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163 Cards in this Set
- Front
- Back
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centroid
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center of area
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area
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two dimensional size of a region
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counting method for area
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putting a grid over an area and counting the number of squares that it fills
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using a computer to measure area
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fill in an area with color and use pixels to find out area
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when using the counting method what do you divide the total number of partial cells by
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2
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dot grid counting method
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grid of dots is placed over an area
count the dots in the area add the number of either open/closed dots that are around the boundary |
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strip method
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put equally space parallel lines over an area
draw vertical lines to show the end of each strip |
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polar planimeter
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a tool that is used on maps and aerial photographs
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4 main parts of a planimeter
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1. pole are with a pole weight that is stabilized by a needle
2. Pole arm connects at a pivot with a tracer arm and at the end is a tracer lens 3. carriage which slides along the tracer arm and has a measuring wheel 4. counting dials which display the results of you work |
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planimetric coordinate method of measuring area
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based on area of trapezoids
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area of a trapezoid in coordinates
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area = (xi + xi+1)/2 X (yi - yi+1)
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spherical coordinate method for determining area
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based on geographic coordinates (lat/long) and uses spherical triangles
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spherical triangle area
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(alpha + beta + change of gamma - 180 ) X R^2
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what is an issue with planimetric area calcluations that are often used in gis
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they assume that the earth's surface is flat
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TIN
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triangulated irregular network
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why use TIN
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by choosing 3 points and finding hte disance between them you can use them to calculate the area of an irregular surface
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Heron's formula
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sqrt( s (s-a) (s-b) (s-c)
s= (a+b+c)/2 |
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finding area on a equal area map projection
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you can use squares and rectangles
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what must be assumed to calculate the centroid?
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that the surface is completely flat
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centroid placement in squares and rectangles
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1/2 w x 1/2 h
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centroid placement in triangles
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1/3 w x 1/3 h
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what are centroid locations defined by
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grid coordinates
x = sum xi x areai / area total y = sum yi x areai / area total |
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discrete ordinate method of determining volume
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determine the average height or depth and multiply by the area
compare elevation differences within an area using contours as a way to confine the area that you are talking about |
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slab summation method
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slicing a feature horizontally and summing the volume of all slabs
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shape
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an area feature's two dimentional form
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shape index
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an objective way of describing an area in numerical term
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how shape index is calculated
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1.0 - (intersection of the feature with a standard shape / union area of a feature and a standard shape)
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compactness
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an area feature that occupies little space in relation to its area
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compactness index
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A x 4pi / P
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slope
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vertical change in elevation
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how to determine elevation change
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find the rise (elevation difference)
and measure the map distance between the two points (run) set up a triangle and solve for the hypotenuse |
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slope ratio
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rise/run between two points
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slope percentage
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multiply the slope ratio by 100
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slope angle
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inverse tangent of the slope ratio
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constant slope path
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a path that maintains constant steepness
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map divider
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an instrument that allows you to set a specified distance so you can "walk" along a path
ex: compass set at a specific distance |
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maximum slope path
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a path that does not exceed a certain slope angle
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gradient
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a vector that describes the magnitude and direction of the maximum amount of vertical change on a surface and the direction that the change occurs on
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aspect
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the downslope direction of the maximum vertical change in the surface determined over a given horizontal distance
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another way of thinking of aspect
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a compass direction of where the hill faces
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how aspect is expressed
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0 to 360
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illumination
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the amount of light that hits a surface
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what is needed to define illumination
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azimuth - angular direction of the sun
altitude - angle of the sun above the horizone |
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curvature
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the amount that a surface deviates from being flat
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areas of cuvature
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summit
shoulder backslope footslope toeslope |
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three types of slopes
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linear
convex - pushes out concave - curves in |
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positive profile curvature
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concave
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negative profile curvature
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convex
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profile curvature
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direction parallel to the direction of the maximum slope
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planform curvature
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perpendicular to the direction of the maximum slope
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positive planform curvature
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convex at horizontal
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negative planform curvature
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concave at horizontal
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forward lap and sidelap in aerial photography
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how much pictures overlap from front to back and side to side
frontlap = 60 to 80 percent sidelap = 20 to 30 percent |
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what is useful about color infrared film
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it is most reflective off of plant material so you can distinguish aritificial camoflage material
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parameter for a low altitude photo
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between the ground and 1500 ft
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high altitude photographs
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as high as 10 miles above ground
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geometric distortion on aerial photos
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the disortion increases radially from the center
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fiducial marks
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registration marks on the edge of a picture that if you draw lines to connect you will be able to tell where the center of the picture is
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principle poin
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center of the photo
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relief displacement
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the "leaning out" of the top of a higher object in a vertical photo
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camera tilt
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the influence on the scale variation and relief displacement based upon the level of the aircraft
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Photo rectification
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a way of correcting for scale distortion by altering the geometry of the photo
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orthphoto
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a photo that has been geometrically corrected through retification
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orthophotomaps
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maps that use either an annotate or unannotated orthophoto as the base
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annotated orthophotomaps
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maps that overlay conventional map symbols onto an orthophoto
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orthoimage
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an image that has been processed to remove systematic geometric distortions
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GOES stands for?
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Geostationary Operational Environmental Satellite
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geostationary
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means the satellite is always in the same position with respect to the rotating earth
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near-polar orbit
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satellite orbit such that they circle with a near-polar inclination (the angle between the equatorial plane and satellite orbit is about 90 degrees)
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sun-synchoronous orbit
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satellite passes over the same part of the earth at roughly the same local time each day
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GOES West and East
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satellites that obtain images of the western and eastern united states to usein television weather
get images every 15 minutes |
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compositing
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combining multiple images to produce a single area
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isobar
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lines of equal atmospheric pressure
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Landsat
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a 1960s project of satellites produced by NASA to collect remote sensed images
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ETM+
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Enhanced Thermatic Mapper Plus
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What does ETM+ do
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It provides images with blue, green, red, near IR, and mid-IR image, thermal infrared, and panchromatic band
These are all in a bands in the same place |
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SPOT
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Stands for the French Satellite program
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imagery from SPOT
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black and white
true color CIR and mroe |
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IKONOS
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1999 satellite launched by the Satellite Imaging Corporation
sun synchronous. the same area is imaged every 3 days |
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QuickBird
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developed by Digitalglobe in 2001
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nadir point
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the point directly under the camera
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how to find the RF with an aerial photo
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use the focal length and the height of the place from the ground
1/x = f/H x = H/f |
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when you are calculating the flying height, what must you take into account
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the elevation that the land is at.
altitude - elevation = H |
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radial displacement method of measuring object height
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height of object ho = (Hxd)/r
d = length of displace image r = radial distance from principle point H = height of aircraft |
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how to determine height based upon shadows
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you compare the unknown object witha known object
ho/so = hx/sx ho is known |
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First time aerial photographs were used
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in 1858 from a balloon
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When was camoflague detetction film made
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during WWII
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Panochromatic flim
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black and white
used in photogrammetry |
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Color film
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easy to interpret
fuzzy due to atmospheric scattering |
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black and white infrared
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used for flood mapping
vegetation mapping soils dry/moist |
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false color infrared
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also known as CIR
used in vegetation and water turbidity |
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hill
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rounded surface rising above its surroundings
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hilltop
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highest point of elevation
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ridge
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long narrow hillside
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mountain
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land mass that projects well above its surroundings
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relative steepness
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the distance between contours to show how steep a hillside is
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convex vs concave hills
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concave turns outward as it slopes down
convex is turned down as it goes downward |
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valley
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long and narrow area that is bounded by two areas of higher elevation
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ravine
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deep, narrow, steep-sided vally formed by water erosion on a hillside
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saddle
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lower-elevation pass that slopes gently between two higher-elevation hills/peaks
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depressions
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low areas surrounded by high ground on all sides
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water flowing from a volcano follow what pattern
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radial drainage pattern
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what type of landform do you find dendritic drainage patterns on?
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driftless areas or dissected plateus, lots of gently sloping valleys
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on what type of landfomr do you find parallel drainage patterns
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uniformly sloping plain
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ridge and valleys cause what type of drainage patterns?
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trellis drainage
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what type of landform do you find an annular drainage system on?
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structural dome
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what landform do you find a meandering drainage in?
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a floodplain
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where do you find braided river channels?
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in areas where heavy precipitation falls and large amounts of sediment are deposited
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alluvial fan drainage
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forms in streams carrying a lot of sediment from a mountainous area to a flat valley bottom
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contact
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the boundary between two different rock units
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image interpretation: shape
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shape is the most fundamental clue to what an object is.
natural features have irregular shapes and manmade have geometric form |
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image interpretation: tone
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tone referes to light/darkness of an image
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an objects reflectance depends on
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its surface characteristics and how it is posisitioed in the environment
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mirror reflectors
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shiny surfaces that reflect light in one directions
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diffuse reflectors
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a surface that reflects light in multiple directions
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dry soil vs wet soil and tone
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dry is light wet is dark
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corner reflections
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when objects near each other bounce light off each other to create special effects
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water and infrared light
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water absorbs more infrared than shorter wavelengths of light
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vegetation and near infrared
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plants reflect more infrared light than in the visible spectrum
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thermal-infrared imagery and tone
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light tones are w/ warmer objects
dark tones w/ colder objects |
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three characteristics that affect object's thermal tone
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thermal capacity
conductivity inertia (rate it gains/loses heat) |
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thermal imagery and time of day
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how a picture will look will depend on the time of day because of diurnal differences
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image interpretation: hue
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the spetral asepct of the phenonmenon we call color
color will not look as vibrant as we expect because color intensity decrease with distance from the objet |
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false-color imagery
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where a color is assigned to a phenomena that does not produce color in the visible spectra
ex: infrared |
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image interpretation: size
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size is important to determine what kind of object you are looking at
it's important to make a size check fo rscale |
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pseudoscopic effect
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the apparent reversal of the relief of an object based upon how the shadows are casted
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what does a concave vs convex hillslope look like on a map
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convex is tight at the top and concave is tight at the botom
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how can you tell a ravine on a map
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v shapes on relatively tight shaped contours
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what is the difference between a valley and a saddle
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a valley has more of a deeper elevation than a saddle. Valley also usually have rivers
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characteristics of a volcano landform pattern
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there are concentric circular contours
radial drainage |
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dissected plateau characteristics
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gently sloping ridges and valleys with V shaped contours
created by pleistocene ice sheets dendritic drainage |
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uniformly sloping plain characteristics
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uniform spacing of contours with little Vs in the contours
formed by ancient cataclysmic flooding parallel drainage |
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ridge and valley topography characteristics
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found in the appalachians
formed when pangea was formed with crashing plates and then erosion over time syclines are upturns where streams flows trellis drainage patter |
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structural dome
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tectonic activity bows sediment rock that was eroded over time
cuestas: genly smooth curved ridges hogbacks: steeper ridges annular drainage usually a lake |
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floodplain
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formed by sedimentation in main channel usually from floods that creates marshes
meandering drainage |
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braided river channel
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tributaries deposit more sediment than main channel
found in areas with sporadic rainfall small islands braided drainage |
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alluvial fan
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sediment that is carried from moutain regions is deposited
apex is a canyon fan drainage pattern |
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karst topography
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formed by water dissolving carbonate based rock
lots of signs of erosion; natural bridges; caves; dissappearing features interrupted drainage |
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alpine glaciation
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pleistocene era ice sheets caused erosion
bowl shaped cirques shown by big Us in contours tarn lakes dendritic drainage |
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continental glaciation
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pleistocene ice sheets on relatively level areas
erosion led to flat plains few contours kettle lakes, shallow depressions, marshes deranged drainage |
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anticyclone
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high pressure center
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cyclone
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low pressure center
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weather maps
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show characteristics of the weather (temp, air, pressure, wind) over a landscape
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dew point
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temperature to which air much cool to reach a point of saturation
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climate maps
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demonstrate seasonal patterns and conditions over a landscape
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ex of climate maps
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annual preciptation, maximum temperature, solar radiation, climate types
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species distribution mas
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show how flora and fauna are distributed over a landscape
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species range maps
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shows the habitat extent that an animal migrates through
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GLO township maps
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shows how an urban area develops over time
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land use maps
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reflect zoning and land use policies; shows organization of how humans have used the land
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zoning maps
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reflect zoning made by planners; areas have specific purposes
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landcover maps
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describes vegetation, structures, and other features that cover the land
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demographic maps
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show aspects of different socioeconomic groups and where they reside
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demographics
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characteristics of a population
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ex of demographic maps
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population density, population age, income, education
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how often is the us census completed?
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every 10 years
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census blocks
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an area bound by visible (ex: roads) or invisible features (ex: town lines)
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census tracks
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a small statistical subdivision of a county
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how to calculate the RF of an aerial photo
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1/x = f/H
f = focal length H = flying height OR 1/x / 1/msd = pd/md |
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how to calculate the height of an object on an aerial photo
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h = H x d /r
d = length of displacement r = length of image from prinicple point OR the shadow height equation hx = hoSx/So |
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parallax equation
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h = H x dP / P + dP
dP = (T1 - b1) + (T2-b2) P = b1 + b2 |
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aspects of image interpretation
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shape
tone texture color site and situation pattern |
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rectangle drainage
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is found in areas that have undergone faulting
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