Area describing globe reduced to a line

tjhbtjhb Global Mapper UserPosts: 454Trusted User
edited January 2012 in Bug Report
Mike,

If the Vector Display option "Automatically wrap lat/lon values to (-180, 180)" is enabled, then an area describing the globe displays as a single vertical line at 180°E.

On the other hand, if the digitizer option "Show area and line vertices" is switched on, vertices are displayed in their correct locations. (This does not affect display of the area.)

The problem does not arise if the Vector Display option is disabled.

The area in question has vertices at (-180, 90), (180, 90), (180, -90), (-180, -90), (-180, 90).

I have tested GM 13 build December 10 2011 15:58:56, and GM 12 build May 12 2011 00:49:36.

Tim

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2012
    Tim,

    There are a couple of valid ways of interpreting a data set like that, since the corner coordinates are in theory at the same location on the earth, so the connecting line segments can either be considered to go all the way around the world, or to just sit at the same spot. The option to automatically wrap lat/lon values caused them to be interpreted as going nowhere and just creating a line since they are the same spot on the earth, but I have updated the rendering to treat this as a special case and actually draw it around the world. I have placed a new build at http://www.globalmapper.com/global_mapper13.zip with the change for you to try. Simply download that file and extract the contents into your existing v13.xx installation folder to give it a try. If you are using the 64-bit v13 version there is a new build at http://www.globalmapper.com/global_mapper13_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • tjhbtjhb Global Mapper User Posts: 454Trusted User
    edited January 2012
    Thanks very much Mike. Great.
    There are a couple of valid ways of interpreting a data set like that, since the corner coordinates are in theory at the same location on the earth, so the connecting line segments can either be considered to go all the way around the world, or to just sit at the same spot.

    You're right, though I'm sure I will find the new behaviour more intuitive, and it seems more consistent for the rendering of border and fill to use the same interpretation as the placement of vertices (when "Show area and line vertices" is enabled).

    There might be three ways of implementing the wrapping option generally: as "Automatically wrap lat/lon values to (-180, 180]" (so that +180 was within range but -180 was not); as "... to /B]-180, 180[B])[/B]" (the reverse); or as "... to [B][[/B]-180, 180[B" (so that both extremes were within range and valid). I think the first option was the GM approach, but you have now implemented the third option, either generally or as an exception for particular cases.
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