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Mosaicking images that are not georeferenced

by Technical Evangelist on ‎04-07-2016 08:35 AM (1,094 Views)

Question

Is it possible to mosaic a series of images that are not geo-referenced? Two images, ‘image1’ and ‘image2’, are not georeferenced and need to be contatonated with each other in a vertical direction with ‘image1’ on top of image2’.

Answer

It is possible to mosaic a series of images that are not georeferenced. The file coordinates of the images will need to be changed to align one image on top of the other.

 

For example, let's say that the X and Y pixel dimensions for each image is 1000 x 1000. The file coordinates for both images would be:

Upper Left X: 0.0

Upper Left Y: 0.0

Lower Right X: 999.0

Lower Right Y: -999.0

Keep the coordinates as they are for the first image, but change the coordinates for the second image so that it will be aligned above the first image. The updated coordinates for the second image should be changed to:

Image 2

Upper Left X: 0.0

Upper Left Y: 1000.0

Lower Right X: 999.0

Lower Right Y: 1.0

 

The coordinates for the images can be changed using the Metadata tool. Select ‘Home tab > Information group > Metadata’ to open the Metadata tool. Open the image (Image 2) to be mosaicked above the other image in the Metadata tool and select ‘Edit > Change Map Model' to display the Change Map Info dialog. Using the example above, change the Upper Left X to 0.0 and the Upper Left Y to 1000.0. The Lower Right X and Y coordinates will be updated automatically.

 

After the changes above, these two images should align in the proper vertical position when both images are displayed together in the IMAGINE Viewer.

 

The two images can be mosaicked using ‘File > Save As > View As Image’. This will save all of the data in the IMAGINE Viewer to a single IMG file. One very important item to make note of is to have the Background Transparent option turned on when displaying the images in the Viewer together before using the View As Image command. This option is found under the Raster Options tab in the Select Layer To Add dialog when selecting the image(s) to display in the Viewer.

 

Before using ‘File > Save As > View As Image’, set the zoom level in the IMAGINE Viewer to its default setting (1X) for the images. To do this, right-click in the Viewer window to display the Quick View menu and select `Zoom > Reset.

 

Now select ‘File > Save As > View As Image’ which will display the Select Output File dialog. From the Select Output File dialog, specify the output file name. Under the Options tab, select Full as the Area to Use and make sure that the Maintain Aspect Ratio option is enabled so that the ratio of width to height remains constant as the output image size is adjusted.

 

Helpful Hint: MosaicPro can also be used to mosaic the images after the coordinates of the input images have been adjusted.

 

 

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