[Gdal-dev] definition in the EPSG file

[Frank Warmerdam]

Zhonghai Wang wrote:
> Hi guys,
>  
> I noticed that some definitions for the EPSG codes in the epsg file is 
> not so clear, which means there are no parameters for the epsg codes, 
> for example:
>  
> # ETRS89 / UTM zone 32N
> <25832> +proj=utm +zone=32 +ellps=GRS80 +units=m +no_defs  <>
>  
> the EPSG code for this one is 25832, but there are no other parameters 
> any more, such as longitude, latitude, central meridian, false northing, 
> false easting.....

Zhonghai,

I'm not sure what is wrong with the above definition.  It is the preferred
way of expressing UTM coordinate systems in PROJ.4, and is generally more
readable than the full "transverse mercator with parameters" definition
we see in WKT.

> and also this one:
>  
> # NAD83(HARN)
> <4152> +proj=longlat +ellps=GRS80 +no_defs  <>
>  
> if the epsg code is defined like this, does it mean that the the EPSG 
> code is not valid for use or is not defined?

In this case we don't really understand what to do about the HARN datum
so we fallback to expressing things in terms of the underlying ellipsoid.

It can be used, but it won't do HARN specific datum corrections for you.

Best regards,
-- 
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