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NAME

       i.ortho.rectify   -  Orthorectifies  an  image  by  using  the  image  to photo coordinate
       transformation matrix.

KEYWORDS

       imagery, orthorectify

SYNOPSIS

       i.ortho.rectify
       i.ortho.rectify --help
       i.ortho.rectify    [-ca]     group=name      [input=name[,name,...]]      extension=string
       [resolution=float]      [memory=memory    in    MB]      [method=string]      [angle=name]
       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -c
           Use current region settings in target location (def.=calculate smallest area)

       -a
           Rectify all raster maps in group

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       group=name [required]
           Name of input imagery group

       input=name[,name,...]
           Name of input raster map(s)

       extension=string [required]
           Output raster map(s) suffix

       resolution=float
           Target resolution (ignored if -c flag used)

       memory=memory in MB
           Amount of memory to use in MB
           Default: 300

       method=string
           Interpolation method to use
           Options: nearest, linear, cubic, lanczos, linear_f, cubic_f, lanczos_f
           Default: nearest

       angle=name
           Raster map with camera angle relative to ground surface

DESCRIPTION

       i.photo.rectify rectifies an image by using the image to photo  coordinate  transformation
       matrix   created   by   i.photo.2image   and   the  rectification  parameters  created  by
       i.photo.2target.  Rectification is the process by which the geometry of an image  is  made
       planimetric.   This  is  accomplished  by  mapping  an image from one coordinate system to
       another. In i.photo.rectify the parameters computed by i.photo.2image and  i.photo.2target
       are  used  in  equations  to convert x,y image coordinates to standard map coordinates for
       each pixel in the image.  The result is an image with a standard  map  coordinate  system,
       compensated  for  relief distortions and photographic tilt. Upon completion of the program
       the rectified image is deposited in a previously targeted GRASS LOCATION.

       Images can be resampled with various different  interpolation  methods:  nearest  neighbor
       assignment,  bilinear  and  bicubic  interpolation. The bilinear and bicubic interpolation
       methods are also available with a fallback option. These methods "fall  back"  to  simpler
       interpolation methods along NULL borders. That is, from bicubic to bilinear to nearest.

       The  process may take an hour or more depending on the size of the image, the speed of the
       computer, the number files, and the size and resolution of the selected window.

       The rectified image will be located in the target LOCATION when the program is  completed.
       The original unrectified files are not modified or removed.

       The  optional  angle  output  holds  the  camera  angle  in  degrees to the local surface,
       considering local slope and aspect. A value of 90 degrees indicates that the camera  angle
       was  orthogonal to the local surface, a value of 0 degrees indicates that the camera angle
       was parallel to the local surface and  negative  values  indicate  that  the  surface  was
       invisible  to  the  camera.  As  a rule of thumb, values below 30 degrees indicate problem
       areas where the orthorectified output  will  appear  blurred.  Because  terrain  shadowing
       effects  are not considered, areas with high camera angles may also appear blurred if they
       are located (viewed from the camera position) behind mountain ridges or peaks.

       i.photo.rectify can be run directly, specifying options in the command line or the GUI, or
       it  can  be invoked as OPTION 8 through i.ortho.photo. If invoked though i.ortho.photo, an
       interactive terminal is used to determine the options.

   Interactive mode
       You are first asked if all images within the imagery group should be  rectified.  If  this
       option  is  not  chosen,  you are asked to specify for each image within the imagery group
       whether it should be rectified or not.

       More than one file may be rectified at a time. Each file should have a unique output  file
       name. The next prompt asks you for an extension to be appended to the rectified images.

       The  next  prompt  will  ask you whether a camera angle map should be produced and if yes,
       what should be its name.

       After that you are asked if overwriting existing maps in the target  location  and  mapset
       should be allowed.

       The next prompt asks you to select one of two windows:

             Please select one of the following options
             1.   Use the current window in the target location
             2.   Determine the smallest window which covers the image
             >

       If you choose option 2, you can also specify a desired target resolution.

       i.photo.rectify  will only rectify that portion of the image that occurs within the chosen
       window.  Only that portion will be relocated in  the  target  database.  It  is  therefore
       important  to  check  the  current  window  in the target LOCATION if choice number one is
       selected.

       Next you are asked to select an interpolation method.
             Please select one of the following interpolation methods
             1. nearest neighbor
             2. bilinear
             3. bicubic
             4. bilinear with fallback
             5. bicubic with fallback
             >

       The last prompt will ask you about the amount of memory to be used by i.photo.rectify.

SEE ALSO

        i.ortho.photo
       i.ortho.camera
       i.photo.2image
       i.photo.2target
       i.ortho.init
       i.rectify

AUTHOR

       Mike Baba,  DBA Systems, Inc.
       Updated rectification and elevation map to FP 1/2002 Markus Neteler
       Bugfixes and enhancements 12/2010 Markus Metz

       Last changed: $Date: 2013-02-20 11:16:02 +0100 (Wed, 20 Feb 2013) $

SOURCE CODE

       Available at: i.ortho.rectify source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual