Image Photos vs. Classified Image Which one is better?

Comparing Image Photos and Classified Images for Land Cover Level of detail Level of detail Skill required to create and use Skill required to create and use Time and costs to create and use Time and costs to create and use Utility for automated analysis/modeling Utility for automated analysis/modeling Accuracy – distortions and illusions Accuracy – distortions and illusions Comparing land cover for two different dates Comparing land cover for two different dates

Level of detail Image photo Image photo one can see subtle differences in visual cues (tone and texture) one can see subtle differences in visual cues (tone and texture) can visualize gradients can visualize gradients Classified image Classified image There is no variation within a class There is no variation within a class Patterns of land cover are more obvious but may be misleading Patterns of land cover are more obvious but may be misleading

Skill Required to Create and Use Image photo Image photo Basic image enhancement and interpretation skills are helpful Basic image enhancement and interpretation skills are helpful Requires familiarity of the landscape to interpret accurately Requires familiarity of the landscape to interpret accurately Classified image Classified image Requires thorough understanding of classification methods to create Requires thorough understanding of classification methods to create Very easy to interpret Very easy to interpret

Time and Costs Image photo Image photo Cost usually limited to the cost of the data Cost usually limited to the cost of the data Instantly available after the image is acquired Instantly available after the image is acquired Classified image Classified image Can be very expensive Can be very expensive Can take months or years to complete Can take months or years to complete

Utility for Automated Analysis/Modeling Image photo Image photo Not suitable for quantitative analysis or modeling Not suitable for quantitative analysis or modeling Classified image Classified image Well suited for quantitative analysis and modeling. Well suited for quantitative analysis and modeling.

Accuracy – Distortions and Illusions Image photo Image photo Accuracy difficult to measure - depends on the skill of the interpreter Accuracy difficult to measure - depends on the skill of the interpreter Visual identification of a feature often more reliable then automated classification Visual identification of a feature often more reliable then automated classification Atmospheric effects can distort the image “colors” to make similar cover types look different Atmospheric effects can distort the image “colors” to make similar cover types look different Classified image Classified image Should be accompanied by accuracy assessment results Should be accompanied by accuracy assessment results Accuracy of 80% often considered reasonable Accuracy of 80% often considered reasonable

Comparing Two Different Dates Image photo Image photo Superimpose two images covering the same area by flickering or swiping Superimpose two images covering the same area by flickering or swiping Combine image bands from two image dates into a single RGB image (TM Band 5 or 3 early = Red and TM Band 5 or 3 late = Green and Blue) Combine image bands from two image dates into a single RGB image (TM Band 5 or 3 early = Red and TM Band 5 or 3 late = Green and Blue) Classified image Classified image Automated classification methods can be use to produce a land cover change map Automated classification methods can be use to produce a land cover change map