Gravillons tutorial

Download

You can found this dataset at :http://logiciels.ign.fr/?Telechargement,20
Datasets are available at the bottom of the page, in part test datasets. Then, UnZip the ".zip" archive.

Presentation

This dataset was created by L.Girod in Norway. This dataset was acquired to modelise a volcanoes model realised by O.Galland. File present in the directory are :

• 4 images : 1.JPG, 2.JPG, 3.JPG, 4.JPG.
• GCPs coordinates : Dico-Appuis.xml.
• Mesure of GCPs in images : Mesure-Appuis.xml.
• 1 Mask : 1_Masq.tif/1_Masq.xml
• 2 scripts de commandes : gravillons.sh (Linux) et gravillons.bat (Windows)

During this tutorial, we will approach general concepts, for more details, go further in tutorials or directly in commands pages.

Tutorial

1 Tie-Points research

The first step of each MicMac uses is to determine images which are looking at the same scene, this step is call image matching and performed by the command Tapioca :

mm3d Tapioca MulScale ".*.JPG" 500 1500

The MulScale option is generally faster, because it match images at high resolution (1500px here) only between images which are matching at low resolution (500px here).

2 Internal Orientation+Relative Orientation

If you are familiar with photogrammetry, you know that it's composed of three steps :

• Internal Orientation : which consist to determine camera's paremeter (focal length, PPA, PPS, distorsion center, or distorsion parameters).
• Relative Orientation : which consist to determine position of each camera's from each other in an arbitrary system.
• Absolute Orientation : which consist to bascule the relative orientation to a scaled and oriented system (typically WGS84)