Constraining cutlines

Depending on the cutline-generation method you select, you can also specify options related to constraining polygons, which define regions where cutlines are allowed. This prevents the generated cutlines from crossing the specified regions.

Specifying a local or global cutline-avoidance mask

You use cutline-avoidance masks to prevent cutlines, if possible, from crossing specific areas. Local cutline-avoidance masks are specific to individual images and apply to features that change between images, such as clouds. Global cutline-avoidance masks define areas common among multiple images through which cutlines should not be generated, such as buildings.

Automatically generating a cutline-constraint file

The Auto Constrain check box controls whether to automatically generate a constraining polygon layer. With this check box selected, the Mosaic Preparation module generates one constraint polygon for each input image. When the input images contain a lot of overlap, the constraint polygons limit the data to be considered for cutline generation to only the central parts of each image. This option was designed specifically for airphoto projects because of the typical large amount of overlap in the images. The auto constrain can be adjusted by specifying a value for the associated Thiessen Factor parameter. This value is a percentage between 1 and 100, with greater values causing more overlap between the generated constraint polygons.