Global Mapper v25.0

How to define the Start Vertex of closed line or an area for Export?

sonny
sonny Global Mapper UserTrusted User
edited May 2013 in Technical Support
Hi,

I want to Export closed lines (polygons) or areas to GPX-files. Therefor I want to define the exact start vertex of each exported feature (and if possible the direction of the exported path - clockwise or counterclockwise)

Is this possible with GM, respectively could this be an option to add? ;)

Comments

  • global_mapper
    global_mapper Administrator
    edited January 2013
    The latest builds have an option to include area features when exporting to GPX files (they will export as track lines). The start vertex will be whatever it is in the original data, so if you draw the feature just start where you want. You can also reverse the order of vertices using the Digitizer Tool.

    I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • sonny
    sonny Global Mapper User Trusted User
    edited January 2013
    But what if I'm using imported data, where the starting vertices are at a random position of the area/polygon-line?
    Could I maybe define the order by using digitizer/Split Feature at selected vertex on the desired start vertex and after that combining the 2 part in a special way again?
  • global_mapper
    global_mapper Administrator
    edited January 2013
    There isn't a special option to change where the start/end vertices are for closed features. You would have to create a line from the area border, then split the line at the desired start vertex, then join them back up in an order such that you get the desired start and end.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • sonny
    sonny Global Mapper User Trusted User
    edited January 2013
    I already tried that before by selecting both splitted line parts and Combine them again. I got the same unwanted Startvertex of the imported data like before splitting.
    Now I tried it again the same way, and suddenly the Startvertex is the desired one the splited Point.

    For those who are interested what is the correct order of selecting the 2 line-pieces:

    You have activate to "Render dots at Line endpoints" in Configuration/Vector display. Use digitzer and leftclick at the 2 line-pieces which are starting/ending in the splited Vertex, which should be our start Vertex and look at the color of the enddots at this Vertex. The one line-piece which creates a red dot has to be selected FIRST, hold the "Ctrl"-Key and select the one with the green dot SECOND. Finally combine these 2 selected line-parts again - Voila! :D
  • sonny
    sonny Global Mapper User Trusted User
    edited February 2013
    I just noticed a strange behaviour when working on an 8-shaped line (the upper part and the lower part of the 8 are connected in just 1 vertex). I want upper and lower part of the 8-line be counterclockwise. So I splited the 8 at its middle-vertex and made both parts counterclockwise (by using "Reverse Order of vertices").

    Then I combinded the 2 parts again (Digitizer/Combine). But the result is surprising: The upper part of the 8 changed to clockwise again (the lower part stayed counterclockwise). Why did one part change it's direction? I want "combine" to connect the 2 parts without any change of their current direction.
  • global_mapper
    global_mapper Administrator
    edited February 2013
    When there are multiple vertices incident at a particular location the order that gets selected could vary. What I would do is separate the crossing slightly so there aren't any choices to be made as to which path to follow. Then once the lines are combined in the orientation that you want, join up the center 4 vertices to the same location.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • sonny
    sonny Global Mapper User Trusted User
    edited February 2013
    I see, but the same problem is when combining several closed polygon-lines (/areas as well) which are not tangenting or overlapping each other.
    I want all the vertices of the combined closed polygons/areas be e.g. having counterclockwise orientation. (for some calculations using the combinded areas e.g. size of area, centroid of the resulting area etc. using these features it is very important that each feature has a defined orientation).

    Ideal would be a digitizer option "COMBINE clockwise" or "COMBINE with current orientation".
    Ok, but still I'm able to change the vertex-direction of each line/area myself and then COMBINE everything. But this is useless if the orientation of some lines is changed again after COMBINE.
  • global_mapper
    global_mapper Administrator
    edited February 2013
    I took a look and was able to re-arrange the logic so that if multiple path choices are available that one that maintains the original orientation of the lines is preferred over one that requires a reversal. Previously you had a 50/50 shot depending on which line was selected first. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • sonny
    sonny Global Mapper User Trusted User
    edited February 2013
    Thanks Mike, amazingly fast reaction from you - as used from you :D
  • Griffon
    Griffon Global Mapper User Trusted User
    edited May 2013
    I have a similar issue I'm trying to solve. Hopefully it fits under this thread.

    I would like to place a series of equally spaced points along a line or polygon perimeter. When I choose this digitizer option (Advanced Feature Creation, Create Point Features Spaced Along Selected Feature), the points stop and end at the beginning vertex of the feature. I'd like to be able to randomize this starting point, not just use the one associated with that polygon.

    (I'd define that random point by creating, say, 1000 points along the polygon, then randomly select a point.)

    Is there an option for that? Does the splitting/combining approach help me?
  • global_mapper
    global_mapper Administrator
    edited May 2013
    There isn't currently a way to directly cause the evenly spaced points to be based somewhere other than the start point. What you can do is convert the polygons to line features, then select the vertex to start at and split the line at that vertex. Then select the 2nd piece of the line (the part from the latter half of the original line) first, then Ctrl+Left Click to select the first part, then choose the toolbar option to create areas from the selected lines. This should give you a new area with the start point at the location you split the line at. You can then resample along that.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • Griffon
    Griffon Global Mapper User Trusted User
    edited May 2013
    Worked like a charm, thanks.