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Generate ortho mapping products using the Custom wizard

Available with Advanced license.

The Custom Product wizard provides a flexible guided workflow for generating you ortho mapping products. For example, you can generate a digital elevation model (DEM) and an orthomosaic at the same time, using the Custom wizard. Or you can generate a mosaic by disabling steps that are not needed for you workflow, such as turning off color balancing if the image colors are already homogeneous.

Custom Products pane

Product Generation Settings page

This page in allows you to specify which ortho mapping products you want to create. This wizard allows you to create a digital elevation model (DEM), an orthomosaic, or both. Check on the products you want to create. Each ortho mapping product also has options for to perform specific tasks during its creation.

Checkbox nameDescription

Digital Elevation Model

Check this box to create a digital elevation model ortho product.

You will need to complete the Point Cloud Settings page. If you do not check the Interpolate DEM from Solution Points checkbox, then you will also need to complete the DEM Interpolation Settings page.

Interpolate DEM from Solution Points

Check this box to create your digital elevation model by interpolating from solution points. When you check this box, you only need to complete the Point Cloud Settings page.

Orthomosaic

Check this box to create an orthomosaic product.

Generate Seamlines

Check this box to build seamlines during the orthomosaic creation. If you choose to build seamlines, you will need to complete the Seamline Settings page.

Color Balance

Check this box to color balance the image collection during the orthomosaic creation. If you choose to color balance, you will need to complete the Color Balance Settings page.

Generate Orthomosaic

Check this box to create a raster dataset output for the orthomosaic. If you choose option, you will need to complete the Orthomosaic Settings page.

Point Cloud Settings page

Parameters for Point Cloud Settings

Parameter nameDescription

Matching Method

There are three matching methods for generating point cloud:

  • ETM (Extended Terrain Matching)—is a feature-based stereo matching in which the Harris operator is used in detecting feature points. It is recommended for DTM generation.
  • SGM (Semi-Global Matching)—is an algorithm which produces points that are denser and with detail info of the terrain. It can be used for images of urban areas. This is more computational intensive than ETM.1
  • ESGM (enhanced SGM)—produces sharper edges for buildings.

Maximum Object Size (in meters)

A search radius that is used to filter out objects above ground. Objects smaller than the threshold will be filtered as ground otherwise it will be treated as objects such as buildings, bridges, or trees.

Point Ground Spacing

Defines the spacing, in meters, at which the 3D points are generated.

The default spacing is five times the source image pixel size.

Minimum Intersection Angle (in degrees)

The value, in degrees, that defines the minimum angle the stereo pair must meet. The default is 10.

Maximum Intersection Angle (in degrees)

The value, in degrees, that defines the maximum angle the stereo pair must meet. The default is 70.

Minimum Area Overlap

The percentage of overlapping area over the whole image. The default is 0.6.

Maximum Omega / Phi Difference (in degrees)

The maximum threshold for the Omega/Phi difference, between the two image pairs. The Omega values and Phi values for the image pairs are compared. If the difference between either the two Omega or the two Phi values is above the threshold, the pairs will not be formatted as a stereo pair.

The default threshold difference, for each comparison, is 8.

Maximum GSD Difference

The threshold for the maximum ground sample distance (GSD) between two images in a pair. If the resolution ratio between the two images is greater than the threshold value, the pairs will not be built as a stereo pair. The default is 2.

Number of Image Pairs

The number of pairs used to generate 3D points. The default value is a minimum of 2 image pairs.

Sometimes a location may be covered with many image pairs. In this case, the tool will order the pairs based on the various threshold parameters specified within this tool. The pairs with the highest scores will be used to generate the points.

This parameter limits one pair to be used too many times. The parameters that affect the order of the stereo pair, besides Minimum Intersection Angle, Maximum Intersection Angle, Minimum Area Overlap, may also include Maximum Omega / Phi Difference, Maximum GSD Difference, and Adjustment Quality Threshold.

Adjustment Quality Threshold

Specify the minimum adjustment quality that is acceptable. The threshold value will be compared to the adjustment quality value that is stored within the stereo model. Image pairs with an adjustment quality less than the specified threshold will receive a score of 0 for this criteria and will descend in the ordered list. The range of values for the threshold is from 0 to 1. The default value is 0.2, which is equal to 20 percent.

DEM Interpolation Settings page

Parameters for DEM Interpolation Settings

Parameter nameDescription

Surface Type

Create a digital terrain model or a digital surface model.

  • DTM—Create a digital terrain model by interpolating only the raster surface using ground only points.
  • DSM—Create a digital surface model by interpolating a raster using all the points; both ground and above around points.

Cellsize

The cell size of the output raster dataset.

Format

The format for the output raster dataset:

  • Cloud Raster Format
  • TIFF Format
  • Meta Raster Format.

Interpolation Method

The method used to interpolate the output raster dataset from the point cloud.

  • TIN Linear Interpolation—Also known as triangulated irregular network (TIN) linear interpolation designed for irregularly distributed sparse points, such as solution points from block adjustment computation.
  • TIN Natural Neighbor Interpolation—This is similar to triangulation but generates a smoother surface and is more computationally intensive.
  • Inverse Distance Weighted Average Interpolation—This is used for regularly distributed dense points, such as point cloud LAS files from the Generate Point Cloud tool. The IDW search radius is automatically computed based on average point density.

Smoothing Method

Select a filter to smooth the output raster dataset.

  • Gaussian 3 by 3—A Gaussian filter with a 3 by 3 window.
  • Gaussian 5 by 5—A Gaussian filter with a 5 by 5 window.
  • Gaussian 7 by 7—A Gaussian filter with a 7 by 7 window.
  • Gaussian 9 by 9—A Gaussian filter with a 9 by 9 window.
  • No smoothing—No smoothing filter is applied.

Fill Missing Pixels Using

A DEM raster input that is used to fill NoData areas. Areas of NoData may exist where pixels do not have enough information, from the input, to generate any values.

Orthorectify images using DEM

The generated DEM will be used to refine the orthorectification of the image collection. This is the default behavior.

if you do not wish to replace the current elevation model of the with the newly generated DEM, you can uncheck the option.

References

  1. Heiko Hirschmuller et al., "Memory Efficient Semi-Global Matching," ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume 1–3, (2012): 371–376.

Seamline Settings page

Parameters for Seamline 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.

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.

Computation Method

Choose the computation method to use to generate your seamlines:

  • Geometry—Generate seamlines for overlapping areas based on the intersection of footprints. Areas with no overlapping imagery will merge the footprints.
  • 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.
  • Voronoi—Generate seamlines using the area Voronoi diagram.
  • Disparity—Generate seamlines based on the disparity images of stereo pairs. This method can avoid seamlines cutting through buildings.

Cellsize

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.

  • 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

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.

  • 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

Set the units for the Request Size.

  • Pixels—Modify the request size based on the pixel size. This is the default option, which resamples the closest image based on the raster pixel size.
  • 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.

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

Parameters for Color Balance Settings

Parameter nameDescription

Balance Method

The color balancing algorithm to use.

  • Dodging—Change each pixel's value toward a target color. With this technique, you must also choose the type of target color surface, which affects the target color. Dodging tends to give the best result in most cases.
  • Histogram—Change each pixel's value according to its relationship with a target histogram. The target histogram can be derived from all of the rasters or you can specify a raster. This technique works well when all of the rasters have a similar histogram.
  • Standard deviation—Change each of the pixel's values according to its relationship with the histogram of the target raster, within one standard deviation. The standard deviation can be calculated from all of the rasters in the mosaic dataset or you can specify a target raster. This technique works best when all of the rasters 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 of raster datasets and a few different types of ground objects. If there are too many raster datasets or there are too many types of ground surfaces, the output color may become blurred. All the pixels are altered toward a single color point—the average of all pixels.
  • Color grid— Use when you have a large number of raster datasets, or areas with a large number of diverse ground objects. Pixels are altered toward multiple target colors, which are distributed across the mosaic dataset.
  • First 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 pixels are altered toward many points obtained from the two-dimensional polynomial slanted plane.
  • Second 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 a set of multiple points obtained from the two-dimensional polynomial parabolic surface.
  • 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.

Target Raster

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.

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.

Orthomosaic Settings

Parameters for Orthomosaic Settings

Parameter nameDescription

Pixel Size

The pixel size for the output orthomosaic.

The output pixel size should be the same or larger than the pixel size of source image.

Format

The output format for the output orthomosaic.

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

Compression

The compression method for the output

  • None
  • LZW
  • JPEG
  • LERC
  • JPEG2000

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