Global Mapper v25.0

COGO MAG VAR error

zululux
zululux Global Mapper UserTrusted User
edited November 2014 in Bug Report
Hello all,I am trying to do a COGO centred on an existing point. The Projection is -35S, Datum WGS 84. When I attempt to execute the COGO fom the point regardless of whether the measuring tool is set to Tryu or MAG North; it's always 23 deg off.I don't know what else to to. I know though that the average MAG VAR is 23 deg West in South Africa; and I suspect that it is somehow adding the MAG VAR to the desired COGO Bearing. Any input would be appreciated. I'm running version 4.2; and this has never happened before.Regards,Zululux

Comments

  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Correction, I'm running v 14.2
  • bmg_bob
    bmg_bob Global Mapper Programmer
    edited October 2014
    Hello,

    Can you post a data set in the appropriate location and projection that I can use to test this. Also, it would be useful if you could post a screen capture of your COGO screen so I can see the input and options you are using.

    What is the full version (14.2.?) and build date for Global Mapper. You can get this information from Help->About Global Mapper...

    Thank you.

    Cheers,

    Bob
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Thanks Bobbeh,

    I'm about to leave the office now, but I will do as you have instructed when when I get home. I don't know what the time zone between yourseflf and I is. My time-check now is 16h20. Thanks.
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Hi Bob. I hope you're having a good day. I have attached 5 screen shots of the COGO procedure. I have tried unistalling and re-installing as well, to no avail. I will open another postso I can upload the last pic. GM allows a max of 5 per post. Regards, ZululuxLE-RB1.jpgLE-RB2.jpgLE-RB3.jpgLE-RB4.jpgLE-RB5.jpg
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    I forgot to narrate the backSNIP1.PNGground story:

    The red line on the left is a Runway. The Spot elevation smack-bang in the middle is the Airport Reference Point for King Shaka Airport in Durban, ZA. The anchor named TGV directly to the left of LE-ARP is anavigation beacon. The objective is to COGO from TGV so that it'ss parallel with the runway. The runway MAG HDG is 060 deg. The COGO line from TGV is 083 deg. What should've happened with the COGO input parameters is that the line called "test" (COGO from TGV) and the Runway should be parallel.

    I have attached the screenshot of the Variation parameters used. (UTM -35; WGS84)
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    GM version 14.2.6.

    Thanks
  • bmg_bob
    bmg_bob Global Mapper Programmer
    edited October 2014
    Hi,

    Thank you for these screen shots. They are helpful for looking at the results of your COGO operation. Can you post a data set containing the runway and navigation beacons, and also a screen shot of the actual COGO parameter screen that you use? This will allow me to recreate your scenario so I can determine why you are getting this result.

    Thank you.

    Cheers,

    Bob
  • Dave_in_Edmonton
    Dave_in_Edmonton Global Mapper User Trusted User
    edited October 2014
    Not sure about the whole COGO process, but I just went through this in GM (using FALE airport) by placing a point at the VOR Location (not sure that was needed), then using the COGO function in digitizer. My inputs were N37:00:00E6000 (ft) and my line came out parallel to the runway, with the end just past the threshold of Rwy 24. The thing to remember is to subtract the variation to get true heading. See attached thumbnail of my results.
    FALE.png
    FALE.png 711.1K
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Hi Dave,

    Thanks for that. I will try it. Normally tghough, I don't use the method you have used. I normally use the 1st option. (See 6th screen shot). I selected the VOR (TGV) as the anchor point. Then I selected COGO button, and said 'YES' to starting the COGO from TGV. I used 55 in Nautical Miles and bearing of 060.3 deg. The measuring tool was set to Mag. North.

    Let me upload the .gmw file, then I will try your method as well. .What does the format you used (N37:00:00E6000) mean? could you please elaborate on it.

    Thanks a lot for the input.

    Regards,

    Zululux
  • bmg_bob
    bmg_bob Global Mapper Programmer
    edited October 2014
    Hello,

    Thank you for sending the workspace. It allowed me to try out your scenario. Here is what I found:

    The line representing the runway has a heading of 217.3, as calculated from the start point to the end point (the start point is the north-east point in the line.) To get a parallel line running to the northeast from the TGV point, you will need to specify a bearing of 37.3, since this is the number of degrees from the south axis to the runway (calculated as 217.3 - 180, remembering that a bearing of 0 is north, 90 is east, 180 is south, etc.) I added this line to your workspace, and attached it here.

    TEST_KSIA_updated.gmw

    Dave is using the COGO input format. The first character of a COGO input string must be either the character 'N' or 'S' to indicate whether the bearing is relative to the north or south directions. After another space, the angle begins. The angle can be in any angle specification that Global Mapper supports, including degrees, degrees/minutes, or degrees/minutes/seconds. A space follows the angle, and is then followed by either the 'E' or 'W' characters. A space separates the bearing from the distance (which should be in appropriate linear units).

    I hope this helps.

    Cheers,

    Bob
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Thanks for returning the workspace updated..unfortunately, It gave
    me 'Co-ordinate out of Range' because couldnt read the projection.

    ..What baffles me with all this is that I used to routinely do 8
    COGO's in s row using the first option (Dist, Measurement Units,
    Bearing). This never happened before. I don't know if this may have
    anything to do with it, but I downloaded a trial version of Version 16.
    Upon clicking the download button, the downloader just hangs.

    I then uninstalled whatever comonenets of the download were
    downloaded, restarted; but the problem still persists. I'm very
    confuse, and am being chased by a looming dead line.

    Any other suggestions?

    Regards,

    zululux
  • bmg_bob
    bmg_bob Global Mapper Programmer
    edited October 2014
    Hi,

    Did you try creating your line using a bearing of 37.3 instead of 060? If so, did that work for you in Global Mapper 14? I used Global Mapper 16 for my test.

    It might be worth trying again to install a trial version of Global Mapper 16 from this link: Global Mapper Downloads

    Cheers,

    Bob
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Hi Bob,

    I did try to download V16 trial; but the download just hung. I will try again now. Please take into consideration that My meassurent Tool is set to MAG North; so I should get a COGO parallel to Runway 06/24 (Runway track 060 and 240 deg. respectively) without having to set the RWY to MAG and the COGO to TRUE. I've tried, but at some point when the chart gets complicated and I have to use many radii from TGV, I will not be able to apply this temporary fix.

    Regards,
  • bmg_bob
    bmg_bob Global Mapper Programmer
    edited October 2014
    Hello,

    The issue is that COGO tool does not support the input of bearings referenced to magnetic north, regardless of the settings in the measure tool. To create a line parellel to to the runway, you will need to use the true north bearing.

    Cheers,

    Bob
  • zululux
    zululux Global Mapper User Trusted User
    edited October 2014
    Ok,

    Thanks Bobbeh. That makes sense. I will have to re-think my methodology. Normally, when I design airspace I design to true north; and once the draft is done, i then set the Measure Tool to MAG. This gives the most recent MAG Headinggs and tracks. With this chart however, the critical and most important aspects of it are max elevation in a 5 mile radius; and Radii from a facility (TGV).

    Let me think on it. I'll get back to you.

    Thanks for the help
  • zululux
    zululux Global Mapper User Trusted User
    edited November 2014
    Hello Bob and everyone,

    After Bob's last post; it I understood about the COGO input. I will continue with Bob's advice. It makes sense now.

    Thanks for the excellent customer support. It really makes a big difference to one's experience with GM.

    Also, I'm looking for ASTER GDEM/SRTM/LANDSAT; or any other source of DTM with post-spacings of 1, 3, 5, or even a maximum of 10m for Africa, below the equator. I have been looking, but at best; have acquired 1.5-ARC-SEC accuracy data for free. I have tried Astrium (Airbus) and ESRI. Awaiting quotes from them. I will obviously have to pay, but I would appreciate any other eligible sources. ESRI and AIRBUS are infamous for their non-user-friendly pricing..if I could put it that way.

    Thanks again for the help. I'll be upgrading to V.16 in the next 60 days. I have to support my GM purchases myself, as my company refuse to pay for it; despite the fact that it has saved their rear-ends countless times.

    Have a nice weekend,

    Regards,

    Zululux