problems reprojecting in equal earth

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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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Re: 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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Re: 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 <[hidden email]> 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: 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 <[hidden email]> 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 <[hidden email]> 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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Re: problems reprojecting in equal earth

Andre Joost
In reply to this post by Nicolas Cadieux
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

<https://gis.stackexchange.com/questions/70411/displaying-world-country-shapefiles-centered-on-pacific-ocean-using-robinson-or>

HTH,
Andre Joost

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Re: problems reprojecting in equal earth

Alex Mandel-2
In reply to this post by Nicolas Cadieux
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 <[hidden email]> 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 <[hidden email]> 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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Qgis-user mailing list
>>>> [hidden email]
>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> _______________________________________________
>>> Qgis-user mailing list
>>> [hidden email]
>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
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Re: 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 <[hidden email]> 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 <[hidden email]> 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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Qgis-user mailing list
>>>>> [hidden email]
>>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> _______________________________________________
>>>> Qgis-user mailing list
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>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>> _______________________________________________
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>>
> .
>
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Re: 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


 
716.320-0189 (Google Voice)
E250 Thompson Hall
280 Central Avenue
Fredonia, NY  14063
*************************************

       
                             



On Wed, Aug 21, 2019 at 8:52 PM Nicolas Cadieux <[hidden email]> 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 <[hidden email]> 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 <[hidden email]> 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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Qgis-user mailing list
>>>>> [hidden email]
>>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> _______________________________________________
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>>
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> .
>

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