[Qgis-user] problems reprojecting in equal earth

[Michael Jabot]

Nicolas

THANK YOU so much!!!

What an INCREDIBLE community!!!

With deepest appreciation!!

Mike

*************************************
Michael Jabot, Ph.D.
Professor, Science Education
US Partner - *GLOBE Program*

*NASA Earth Ambassador*Director, *Institute for Research in Science
Teaching*

*Chancellor's Award Recipient for Excellence in Research*The State
University of New York at Fredonia



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jabot at fredonia.edu
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On Wed, Aug 21, 2019 at 8:52 PM Nicolas Cadieux <
nicolas.cadieux at archeotec.ca> wrote:

> Hi,
>
> I figured it out! (Well... you figured it out:)  I created a world grid
> with 1 degree longitudes.  I then densified this grid with the value 10
> 000 (Vector/Geometry tools/densify by count). Then, I selected the
> longitude line I wanted to split (-44). I then used the Split with lines
> found in processing.  Reprojection still gave me those big polygons but
> this time, you can select them by clicking slightly right of the
> polygons (on the right side of the screen) on the reprojected project.
> Then, you can delete the problematic polygons.  Results are in the
> Google Drive.
>
> https://drive.google.com/open?id=1eL6ws8Jc-PugMM2gxV79j0k-TGoWcw6B
>
> Thanks for your help!
>
> Nicolas
>
> On 2019-08-21 3:26 p.m., Alex M wrote:
> > I had this issue once also, I think the clipping method is the most
> > reliable. If I recall the odd/invalid polygons depended on which scale
> > of Natural Earth you use. Try downloading a different scale. I remember
> > actually trying to fix the polygons and Russia was just too complicated
> > to deal with at the time.
> >
> > This is a common problem anytime you wrap the dateline with world data,
> > and you might find more solutions using those search terms.
> >
> > Thanks,
> > Alex
> >
> > On 8/21/19 11:10, Nicolas Cadieux wrote:
> >> Good idea Calvin,
> >> Anyone else with a simpler, faster  solution?  If not, I will try.
> >> Nicolas
> >>
> >>> Le 21 août 2019 à 13:43, C Hamilton <adenaculture at gmail.com> a écrit :
> >>>
> >>> The way I more or less solved something like this was by pre-clipping
> the Natural Earth data at the boundaries of the projection and made two
> different vector layers You then will not get the wrap around. If need be
> you can shift the longitude of one of layers by 180 degrees and then
> attempt to merge the two pieces together. For countries that now have a cut
> line down the middle you can then merge the pieces together. It can be time
> consuming, but will work. I don't know if there is an easier way.
> >>>
> >>> Calvin
> >>>
> >>>> On Wed, Aug 21, 2019 at 1:17 PM Nicolas Cadieux <
> nicolas.cadieux at archeotec.ca> wrote:
> >>>> Hi,
> >>>>
> >>>> These are the nasty polygons.  I am hoping you will see the image.
> >>>>
> >>>> <djfpggkfmkkepjkp.jpg>
> >>>>
> >>>>> On 2019-08-19 12:26 p.m., Nicolas Cadieux wrote:
> >>>>> Hi,
> >>>>>
> >>>>> Trying to help another Qgis user that posted earlier.
> >>>>>
> >>>>> We have Natural Earth vectorial Data that we what to reproject in
> Equal Earth.  We want Austria to be in the middle of the map so we created
> a Equal Earth Project using  custom CRS  using +proj=eqearth +datum=WGS84
> +wktext +lon_0=136 with the help of
> https://proj.org/operations/projections/eqearth.html. Using  lon_0=136
> puts Australia in the middle and limits the distortion in that longitude.
> >>>>>
> >>>>> Data was reprojected and saved in the new projection (vector/Data
> Management tools/Reproject Layer).  Project is also in the Equal Earth
> projection so no reprojection on the fly is happening behind the scenes.
> >>>>>
> >>>>> Question: How so we take care of the nasty polygons that appear when
> we add the "+lon_0=136" parameter?  See the zip.
> >>>>>
> >>>>> You can find the data here:
> https://drive.google.com/open?id=1eL6ws8Jc-PugMM2gxV79j0k-TGoWcw6B
> >>>>>
> >>>>> Qgis 3.8.1 on Windows 10_64
> >>>>>
> >>>>> Thanks
> >>>>>
> >>>>> Nicolas
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
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