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Generate an orthomosaic using the Orthomosaic wizard

Available with Advanced license.

An orthomosaic is a photogrammetrically orthorectified image product mosaicked from an image collection, where the geometric distortion has been corrected and the imagery has been color balanced to produce a seamless mosaic dataset.

Color balanced imagery showing seamlines and the resulting orthomosaic

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:

  1. Color balancing
  2. Seamline generation
  3. 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.

Color Balance Settings

Modify the settings to color balance your orthomosaic. Color balancing adjusts the appearance of individual images to make the transition from one image to an adjoining image appear seamless.

Parameters for Color Balance Settings

Parameter nameDescription

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.

Balance Method

The color balancing algorithm to use.

  • Dodging—Adjust image pixel values toward a target color surface using a dodging window and the corresponding gamma function established from the local statics of the window and the target color surface. The color surface can be calculated from the input image collection with the specified color surface type or from an external target raster. This is the default.
  • Histogram—Adjust image pixel value by matching the histogram of each image and histogram of total image collection or the histogram of the external target raster if specified. This technique works well when all of the images to be color balanced have a similar histogram.
  • Standard deviation—Adjust image pixel value by matching the histogram within one standard deviation between each image and the whole image collection or the target raster if specified. This technique works best when all of the images to be color balanced have normal distributions.

Color Surface Type

When using the Dodging balance method, each pixel needs a target color, which is determined by the surface type.

  • Single color—Use when there are only a small number images and a few different types of ground objects. If there are too many rasters or there are too many types of ground surface features, the output color may become blurred. All the pixels are altered toward a single color point, which is the average of all pixels.
  • Color grid—Use when you have a large number of images, or areas with a large number of diverse ground objects. Pixels are altered toward a grid of color points, which are distributed across the image collection.
  • First order—A color surface (a slanted plane) represented as first order polynomial. This technique tends to create smoother color changes and uses less storage in the auxiliary table, but it may take longer to process compared to the color grid surface. All pixels may be altered toward many points obtained from the two-dimensional polynomial slanted plane. The result is similar to that of Single color.
  • Second order—A color surface represented as a second order polynomial. This technique tends to create a smoother color change and uses less storage in the auxiliary table, but it may take longer to process compared to the color grid surface. All input pixels are altered toward a set of multiple points obtained from the two-dimensional polynomial parabolic surface. This method produces an intermediate result between that of Single color and Color grid. This is the default.
  • Third order—This technique tends to create a smoother color change and uses less storage in the auxiliary table, but it may take longer to process compared to the color grid surface. All input pixels are altered toward multiple points obtained from the cubic surface. The result is similar to that of Color grid.

Target Raster

The raster you want to use as a target to color balance the image collection. It can be a raster dataset, a mosaic dataset or an image service. The statistics required by the balance method and color surface type, if applicable, will be derived from this target image.

Recalculate Statistics

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.

Number of Columns to Skip

The number of horizontal pixels between samples.

A skip factor controls the portion of the raster that is used when calculating the statistics. The input value indicates the horizontal or vertical skip factor, where a value of 1 will use each pixel and a value of 2 will use every second pixel. The skip factor can only range from 1 to the number of columns/rows in the raster.

The value must be greater than zero and less than or equal to the number of columns in the raster. The default is 1 or the last skip factor used.

The skip factors for raster datasets stored in a file geodatabase or an enterprise geodatabase are different. First, if the x and y skip factors are different, the smaller skip factor will be used for both the x and y skip factors. Second, the skip factor is related to the pyramid level that most closely fits the skip factor chosen. If the skip factor value is not equal to the number of pixels in a pyramid layer, the number is rounded down to the next pyramid level, and those statistics are used.

Number of Rows to Skip

The number of vertical pixels between samples.

A skip factor controls the portion of the raster that is used when calculating the statistics. The input value indicates the horizontal or vertical skip factor, where a value of 1 will use each pixel and a value of 2 will use every second pixel. The skip factor can only range from 1 to the number of columns/rows in the raster.

The value must be greater than zero and less than or equal to the number of rows in the raster. The default is 1 or the last y skip factor used.

The skip factors for raster datasets stored in a file geodatabase or an enterprise geodatabase are different. First, if the x and y skip factors are different, the smaller skip factor will be used for both the x and y skip factors. Second, the skip factor is related to the pyramid level that most closely fits the skip factor chosen. If the skip factor value is not equal to the number of pixels in a pyramid layer, the number is rounded down to the next pyramid level, and those statistics are used.

Seamline Settings

Specify the seamline settings for your orthomosaic. Seamlines are polygons that are used for defining mosaicking boundaries and resolving the image overlaps.

Parameters for Seamline Settings

Parameter nameDescription

Computation Method

The computation method to use to generate your seamlines:

  • Disparity—Generate seamlines based on the disparity images of stereo pairs. This method can avoid seamlines cutting through buildings.
  • Voronoi—Generate seamlines using the area Voronoi diagram. This is the default.
  • Radiometry—Generate seamlines based on the spectral patterns of features within the imagery.
  • Edge Detection—Generate seamlines over intersecting areas based on the edges of features in the area.
  • Geometry—Generate seamlines for overlapping areas based on the intersection of footprints. Areas with no overlapping imagery will merge the footprints.

Advanced Options

Pixel Size

The pixel size to use for seamline generation. Sometimes, a mosaic dataset contains raster items with different resolutions. This parameter allows you to choose the pixel size to use to generate your seamlines.

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.

Processing

Blend Width Units

The unit of measurement to use for blend width:

  • Pixels—Measure using the number of pixels. This is the default.
  • Ground units—Measure using the same units as the mosaic dataset.

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.

Blend Type

The method for blending one image into another over the seamlines. Options are to blend inside the seamlines, outside the seamlines, or both inside and outside.

  • Both— Blend using pixels on either side of the seamlines. For example, if the Blend Width is 10 pixels, then five pixels will be blended on the inside and outside of the seamline. This is the default.
  • Inside—Blend inside of the seamline.
  • Outside—Blend outside of the seamline.

Request Size Type

The units for the Request Size.

  • Pixels—Modify the request size based on the pixel size. This option resamples the closest image based on the raster pixel size. This is the default.
  • Pixel scaling factor—Modify the request size by specifying a scaling factor. This option resamples the closest image by multiplying the raster pixel size (from cell size level table) with the pixel size factor.

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.

Sliver Removal Options

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

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.

Orthomosaic Settings

Specify the output settings for your mosaic.

Parameters for Orthomosaic Settings

Parameter nameDescription

Pixel Size

The pixel size for the orthomosaic.

Format

The output format for the orthomosaic:

  • Cloud Raster Format
  • TIFF Format
  • JPEG Format
  • JPEG2000 Format
  • Meta Raster Format

Compression

The compression method for the output. The following options will be available based on the Format you choose:

  • None
  • LZW
  • JPEG
  • JPEG2000
  • LERC

Optional

Orthorectify Source Image Collection Using

The Digital Elevation Model (DEM) you will use to orthorectify the orthomosaic. If nothing is specified, the DEM associated with the image collection is used.

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