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Problem with raster converter
11-29-2007, 06:44 AM (This post was last modified: 11-29-2007 07:34 AM by AntonM.)
Post: #5
RE: Problem witrh raster converter
OK, I've tested co-ords now with MM and with Google Earth -- and I'm now really confused.

Both MM and GE give me the same Y:X 1:2 aspect ratio to what looks to me like a more or less square piece of earth.

I'm attaching a screenshot of GE, centred approximately around 53.0104 and -2.227, at the level shown, so it should be easy to reproduce the situation. The same area in MM gave more or less the same co-ordinates.

The co-ords at the edges (in GE) are:
top: 53.025690
left: -2.260963
right: -2.192941
bottom: 52.992256

According to my calculator, that gives a North/South difference of 0.033434 and an East/West difference of 0.076689.

It's been pointed out to me that the curvature of the earth is what's causing this, as at these latitudes, lines of longitude are getting a lot closer together. That sounds sensible, but then any flat representation of that piece of earth should be portrayed as it actually is (in this case, a square).

I've also attached the converter window of the GE display. as you will see, it also gives the aspect ratio warning: "Warning: Width/Height ratio should match, image=1.2190889, coordinates=2.0345142". I agree that there is a disparity between the image's aspect ratio and the co-ordinates' aspect ratio -- but is that not to be expected when, at these latitudes, co-ordinate "squares" are actually oblongs?

Somewhere I'm missing something in the whole process. I really want to get this worked out, because it will be an extremely useful feature.


Attached File(s)
.jpg  GE.JPG (Size: 83.94 KB / Downloads: 1)
.jpg  Converter.JPG (Size: 59.99 KB / Downloads: 2)
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Messages In This Thread
Problem with raster converter - AntonM - 11-28-2007, 10:24 AM
RE: Problem witrh raster converter - AntonM - 11-29-2007 06:44 AM
RE: Problem with raster converter - AntonM - 11-29-2007, 09:52 AM

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