Re: [Qgis-user] problems reprojecting in equal earth

[Michael Jabot]

Nicolas

THANK YOU so much!!!

What an INCREDIBLE community!!!

With deepest appreciation!!

Mike

*
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Professor, Science Education
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On Wed, Aug 21, 2019 at 8:52 PM Nicolas Cadieux <
nicolas.cadi...@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  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.cadi...@archeotec.ca> wrote:
>  Hi,
> 
>  These are the nasty polygons.  I am hoping you will see the image.
> 
>  
> 
> > 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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Re: [Qgis-user] problems reprojecting in equal earth

[Nicolas Cadieux]

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  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  
wrote:
Hi,

These are the nasty polygons.  I am hoping you will see the image.




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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Re: [Qgis-user] problems reprojecting in equal earth

[Alex M]

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  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 
>>>  wrote:
>>> Hi,
>>>
>>> These are the nasty polygons.  I am hoping you will see the image.
>>>
>>> 
>>>
 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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Re: [Qgis-user] problems reprojecting in equal earth

[Andre Joost]

Am 19.08.19 um 18:26 schrieb Nicolas Cadieux:



Question: How so we take care of the nasty polygons that appear when we
add the "+lon_0=136" parameter?  See the zip.



See my answer at



HTH,
Andre Joost

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Re: [Qgis-user] problems reprojecting in equal earth

[Nicolas Cadieux]

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  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 
>>  wrote:
>> Hi,
>> 
>> These are the nasty polygons.  I am hoping you will see the image.
>> 
>> 
>> 
>>> 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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Re: [Qgis-user] problems reprojecting in equal earth

[C Hamilton]

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.cadi...@archeotec.ca> wrote:

> Hi,
>
> These are the nasty polygons.  I am hoping you will see the image.
>
> 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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Re: [Qgis-user] problems reprojecting in equal earth

[Nicolas Cadieux]

Hi,

These are the nasty polygons.  I am hoping you will see the image.

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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[Qgis-user] problems reprojecting in equal earth

[Nicolas Cadieux]

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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