Polygon corruption when changing projections

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  • #3500

    David Medeiros
    Participant

    Using the land 1:110m shapefile with MAPublisher, when I change the projection from WGS 84 to Van der Grinten the polygon becomes corrupted. Some portions of the eastern part of the map flip over to the west causing banding across the map area. This only happens with certain projection transformations and with certain NE area files, but it seems to always be the ones I want to use.

    Any idea why this happens and how I can fix or avoid it? Is this an issue with the file or with MAPublisher?

    #4297

    Nathaniel
    Keymaster

    Are you using the latest version 1.4 off the website today?

    #4298

    David Medeiros
    Participant

    Sorry forgot to mention that, yes, I just downloaded a new copy of the data set this morning just to be sure. If you want to see what this looks like you can go here: http://www.cartotalk.com/index.php?showtopic=7777

    #4299

    Nathaniel
    Keymaster

    What extents does the NE data show in geographic before you project it? Is it all within the ±90/±180 envelope?

    #4300

    David Medeiros
    Participant

    I just arrived at work and don’t have the file or software here to look at. I’ll check this afternoon when I get home and get back to you.

    #4301

    David Medeiros
    Participant

    Nathaniel, I’m looking at the file now, not sure what you are referring to. None of the polygon extends beyond the art board in Illustrator if that’s what are you asking about.

    #4302

    Nathaniel
    Keymaster

    @David:

    In QGIS (available for Mac for free), you can view the extent metadata for the countries SHP:

    Extents:

    In layer spatial reference system units : xMin,yMin -180,-89.9998 : xMax,yMax 180,83.6338

    Not sure how to get that in MP. Don’t see it immediately in my copy.

    So if you’re using 1.4, this error shouldn’t be happening. In fact, when I project to Winkel Tripple, I get the expected result. My guess is your page is set to be small (letter?) and when MP imports the data, it rounds out of the ±180/±90 envelope, creating this problem?

    I suggest you take it up with MP support and report back here, please.

    _Nathaniel

    #4303

    David Medeiros
    Participant

    Ok, I tried it with a page set to 24″ x 24″, re projected with no issues so it is the page size. Not sure I understand why that matters since the imported map always fill the page width exactly no matter the size. I’ll take it up with MP and see what they say. Thanks!

    #4304

    Nathaniel
    Keymaster

    If your map is that small, you should consider using the 50m NE data, not the 10m data.

    _Nathaniel

    #4305

    David Medeiros
    Participant

    I’m actually using the 110m data. The final product is a small global locator map about 2″x3″, part of a larger route map for magazine publication.

    http://www.sonic.net/~dmed/MedeCart/Portfolio_files/Darien%20Gap-01.jpg

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