[Proj] Convert X and Y to Lat and Lon

[don_nell]

Hamish,

That's amazing. Thank you so much.

I've been struggling with this for a few days now and finally have the
answer.

Would you happen to know how to go the other way too? If I have the Lat and
Lon, how would I know the X and Y.  I'm still very new to this.

Thanks again for your time.

Don




hamish-2 wrote:
> 
> don_nell wrote:
>> I'm very new to mapping and I'm trying to use cs2cs.exe
>> from Proj4 to
>> convert the X and Y values from an ESRI shape file (roads
>> from the state of
>> Georgia) into Lat and Lon coordinates.  However, I'm
>> not sure what
>> parameters I need  to accomplish this. 
>> 
>> I've gotten pretty close using the parameters below (plus
>> or minus a city
>> block), but I'm sure I could do better.
>> 
>> +proj=tmerc +units=us-ft +datum=NAD83 +lat_0=-1.77517
>> +lon_0=-83.5 +k=0.9999
>> +x_0=0.0 
>> 
>> The "+lat_0" parameter was derived by trial and error. 
>> 
>> Can anyone tell me the correct parameters to use to make
>> this work? 
>> 
>> The contents of the associated .prj file are as follows. 
>> 
>> Thanks in advance. 
>> 
>> Don 
>> 
> 
> 
> PROJCS["NAD_1983_Georgia_Statewide_Lambert"
> ,GEOGCS["GCS_North_American_1983"
> ,DATUM["D_North_American_1983"
> ,SPHEROID["GRS_1980",6378137.0,298.257222101]]
> ,PRIMEM["Greenwich",0.0]
> ,UNIT["Degree",0.0174532925199433]]
> ,PROJECTION["Lambert_Conformal_Conic"]
> ,PARAMETER["False_Easting",0.0]
> ,PARAMETER["False_Northing",0.0]
> ,PARAMETER["Central_Meridian",-83.5]
> ,PARAMETER["Standard_Parallel_1",31.41666666666667]
> ,PARAMETER["Standard_Parallel_2",34.28333333333333]
> ,PARAMETER["Latitude_Of_Origin",0.0]
> ,UNIT["Foot_US",0.3048006096012192]]
> 
> 
> try:
> 
> +proj=lcc
> +datum=NAD83
> +x_0=0.0
> +y_0=0.0
> +lon_0=-83.5
> +lat_1=31.41666666666667
> +lat_2=34.28333333333333
> +lat_0=0.0
> +units=us-ft
> 
> 
> that is just by hand, I think there is some util which comes
> with the gdal(?) source code for translating WKT to +proj4
> syntax.
> 
> there is one South Georgia LCC in the EPSG file, but it's a
> bit different.
> 
> 
> Hamish
> 
> 
> 
>       
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> 

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