[Proj] [delphi proj api]: Setting up TCoordinateTranslator

[Christian Kirchhoff]

Hello Paul,

thanks very much, you are perfectly right. I wasn't paying enough 
attention to the order of parameters of the procedure Calc in one of the 
demos of the PROJ API. The Google API always wants the latitude fiorst, 
and that's what I was focussing on. But the procedure Calc (and the DLLs 
CalcForward as well) need the parameters vice versa.

Thanks for that help.

Best regards,

Christian
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Paul Kelly schrieb:
> On Fri, 7 Mar 2008, Christian Kirchhoff wrote:
>
>> Hello,
>>
>> I'd like to use the Delphi PROJ API to translate coordinates. The 
>> coordinates come from GoogleMaps, thus are lat/lng values.
>>
>> I want to match them to shapes from a shape file which I can read 
>> with the ShapeAPI. I have got the following information the the prj 
>> file of the shape:
>> PROJCS["Germany_Zone_3",GEOGCS["GCS_Deutsches_Hauptdreiecksnetz",DATUM["D_Deutsches_Hauptdreiecksnetz",SPHEROID["Bessel_1841",6377397.155,299.1528128]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",3500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",9.0],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]] 
>>
>>
>> Therefore I thought that the TCoordinateTranslator I named "Proj" 
>> should be opened with:
>> Proj.Open('+proj=tmerc +ellps=bessel +lon_0=9 +x_0=3500000');
>>
>> ...but I am not very familiar/experienced yet.
>>
>> Anyway I have test coordinates from GoogleMaps, e.g. 
>> (50.1056069418592, 8.404541015625). The region this coodinates lay in 
>> as exactly the region that is covered by shapes in the shape file. 
>> The bounds of the shape file are, according to what the ShapeAPI 
>> returned:
>> ( 3394468.028, 5504381.719,0.00,0.00) to ( 3424916.697, 
>> 5537463.422,0.00,0.00)
>>
>> But the translated Google coordinates are:
>> 8451430,97 m, 1229074.77 m
>>
>> Which is totally elsewhere.
>>
>> My question is: Did I read the values from the shape's prj file 
>> wrong? Or did I use the wrong parameters when setting up the 
>> TCoordinateTranslator?
>
> I think you have passed the latitude and longitude values in the wrong 
> order. It should be longitude first, followed by latitude. Here is 
> quick test I did using your values and the cs2cs program that comes 
> with PROJ.4:
>
> cs2cs +proj=longlat +a=6377397.155 +rf=299.1528128 \
> +towgs84=606.000,23.000,413.000 +to +proj=tmerc +lat_0=0 +lon_0=9 \
> +k=1 +x_0=3500000 +y_0=0 +no_defs +a=6377397.155 +rf=299.1528128 \
> +towgs84=606.000,23.000,413.000 +to_meter=1
> 8.404541015625 50.1056069418592
> 3457407.04      5552194.69 0.00
> 50.1056069418592 8.404541015625
> 8451430.97      1229074.77 0.00
>
> Best regards,
>
> Paul
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