Flashcards
RS I Test 2
Cards in this deck (89)
- 1Definition of a hyperspectral imagean image in which the reflectance from each pixel is measured at many narrow contiguous wavelength intervals.
such an image provides spectral signatures for every pixel. - 2Is hyperspectral defined by the number of wavelengths measured?No. Hyperspectral is define by the narrowness and contiguous nature of the measurements.
- 3Definition of reflectancethe percentage of light hitting an object and reflecting.
- 4Spectral Librarycollections of reflectance spectra measured from materials of known composition, usually in the field or laboratory
- 5What marked the approximate beginning of widespread interest in digital image processing and when?The launch of Landsat 1 in 1972.
- 6What are the advantages of digital image processing?Cost effective
yields consistent results
can simultaneously interpret data in several bands
high speed
output is compatible with other data - 7What is preprocessing?The operations that are normally required prior to main data analysis.
- 8What are two types of pre-processing?Radiometric and geometric corrections.
- 9What is radiometric correction?correcting data for sensor irregularities and unwanted sensor noise
- 10What is geometric correction?correcting for geometric distortions due to sensor-Earth geometry variations
- 11What necessitates radiometric correction?Variations in scene illumination and viewing geometry
atmospheric conditions
sensor noise and response - 12Why is it desirable to convert and/or calibrate data to known radiation or reflectance units?So you can compare it with other data
- 13How can you correct variations in illumination and viewing geometry for optical sensors?By modeling the geometric relationship and distance between the area of the Earth's surface imaged, the sun, and the sensor
- 14What is sensor noise?It may be caused by irregularities or errors that occur in the sensor response and/or data recording and transmission.
Common forms are systematic striping and dropped lines - 15List the major factors causing geometric distortionperspective of sensor optics
motion of the scanning system
motion of the platform
platform altitude, attitude, and velocity
terrain relief
curvature and rotation of the earth - 16What is geometric rectification/registration?The process of identifying image coordinates of clearly defined points called Ground Control Points (GCP) and matching them to their true positions in ground coordinates (lat and long)
- 17What is resampling?The process of calculating new pixel values from the original digital pixel values in the uncorrected image
- 18What are the types of resampling?Nearest neighbor analysis
Bilinear interpolation
Cubic convolution - 19Explain nearest neighbor analysisAssigns each "corrected" pixel the value from the nearest "uncorrected" pixel
It is simple and preserves the original values
But there are noticeable positional errors - 20Bilinear interpolationcalculates a value for each output pixel based upon a weighted average of the four nearest input pixels
- 21Cubic Convolutionuses a weighted average of values within a neighborhood of some sixteen adjacent pixels.
- 22What is the goal of image enhancement?To make it easier for visual interpretation and understanding of imagery
- 23What are two types of image enhancement? (Manipulating pixels)Point operations
Local operations - 24Define point operationsthey modify the brightness of each pixel value in an image data set independently
- 25Define local operationsthey modify the value of each pixel based on neighboring brightness values
- 26What is contrast manipulation?It involves changing the original values so that more of the available range is used, thereby increasing the contrast between targets and their backgrounds
Think about histograms - 27Define linear contrast stretchThe uniform expansion
- 28Define histogram-equalized stretchImage values are assigned to the display levels on the basis of their frequency occurrence
- 29Define spatial frequencythe frequency of variations in tone that appear in an image
Rough - changes in tones are abrupt over a small area
Smooth - little variation over several pixels - 30What are spatial filters designed to do?They are designed to highlight or suppress specific features in an image based on their spatial frequency
- 31High pass makes things look...Sharper
- 32Low Pass makes things look...blurrier
- 33What is an information class?They are the categories of interest to the users of the data (crops, forest types)
Typically composed of numerous spectral sub-classes, spectrally distinct groups of pixels that together may be assembled to form an information class - 34Define spectral classesgroups of pixels are uniform with respect to brightness in their spectral channels
- 35Advantages of supervised classificationAnalyst has control of a set selected menu of information classes tailored to a specific purpose and geographic region
Tied to specific areas of known identity, as provided through the process of selecting training areas - 36Disadvantages of supervised classificationthe operator defined classes may not match the natural classes within the data
training data selected by the analyst may not represent conditions throughout the image - 37Minimum-distance-to-means classifierThe unknown pixel is assigned to the "closest" class
Mathematically simple and computationally efficient
Insensitive to different degrees of variance in the spectral response data - 38Parallelepiped classifierConsiders the range of values in each category training set (highest and lowest DN values)
sensitive to category variance
increases the opportunity for categories to overlap data space - 39Maximum likelihood classifierUses the training data to estimate means and variances of the categories and then uses them to estimate the probabilities for membership in each category
Considers not only the mean values in assigning classification, but also the variability of brightness values in each class
Requires intensive calculation - 40Unsupervised classificationReverses supervised.
Spectral classes are grouped first, based solely on the numerical information in the data, and are then matched by the analyst to information classes (if possible) - 41Advantages of unsupervised classificationNo extensive prior knowledge of the region is required
The opportunity for human error is minimized and the classes are spectrally uniform - 42Disadvantages of unsupervised classificationIt identifies only spectral classes (spectrally homogeneous classes), which do not necessarily correspond to the informational categories that are of interest to the analyst
The analyst has very limited or no control over the menu of the classes and their specific identities - 43Clustering algorithmsused to determine the natural (statistical) groupings or structures in the data
Usually, the analyst specifies how many groups or clusters are to be looked for in the data
In addition to specifying the desired number of classes, the analyst may also specify parameters related to the separation distance among the clusters and the variation within each cluster
The final result of this iterative clustering process may result in some clusters that the analyst will want to subsequently combine, or clusters that should be broken down further - each of these requiring a further application of the clustering algorithm - 44TIRSThermal Infrared Sensor
2 thermal bands, 100m res - same as ETM+
spectral resolution arguable more important than spatial resolution - 45SPOT1986 - French Satellite
was the highest quality for environment and natural resources monitoring
push broom - 46SPOT 1, 2, and 3 sensorsTwo identical HRV (High Resolution Visible) imaging instruments
2 modes of sensing
a 20m-resolution multispectral (XS) mode
10m resolution panchromatic mode - 47What are stereo pairs used for, mainly?Stereo pairs are mainly used for stereoplotting, topographic mapping, and automatic stereocorrelation, from which Digital Elevation Models (DEMs) can be directly derived without the need for maps
- 48IRS-IIndia's. 23m spatial resolution. 5.8m panchromatic images, 188m resolution for wide field
- 49JERS I and JERS IIJapanese in the 1990s
- 50TIROS - ITelevision and Infrared Observation Satellite
The first true weather satellite. Launched in 1960 by US. - 51GOESGeostationary Operational Environmental Satellite
The follow up to the ATS series. Designed by NASA for NOAA - 52NOAA AVHRR IWeather satellite
Bad resolution
2 thermal bands = temperature data - 53DMSPDefense Meteorological Satellite
- 54EOSEarth Observing System
NASA - 55All objects above absolute zero do what?Emit thermal radiation.
- 56Wavelengths of thermal radiation?> 3 um (3-14 um)
- 57In visible and near-IR, we examine contrasts in the abilities of objects to reflect direct solar radiation to the ____Sensor
- 58In thermal IR spectrum, we sense differences in the abilities of objects and landscape features to ___ ____emit energy
- 59What is a blackbodyan object that acts as a perfect absorber and emitter of radiation
- 60What is emissivity?A ratio between emittance from an object in relation to emittance from a blackbody at the same temperature
- 61Which objects are better at absorbing and emitting energy? Dark or Light colored?Dark
- 62The greater the surface roughness, the higher the ____emissivity
- 63Moisture increases emissivity (T or F)True
- 64What is a graybody?Objects that have emissivities less than 1.0 but have a constance emissivity over all wavelengths
- 65What is radiant temperature?Also known as Apparent temperature. It is the measure of the emitted energy of an object.
Denoted as T rad - 66What is kinetic temperature?Also known as True temperature. It is the average thermal energy of molecules within a substance.
It is measured using the usual temp scales (F, C, K)
Denoted as T kin - 67What is the Stefan Bolztmann law?Total energy emitted from an object increases very rapidly with increase in temperature
- 68What are the most widely used imaging sensors for thermal remote sensing?Thermal scanners
- 69What can sense radiances of features beneath the aircraft flight path and produce digital and/or pictorial images of the terrain beneath the aircraft?Thermal scanners
- 70What does not include the reference source that permits rather precise quantitive measurement of radiance?Thermal scanners
- 71What are sensors that measure the intensity of radiation received within a specified wavelength interval and field of view?Thermal radiometers
- 72A thermal scanner generates what kind of image?A black and white depicting contrasts in the landscape as variations in gray tones (usually brighter to represent warmer features)
Must know the time of day the image was acquired. - 73What are the two distinctive characteristics of microwave energy?Microwaves are capable of penetrating the atmosphere under virtually all conditions
Microwave reflections or emissions from the earth materials bear no direct relationship to their counterparts in the visible or thermal portions of the spectrum - 74Active microwave sensing systemRefers to those that supply their own source of energy
Radar (radio detection and ranging) - 75Passive microwave sensing systemsSense microwave energy that are naturally emitted and/or reflected from terrain features
microwave radiometer - 76Radar systemsUse short bursts, or pulses, of microwave energy in the direction of interest and recording the strength and origin of "echoes" or "reflection" received from objects within the system's field of view
- 77Factors influencing radar returnsGeometric characteristics such as local incidence angle
Radar Shadows are produced in areas that are not illuminated by the radar beam
Three reflectors
Moisture - 78Three types of reflectorsDiffuse
Specular
Corner - urban areas common - 79LiDARLight Detection and Ranging
Active Remote Sensing
Using narrow beams of near IR - 80Land coverthe type of material present on the landscape (water, sand, crops, forest)
- 81Land useWhat people do on the land (agriculture, commerce, settlement)
- 82Mutually exclusivethere is no taxonomic overlap (or fuzziness) of any classes (i.e., deciduous forest and evergreen forest are distinct classes).
- 83Exhaustiveall land-cover classes present in the landscape are accounted for and none have been omitted.
- 84Heirarchicalsublevel classes (e.g., single-family residential, multiple-family residential) may be hierarchically combined into a higher- level category (e.g., residential) that makes sense. This allows simplified thematic maps to be produced when required.
- 85Difference between information and spectral classesInformation classes are those that human beings define.
Spectral classes are those that are inherent in the remote sensor data and must be identified and then labeled by the analyst - 86American Planning Association SystemLand-Based Classification System
- 87USGSLand Use/ Land Cover Classification System for Use with Remote Sensor Data and its adaptation for the U.S. National Land Cover
Dataset and the NOAA Coastal Change Analysis Program (C-CAP - 88US Fish and WildlifeService Classification of Wetlands and Deepwater Habitats of the United States;
- 89US National Vegetation and Classification SystemYeah
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- Flashcards on RS I Test 2, created by blbates on 08/12/2014.
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