NR 322: Scale and Resolution Jim Graham & Alex Daniels Fall 2010 Chapter 2

Scale Scale is the scale of the map relative to the true size of the items on the map e.g 1:750,000 –1 unit on the map is equivalent to 750,000 units on the earth Small scale vs Large scale Which number is larger –1 / 750,000 or 1 / 2

Map Scale

Misunderstood Terminology Small Scale = Large Extent –Think of the divisions on the scale being small –Miles are smaller at small scale Large Scale = Small Extent –Think of the divisions on the scale being big –Miles are larger at large scale Recommendation: –Use Large Extent or Small Extent –Use Low Resolution or High Resolution

Scale can vary on a map What is the scale in kilometers on a Geographic Projection map?

Scale can Vary What is the scale on a google earth map?

Resolution Resolution is the ability to resolve detail We mostly refer to Spatial Resolution –For Rasters/Grids/Digital Photos this means the size of the pixels. –What distance on the ground does one pixel represent? 30 Meters

30m vs. 1m Spatial Resolution

Washington D.C. ~ 30m

Washington D.C. ~ 5 m

Resolution High resolution is awesome, why don't we make everything 1m data or better? The number of pixels increases exponentially as you increase spatial res. Resolution x 2 Pixels x 4

High Resolution ~ Big Files Rasters and photos can get really big really fast. Civilian satellites now can take satellite photos as high as 41 cm resolution i³ in Fort Collins has 1m Satellite Photos that take 300 Gigabytes for just one area.

Low spatial resolution Low resolution averages data

Accuracy and Precision Accuracy is how close something is to the true value Precision is how close of a measurement you can make High accuracy doesn't mean high precision