much...

    First - the datum... I assume you used SBAS or RTX as correction source.

    With those two correction source types you get positions in ITRF2014(current) - which is EPSG 1165. This is equivalent to WGS84. 

    TMM only corrects for geodetic datums - so shifts introduced due to plate tectonic and such. There is also an EPSG 1165 for Eritrea - but this is a coordinate transformation. 

    EPSG IDs are only unique in their category - so you can have the same EPSG for different things... I think thats whats causing the head scratching.

     

    Next part - EPSG 4326 is WGS84. WGS84 on the other hand is based on ITRF2014 (or the global and time dependent reference frame). 

    The ITRF2014 frame we have in the TMM drop down refers to the reference frame of ITRF2014 - meaning ITRF2014(2010), the creation date of ITRF2014.

    In contrast WGS84(current) translates to the current TRF2014(2020.04) at the moment (16.1.2020).

    I'll ask one of our NZ guys to be on the save side - but assuming WGS84 was your goal all should be good.