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Author Topic: large numbers  (Read 6137 times)

JMR

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large numbers
« on: June 27, 2011, 08:55:09 AM »
Hi, folks
I've found that ground coordinate system with long figures (ie. 123456.789, 1234567.890, 123.456) but set as local system make PS to generate ugly orthophotos.
I guess it might be related to a loss of precission associated to rounding numbers.
I'd suggest to PS team to declare a huge translation variable to shorten numbers during input and restore them to long during output.

Alexey Pasumansky

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Re: large numbers
« Reply #1 on: June 27, 2011, 02:44:04 PM »
Hello,

Could you please describe the problem in more detail.

Could you also attach an image of "ugly orthophoto", does it differs from the one built from the same set of images with "short" coordinates?
Best regards,
Alexey Pasumansky,
Agisoft LLC

JMR

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Re: large numbers
« Reply #2 on: June 27, 2011, 04:03:43 PM »
Yes, of course:
My ground coordinates are something close to 462000,4628000,900
Y created a file for the GCP as follows

<?xml version="1.0" encoding="UTF-8"?>
<keypoints coordinates="local" units="meters">
<marker name="point 1">
<x>462582.342</x>
<y>4628588.892</y>
<z>940.461</z>
</marker>
<marker name="point 2">
<x>462767.209</x>
<y>4628712.763</y>
<z>940.718</z>
</marker>
<marker name="point 3">
<x>462687.261</x>
<y>4628775.345</y>
<z>927.825</z>
</marker>
<marker name="point 4">
<x>462543.799</x>
<y>4628672.434</y>
<z>926.673</z>
</marker>
</keypoints>

So I imported them and calculated with final residuals being arround 22cm
I then exported orthophoto with 0.05m/pix as aimed resolution resulting in what I called ugly ortho :P
Then I simply changed coordinates by substracting 462000, 4628000, 900 and tried the same ortho... the results are better looking now. Have a look
http://imageshack.us/photo/my-images/718/8pugly.jpg/ before
http://imageshack.us/photo/my-images/143/8dfine.jpg/ after

Alexey Pasumansky

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Re: large numbers
« Reply #3 on: June 27, 2011, 06:02:18 PM »
Thanks for reporting the problem.

We reproduced it and now are looking where it came from.


Best regards,
Alexey Pasumansky,
Agisoft LLC