Mike Craymer

Re: 23 Jul 2011 post by muhammad faiz pa'suya

Dear Muhammad: The ell2utm function will automatically determine and output the standard UTM zone in which your input coordinates fall. To also have it output the central meridian for the zone(s), change the first line of the ell2utm.m function from

     function [N,E,Zone]=ell2utm(lat,lon,a,e2,lcm)
to
     function [N,E,Zone,lcm]=ell2utm(lat,lon,a,e2,lcm)

This will be implemented in the next version of the Toolbox. To understand how the zones are determined, see the Wikipedia entry for UTM.

A new version 2.95 of the Geodetic Toolbox is now available. Unfortunately, I am unable upload it to the MATLAB Central File Exchange (keep getting an error). Until the Mathworks resolves the problem, you can find the new version at <http://www.craymer.com/software/matlab/geodetic/>;.

Updates include:

- Added new jd2mjd & mjd2jd functions for modified Julian date conversions.
- Modified ct2lg & lg2ct functions to optionally use different lat,lon for each point.
- Corrected use of ell2utm function in ToUTM example script.
- Removed "clear all" in example scripts to avoid clearing user's workspace.
- Modified functions to use GRS80 reference ellipsoid by default.

See Content.m for the full list of changes.

Dear Ram,
By default, the ell2utm function uses the standard UTM zone definition where the earth is divided into 60 zones each 6 deg of longitude in width. Zone 1 is bounded by longtiudes 180 deg E and 186 deg E.

<http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system>;

By this definition, Zone 44 is bounded by longitudes 78 deg E and 84 deg E, while Zone 45 is bounded by 84 deg E and 90 deg E. That is, Zone 44 starts at 180+(44-1)*6-360=78. The boundary between Zones 44 and 45 therefore bisects what you call Zone 45R. You can verify this with the on-line version of GeoConvert at

<http://geographiclib.sourceforge.net/cgi-bin/GeoConvert>;

In any case, the ell2utm function allows you to specify the central meridian for any non-standard zone definitions. See help ell2utm for more information.

-Mike

Very useful! Thank you very much.

It is really a good toolbox. Thank you for making my life little easy. One suggestion for the author on Julian dates. In the function jd2cal, jd has to be positive. jd can be negitive (if they exist), following modification needed to the code

if(a==0)
   dy = c - e - fix(30.6001*f) + rem((jd+0.5),max(a,1));
else
 dy = c - e - fix(30.6001*f) + rem((jd+0.5),a);
end

In above case you are able to get 1st gragorian date for zeroth julian day. otherwise greogrian calander start from 2nd jan.

Dr. Vihang Bhatt