DIVISION C

NC Science Olympiad 2008 Coaches Institute

Remote Sensing

Remote Sensing Image Scale Tutorial

Determining the scale of an image.

Mt. St. Helens

This ASTER image of Mt. St. Helens volcano in Washington was acquired on August 8, 2000 and covers an area of 37 by 51 km. The image is centered at 46.2 degrees north latitude, 122.2 degrees west longitude.

Step (1) Convert the real world distance into centimeters ...

(37 km) X (1,000 m/km) X (100 cm/m) = 3,700,000 cm

Step (2) Divide the real world distance (3,700,000 cm) by the

measured length from the image (12.5 cm) ...

3,700,000 / 12.5 = 296,000.

12.5 cm

in image

37 KM

Real World

Step (3) The non-dimensional scale is ...

1 unit in the image equals 296,000 units in the real world,

the non-dimensional image scale is 1 : 296,000.

51 KM

Real World

Step (4) To express the scale as cm in the image per km in the real world ...

divide 296,000 by 100 cm/m and then by 1,000 m/km.

(296,000cm) / (100 cm/m) / 1,000 m/km) = 2.96 km.

The image scale is 1 cm = 2.96 km

NOTE: measurements in this sample calculation may not match those from your printout due the size of paper you’ve printed, or automatic shrinking/stretching accomplished by your software and/or printer.

October 24 – 25, 2008

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Slide 1