User:Kagee/Converting NGO WGS84

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NGO Akse III

echo 'east-scaled north-scaled' | LC_ALL=C cs2cs +proj=tmerc +lat_0=58 +lon_0=10.722917 +k=1 +x_0=0 +y_0=0 +a=6377492.018 +b=6356173.508712696 +units=m +towgs84=278.3,93,474.5,7.889,0.05,-6.61,6.21 +no_defs +to +proj=latlong +datum=WGS84 -f '%.13f'

Tests from aafjord-1630vbas.sos

id : type .. coord order
east north height
east-scaled north-scaled 
east north (as staded by kart.statkart.no when converting from "NGO1948 Gauss-K. Akse 3" to "EU89-Geografisk"
east north (from cs2cs (-f '%.13f'))
east north (result from line above, rounded manually at 6. and 7. decimal)
.PUNKT 26: Ferjekai ..NØH
67346310 -3333560 260 ...KP 1
-33335.60 673463.10
10.0351573957103 64.0432636388396
10.0351563744381 64.0432636022641
10.035156        64.0432636
.PUNKT 33: Kommunedele ..NØH
66807090 306990 26560 ...KP 1
3069.90 668070.90
10.7802329241666 63.9965043442247
10.7802319011236 63.9965043149692
10.780232        63.9965043
.PUNKT 1938: Vegbom ..NØH
66398470 -2393030 2400 ...KP 1
-23930.30 663984.70
10.2291617894231 63.9590230458252
10.2291607711611 63.9590230118958
10.229161        63.9590230

Other stuff

Converting to WGS84

hildenae@toolmaster:~$ proj -le | grep bessel
  bessel a=6377397.155    rf=299.1528128   Bessel 1841

The ellipsoid used in NGO1948 is a modified Bessel ellipsoide. [1] It's paramters are:

  • a = 6 377 492.0176
  • b = 6 356 173.5083
  • f = 0.0033427731816
  • 1/f = 299.15281285


http://trac.osgeo.org/proj/wiki/FAQ#ChangingEllipsoidWhycantIconvertfromWGS84toGoogleEarthVirtualGlobeMercator

cs2cs +proj=latlong +datum=WGS84 
   +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 
                  +x_0=0.0 +y_0=0 +k=1.0 +units=m +no_defs

Attempt one

Assuming tmerc : Transverse Mercator equals Gauss-Krüger (Transversal Mercator) as stated in [1].


cs2cs +proj=tmerc +a=6377492.0176 +b=6356173.5083 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +no_de +to +proj=latlong +datum=WGS84


NGO-3

proj +proj=tmerc +lat_0=58 +lon_0=10.722917 +k=1.000000 +x_0=0 +y_0=0 +a=6377492.0176 +b=6356173.5083 +towgs84=278.3,93,474.5,7.889,0.05,-6.61,6.21 +pm=oslo +units=m +no_defs no_defs

Ved bruk av NGO-Norsk aksesystem an- gis nord-koordinat i meter nord for 58° nord. Øst-koordinat angis i meter fra berøringsme- ridianen. Det betyr at posisjoner på vestsi- den av en berøringsmeridian får negative øst-koordinater. Koordinatene i NGO-Norsk aksesystem er ikke påført noen fast måle- stokkskorreksjon. Skaleringsfaktoren er med andre ord 1.0.

Berøringsmeridianen for NGO-3 er 10° 43’ 22.5” øst/ 10.722917 / 10 43.375

[2]

If you look in the PROJ4 documentation, and look for a file for either ESRI or EPSG, and search for Oslo, you get some references that look familiar:

  1. NGO 1948 (Oslo)
+proj=longlat +a=6377492.018 +b=6356173.508712696 +towgs84=278.3,93,474.5,7.889,0.05,-6.61,6.21 +pm=oslo +no_defs  no_defs 

for the longlat,

  1. NGO 1948 (Oslo) / NGO zone I
+proj=tmerc +lat_0=58 +lon_0=6.056250000000003 +k=1.000000 +x_0=0 +y_0=0 +a=6377492.018 +b=6356173.508712696 +towgs84=278.3,93,474.5,7.889,0.05,-6.61,6.21 +pm=oslo +units=m +no_defs no_defs

and so on for the other zones. I don't know if this is precise enough, though.

Roger

Almost works, what is wrong

echo '-8438.20 681046.80' | cs2cs +proj=tmerc +lat_0=0 +lon_0=10.722917 +k=1.000000 +x_0=0 +y_0=-6430707.919 +a=6377492.0176 +b=6356173.5083 +towgs84=278.3,93,474.5,7.889,0.05,-6.61,6.21 +pm=oslo +units=m +no_defs -f '%.8f'
echo '-8438.20 681046.80' | cs2cs +proj=tmerc +lat_0=0 +lon_0=10.722917 +k=1.000000 +x_0=0 +y_0=-6430707.919 +a=6377492.0176 +b=6356173.5083 +proj=latlong +datum=WGS84 +no_defs -f '%.8f'

gives

  • 10.54975342 64.11244149

statkart gives

  • 10.54433467 64.11280671

this is a offset of approx 5.55 km and 444 meters [4]

Sources