Politecnico di Milano-BEST Department – Faculty of Architecture

National Technical Uni. of Athens – Rural & Surveying Engineering

Workflow

Photomodeler Scanner v.2012

Image Orientation

Bregianni Angeliki

Diploma Thesis

aggelikh@msn.com

Milan, March 2012

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Abstract

The present manual describes the process of the relative orientation in Photomodeler Scanner (PM), as it was done during March of 2012 in the diploma thesis for the church of Santa Maria in Scaria, Intelvi.

Orientation of the Photos

1. Open Photomodeler 2. From the menu choose Automated Project

3. Choose Smartpoints Project and then next

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This means that the procedure of recognizing common points in the photos is fully automated by an algorithm that Photomodeler runs.

4. Now, you need to import the photos you want to orientate. Click on Add Photo(s). A Windows explorer window will open. Choose the photos you need and click ΟΚ. Then Next.

5. Then the dialogue menu asks you to import the camera’s calibration information. Choose the .pmr or .cam file that you have saved the calibration parameters into. Click Apri and then Next.

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7. In this point you are ready to do run the SmartPoints process. Click Run and when it end click Close.

8. Now all the photos are imported and you can see them in PM. Choose them all by using Ctrl+A. Right-click, then Open selected photos. Now you can also see the common points detected by PM in step 7.

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9. Now you can start the process of Referencing by clicking the button from the toolbar. The referencing menu will open on the left of the screen.

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10. Now you can see that if you move the curse up to a photo it has changed shape and it is a cross (referencing mode).

ZOOM: mouse roller or +/- buttons from the keyboard In addition you can press Alt and a smaller window with a zoom-in appears. You can move in this window by moving the mouse and holding pressed the Alt button.

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11. Pick the same point in the other photos that it is visible. By default it is chosen that the epipolar lines are visible (to change that: Menu-Referencing-Show/Hide Reference Helper Lines)

*After marking the point on all images you can right click on it, go to Properties and put his “true” name (this on the monographies) on the field ‘Name’, then click Apply-Ok. *If you do a mistake you can use Ctrl+Z to undo it. *If for any reason you stopped the referencing of one point you must choose this point in one of the images you have already marked it and continue with those which remain. (While you proceed the epipolar lines make the recognition of the point easier, as their intersection defines it. But don’t use exactly the point that PM suggests, as the errors need to be adjusted.)

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12. After finishing with one point you can compute the RMS error of the orientation. From the toolbar choose the button Process Then this dialogue will appear: Click Process.

When it’s finished you can see the final error, how many photos were orientated and the number of the integrations done. Usually we need the error under 1 pixel.

You can do the same procedure for each point you add in order to know which point you need to exclude in case the error gets worse or really big (in this case probably you have picked a completely other point).

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13. Set a scale to your project:

First draw a line that connects two points (two new points) that you know approximately their distance with the button that it is shown next:

Then you need to set a scale to the project. Do that by clicking in the toolbar the button:

Set the units (meters) and then press Next:

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Set the known distance and then press Next:

Choose the line you have drown before and then press Next:

Then choose Finish wizard.

14. With the procedure described in step 13 you have now set a scale to your project and you are able to check the precision of your measurements. a. Open the Point table-All window from the menu Table Windows on the toolbar.

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Now you can see on the right part of the screen a table that has different below (x, y, z precision- RMS residual):

You can sort your point per each one of the columns so that you know the max and min precision and also the mean by looking at the middle of the columns. b. Another way to check the precision is to use the Measurements function from the toolbar. A new window appears on the right. In this window every time you click on a point or a line it shows you its coordinates and their precision.

15. Photomodeler gives you also the ability to see a 3D view of the points and also the

camera’s positions by using the 3D Viewer . The result is something like this:

You can rotate and move object with the toolbar on the below right corner of the 3D Viewer.

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16. At the end you can Idealize your images from the menu Project-Idealize Project. This means that you produce distortion-free images to work with in the future (external orientation, DSM and orthophoto generation etc.).

PM calculates a default number of images to process with. Sometimes this doesn’t work, so you need to try with 2-3 photos each time and when the idealization is successful you may add more images. *An error about the calibration camera may appear in case you have done it with different software. You may ignore it and continue.

17. Now click again on Process. The error should be less than the one before.

*The points that are measured manually are called GCPs=Ground Control Points, which means that they are common points measured in more than 3 pictures with known geodetic coordinates.