Geog 180 Exam 3

remote sensing

data is acquired through photography

Joseph Niepce

French inventor who took the first photograph of his home

Aerial photography

Photos captured from the sky, capturing the Earth’s surface at greater distances

Can be captured through airplanes, rockets, and satellites

Gaspard-Felix Tournachon (Nadar)

took the first aerial photograph

James W. Black

Took a series of surviving aerial photographs by attaching a camera to balloons

George Lawrence

Photographer who documented San Francisco in Ruins after the 1906 earthquake through aerial photos

WWII

Aerial photography changed combat by collecting information

U-2

Spy plane that flew at an altitude of 70,000 feet to take aerial photos of the Soviet Union during the Cold War

Sr-71 Blackbird

Improved spy plane that could fly higher and faster than the U-2 during the Cold War

UAS

unmanned aircraft systems that collect aerial imagery and combat strikes

sUAS

small unmanned aircraft system

operate like UASs’ but weight less than 55 pounds

vertical photo

aerial photos from a camera pointed directly at the ground

nadir

the spot on the ground directly beneath the camera

Panchromatic imagery

only captures images in grayscale

Color infrared photo (CIR photo)

aerial photos taken with a special type of film that is sensitive to infrared light

useful in environmental studies to portray green plants as red in pictures

Principal point

center of the photo

relief displacement

when tall objects lean away from the center point of the photo towards the edges

warped perspective

orthophotos

photos that have uniform scale

orthorectification

removes the effects of terrain and relief displacement, enforcing the same scale across the whole photo

true orthophoto

an image that has the appearance of looking straight down on all objects in the image

achieved by taking several photos that are then overlaid

digital orthophoto quadrangles (DOQ)

a type of orthophotograph that covers 3.75 minutes latitude and 3.75 minutes longitude

Cover one quarter of the size of a topographic map

National Agriculture Imagery Program (NAIP)

produces DOQs and makes them publicly available

works under the U.S Department of Agriculture’s Farm Service Agency

Oblique photo

a tilted photo that is positioned not in nadir, but at an angle

San Francisco Destruction aerial photos is an example of this photo

visual image interpretation

the process of identifying objects and features in an aerial image based on a number of distinct elements

pattern

physical arrangement of objects in an image whether repetitive or unusual

site and association

location characteristics of an item and its relationship to nearby features in an image

size

relative length, width, and area of an object in an image

shadow

dark shapes cast by a source of light

can help determine shape and scale of structures

shape

the form of an object

texture

differences in shading and color

tone

differences in shading or color throughout the image

photogrammetry

process of obtaining measurements from aerial photos

photo scale

representative fraction (i.e 1:1000 meters)

relies on the length of the camera lens and altitude of the plane when the image was captured to make accurate measurements

Representative fraction

photo distance divided by ground distance

wavelength

distance between the crests of two waves

electromagnetic spectrum

light energy wavelengths

micrometers

millionth of a meter

nanometer

billionth of a meter

visible light spectrum

light that can be seen by humans

0.4 - 0.7 micrometers

ultraviolet light (UV)

shorter wavelength than the visible light spectrum

band

a specific form of light wavelength

blue band

form of light that is 0.4 - 0.5 micrometers long

green band

form of light that is 0.5 - 0.6 micrometers long

red band

form of light that is 0.6 - 0.7 micrometers long

infrared light (IR)

wavelength between 0.7 - 100 micrometers

near infrared (NIR)

wavelength between 0.7 - 1.3 micrometers

Shortwave infrared (SWIR) or middle infrared (MIR)

wavelength between 1.3 - 3.0 micrometers

Thermal infrared (TIR)

wavelength between 3.0 - 14.0 micrometers

red edge

additional band between red visible light and infrared light

atmospheric windows

wavelengths of energy that pass through the atmosphere

Rayleigh scattering

scattering of light caused by atmospheric particles smaller than the wavelengths being affected

Mie scattering

scattering of light caused by atmospheric particles that are the same size as the wavelengths affected

Non-selective scattering

scattering of light caused by atmospheric particles larger than the wavelengths affected

transmission

occurs when a wavelength of energy simply passes through a surface to interact with something else later

absorption

occurs when energy is trapped and held by a surface

Incident energy

the total amount energy per wavelength that interacts with an object through transmission, absorption, or reflection

spectral reflectance

percentage of total energy per wavelength that is reflected off a target

spectral signature

unique identification on a specific object based on the percentage of reflected energy per wavelength

Normalized Difference Vegetation Index (NDVI)

when an image is processed to measure the health of vegetation

National Aeronautics and Space Administration (NASA)

a program established in 1958 in the U.S

Corona

U.S government program that monitored satellites when they began to use remote sensing reconnaissance and surveillance in 1960

Geostationary orbit

when satellites rotate at the same speed as Earth

Near polar orbit

north-to-south path wherein the satellite moves close to the North and South Poles as it makes several passes a day around Earth

Swath width

measurement of the width of ground the satellite can image in one pass

Landsat satellite sensor

has a swath of 185 kilometers, capturing a 185 kilometer wide area as it makes a pass overhead

Passes over the same swath every 16 days

sun-synchronous orbit

when a satellite’s orbit always takes it over the same swath of Earth at the same local time

images collected will have similar lighting conditions when viewed overtime

along-track scanning

linear array scans the ground along the satellite’s orbital path

across-track scanning

rotating mirror that moves back and forth over a swath to collect information

National Oceanic and Atmospheric Administration (NOAA)

U.S federal agency focused on weather, oceans, and atmosphere

European Space Agency (ESA)

organization representing multiple European countries that are dedicated to space exploration

Japanese Aerospace Exploration Agency (JAXA)

Japan’s national space exploration organization

Terra

“flagship” satellite of the NASA Earth Science missions

launched in 1999 as a collaboration among NASA’s Goddard Space Flight Center, NASA’s Jet Propulsion Laboratory, and the NASA Langley Research Center and agencies in Canada and Japan

continues its remote sensing mission today.

means “Earth” in Latin

five instruments on board and has a sun synchronous orbit

Aqua

key Earth observation satellite

means “water” in Lating

Analysis of water in all its forms — solid, liquid, and gas — is the key focus of all the instruments onboard

sun-synchronous but operates in the opposite path of another satellite

Moderate Resolution Imaging Spectroradiometer (MODIS)

sensor onboard both Terra and Aqua that conducts environmental monitoring

Visible Infrared Imaging Radiometer Suite (VIIRS)

instrument onboard other satellites that improves upon several aspects of MODIS

z-value

when x/y pairs are assigned coordinates that indicate elevation

vertical datum

a baseline used as a starting point in measuring elevation values (which are either above or below this value)

North America Vertical Datum of 1988 (NAVD88)

origin point for elevations and coastal terrain models for geospatial data in North America

North American-Pacific Geopotential Datum of 2022 (NAPGD2022)

new datum created by the NGS that will replace NAVD88

contour lines

imaginary lines drawn on the map that join points of equal elevation

contour interval

elevation or vertical difference between contour lines

topographic map

widely used method of representing terrain features using contour lines

Digital Raster Graphic (DRG)

digital format of topographic maps that have been scanned and georeferenced

Digital Line Graph (DLG).

specific features being digitizes with their own geospatial layers

an individual vector GIS dataset representing contours, transportation features, hydrography features, or boundaries.

US Topo

delivered in 7.5-minute quad sections

has multiple layers of data stored on the same map, include contours, recent transportation features (roads, railroads, airports), transportation names, contours, boundaries, and orthophoto images, all as separately accessible layers

collar

the white, information-filled border around a US Topo

digital terrain model (DTM)

a model of the landscape that is used in conjunction with GIS or remotely sensed imagery

2.5D model

a single z-value can be assigned to each x/y coordinate as a measure of elevation at that location

3D

multiple z-values can be assigned to each x/y coordinate

TIN (triangulated irregular network)

in which selected elevation points of the terrain — those that the system deems the “most important” — are used in constructing the model

Points are joined together to form nonoverlapping triangles that represent the terrain surfaces

DEM (digital elevation model)

based on regularly spaced point data of elevations

SRTM Shuttle Radar Topography Mission

a mission of the space shuttle Endeavor in February 2000 that mapped Earth’s terrain and topographic features from orbit,

3DEP (3D Elevation Program)

a U.S. government program that provides digital elevation data for the entire United States

Lidar

uses a laser beam to measure the terrain, reflecting from the ground back to the plane

an additional remote sensing method of terrain mapping

point cloud data

data collected by lidar

high volume of point locations measured up

DSM (digital surface models)

measure the heights of features such as tree canopies or roofs of buildings and can be used to create realistic-looking 3D models of these objects on Earth’s surface

bathymetric lidar

that uses a green laser beam for measuring underwater terrain heights

viewshed

maps that show what can be seen (or not seen) from a particular vantage point

used for determining a person’s visibility (that is, how far the person can see) from a location before their view is blocked by the terrain

slope

represents the change in elevation (and the rate of change) at a location

by calculating the rise (vertical distance) over the run (horizontal

distance)

pseudo-3D

really 2.5D and are not really full 3D models