[OSRS-PROJ] Re: Quick 'how-to' to on PROJ.4

[Frank Warmerdam]

Precedence: bulk
Reply-To: osrs-proj at remotesensing.org

"Petri J. Riipinen" wrote:
> Ok, I almost managed to do it, except that fl_transform returns an error
> code (100)
> 
> First I want to mention that I found the Finnish KKJ-definitions in the
> epsg-file and they are below:
> # KKJ / Finland zone 1
> <2391> +proj=tmerc +lat_0=0.000000000 +lon_0=21.000000000 +k=1.000000
> +x_0=1500000.000 +y_0=0.000 +ellps=intl +units=m  no_defs <>
> # KKJ / Finland zone 2
> <2392> +proj=tmerc +lat_0=0.000000000 +lon_0=24.000000000 +k=1.000000
> +x_0=2500000.000 +y_0=0.000 +ellps=intl +units=m  no_defs <>
> # KKJ / Finland Uniform Coordinate System
> <2393> +proj=tmerc +lat_0=0.000000000 +lon_0=27.000000000 +k=1.000000
> +x_0=3500000.000 +y_0=0.000 +ellps=intl +units=m  no_defs <>
> # KKJ / Finland zone 4
> <2394> +proj=tmerc +lat_0=0.000000000 +lon_0=30.000000000 +k=1.000000
> +x_0=4500000.000 +y_0=0.000 +ellps=intl +units=m  no_defs <>
> 
> I'm guessing that the Uniform Coordinate System is the one that I should
> use with Shapefiles and then different zones with different "vertical
> stripes" of Finland, when dealing with raster images.
...
> GPS-measurements:
> 1        6010.570       2455.930      GPS: FINLANDIA-HOUSE
> 2        6012.467       2456.127      GPS: RAILWAY YARD
> 3        6013.045       2458.826      GPS: VIIKKI MUSEUM
> 
> Output in KKJ:
> 1        6674205.       2551915.      GPS: FINLANDIA-HOUSE
> 2        6677730.       2552047.      GPS: RAILWAY YARD
> 3        6678839.       2554525.      GPS: VIIKKI MUSEUM

Petri,

As suggested your main problem is that these angles need to be translated
into degrees minutse and seconds (or decimal degrees) rather than the odd
DDMM.mm format. 

Given that I tried a few experiments and still wasn't able to get very close
results.  The uniform coordinate system gave results that were way off, but
zone 2 gave me this (once without datum shift, once with).

warmerda at gdal[139]% cs2cs +proj=tmerc +lat_0=0 +lon_0=24 +k=1.0 +x_0=2500000.0 +y_0=0.0 +ellps=intl +units=m +towgs84=-87,-98,-121 +to +proj=latlong +ellps=intl
2551915 6674205
24d56'7.162"E   60d10'33.578"N 0.005
warmerda at gdal[140]% cs2cs +proj=tmerc +lat_0=0 +lon_0=24 +k=1.0 +x_0=2500000.0 +y_0=0.0 +ellps=intl +units=m +towgs84=-87,-98,-121 +to +proj=latlong
+datum=WGS84
2551915 6674205
24d56'3.778"E   60d10'32.451"N 17.536

However, this is still something like 15 seconds off in the easting which is
pretty dramatic.  

I am not sure what to do next to get proper results. 

Best regards,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent
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