Available with Advanced license.
An orthomosaic is a georeferenced image product mosaicked from an image collection, where the geometric distortion has been corrected and orthorectified.
The Orthomosaic wizard provides a common workflow for generating ortho image mosaics from the adjusted image collection. The Orthomosaic wizard provides a guided workflow with three preconfigured steps to generate a photogrammetrically corrected image from your image collection:
- Seamline generation
- Color balancing
- Orthomosaic settings
You can modify the default processing parameters, but you cannot remove a step. If you want to perform a specific step, you can use the Custom wizard.
Seamline Settings page
The first page to create a mosaic is to specify the seamline settings. Seamlines are polygons that are used for defining mosaicking boundaries and resolving the image overlaps.
Parameters for Seamline Settings
Select Mosaic Candidates
The Select Mosaic Candidates parameter is normally used for image collection with dense overlaps such as drones. It is used to find an optimum set of images that can be used in mosaicking images. The selected images will be used in seamline building, color balancing, and output mosaic operation.
Check on the checkbox to perform the selection of the best image candidates to use.
Maximum Overlap Area
The maximum amount of overlap that you want between the mosaic dataset and the footprint of each image in the mosaic dataset. If the percentage of overlap is higher than this threshold, the image is excluded since it will have too much redundant information.
The percentage is expressed as a decimal. For example, a maximum overlap of 60 percent is expressed as 0.6.
Maximum Area Loss Allowed
This is the maximum percentage of area that can be excluded by the candidate images. After the tool chooses the best candidate images based on the Maximum Area Overlap, it will then check to see if the maximum excluded area is below the threshold specified. If the excluded area is greater than the specified threshold, the tool will add more candidate images to fill in some of the voids that were missing. Most of these excluded areas will likely be along the border of the mosaic dataset.
The percentage is expressed as a decimal. For example, a maximum excluded area of 5 percent is expressed as 0.05.
Choose the computation method to use to generate your seamlines:
Generate seamlines for raster datasets that fall within the following range of spatial resolutions.
Minimum Region Size
Specify the minimum region size, in pixel units. Any polygons smaller than this specified threshold will be removed in the seamline result. The default is 100 pixels.
Blend Width Units
Specify the unit of measurement for blend width.
Blending (feathering) occurs along a seamline between pixels where there are overlapping rasters. The blend width defines how many pixels will be blended.
If the blend width value is 10, and you use BOTH as the blend type, then 5 pixels will be blended on the inside and outside of the seamline. If the value is 10, and the blend type is INSIDE, then 10 pixels will be blended on the inside of the seamline.
Determine how to blend one image into another, over the seamlines. Options are to blend inside the seamlines, outside the seamlines, or both inside and outside.
Request Size Type
Set the units for the Request Size.
Specify the number of columns and rows for resampling. The maximum value is 5,000. Increase or decrease this value based on the complexity of your raster data. Greater image resolution provides more detail in the raster dataset but also increases the processing time.
Minimum Thinness Ratio
Define how thin a polygon can be, before it is considered a sliver. This is based on a scale from 0 to 1.0, where a value of 0.0 represents a polygon that is almost a straight line, and a value of 1.0 represents a polygon that is a circle.
Slivers are removed when building seamlines.
Maximum Sliver Size
Specify the maximum size a polygon can be to still be considered a sliver. This parameter is specified in pixels and is based on the Request Size, not the spatial resolution of the source raster. Any polygon that is less than the square of this value is considered a sliver. Slivers are removed when building seamlines.
Color Balance Settings page
The second page covers color balancing your mosaic. Color balancing makes transitions from one image to an adjoining image appear seamless.
Parameters for Color Balance Settings
The color balancing algorithm to use.
Color Surface Type
When using the Dodging balance method, each pixel needs a target color, which is determined by the surface type.
The raster you want to use to color balance the other images. The balance method and color surface type, if applicable, will be derived from this image.
Once color balancing has been performed, there may be new pixel values within your raster. Check the checkbox to calculate the statistics with latest pixel values.
The third page covers the output settings for your mosaic.
Parameters for Orthomosaic Settings
The pixel size for the output orthomosaic.
The output pixel size should be the same or larger than the pixel size of source image.
The output format for the output orthomosaic.
The compression method for the output