World Projection Peace

[Gerald I. Evenden]

>From: kang at risca.rs.msu.edu
>Date: Tue, 25 Oct 1994 16:30:01 -0400
>Sender: grass-lists-owner at moon.cecer.army.mil
>To: grassu-list at max.cecer.army.mil
>Subject: Re:  World Projection Peace
>
>Does GRASS include the Helmert 1906 spheroid?  If not, is there a projection
>package allow me to transfer a set of xy coordinates from Transverse Mercator
>with Helmert 1906 spheroid to UTM with interanational 1909 spheroid?
>
>Yung-Tsung Kang
>Center for Remote Sensing, Michigan State University

In *proj* parlance, inverting with "+ellps=helmert" and forwarding with
"+ellps=intl" would do the trick.  If the ellipsoids cannot be referenced
by name, their values are:

Helmert 1906: a=a=6378200.  rf=298.3  ("rf" is 1/f or reciprocal of flattening.)

International 1909: a=6378388.0  rf=297.

You will need to know the other projection factors associated with the
Transverse Mercator projection such as central meridian, scale factor
at central meridian, false eastings/northings, etc.

As far as GRASS versions of proj (?.proj) I do not know the details of
execution, but if these fail, you can definitely do the job with
*proj* from the PROJ.4 package on charon.er.usgs.gov (128.128.40.24).

Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
voice: (508)563-6766          Postal: P.O. Box 1027
  fax: (508)457-2310                  N.Falmouth, MA 02556-1027