i.ortho.photo

Radoslav Bonk bonk at fns.uniba.sk
Fri Oct 9 03:14:14 EDT 1998


Hi, Taravudh
I worked with i.ortho.photo a time ago. I.ortho.photo works like script a
allow you to use them interactively. It will help you during all the
orthorectification proces.
You will need
1. DEM model of your area of interest, with a resolution of 1m /with g.
region you can do this/, physical resolution can be smaller eg.10m. Bigger
resolution, the better.
2.You need to scan your aerial photos together with fiducial marks at the
corners. Its enough to scan 5 of them. As for resolution, it depends from
your needs,/please check the manual/ 400 dpi lokks enough for identifying
landuse areas.
 3.You need coordination of fiducial marks and followed
parametres of camera:-camera name
       -identify number of the camera
       -focus length of the camera
       -center of the photo at X direction
       -center of the photo at Y direction
       -coordination of fiducial marks at the corners of the photo
These parametres you can get from your provider of aerial photographs
4.Put your photograps into to 256 color mode and put them into the GRASS.
You need to scan also a map sheet, from which you digitized contours and
georeference it into the GRASS.
5.So you now have at your "grassdata" directory with a mapset with raster
of -DEM
   -aerial photo
   -topographic map
6. You will start with. i.ortho.photo /sometimes  I had to start with
i.group and then continue with i.ortho.photo/. i.ortho.photo will provide
you during the orthorectification proces. An aerial photograph will looks
poor at the graphic window /due the the 8bit model/, but with original
photo is possible to work.


When you will pick control points from the map, you need at
least 15 control points. More control point, better orthorectification,
even the RMS error is higher.
For your help you can check a GRASS manual pages for a programs and
"M.Neteler:Introducing GRASS manual"/I think its German and India project/

Rado Bonk


*************************************************
 Radoslav Bonk
 Comenius University,Faculty of Natural Sciences
 Department of Physical Geography and Geoecology
 Mlynska Dolina 842 15,Bratislava SLOVAKIA
 fax:07/65429064
 e-mail: bonk at fns.uniba.sk
 PRIVAT: Svinia 221, 082 32; tel:+421/91/958 187
*************************************************


On Fri, 9 Oct 1998, taravudh wrote:

> Hi, all
> 
> I'm Taravudh. I'm interested in orthophoto processing by using GRASS,
> but I didn't know how to start and prepare necessary image data for it.
> If you have experience about this process , please introduce me.
> 
> Thank you very much..
> Taravudh.
> 
> 
> 
> 



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