[OSGeo Africa] PRR: UTM latitude bands

[Aslam Parker]

HI All
 
Universal Transverse Mercator is a coordinate system (just as with
Gauss Conform) and is a special case of the Transverse Mercator
Projection.  It was designed to stretch the TM projection to the
longitudinal limit and spreads the distortion across the 6 degree design
extent. 
 
The cylinder wraps around the earth in the Transverse aspect and
therefore do not have latitudinal bands (besides the equator which is
the natural nortings origin)
 
I have uploaded a document describing the UTM projection as well as a
discussion on distortions. 
https://sites.google.com/site/mapprojections/downloads .The document is
called "The UTM projection.doc". 
 
I hope this assists
 
 
 

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>>> Peter Newmarch <newmarch at land-surveyors.com> 2014/08/25 02:08 PM
>>>
Hanlie,

UTM only has Longitudinal bands. Their are no, and have never been, any
Latitude bands.

There is distortion on the central meridian of 4cm per 100m, and the
same at the 3 degree edges on either side. At 1 1/2 degrees from the
central meridian - the scale is 1.

Regards

Peter

Peter Newmarch
Professional Land Surveyor
4Y GeoInformatics Pty Ltd
Tel       : +27 31 5642856
Fax       : +27 31 5643074
Mobile    : +27 82 5705859
eMail     : newmarch at land-surveyors.com On 2014/08/25 12:05 AM, Tim
Sutton wrote:


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Hi Hanlie

On 13/08/2014 08:26, Hanlie Pretorius wrote:

Hi,

I've noticed that GIS packages such as QGIS and libraries such as 
PROJ4 (which QGIS uses, I think) don't use the latitude bands in
the UTM grid.

Does anyone know why the full UTM grid with latitude bands is not 
implemented? Does it result in any additional distortions as one
moves away from the equator?

I have Googled about this and have not been able to find the
answer.I guess this is an upstream question for the epsg, gdal and
proj4
projects (which we rely on for most of the projection work in QGIS). I
am not aware if it results in additional distortions as you move away
from the equator or if the bands simply provide false northings for
convenience. My limited understanding is that their distortion will
increase as you extend away in the longitudinal direction but not in
the latitudinal.

Regards

Tim


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intended recipient, any disclosure, copying, distribution or any action
taken or omitted in reliance on this, is prohibited and may be unlawful.
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