[PROJ] Latitude of natural origin in Transverse Mercator

[Ron Russell]

Note that the National Grid of Great Britain also includes a False 
Easting of 400km, to ensure that all coordinates in the system are positive.

There is also a Scale Factor on the Central Meridian (2 deg West) of 
0.9996012717 to reduce the scale distortion at the extremes of the 
projection. This means that the projected distance on the central 
meridian is slightly too small, there are two two lines where the local 
scale factor is 1.0 and outside these lines the lsf is greater that 1.0.

Regards,

Ron

Ron Russell
Tel : 01823 270308 email : ronrussell902 at gmail.com

On 13/01/2023 15:13, Charles Karney wrote:
> These are two interchangeable ways of shifting the northing component of
> the projected coordinate.  Mathematically they both do exactly the same
> thing and there's nothing the matter with specifying both a latitude of
> origin and false northing.  Indeed the Ordnance Survey grid system for
> Britain specifies
>
>  central longitude = -2 deg
>  latitude of origin = 49 deg
>  false northing = - -100 km
>
> This means that a shift is added to the northing component to ensure
> that the northing at latitude/longitude = (49 deg, -2 deg) is -100 km.
>
>
> On 1/13/23 09:28, Javier Jimenez Shaw wrote:
>> Hi
>>
>> I have a question about Transverse Mercator.
>> What is the impact of the parameter "Latitude of natural origin", 
>> compared with the "False Northing"? (apart from the fact that one is 
>> in degrees and the other in meters)
>> Is there any difference on using a Latitude of natural origin of, 
>> let's say, 40 degrees, or compute the equivalent False Northing?
>>
>> Thanks.
>> Javier
>> .___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
>> Entre dos pensamientos racionales
>> hay infinitos pensamientos irracionales.
>>
>>
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