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Automatic Mosaicking

PCI Geomatics -

The purpose of this tutorial is to highlight Geomatica’s advanced automated mosaicking capability. The primary mosaicking operations that will be exposed in this tutorial are image normalization, cutline editing and image colour balancing. New colour balancing tools have been added in Geomatica 2015 which are outlined in the colour balancing section of this tutorial.

Project Setup

1. Open the Geomatica 2015 OrthoEngine application

2. In the OrthoEngine menu bar, click File > New

3. Give your project a Filename, Name and Description

  • Select None (mosaic only) as the Math Modeling Method
  • Click OK

4. Input the appropriate Output projection and Resolution for the project

 5. Click OK

 

Adding Images to the Project

1. In OrthoEngine, change the Processing step to Image Input

2. Click on Open new or existing image button

3. In the Open Image panel, click New Image

4. In the File Selector navigate to the images you want to input

5. Click OK to the pop up message

6. Click Close

 

Define Mosaic

1. In OrthoEngine select the Display Project Overview button

2. The Project Overview window opens to display all of the images in the project.

3. Close this panel

4. In OrthoEngine, change the Processing step to Mosaic

5. Click the Define Mosaic Area button

6. In the Define Mosaic Area panel, click Browse

7. In the File Selector, select the output file name and location for the mosaic fill

8. Leave everything else as default in Define Mosaic Area Dialog box

9. Click Ok

Note: Footprints
The Define Mosaic panel allows the user to define the mosaic file that will be used to hold the mosaicked imagery. In this panel, the user can:

  • Set which images to include in the mosaic, by selecting/unselecting the footprints
  • Set the mosaic bounds by dragging the red rectangular boundary extent
  • Specify, which channels to include and the bit-depth of the channels

 

Generate Preview or Mosaic

1. In OrthoEngine, click the Automatic mosaicking button

2. In the Automatic Mosaicking panel, change the Normalization method to Adaptive Filter by selecting it in the dropdown list and click Apply All. For optical imagery, the Adaptive Filter and Hotspot are the only 2 normalization methods that are relevant. 

3. Under Mosaicking Options, ensure Bundle method is selected. This option must be selected in order to use the new colour balancing tools. Leave the Cutline options as their defaults.

5. Under File Options, click Browse next to preview file and ensure this is saved to your desired directory.

6. The panel should look like below:

7. Click Generate Preview

Note: Mosaic Preview and Generation
Generate Preview creates a low-resolution version of the mosaic. The preview file is saved under the path and file name specified in the Preview File box. You can use the preview of the mosaic to verify the color balance and cutline selection before continuing with the full resolution version. Click on Generate Mosaic and this will process all files and create the full-resolution version of the mosaic. The output mosaic is saved under the path and file name defined in the Define Mosaic window.

8. The Progress Monitor opens

9. The following preview will appear:

Note: About the Preview
The preview mosaic is a very valuable output, because it is a low resolution preview of the final mosaic, which provides the user with a strong idea of how the automatic settings for the color balancing and cutlines will turn out. Preview takes a fraction of the time to generate as compared to the final full resolution mosaic, so different settings can be used in different runs to compare which parameter set will provide the best results.

10. If you are satisfied with the results, you may click the Generate Mosaic button on the Automatic Mosaicking window to generate the full-size mosaic. If you are not satisfied, you may try different color balancing methods and running the Generate Preview again. If you are generally satisfied with the results, but see a few areas where the automatic color balancing was not correct, you may open the Manual mosaicking tool and edit these areas yourself. This will be covered in the Colour Balancing step in this tutorial.

 

Edit a Cutline
Once you have generated the mosaic preview using the Bundle colour balance method you can perform edits and additional colour balancing by choosing the Manual Mosaic tool. Before you perform colour balancing you should fix any cutline issues.

1. Open the Manual Mosaicking tool from the Orthoengine toolbar.

2. In the manual mosaic window select your working image from the image tree list. Click the Collection View button

3. The collection viewer opens and your working image is shown on top. Using the neighbors toggle button you can choose to display the neighboring image underneath.

4. Zoom into one section of your image along the cutline that overlaps the neighboring image. You can experiment with blend width, contrast, brightness and visualization mode.

5. To edit the cutline, click on the Vector Editing Toolbar icon The Vector Editing Tools window opens. You must select the cutline using the find button in the vector editing toolbar. Once selected, the vector editing tools will be available.

6. You can add vertices or move current vertices and reshape your cutlines. For instance you may wish to reshape cutlines that fall in a waterbody since these are likely to change colour across the images. In the images below a cutline through a lake has been edited. You will also notice that the cutline clipping is enabled in the second image. This option allows the user to clip the working image to the cutline.

 

Colour Balancing

Once you have edited the cutlines to minimize large colour matching issues you can edit the colour balancing for areas of poor matching.

1. In the Manual Mosaic window the colour balancing toolbar will be available.

2. Zoom to an area of the image where the images did not match well, such as the blue highlighted area above.

3. Use the Select tool and select the left image. It will flash cyan to indicate that it has been selected. In the situation above the image on the right is darker and more blue than the image on the left. We will add edge dodging points and change the colour and brightness of this area.

4. Using the add edge point tool place three dodging points along the edge of the colour change.

5. Select all three points and open the dodging brightness slider.

6. You can adjust this slider to change the brightness of the image that you selected. You can also chose to only change specific bands by changing the channel selection

7. For this section of the image the channel selection will be changed to blue. You can then increase the dodging brightness. Continue adjusting the brightness of each band until you have a satisfactory result.

8. Another type of dodging points are floating dodging points. You can use these points to fix local problems without affecting other areas of the image.

9. On the toolbar, click on Floating Dodging Points button

10. Right click to place a floating dodging point in about the following location.

11. In order to prevent the brightness changes made to this point from spreading to the rest of the image you can place other dodging points around the one you created.

12. You can now select the middle (red) point and adjust the brightness of that dodging point.

13. Place additional dodging points and adjust their brightness as required.

14. Close the MosaicTool after you have made all the edits you want, and be sure to save your project using File > Save on the OrthoEngine panel.

 

Generate the Mosaic

In this step you will generate the full mosaic that includes your Manual Mosaic edits.

1. Click the Automatic mosaicking button on the OrthoEngine toolbar to open the Automatic Mosaicking panel.

2. If you edited the cutlines you will need to check the “Use Existing Cutlines” box in the Automatic Mosaicking window.

3. Click Generate Mosaic. This will begin the automatic mosaicking process, and a progression bar will pop up displaying relevant information.

4. When the process is finished, a message will appear telling you that the automatic mosaicking is complete. Close the message by clicking OK and use your file explorer to browse to your completed mosaic file. You will see that the mosaic includes all of the edits that you made in the manual mosaic tool.

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Comments

  • Avatar
    Alejandro Chambi Buscaglia

    Hi,
    Nice manual. Just one question: working with satelite images that requieres Orthorectification and Atmospheric corrections such as WorldView 1-2 or 3 images, which should be the coorect approach, first perform Ortho process, then the Atmosferic Correction and then the mosaic building? or the orther doesnt matter. I said this because, the entry parameters for Orthorectification and Atmospheric correction comes with the original values.

    Thanks for your time and support,

    Alejandro

  • Avatar
    PCI Geomatics

    Hi,
    If you are performing atmospheric correction and orthorectification you would first run ATCOR on the image and then use the corrected image as the ortho input. ATCOR requires the raw file in order to read in the metadata and correct pixel values.

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