GSEI 5430 Exam 1

Acquisition of information about the state and condition of an object through sensors that do not touch it.

Remote sensing

Rely on energy from external sources; e.g., solar energy reflected from a surface or naturally occurring energy.

Passive sensors

Provide their own energy source for illumination.

Active sensors

What nanometers are blue, green, red, and NIR at on the electromagnetic spectrum?

• Blue: 0.4-0.5

• Green: 0.5-0.6

• Red 0.6-0.7

• NIR: 0.7-1.2

Low reflectance of healthy vegetation in the red band is caused by what?

Chlorophyll absorption

What is the formula for NDVI?

NIR - RED / NIR + RED

Particles are small compared to the wavelength of the radiation.

Rayleigh scattering

What are some examples of Rayleigh scattering?

• Sunsets

• Blue sky

Particles are about the same size as the wavelength of radiation.

Mie scattering

What are some examples of Mie scattering?

• Dust

• Pollen

• Water vapor

Regions of the Em spectrum not severely influenced by atmospheric absorption.

Atmospheric windows

Is the pixel size of an image always the same as spatial resolution of the sensor that acquired the image?

No

Area on the ground each pixel covers.

Spatial resolution

Number of bands and spectral bandwidths.

Spectral resolution

Observation frequency or revisiting period provided by the sensor.

Temporal resolution

The range of values used for recording input radiance.

Radiometric resolution

Grabs the value from the old cell that falls at the center of the new cell. It preserves the original value and should always be used with categorical data.

Nearest neighbor resampling

Calculates a new value from the four cells that fall closest to the center of the new cell. Best used with continuous data like elevation.

Bilinear resampling

Calculates a new value from the sixteen cells that fall closest to the center of the new cell. Best used with continuous data like elevation.

Cubic convolution resampling

The radiometric resolution of Landsat 9 is 14-bit, improved from Landsat 8’s 12-bit resolution. This means that Landsat 9 can distinguish ________ shades of a given wavelength.

16,384

To see more variations in energy measurements, you would want to use a satellite with higher _________ resolution.

Radiometric

Why would data from the Landsat TM sensor may be more useful than data from the original MSS sensor?

TM has better spatial resolution (30m) and a better radiometric resolution (8-bit) when compared to the MSS (60mx80m; 6-bit).

Apart from Landsat, what is one other earth-observing program (or satellite series) that has adopted a free, and open data policy?

• Series: Sentinel

• Program: MODIS, Copernicus

What satellite program is managed by a private company?

Worldview

What is the main observation advantage of a geostationary satellite?

Temporal resolution

What should be the main criteria to discriminate irrigated crops from urban gardens?

Spatial context

The relevance of shapes in visual analysis depends on?

Spatial resolution

What are the 3 phases of digital image classification?

• Training — digital definition of categories based on sample pixels.

• Assignment — allocation of whole image to one of the previously defined categories.

• Validation — assessment of results.

Spectral classes are defined first based on information in the data and then matches to information classes by the interpreter.

Unsupervised classification

Assumes prior knowledge of the area to allow the interpreter to identify areas representative of each target category.

Supervised classification

Agreement with reference/ground truth data.

Accuracy

Consistency or repeatability of measurements/classifications.

Precision

The proportion of unassigned pixels versus the total number of pixels that are in that category.

Errors of omission (OE)

• (Downward pixel total - class pixel) / downward pixel total

Pixels that are included in a given category when they are not in fact part of that category.

Errors of commission (CE)

• (Sideways pixel total - class pixel) / sideways pixel total

Probability that a pixel is class A, given that the classifier labeled the class as class A.

User Accuracy (UA)

• Class pixel / sideways pixel total

Probability that a pixel is classified as belonging to class A given the ground truth pixel is class A.

Producer accuracy (PA)

• Class pixel / downward pixel total