What We're Measuring

What We're Measuring

introduction

a quick remote sensing primer

understanding 30-meter resolution

images to land cover

what we mean by developed

pixels vs. parcels

curious trends: water vanishes and wetlands expand

curious trends: other grasses and agriculture grows

curious trends: turf and grass in a steady state

Understanding 30-meter Resolution and its Limits

Resolution is the smallest possible level of detail of a given sensor (for you cartographers, the “minimum mapping unit.”) No feature on our land cover maps can be smaller than our minimum unit, which is 30 meters – that’s about 10,000 square feet, or ¼ acre. Thus, small features are often missed, and each square, or pixel, represents our best estimate as to the predominant land cover of that pixel.

To the right is a high resolution aerial photograph, with a 30 meter resolution grid superimposed. Pixel #1 is a homogenous pixel almost covered with trees, and would likely be interpreted by our project as a forested pixel. Pixel #2 is a “mixed pixel” with both vegetation and a large house; because the house covers a good portion of the pixel, this one would likely be interpreted as a “developed” pixel. Pixel #3, however, has a smaller structure, and might be interpreted as either “forest” or “developed,” depending on how the computer interprets the data.

Comments or Suggestions? Email us at clear@uconn.edu.