Pierrerue tutorial

Download

• There is a direct download link to download this dataset at :http://micmac.ensg.eu/data/pierrerue_dataset.zip
  

Once you have download it, you have to UnZip the ".zip" archive.

Description

• 31 JPG images
• 1 file containing the support points (Pierrerue.xml)
• We will use the folder 001_Elements-de-georeferencement

About the data

The shooting contain 31 images, taken with the Sony alpha850 with a 244mm lens. Check taht the folder contains images recovering :

• facade n°1
• facade n°2
• the corner between these 2 façade (images link).

Support points are available and allows to georeference the readings (see the folder 001_Elements-de-georeferencement).

Tutorial

1. Set up the images

All the images should be set up simultaneously, in order that the georeference process will be expressed into one only cordinate system. First, we can run the tie-points search :
mm3d Tapioca MulScale ".*JPG" 600 2000
Then, we have to define the settings of the camera used from the images covering the corner between the 2 facades (more suitable than the others, because of the depth).
mm3d Tapas RadialStd "angle.*JPG" Out=Calib24mm
Into the command prompt, we can check if the residual from the images is admissible (around the half pixel). We can check also the number of connection points, aswell as the percentage of points keeped ("99.8258 of 28466" : 99.8% of the connection points keeped from 38466 points calculated).
We can process yet the setting up of all the images. starting from the camera we calculated before.
mm3d Tapas RadialStd ".*JPG" InCal=Calib24mm Out=MEP
Into the command prompt, we can control residual during the process. At the last step, we can see that the image residual are, for all the images, less than a half-pixel. We control also the number of support points, aswell that the percetage of points keeped ("99.8258 of 38466" : 99.8% of the support points keeped from the 38466 points calculated).
The AperiCloud command alllows to generate 3D clouds, containing all the support points obtained with Tapioca, and the position of the cameras obtained from the Tapas output.
mm3d AperiCloud ".*JPG" Pierrerue
The result of this command can be seen for example with the meshlab software.

2. Set up the images into the coordinates system of the support points

Now we have to measure the support points available to georeference the images, and so the incoming products, into the reference coordinate system.
Explaining the process :

• 1. We measure 3 support points well distributed (SaisieAppuisInit command) ;
• 2. We can now create a 3D similarity (transformation from 7 settings containing one scale coefficient, one translation into space and one space rotation) between the arbitary system calculated while the setting up and the coordinate system chosen (GCPBascule command) ;
• 3. We have now to measure the remaining points : the absolute orientation calculated from the previous step, allows to suggest an approximated position for each points (SaisieAppuisPredic command) ;
• 4. We affine the absolute orientation (GCPBascule command) ;
• 5. We start the final computation for the setting up (this offset allows to find the best position/orientation of the cameras while using the points measurements on the linking points and on the support points) ; (Campari command).