Dear Gerald,

Thanks to your suggestion. In trying to give you a sample of expected output I've tested things more thoroughly (I'm a chemical engineer by training, so this geo-referenced mapping stuff is all new to me) and it does appear to be working correctly -- almost.

my input file, "Desktop/proj" had this:
27.5 0.00
27.5 10.0
27.5 20.0
27.5 30.0
27.58676 26.18728

My commands and output from the console:

neil <at> neil:~$ proj +proj=tmerc +ellps=WGS84 +lon_0=27 Desktop/proj
55660.46    0.00
54820.34    1105896.37
52324.06    2212444.34
48243.45    3320218.65
58652.24    2897715.76

In each case, the magnitudes are correct (as far as I can tell using other software) but the first column of values should all be negative.

i.e. Desired output:
-55660.46    0.00
-54820.34    1105896.37
-52324.06    2212444.34
-48243.45    3320218.65
-58652.24    2897715.76


Gerald I. Evenden wrote:

On Monday 11 August 2008 4:07:58 am Neil Robinson wrote:

Hi Gerard, Thanks for your response. I realise that this isn't a support forum, but I'm not getting any joy anywhere else and you are clearly very knowledgeable on this topic

...

I tried lodging a bug with qgis [1], but they seemed to think the problem was with proj4 (although, through my ignorance that was my guess, so I might have planted the seed of that conclusion).

I would just use +proj=tmerc and put some added '-' flags to juggle the I/O. But that's somebody else's job as I only work on the library.

I tried this suggestion (I think I did), but negative zero doesn't make any sense to proj4. Without adding the '-' flags, this is what I think the parameters need to be for one of the projections I'm interested in: +proj=tmerc +ellps=WGS84 +lat_0 +lon_29 +k=1 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

Can you give a sample input (lat/lon) and an approximation of what you expect (without datum conversion which I cannot handle). Under normal circumstances the above would generate (viewed as a console screen capture): gie <at> charon:~$ lproj +proj=tmerc +ellps=WGS84 +lon_0=29 31 45 157693.72 4986890.93 Note; option +towgs84 and +no_defs is not on my software and the other options are defaulted as you explicitly specified. The input is longitude(31), latitude(45) and the output is easting(x) and northing(y) in meters. What output would you prefer to see?

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