[Proj] PROJ4 7 parameter datum shift Beijing 1954

[Noel Zinn (cc)]

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

The information contained in this message may be privileged or confidential information intended solely for the use of the addressee(s).  Any views or opinions presented in this communication do not necessarily represent those of Triton Imaging, Inc.  If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited.  If you have received this communication in error, please immediately notify me and you are hereby instructed to delete all electronic copies and destroy all printed copies.

 



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