[QGIS-Developer] How to find pxiels per meter resolution

[Colin Sare-Soar]

You want to draw a complex poligon in your application, so how are the points of the poligon defined, what datum etc.
There are many utilities to convert from one datum to another, or libraries you could build into your application. 
> On 23/07/2023 02:00 +07 qgis-developer-request at lists.osgeo.org wrote:
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>    1. Re: How to find pxiels per meter resolution (Vedran Stojnovi?)
>    2. Re: How to find pxiels per meter resolution (Greg Troxel)
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> Hi Gabriele,
> 
> WGS84 is not a projection, it's an ellipsoid - a mathematical model of the Earth. You are probably talking about the so-called "Plate carrée" projection where latitudes and longitudes are mapped as X and Y values.
> And this is a complicated thing because dX is different from dY (meridians are ellipses and parallels are circles).
> 
> I would suggest contacting a consultant who is specialized in this area to point you in the right direction for your custom need.
> I can recommend my colleague Dražen Tutić, he is a professional in this area and did a lot of programming in the context of mapping and projections.
> You can see some of his work on https://www.north2south.eu/map-projections-and-coordinate-reference-systems/
> 
> You can contact him via:
> Linkedin: http://www.linkedin.com/in/drazen-tutic-0975574
> Email: info at north2south.eu
> 
> sub, 1. srp 2023. u 19:01 Gabriele Ascolese via QGIS-Developer <qgis-developer at lists.osgeo.org> napisao je:
> > 
> > Hy all,
> > 
> > i'm developing a c++ gis using qgis api. I have a project in wgs84 projection.
> > 
> > I need to draw a complex poligon, so i need to find how is the pixel resolution per meters, so i can find how many pixel are in 1 meters and use this value to draw at real dimension.
> > 
> > How can i find the pixel per meter resolution using QGIS ?  I see that WGS84 projection use degrees as measure unit..but i need meter.
> > 
> >  
> > 
> > Thank you
> > 
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> 
> --
> Srdačan pozdrav / Kind regards,
> Vedran Stojnović.
> Vedran Stojnović via QGIS-Developer <qgis-developer at lists.osgeo.org>
> writes:
> 
> > WGS84 is not a projection, it's an ellipsoid - a mathematical model of the
> > Earth.
> 
> To be pedantic (a virtue :-), WGS84 is a family of specifications,,
> which define not only the ellipsoid (same for all in the family,
> thankfully), but also the position/orientation of coordinates and a
> definition of orthometric height.  Included in this, perhaps implicitly
> since it is not really about a particular datum, is transforming from
> XYZ to LLh.  But, agreed that this list of components does not include a
> projection to the plane.
> 
> The OP probably meant to say that the data is in the WGS84 Coordinate
> Reference System, or that the project projection is WGS84 Web Mercator.
> 
> (I agree that the OP appears to need a consultant.)