Aerial Photography and Remote Sensing – Study Outline

land use/land cover

A. definitions

1. land cover – the surface material and vegetation. Strictly speaking this is all you can see on an aerial photo.

2. land use – how humans are using the land. This must be interpreted from the observed land cover

3. A land use/land cover classification scheme allows you to divide observed land cover into useful categories that can be mapped, measured and compared.

B. a useful land use/land cover classification scheme to be used with remote images should meet certain goals

1. the classification should be accurately determined from remote sensing >85% of the time

2. the accuracy of classification of different categories should be about the same

3. the scheme should be repeatable with different interpreters and at different times

4. it should be applicable to large area

5. it should allow interpretation of land use from land cover if possible

6. it should give the same result from images remotely sensed at various seasons

7. categories should be divisible

8. categories should be able to be aggregated

9. comparison with future images and classifications should be possible

10. it should recognize multiple use when possible

C. Many LU/LC classification schemes exist, from those developed specifically to manage one natural area to scheme that allow classification of the entire world.

D. One scheme that is frequently referenced and often serves as a basis for other schemes is the USGS scheme

E. USGS

1. The scheme has four levels each more detailed than the last

a. the 1^st two levels can be easily determined from remote images

2. level 1 includes seven classes

a. urban, agriculture, range, forest, water, wetland, barren, tundra

b. definitions must make it clear which class dominates when they might otherwise overlap, e.g. a heavily forested subdivision is urban, not forest.

F. practicalities

1. in classifying an image you must determine what your minimum mapping unit will be. What is the smallest area that will be meaningful?

2. when interpreting multiple images, the boundaries from one image must be transferred to the next image to avoid overlapping. Vertical parallax may make the boundary different shapes on adjacent images, so the boundary must be based on image features, not just straight lines.

3. in some cases land use can only be determined by ground investigation

a. is a forested area designated for hiking only? hunting? timber? (though careful interpretation of a photo might provide some clues…)

b. is grassy field hay land or pasture?

c. classification is often an iterative process,

i. examination of an image leads to interpretation questions

ii. field investigation of a site clarifies the classification

iii. interpretive keys are determined while at the site that allow additional similar sites to be classified without a site visit

4. vertical parallax may skew area measurements, since high areas are bigger than low ones