Image Prep Flashcards
3 Steps to Image Prep
Layer Stacking, Image Mosaicking, Image Subsetting
Layer Stacking deffinition
Stacking all spectral bands captured by a sensor to make a single image
Checklist for Layer Stacking
- are all from the same sensor at the same time
- have same spatial extent
- all georectified (have same coordinate/projection system)
Image Mosaicking definition
Combining multiple images with the same geographic extent into one seamless extent
Check list for Image Mosaicking
-Neighboring images have overlap
-Same spatial resolution (or resample to finer resolution)
-Check projection, spatial ref, and datum
-match image stretching algorithms
-Pick a Mosaic Operator
Mosaic Operator definition
How the computer determines pixel values (DNs, brightness values, etc.) of overlapping pixels
Mosaic Operator list of options
-Minimum
-Maximum
-Mean
-First/Overlay
-Last
-Sum
-Blend/Feather (most common)
Blend/Feather mosaic operator
a distance weighted algorithm
The closer a pixel is to the center of one raster then the greater wight that DN
Image Subsetting definition
Limiting/reducing the image to only the Area of Interest (AOI)
Like clipping but its not raster data
Can only refine to squares/rectangles cause its a computer
Elements of an image to interpret (list)
-Tone/Color
-Shape
-Size/Scale
-Texture
-Pattern
-Shadow
-Site/Association
-Expert/Local Knowledge
Tone definition in image interp
Tone refers to brightness in black and white images
Texture definition in image interp
-The spatial arrangement of features in a systematic way
-Repetitions of tone or color
-Rough vs Smooth
Pattern definition in image interp
-Spatial arrangement of features in a landscape
-Moran’s I quantifies this (clustered vs dispersed)
Shadow notes in image interp
-Related to height
-Can be used for time of day
-Can be used to find the height of an object
-Better at higher latitudes
