Ideal isolated targets are defined by templates that are not blurred, have prefect edges, and have a black border of at least one pixel all around the targets in the template image file. These are used to mark isolated targets in photos (that is targets that are surrounded completely by a uniform background). The targets in the photos can be any size and any orientation and they are marked to sub-pixel precision. Distinct targets with a uniform, high contrast background will generally provide better solutions.
The program ships with two cross-shaped ideal isolated targets.
The program ships with two different cross targets to point out an issue to be considered with some types of targets. The ratio of the width of the arms to the length of the arms is important for getting good solutions. Another way to think about it is that the shape of the cross matters but the overall size does not. The target template should have similar arm width to arm length ratio as in used in the project’s photographs. For example, a cross with short, thick and stubby arms would not work well if the crosses in the photograph had slender and long cross arms. You can create your own cross template to match the crosses uses in your imagery.
The two provided templates are named “Cross 3/29” and Cross 5/23” to denote the ratio of cross arm width to its length. The Cross 5/23 is a “stubbier” cross as the ratio of the width of its arms to the length of its arms (in this case the height of the whole cross target) is 5 to 23.
When manually marking an Ideal Isolated target, it is important to outline a region around the target that is similar in size proportionally to the border of pixels in the template target. Marking may fail if the region outlined around the target is too tight on the target. It is better to err on a larger region, but it is best to avoid including too much ‘noise’, or other high contrast shapes.