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Measuring gum smudges  

My plan is to extend a lesson I have used in the past through the use of imagej to calculate areas of irregularly shaped objects.

In the spring I will be doing a unit on measurement. One of the things I emphasis is that every measurement is an estimate and that trade offs are always made between accuracy, precision and cost.

To do so I explore different ways of calculating areas. Starting with the simple problem of finding the area of the hallway floor outside my room(being careful not to specify what exactly I mean by the "hallway"). I move onto irregularly shaped objects - gum smudges.

Our school sidewalk is covered with different layers, shapes and sizes of gum smudges. I send students out with paper and pencil to do rubbings of several smudges which we then return to the classroom and calculate the areas of.

I ask them to use several techinques to calculate areas, superimposed grid, Pick's Theorem and polygon approximation and to experiment with the calulations to see the trade offs between precsion and cost in time.

I have done this the last couple years and it has worked well. This year I plan to add to the mix some digital photos of the smudges and the task of analyzing them in imagej to find the areas. The challange will be to decide how to best take the photos and what parts of imagej to teach, I want a minimum set so as not to distract from the lesson on measurement. I see this addition as a way to do some differentiated instruction providing a more of a challenge to some students.

I am also toying with the idea of having them use mapping software to map the locations of the collected smudges, but as this does not fit the goals of the unit we will be doing at the time, I am not sure I want to invest the time into it.

Let me know what you think



Share edittextuser=707 post_id=1203 initial_post_id=0 thread_id=374

Adding the use of ImageJ to find area seems to fit into your existing activity very well. It's also a good way to demonstrate an approach to image analysis that is being used in many fields right now.


Share edittextuser=704 post_id=1209 initial_post_id=0 thread_id=374

The idea of taking a bunch of kids out on the sidewalk to analyze gum smudges is all-time classic. I can only imagine the commentary this must generate. As for the software, maybe you could do something similar to what we did with the Boston harbor by "clicking" around the outside edge of the smudge to define the area (I think we used GIS for this though)? Just a thought. Great idea and good luck with it.


Share edittextuser=703 post_id=1212 initial_post_id=0 thread_id=374

I am going to try this in sthe spring. What a great idea. your students could go on to calculate percentage of area covered by gum. They could predict the best places to put "gum collectors".


Share edittextuser=877 post_id=1213 initial_post_id=0 thread_id=374

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