# [Proj] PROJ4 7 parameter datum shift Beijing 1954

Noel Zinn (cc) ndzinn at comcast.net
Mon Mar 28 14:11:00 EST 2011

```First thing to try is to reverse the signs of the three rotations.  I believe that proj.4 uses a “position vector” rotation sense.  This may be a “coordinate frame” transformation.  Judging from the RZ value and the differences in Eastings, this might work (but I haven’t run the numbers).  -Noel

Noel Zinn, Principal, Hydrometronics LLC
+1-832-539-1472 (office), +1-281-221-0051 (cell)
noel.zinn at hydrometronics.com (email)
http://www.hydrometronics.com (website)

From: Geoff Shipton
Sent: Monday, March 28, 2011 1:44 PM
To: proj at lists.maptools.org
Subject: [Proj] PROJ4 7 parameter datum shift Beijing 1954

Greetings to all,

I am looking for some assistance with a problem we have using the PROJ4 libraries, I am not a programmer neither am I geodesist – however I know enough to be dangerous! Please bear with me…

We have a customer in Shanghai China that is uses something he refers to as the Shanghai Local projection.

It is built on Beijing 1954 and uses that datum, the 7 parameter shift he gives are as follows:

TX:          170.076

TY:          154.924

TZ:          97.308

RX:         1.666408

RY:          0.872624

RZ:          -8.648183

K:            0.00000186

The Ellipsoid is Krassovsky 1940

The local coordinate system parameters are TM:

CM: 121.46716061

Scale: 1.0

False Eastings: 0

False Northings: -34587140.589

I constructed the following PROJ4 string:

+proj=tmerc +lat_0=0 +lon_0=121.46716061 +k=1 +x_0=0 +y_0=-3457140.589 +ellps=krass +towgs84=170.0760,154.9240,97.3080,1.6664,0.8726,-8.6482,0.00000186 +units=m +no_defs

However I am not getting the correct results, for example.

WGS84 coordinate

31° 17' 27.50965" N          121° 35' 54.41138" E        13.7729

Should give Shanghai Local coordinate

12501.0727E       6164.1228N

However the position from PROJ4 is:

12953.30E            6042.97N

We very rarely need to invoke this type of transformation so it’s quite possible something is awry with our code, but I sure would appreciate any thoughts on the problem.

Geoff Shipton,
Triton Imaging Inc.
Customer Support.
Capitola CA.
geoff at tritonimaginginc.com

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