Make parallel line from existing without creating a buffer?

SwoodySwoody Global Mapper UserPosts: 97Trusted User
edited June 7 in Vector Data
Is there any way to create a parallel line (from existing lines) without creating a buffer?  Ideally, I would like to create multiple parallel lines in spaced intervals of 300, 600, 900 feet, etc. Anyway to do that without creating a buffer, since I then have to go the extra steps to delete parts of my areas so they aren't enclosed?  I know I can copy and paste my line and move it 300, 600 feet, but need to do many, and would like to be exact. Thanks!
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Best Answer

  • MykleMykle Global Mapper User Posts: 392
    Answer ✓
    While I will frequently use a spreadsheet to calculate coordinates of stations along parallel lines, you can do it within GM by constructing a perpendicular temp line to one you have already drawn.  Create points along the temp line at the interval of your line spacing.  Then create perpendicular lines to your temp line at each of your points.  Voila!

    Gory details for the spreadsheet method, assuming a rectangular projection like UTM:
    Calculate the difference between coordinates of two points along your line:
    DX and DY define the slope of the line = DY/DX.  A perpendicular line has a slope of DX/DY.

    Calculate stations along your line at a fixed spacing.  The line length is sqrt(DX^2+DY^2).  Stations are spaced with changes in coordinates of dx and dy that are proportional to DX and DY:
    ss = station spacing, and LL = line length
    dx/ss = DX/LL and dy/ss = DY/LL, so dx= ss*DX/LL and dy=ss*DY/LL. 
    p1x = p0x + dx and p1y = p0y + dy, where p0 and p1 are point coordinates and you know p0 coordinates. 

    Depending upon which way you are moving along the line (or perpendicular line), you may have to flip signs so your calculated stations move the direction you need.  I usually create rows of station coordinates, then copy them to a text file, import into GM, and verify that points appear as desired.  If not, usually a sign needs flipping: rinse and repeat. 

    NOTE THAT TRIGONOMETRY IS NOT NEEDED, just geometry. 
    (unless you really like your sines and cosines and tangents, and arc-eachofthem!)

    [none of this is suitable if you are not using a rectangular projection.  good luck with that.]

    Adjustments may be easier in the spreadsheet than constructing lines and points in GM, so you get to choose the method that is most useful for you. 

Answers

  • SwoodySwoody Global Mapper User Posts: 97Trusted User
    Hi @Mykle - thank you so much - that is a great idea!  Still wish there was a way to automate this with GM, however you rmethod gives me a way to work with it in the meantime.  Thanks again - much appreciated!
  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,698
    Swoody said:
    Hi @Mykle - thank you so much - that is a great idea!  Still wish there was a way to automate this with GM, however you rmethod gives me a way to work with it in the meantime.  Thanks again - much appreciated!
    Hello,

    We have an open feature request for this functionality (#18398).  I have added your information to the request, and we will post a message on this thread when its status changes.

    Cheers,
    Bob
  • SwoodySwoody Global Mapper User Posts: 97Trusted User
    edited June 7
    That is very good news - thanks bmg_bob
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