Make CenterLine filter makes it easy to measure area. You don’t need to stretch the selection to fit it through center of the boundary. So, you will get the area at a time.
Measure image taken by camera
Earth orbit script
Get same area always
In version 5.25 “Mean” option added in Main Menu>Tools>Option>Magic Selection/Color Bucket Settings…. Enabling this option makes area always same and accurate at a particular tolerance, even in noisy environment and clicking anywhere in a region. You will get this image in “Trial Images” folder to test yourself.
Accurate measurement with Measurement palette
For accurate map measurement the selection have to go through the center of the map border. But if your map border is thick then you have to grow the selection for setting it through the center line of the border. By measurement palette you can grow or shrink the selection separately width or height or both and you will get the area, width, height of stretched selection same time.
For example, if your border is 2px thick and after selection and clearing noise width is 129px in Result palette. Then new width in measurement palette have to be 130px. If you are measuring map then don’t forget to enable the “Calculate with border” option.
Accuracy comparing of Whoitam Image Measurement with other internet resource
Whoitam Image Measurement is accurate than any other software in internet up to now. You see it in this video. It is only an example. Here a script is used to draw the circle to test. Because, circle drawn by this method makes more accurate shape than other circle drawing method. you will find this script in “Script Samples” folder.