Take me to pcigeomatics.com

PCI Geomatics Help Center

How can we help you today?

Adjust Orthos

PCI Geomatics -

Adjust Orthos - TPS Model is a tool designed to fix misalignments between orthos using a thin plate spline method. This method allows for an overall better mosaick. It is common to have misalignment between orthos due to inaccuracy in ground control points (GCP’s) or a low accuracy DEM.

Found below is an example of a high resolution airphoto of Richmond Hill, Ontario. This airphoto has been corrected using only SRTM DEM. As a result the orthos do not aligned with each other.

The task of the TPS Model is to correct the overlap area of only one of the orthos. When this correction is made, both orthos will overlap each other. Areas outside the overlapped area will remain unchanged. This tutorial will show the steps taken to correct the misalignment between os188_tordem.pix and os189_dem.pix.

 

Project Setup

Open Geomatica 2013’s OrthoEngine application through the Geomatica toolbar, then click on the OrthoEngine button

Start OrthoEngine and click ‘New’ on the File menu to start a new project. Give your project a ‘Filename’, ‘Name’ and ‘Description’. Select ‘Adjust Orthos’ as the Math Modeling Method. After accepting this panel you will be prompted to set up the projection information for the output files, the output pixel spacing, and the projection information of GCPs. Enter the appropriate projection information for your project.

 

Data Input

1. On the OrthoEngine window in the Processing Step list, select GCP Collection

2. On the GCP Collection toolbar, click Open a new or existing image

3. Click New Image

4. From the appropriate folder, select os_188_tordem.pix and os_189_tordem.pix

5. Click Close

The two images are listed in the Open Image dialog box

You should save your project at this point. To save your project file, select “Save” from the “File” menu in the main OrthoEngine toolbar.

 

Collecting Ground Control Points Manually

1. On the OrthoEngine window in the Processing Step list, select GCP Collection

2. On the GCP Collection toolbar, click Collect GCP’s Manually

3. The GCP Collection window opens

4. In the Filename box click on Browse. Find file os_189_tordem.pix

5. Manually collect GCP’s

Another way to collect GCP’s would be to run Automatic GCP

 

Collecting Ground Control Points Automatically

Automatic GCP allows you to collect a number of points and then manually remove points that are mismatched or not at ground level. Points at roof tops or building tops should be removed. The automatic GCP collection was modified for this tutorial so that most of the points collected are at ground level.

1. On the OrthoEngine window in the Processing Step list, select GCP Collection

2. On the GCP Collection toolbar, click Collect GCP’s Automatically

3. The Automatic GCP Collection dialog box opens

4. In the Filename box click on Browse. Find file os_189_tordem.pix

5. In the Number of GCP’s per image enter 200

6. In the Images box click on Use os_188_tordem.pix

7. In the Automatic GCP Collecting dialog box click Match GCPs

8. Click Add GCPs to Project

9. Click Close

10. Repeat step 1 -9 for image os_188_tordem.pix

 

Viewing Collected GCPs

1. To view the result after automatic GCP collection, click on Display overall input layout in the OrthoEngine window

2. Click on the image you would like to see in the Overview window on the left

3. Double click on the image on the right

4. Zoom to Overview on the image displayed in the Viewer window

 

Defining Boundaries

Defining a binding polygon boundary is extremely important in Adjust Orthos as any area outside of the polygon will not be modified. The polygon drawn should include all the GPCs collected for the image.

1. On the OrthoEngine window in the Processing Step list, select Geometric Correction

2. On the Geometric Correction toolbar, click Define Bounding Polygons

3. The Viewer window and the Define bounding polygons window open

4. Click on the red box in the Viewer window and move it across the image to adjust the polygon to include the area you want

5. You can also input x and y values in the Upper Left, Upper Right, Lower Right, Lower Left input boxes in the Define bounding polygon window

6. Click Close

 

Generating an Ortho

1. On the OrthoEngine window in the Processing Step list, select Geometric Correction

2. On the Geometric Correction toolbar, click Schedule geometric correction

3. The Geometric Correction Image Production window opens

4. Move os_188_tordem.pix from Available images to Images to process

5. Select Browse under Corrected Images and select a destination folder

6. Input 256 as a Working cache

7. Select Cubic from the Resampling list options

8. Select Correct Images from the Geometric Corrected Image Production window

 

Viewing the Generated Ortho

The  output  new  ortho  generated  is  oos188_tordem.pix.  In  general,  the  result  should  be accurate at all the GCP location.

1. Open Focus

2. Navigate to the folder were you stored the corrected image

3. Open all 3 images to view the corrected alignment results oos188_tordem.pix, os188_tordem.pix, oos189_tordem.pix

Have more questions? Submit a request

Comments

Powered by Zendesk