lat/long

[Gerald I. Evenden]

>Date: Wed, 1 Jun 1994 16:35:47 +0800
>From: Joe Leone <Joe.Leone at per.dwe.csiro.au>
>To: grassu-list at max.cecer.army.mil
>Subject: lat/long
>
>Hi,
>
>I'am trying to convert data from lat/long format to UTM
>I seem to get different results depending on the conversion program I use and the format that the lat/long is provided.
>
>The lat/long I want to convert is:
>
>117.646439W 31.526952S
>
>My calculation say this equals 117:38:47W  31:31:37S
>
>I've used m.proj and m.ll2u. Here are the results
>
>m.proj					x	y		utm zone
>117.646439W  31.526952S		561371.86   13488193.98
>117:38:47W    31:31:37S		5400100.89   -22794869.83

*proj* from PROJ.4 executed with the following script

proj +proj=utm +zone=11 +south <<EOF
117.646439W  31.526952S
117d38'47W    31d31'37S
EOF

yields:

438627.09       6512001.01
438631.84       6512001.88

Slight differences are due to DMS form has less precision than the
decimal degree values.  Also, proj does not use GRASS :: DMS.  This
coordinate is somewhere in the wilds of the South Pacific.

>m.ll2u
>
>117.646439W  31.526952S		561371.8589...   3488193.99...   -11
>117:38:47W    31:31:37S		438632.9113...	 6511803.89...    50
> 
>m.ll2u would not accept the correct utm zone of 50

??? The longitude specified is in UTM zone 11!  The first line looks
like the 10,000,000m false northing for the southern latitudes was
not applied.  The zone of the second set is rediculous for a western
longitude.  Are we talking about Western Australia?  Thus:

proj +proj=utm +zone=50 +south +ellps=WGS84 <<EOF
117.646439E  31.526952S
EOF

561371.62       6511815.12

>Has anybody any suggestion for the differences and/or how to convert from the coordinates?
>
>Thanks in advance
>Joe leone
>Email joe.leone at per.dwe.csiro.au

First, lets get our ducks in order---South Pacific or Western Australia.
Second, what ellipsoid?  The number used and the results are confusing.

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