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Area of Sicily
In this task we will try to measure area of island of Sicily in the satellite image of Italy (Apenine peninsula).
- Open italy.jpg
- Zoom-in to the lower right part of the image. To do this, select 200% in the Zoom factor combo box (you can use mouse-wheel to zoom in/out if you have it). Use scroll bars of the image to scroll to right and down.
- Calibrate measure tools (if you donít know how, read lesson 2). Correct calibration factor is around 1 pixel = 2.27 km.
- Select Area of Polygon mode (top right-most button of toolbar).
- Left-click on any point of islandís shore. Click to nearby shore point. Keep clicking until you come around the island. In the end click with right-mouse button to calculate area of polygon.
- In the shown case, Able Image Analyser has calculated area of 26574 square kilometres. Correct area of Sicily is 25706 sq. km, so our error is only 868 sq. km, which is only around 3.5%. If we selected more points (more accurate representation of shore), we would get even better result.
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