Raster Processing and Analysis

Question 1

What is a profile graph?

Answer 1

Profile graphs allow you to visualize elevation change over a continuous distance using 3D line geometry.

Question 2

What information can a raster cell hold?

Answer 2

-Measured value
-Reflectance
-Classified/Coded value

Question 3

What is oblique imagery?

Answer 3

Imagery taken at a 40 to 50 degree angle (i.e., not an exact overhead shot)

Question 4

What is ortho imagery

Answer 4

Imagery taken at the nadir position (straight down)

Question 5

Certain types of landcover are known to reflect specific ranges of light. What is the term for this?

Answer 5

Spectral signatures

Question 6

What are the Normalized Difference Vegetation Index (NDVI) ranges and what do they mean?

Answer 6

NDVI values range from +1.0 to -1.0. The closer to +1 the healthier the vegetation. 0 is rock, sand, or snow. -1 is water.

Question 7

What are the two types of image classification methods?

Answer 7

-Supervised: the user trains the model on how it should classify images
-Unsupervised: the model classifies images on its own through pattern recognition

Question 8

What is object-based classification/segmentation?

Answer 8

Objects are classified based on shape, size, spatial, and spectral properties.

Question 9

What is the difference between Lossy and Lossless compression?

Answer 9

Lossy compression loses some data lossless does not.

Question 10

What are some examples of Lossless compression

Answer 10

LZZZ, Run-length encoding

Question 11

What is the difference between single band and multiband rasters?

Answer 11

Single band rasters only have one value associated with it while multiband has multiple

Question 12

What is bit depth?

Answer 12

Determines the range of values that can be stored in a raster cell. Rasters can range from 1 bit to 64 bit.

Question 13

What is the difference between signed and unsigned bit depth?

Answer 13

Signed bit depth includes negative integers. For example, an unsigned 8-bit raster has values that range from 0 to 255 while a signed 8-bit raster range from -128 to 127

Question 14

What is Band Interleaved by Line (BIL)?

Answer 14

An image storing method in which each line of the raster is written to the file by writing all red values for pixels in line one, then green, then blue.

Question 15

What is Band Interleaved by Pixel (BIP)?

Answer 15

An image storing method in which the RGB values of each pixel are written in order of pixel

Question 16

What is Band Sequential (BSQ)?

Answer 16

An image storing method in which all of the red values are stored (for the entire raster), and then green, and then blue.

Question 17

What is a raster pyramid?

Answer 17

Raster pyramids are used to improve display performance by retrieving only the data at a specified resolution that is required for the display. Each successive layer of the pyramid is down-sampled at a scale of 2:1. Uses .RRD extension.

Question 18

What is Inverse Distance Weighting (IDW)?

Answer 18

An interpolation method that averages values of sample points near cell

Question 19

What is Natural Neighbor?

Answer 19

An interpolation method. Area-weighting of sample points near cell

Question 20

What is Spline?

Answer 20

An interpolation method that creates a smooth surface through the sample points

Question 21

What is Trend?

Answer 21

An interpolation method that fits a polynomial equation to the surface

Question 22

What is Kriging?

Answer 22

An interpolation method that models the autocorrelation to simulate unsampled locations

Question 23

What is resampling?

Answer 23

The process of resizing raster grid cells.

Question 24

Snap Raster

Answer 24

Sets a raster that is used to define the cell alignment of an output raster.

Question 25

What is a Con statement?

Answer 25

A Con statement is used to write a conditional statement in the raster calculator.
-Syntax: Con(CONDITION, TRUE, {FALSE}

Question 26

What is Least Cost Path Analysis?

Answer 26

Determines the least-cost path from a destination point to a source.