www.sdlsuite.com Forum Index www.sdlsuite.com
Discussion of technical aspects of the SDL Component Suite
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Calibration question: setting corners as calibration point

 
Post new topic   Reply to topic    www.sdlsuite.com Forum Index -> GeoPack
View previous topic :: View next topic  
Author Message
jvgoor



Joined: 07 Sep 2011
Posts: 42
Location: Maasland, The Netherlands

PostPosted: Wed Apr 18, 2012 12:15 pm    Post subject: Calibration question: setting corners as calibration point Reply with quote

There is a maximum number of calibration points to be used and set at a maximum of 200. As calibration model I use cmBiquadraticPn.

I have some quite large images with maps at a smaller scale (1:25.000) to use. When calibrating these I think to put a grid over the image with many calibration points. I also place a calibration point at each corner of the image. In the description of the calibration data there is also an array Corners, which are calculated from the calibration data.

So if this is done, can I then forget about setting a calibration point at the corners?

Looking forward for your answers.
_________________
Jaap van Goor
Promanent b.v.
Back to top
View user's profile Send private message Visit poster's website
hlohning



Joined: 08 Sep 2006
Posts: 277
Location: Austria

PostPosted: Wed Apr 25, 2012 11:47 am    Post subject: Reply with quote

Jaap,

the "Corners" array is meant to get an easy access to the extents of the map. If your calibration is fine, the calculated corners should match the actual corners on the map to plus/minus 1 pixel - no matter wheter you included the corners into your calibration.

Kind regards,

Hans
_________________
Hans Lohninger
Software Development Lohninger
http://www.lohninger.com/
Back to top
View user's profile Send private message Visit poster's website
jvgoor



Joined: 07 Sep 2011
Posts: 42
Location: Maasland, The Netherlands

PostPosted: Wed Apr 25, 2012 12:33 pm    Post subject: Calibration question: setting corners as calibration point Reply with quote

Hans,

Thanks for the reply. It is true that using 200 or 196 calibration points should not realy matter if these include the corners. However with smaller scale maps and overlaying these or trying to "glue" them together one pixel difference is visible.

This is because the georeferencing and calibration of source material is also a calculation of the reality.

Greetings,

Jaap
_________________
Jaap van Goor
Promanent b.v.
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    www.sdlsuite.com Forum Index -> GeoPack All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group