[Proj] NAD_1983_To_WGS_1984_5

[Roger Bivand]

Hi,

I'm aware of Frank's reply:

http://lists.maptools.org/pipermail/proj/2008-September/003833.html

but would value clarification of why this happens (further details on:

https://stat.ethz.ch/pipermail/r-sig-geo/2014-August/021611.html

from WGS84 geographical coordinates to NAD27 via WGS84_5).

(code attached to get around line breaks)

The first test using cs2cs is wrong because it doesn't use +towgs84= to 
use *_5:

(the test is against benchmark coordinates)

The works in the first sub-step (geographical to WGS84_5 State Plane):

So locs.step1 are OK, but the next step gets the same errors as ignoring 
*_5

Turning on -v shows:

cs2cs -v -f "%16.9f" +proj=lcc +lat_1=38.43333333333333 
+lat_2=37.06666666666667 +lat_0=36.5 +lon_0=-120.5 +x_0=2000000.0 
+y_0=500000.0 +ellps=GRS80 +datum=NAD83 +units=us-ft +no_defs 
+towgs84=-0.991,1.9072,0.5129,0.025789908,0.0096501,0.0116599,0.0 +to 
+init=epsg:26743 < locs.step1

# ---- From Coordinate System ----
#Lambert Conformal Conic
#	Conic, Sph&Ell
#	lat_1= and lat_2= or lat_0
# +proj=lcc +lat_1=38.43333333333333 +lat_2=37.06666666666667 +lat_0=36.5
# +lon_0=-120.5 +x_0=2000000.0 +y_0=500000.0 +ellps=GRS80 +datum=NAD83
# +units=us-ft +no_defs
# +towgs84=-0.991,1.9072,0.5129,0.025789908,0.0096501,0.0116599,0.0
#--- following specified but NOT used
# +ellps=GRS80 +towgs84=0,0,0
# ---- To Coordinate System ----
#Lambert Conformal Conic
#	Conic, Sph&Ell
#	lat_1= and lat_2= or lat_0
# +init=epsg:26743 +proj=lcc +lat_1=38.43333333333333
# +lat_2=37.06666666666667 +lat_0=36.5 +lon_0=-120.5 
+x_0=609601.2192024384
# +y_0=0 +datum=NAD27 +units=us-ft +no_defs +ellps=clrk66
# +nadgrids=@conus, at alaska, at ntv2_0.gsb, at ntv1_can.dat

Puzzled,

Roger

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no
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