Lecture 14 - Change Detection

Question 1

What has to be kept the same when comparing change detection data?

Answer 1

• Spectral and Spatial resolution
• Imagery from the same time of the day
• Images from the same time of the year
• Vegetation should be in a similar phenological stage

Question 2

What is image differencing?

Answer 2

The imagery of one data is subtracted from the imagery of another date.
Imagery can be of reflectance wavebands or band ratios e.g NDVI
Both positive and negative values are interpretable

Question 3

What is the threshold value?

Answer 3

Determine threshold value to differentiate change/no change

Question 4

What is an image time series analysis for?

Answer 4

Widely applied to detect land surface changes e.g wildlife, deforestation, regeneration
Can be done from daily to annual temporal image frequency.

Question 5

What is involved in a post-classification analysis?

Answer 5

Independently classifying images from two dates.
An algorithm is used to compare the classified images to produce a map of the change