Re: [OpenMap Users] TM Projection

Hi Mark,

On Dec 8, 2003, at 6:51 AM, Gatrell, Mark (UK) wrote:

>
> Don/All
> Has anyone produced a Transverse Mercator Projection class for
> general use?

I haven't seen one, and I haven't heard of anyone working on one.

> I am trying to use the CSVTiledImagePlugin class to display some UK
> Ordnance Survey raster scanned maps. My problem is that the OM system
> does not have a TM projection class available and so when I try and
> put 2 tiles alongside each other, they mismatch by about .75 Km if I
> use any of the available projections.
>
> The OS maps are drawn using a Transverse Mercator projection on an
> airy spheroid (I'm sure you know that, Just clarifying!).
>
> I must admit, I thought that if I used the gnomonic projection I
> would get a better result, but it appears to be about the same.
>
> So first of all if someone has a TM class I could use I would be most
> grateful.
>
> Have I understood the principal of operation for these projections??
> I.E. If I take an image of a map that has been produced with a common
> projection system and overlay it at the correct geographic coodinates
> on the OM system with the same projection, Would the maps
> goegraphically tie up with (a) each other and (b) Any vector map
> information that I have as standard already (I.E. VMapL0)?.

Yes to both.

Regards,

- Don

>
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