[Xastir] Maps, again!

[Gerry Creager n5jxs]

Reality check.  Edge matching and gap removal are significant and 
humanlabor intensive.  There a couple *expensive* systems that attempt 
decent edge matching automagically.  What you appear to deacribe in the 
comment about gaps and whitespace is an edge matching problem.

One other consideration is that a rigorous image registration process 
requires at least 5 coordinate pairs be known and that they be 
distributed around and within the near-centroid of the image.  If you 
acquired the images from someone who did it right, and if you're 
absolutely certain of the datum and projection the images are in... AND 
if they're well rectified (camera tilt removed, distortion from 
off-vertical-angle imagery compensated for) then you can safely start 
the process of stitching the images together.

I've not looked at your pages yet: the apparent misunderstanding 
required a quick response.  I reserve the right to revise my comment 
again after a review of your pages!  :-)

73, gerry

John Ronan wrote:
> Hi There again,
> 
> I'm about to head up to my folks place (30 miles or so - EI7IG-9), I've 
> been busy putting in the sections of the map so that I can see it 
> afterwards.
> 
> Each Tiff is 4724 x 4724 and the boundarys are the lines in the map.  So 
> I've been using
> http://www.megalithomania.com/conversion/
> 
> To convert from Irish Grid to Degrees Minutes Seconds and then
> http://www.uky.edu/KGS/gis/converter.htm
> 
> to convert to decimal Lat/Long.
> 
> I'm wondering what others use to convert to decimal lat/long as I'm 
> seeing gaps/slight overlaps in the pictures.
> 
> Tomorrow I'll check it out a bit more, but It looks to me like a 
> rounding error of some sort as two of the maps (I've done a square) that 
> I have done have the northeast/southwest corners at the correct point.
> 
> Bearing in mind that I know little or nothing about maps except that 
> they are all a 'projection' of some sort.  Can I assume that as I go 
> further and further from the 'point' mentioned above that I will begin 
> to see gaps in the projection.
> 
> Thanks for the help (and a great application)
-- 
Gerry Creager -- gerry.creager at tamu.edu
Network Engineering -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020
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Office: 903A Eller Bldg, TAMU, College Station, TX 77843