[Proj] convert from Equidistant Cylindrical to Eckert I

Wang Leslie wqyuwss at hotmail.com
Wed May 25 11:27:08 EST 2016

I thought this association is standard. In other words, given the size of one image and type of cylindrical projection, each pixel should be associated to correct (longitude, latitude) at sphere. My assumption is the image is assumed to unwrap the complete sphere.

Best Regards


From: proj-bounces at lists.maptools.org <proj-bounces at lists.maptools.org> on behalf of Jose Gonçalves <jagoncal at gmail.com>
Sent: Wednesday, May 25, 2016 11:51 AM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] convert from Equidistant Cylindrical to Eckert I

An image is georeferenced if there is some form of associating pixel positions (row, column) to geolocation, in geographic or cartographic coordinates.
Proj, or any other program that uses proj, needs that to apply map projection formulas
In your case you must simulate that your image is georeferenced, giving it an extent of 360 degrees in longitude (row) and some proportional extent in latitude (column).


2016-05-25 0:34 GMT+01:00 Wang Leslie <wqyuwss at hotmail.com<mailto:wqyuwss at hotmail.com>>:

Hi Jose,

Thanks for the quick reply.

What do you mean "be geo-referenced"? What I'm thinking is to use these tools to convert a 360 panorama picture, such as https://upload.wikimedia.org/wikipedia/commons/3/35/Space_Needle_360_Panorama.jpg, which is an equidistant cylindrical projection, to other type of projection, which keeps same quality but with smaller size. Thus I can save some storage spaces. In this case, these 360 picture doesn't have any geo-referenced data. Can I still use these tools?

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