Vertical Near-Side Perspective Projection

K_AmbrozK_Ambroz Global Mapper UserPosts: 3
edited March 2012 in Projection Questions
Hallo,
I have a problem with setting projection.

In Image Rectifier I marked GCPs and set Longitude and Latitude of this point. Than I clicked on the button Select Projection and selected Vertical Near-Side Perspective Projection. But when I wanted to reproject GCPs to new projection the GM threw a message: The GCP Point no.XX could not be reprojected to the new projection. It will be interpreted instead.

Could you help me.
Thank you Klara

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2012
    Klara,

    That means that the lat/lon locations that you entered could not be projected to the Vertical Near Side Projection that you set up, likely because they were on the other side of the world from the projection center or something. What are the lat/lon values you are using (just one sample is fine) and how did you setup the Vertical Near-Side projection (i.e. what parameters)?

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • K_AmbrozK_Ambroz Global Mapper User Posts: 3
    edited March 2012
    Thank you for your answer. I thought that I have an error in parameters of projection. Could you help me with calculating of right values (some formulas maybe).

    Thanks, Klara.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2012
    Klara,

    You probably just want to set your central longitude and central latitude for the projection to a location of the center of your image (assuming it was taken from directly overhead). The Height of Perspective Point would typically be the height (in meters) from which the picture was taken, such as the elevation of the satellite above the surface of the earth.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • K_AmbrozK_Ambroz Global Mapper User Posts: 3
    edited March 2012
    But my problem is, that I know the approximate geographic coordinates and pixel coordinates of the projection centre, then the geographic coordinates and pixel coordinates of GCPs, but the height of perspective point is unknown and I need calculate it.

    Thanks, Klara.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2012
    Klara,

    I don't know an easy way to calculate that, but really for rectification purposes you don't need to know the exact parameters of the original projection, so long as you know exactly some coordinates and approximately the original projection your rectification should be very good. Even if you don't know the original projection at all if you know enough control points you can get arbitrarily good results.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
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