Crater counting
QUESTION
1) Watch the YouTube tutorial, read the Examples & FAQs at the end of this document, and read the Background & Methods pdf. Review Module 3’s Falling Space Objects.
2) Now, on to our Martian images! Click on the image, you will notice the entire image is selected (little handles appear on the edges).
3) A click on a circle selects the circle and then you can move it (with your mouse, or the arrow keys). Copy the circle and paste it to make a new one (CTRL + C then CTRL + V, or just CTRL + D). You’re going to want to be zoomed in. If you stretch a circle resize it with the scale bar.
4) Move a circle over a crater of the proper size range. In the example above, the crater is more than 32km but less than 64 km in diameter; it is therefore in the 32-64 km category (red circle). The picture has a 32km green circle to show the crater is too large for that group.
5) While a circle is selected, (it still has the little handles for rescaling and moving on it), press CRTL +D (hold control key and press D) to make a second circle of the same size near the first one. Move the second circle to another crater and generate the next circle with CTRL+D again. Move across the image systematically until all craters of that size are filled. Probably best to count whilst using the provided circles (make tic marks on a sheet). You have CTRL + Z to undo a mistake.
Notes:
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