[Proj] So close -- Lat / Long to Pennsylvania State Plane North NAD27

[Andre Joost]

Am 26.07.2013 14:22, schrieb jdawg:
> sorry...bumping this message to get it on the mailing list... :)
>
>

Unfortunately, your first message did not get to the mailing list, only
to nabble readers. For the record, I paste it below.

I did some tests with the following commands on GDAL 1.10.0:
@echo off

echo WGS84-NAD27 >out.txt
cs2cs +init=epsg:4326 +to +init=epsg:4267 WGS84.txt >>out.txt
echo WGS84-NAD27PAft>>out.txt
cs2cs +init=epsg:4326 +to +init=epsg:32028 WGS84.txt >>out.txt
echo NAD27-NAD27PAft>>out.txt
cs2cs +init=epsg:4267 +to +init=epsg:32028 WGS84.txt >>out.txt

with the follwoing input file WGS84.txt:
-75.921819 41.295735

and got those results:

WGS84-NAD27
75d55'19.837"W	41d17'44.355"N 0.000
WGS84-NAD27PAft
2502234.97	416637.87 0.00
NAD27-NAD27PAft
2502332.66	416669.38 0.00

So you get the first result if the input is regarded as WGS84 degrees, 
and the second if the input is regarded as NAD27 degrees (EPSG:4267).

HTH,
André Joost


Original message:

> This is my first time using Proj.4, and I'm struggling with
> converting Lat/Lon in decimal degrees to Pennsylvania State Plane
> North NAD27. I'm very unfamiliar with coordinate system terminology.
> Here's what I'm expecting based on what our mapping system tells me
> are the coordinates between the two systems:
>
> -75.921819, 41.295735
>
> should return
>
> 2502235.76228      416637.89162
>
> when I convert it using cs2cs. (I'm expecting these values because
> when I use ArcMap to convert the coordinate system using the
> transformation called "NAD_1927_To_WGS_1984_79_CONUS", I get those
> values.) But what I'm getting from cs2cs is:
>
> 2502332.66      416669.38
>
> This is the command line syntax I'm using, along with the output:
>
> C:\proj\bin>cs2cs -v +proj=latlong +datum=NAD27 +ellps=clrk66
> +nadgrids=conus,nt v1_can.dat +to +init=epsg:32028 # ---- From
> Coordinate System ---- #Lat/long (Geodetic) # # +proj=latlong
> +datum=NAD27 +ellps=clrk66 +nadgrids=conus,ntv1_can.dat #---
> following specified but NOT used # +ellps=clrk66
> +nadgrids=conus,ntv1_can.dat # ---- To Coordinate System ----
> #Lambert Conformal Conic #       Conic, Sph&Ell #       lat_1= and
> lat_2= or lat_0 # +init=epsg:32028 +proj=lcc +lat_1=40.88333333333333
> +lat_2=41.95 # +lat_0=40.16666666666666 +lon_0=-77.75
> +x_0=609601.2192024384 +y_0=0 # +ellps=clrk66 +datum=NAD27
> +to_meter=0.3048006096012192 +no_defs # +nadgrids=conus,ntv1_can.dat
> #--- following specified but NOT used # +ellps=clrk66 -75.921819
> 41.295735 2502332.66      416669.38 0.000
>
>
> The values are so close, but not close enough, and I can't figure out
> where the discrepancy is! Can any of you gurus advise me in this
> matter?? Thanks very much!!
>
> Jeremy