[Qgis-user] How to reproject maps of world grasslands

[Paulo van Breugel]

On 20-03-17 13:30, Martin wrote:
>
> Thank you very much. I tried this suggestion and it works perfectly! 
> Forgive my ignorance, but how did you know that '+proj=igh' would 
> produce the correct result? I understand that igh means Interrupted 
> Goode Homolosine, but where did you find this information (this is for 
> my education)?
>
See the link Raymond gave you, http://proj4.org/projections/igh.html.
>
> I am going to write to WWF and suggest that they make the grasslands 
> shape file available in WGS84 (i.e. EPSG 4326), as I would like to 
> direct others to it without the need for providing an explanation of 
> how to transform the data.
>
Yes, that is a good idea.
>
> I discovered that ArcGIS understands the Interrupted Goode Homolosine 
> CRS. A friend with ArcGIS has now converted it to EPSG 4326 for me and 
> this also works fine and produces the same result as your excellent 
> suggestion.
>
> Ciao, Martin
>
>
> On 20/03/17 07:54, Paulo van Breugel wrote:
>>
>> Using the definition on the proj4 page, you can define a custom CRS 
>> (settings --> custom crs). Just fill in under parameters '+proj=igh'. 
>> I just tried and it gives a good match
>>
>>
>> Note that this grassland layer is based on the terrestrial 
>> ecoregional map of WWF [1]. If you over overlay that on your 
>> grassland layer, using for the latter the Interrupted Goode 
>> Homolosine CRS, you see they will overlap perfectly. You could in 
>> fact easily recreate the map using the ecoregional map.
>>
>> Cheers,
>>
>> Paulo
>>
>> [1]https://www.worldwildlife.org/publications/terrestrial-ecoregions-of-the-world
>>
>>
>> On 20-03-17 07:46, Martin wrote:
>>> Many thanks Raymond: that is helpful. Now at least I know what the 
>>> projection is! As QGIS has so many projections it never occurred to 
>>> me that there may be one that it didn't include. I will now see if 
>>> there is some other way - outside QGIS perhaps? - to convert this 
>>> projection into something more friendly (so to speak).
>>>
>>> Martin
>>>
>>>
>>>
>>> On 19/03/17 21:30, Raymond Nijssen wrote:
>>>> Hi Martin,
>>>>
>>>> Sorry, I cannot really help you.
>>>>
>>>> Your data seems to be in the (quite odd for distributing data) 
>>>> projection:
>>>> https://en.wikipedia.org/wiki/Goode_homolosine_projection
>>>>
>>>> And it is not recognized by qgis.
>>>>
>>>> Proj4 seems to know it though:
>>>> http://proj4.org/projections/igh.html
>>>>
>>>> And I found this:
>>>> http://gis.stackexchange.com/questions/17263/is-it-possible-to-use-the-goode-homolosine-projection-in-qgis 
>>>>
>>>>
>>>> Hope it helps (a bit),
>>>> Raymond
>>>>
>>>>
>>>> On 19-03-17 20:49, Martin wrote:
>>>>> Hello folks!
>>>>>
>>>>> I would like to plot a simple map of the WWF World Grassland Types 
>>>>> (the
>>>>> shape file is available at
>>>>> https://www.worldwildlife.org/publications/world-grassland-types
>>>>>
>>>>> It is in an unusual projection. The .prj file is:
>>>>>
>>>>> PROJCS["World_Goode_Homolosine_Land",GEOGCS["GCS_WGS_1984",DATUM
>>>>> ["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM
>>>>> "Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION
>>>>> ["Goode_Homolosine"],PARAMETER["False_Easting",0.0],PARAMETER
>>>>> ["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER
>>>>> ["Option",1.0],UNIT["Meter",1.0]]
>>>>>
>>>>> The map does not include the outline countries of the world and
>>>>> therefore I would like to add these (perhaps the NaturalEarth 110
>>>>> million scale country shape file, which is in WGS84).
>>>>>
>>>>> However, I cannot figure out how to align the grassland layer and the
>>>>> 110 million NaturalEarth layer. As I understand it, I should use 
>>>>> Save As
>>>>> to reproject the grassland shape file with a new CRS (perhaps 
>>>>> Mercator).
>>>>> With Enable on the fly CRS transformation enabled I should then be 
>>>>> able
>>>>> to put the two shape files together - but I am darned if I can obtain
>>>>> anything sensible: I cannot get the two layers to align in any way.
>>>>>
>>>>> With grateful thanks for  any help, Martin
>>>>>
>>>>>
>>>>>
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>>>>
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