[HOT] Hot export : coordinate systeme

[Andy Anderson]

Computing area in Mercator is only sensible over small regions. So it’s questionable even for 3857.

I was curious what the difference was between projections 3785 and 3857, and found this reference: http://forums.esri.com/Thread.asp?c=93&f=984&t=288607

“EPSG originally added 'Popular Visualisation CRS / Mercator' in March 2008 with code number 3785. That has now been deprecated and replaced with 3857, 'WGS 84 / Pseudo-Mercator'.”

So it seems that any use of and reference to the former should be updated.

Since a geographic coordinate system like WGS84 is the foundation for every projected coordinate system, and it’s a relatively simple process to convert from the former to the latter with open-source libraries, the question is if there are any programs that we need to support that don’t have projection ability and therefore require a particular projection as input.

— Andy Anderson

On Oct 16, 2014, at 12:24 PM, Andrew Buck <andrew.r.buck at gmail.com> wrote:

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> Having it be selectable would be a good solution.  Paul Norman raised
> an interesting point on the github issue that currently we are
> currently adding a column of 'area' to the polygons table which can
> only be computed sensibly if you are in a projection like 3857, if we
> use wgs84 it would not make sense to have that column.
> 
> Now, since the column is not really used anyway (as far as I know) and
> since you can re-add the column yourself in GIS software, then I see
> no reason not to just drop the column and make setting the projection
> an option.
> 
> - -AndrewBuck
> 
> 
> On 10/16/2014 10:59 AM, Kate Chapman wrote:
>> Hi All,
>> 
>> There was a reason for the current system (though honestly I cant
>> remember what). Can someone else remember why?
>> 
>> Perhaps selecting the projection would be a better choice long term
>> as a new feature for the export tool?
>> 
>> Best,
>> 
>> -Kate
>> 
>> On Thu, Oct 16, 2014 at 4:22 AM, Fran Boon <francisboon at gmail.com>
>> wrote:
>> 
>>> On 16 October 2014 12:18, Fred Moine <frmoine at gmail.com> wrote:
>>>> Hot export: for the shape (export) could we change the
>>>> coordinate
>>> reference
>>>> system Rather than to have Popular Visualisation CRS/Mercator
>>>> ID EPSG: 3785
>>> could
>>>> we have WGS84 ID EPSG: 4326
>>> 
>>> This is logged as this issue here: 
>>> https://github.com/hotosm/hot-exports/issues/80
>>> 
>>> I would definitely support this proposal!
>>> 
>>> F
>>> 
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>> 
>> 
>> 
>> 
>> 
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