Mapping the Environment Final

remote sensing

The process of collecting information related to the electromagnetic energy reflected or emitted by a target on the ground, using a device on board an aircraft or a spacecraft a considerable distance away from the target

History of remote sensing

balloons, kites, WWI and WWII, and the Cold War

Two types of aerial photography

Vertical and Oblique

Vertical aerial photography

Photos taken perpendicular to the ground. Images taken straight above the subject.

Oblique aerial photography

camera angle is less than 90 degrees- features are seen from a more or less familiar point of view

aerial photography color types

Panchromatic, Color and CIR

Panchromatic imagery

black-and-white imagery formed by viewing the entire visible portion of the electromagnetic spectrum

Color imagery

an image formed by placing a band of imagery into each of three color guns (red, green, and blue) to view that image in color rather than grayscale

CIR Photo - Color Infrared Photo

Color-Infrared Photo; a photo in which infrared reflection is shown in shades of red, red reflection is shown in shades of green, and green reflection is shown in shades of blue

Nadir

The location on the ground that lies directly below the camera in aerial photography

NAIP

principal point

the center point of an aerial photo

Relief Displacement

the effect in aerial imagery in which tall items appear to "lean" outward from the photo's center toward the edges

Orthophoto

an aerial photo with uniform scale

True Orthophoto

an orthophoto where all objects look as if they're being seen from directly above

Interpretation

analyzing, understanding, and extracting meaning from spatial data and maps

Pattern

the arrangement of objects in an image, used as an element of image interpretation

Site and Association

information referring to the location of objects and their related attributes in an image, used as elements of image interpretation

Size

the physical dimensions (length, width, and area on the ground) of objects, used as an element of image interpretation

Shadow

a dark shape in an image caused by a light source shining on an object, used as an element of image interpretation

Shape

the distinctive form of an object, used as an element of image interpretation

Texture

repeated shadings or colors in an image, used as an element of image interpretation

Tone

the grayscale levels (from black to white) or range of intensity of a particular color discerned as a characteristic of particular features present in an image, used as an element of image interpretation

Photogrammetry

the process of making measurements using aerial photos

Electromagnetic Energy

a form of energy that travels through space in the form of waves

electromagnetic spectrum

the full range of energy waves that remote sensing tools detect and use in GIS

• (shorter wavelength and more energy) Gamma, X-ray, UV, visible light, Infrared, microwaves, radiowaves (higher wavelength and less energy)

wavelength

the distance between the crests of two waves

spectrum (UV, visible, IR {NIR, MIR, TIR})

Different light wavelengths used

Atmospheric window

wavelengths of electromagnetic energy in which most of the energy passes through Earth's atmosphere

Types of scattering

Rayleigh, Mie, Non-selective

Rayleigh scattering

scattering of light caused by atmospheric particles smaller than the wavelength being scattered (gas)

Mie Scattering

scattering of light caused by atmospheric particles (dust, smoke)

Non-selective scattering

scattering of light caused by atmospheric particles larger than the wavelength being scattered (water vapor)

Incident Energy

the total amount of energy that hits Earth

Incident Energy types

Transmission, Absorption, Reflectance

Transmission

the process by which light passes through a target

Absorption

the process by which light is trapped and held by a target

Reflectance

ρ = (R/I) * 100, the percentage of light reflected off a surface

spectral reflectance

the percentage of the total incident energy that was reflected from that surface

NDVI (normalized difference vegetation index)

A method of measuring the health of vegetation using near-infrared and red energy measurements

Display

Spatial Resolution and Brightness Value

Spatial Resolution

the size of the area on the ground represented by one pixel's worth of energy measurement

Brightness Value (digital number)

the energy measured at a single pixel according to a predetermined scale; abbreviated DN and also referred to as brightness value, or BV

Panchromatic

black-and-white imagery formed by viewing the entire visible portion of the electromagnetic spectrum

Multispectral

remotely sensed imagery created from the bands collected by a sensor capable of sensing several bands of energy at once

Hyperspectral

remotely sensed imagery created from the bands collected by a sensor capable of sensing hundreds of bands of energy at once

Color Guns

name used for equipment used to display color pixels on a screen in the colors red, green, and blue

Color Composite Types

True Color, False Color, Standard False Color

true color composite

an image arranged by placing the red band in the red color gun, the green band in the green color gun, and the blue band in the blue color gun

False Color Composite

an image arranged when the distribution of bands differs from placing the red band in the red color gun, the green band in the green color gun, and the blue band in the blue color gun

Standard False Color

an image arranged by placing the near-infrared band in the red color gun, the red band in the green color gun, and the green band in the blue color gun

Supervised Classification

an image classification method in which the computer assigns pixels to groups based on information provided in training sites

Unsupervised Classification

an image classification method in which the computer creates groups of similar pixels and then the user must identify what each cluster represents

Z-value

the numerical value representing the elevation or height of an object assigned to an x/y coordinate

Vertical Datum

a reference surface used to measure elevations or depths

contour interval

the vertical difference between two adjacent contour lines drawn on a map

Topographic Map

a printed map created by the USGS that shows landscape and terrain as well as the location of features on the land

7.5 minute quadrangle map

7.5-minute quadrangle map is a very detailed map that covers a small area of land, showing features like hills, rivers, roads, and towns. It’s called "7.5-minute" because it maps an area that's 7.5 minutes of latitude and 7.5 minutes of longitude.

DRG

Digital Raster Graphic; a scanned version of a USGS topographic map

DLG

Digital Line Graph; the features (such as contours, roads, rivers, or boundaries) are digitized as vectors (lines) from USGS maps

US Topo

a digital topographic map series created by the USGS to allow multiple layers of data to be used on a map in GeoPDF file format

DTM

Digital Terrain Model; a digital (computerized) 3D representation of the Earth's bare ground surface, with everything like trees, buildings, and vegetation removed. It shows the natural shape of the land — just hills, valleys, slopes, etc.

TIN

Triangulated Irregular Network; a 3D surface model made of connected triangles that represents the shape of the land (terrain) using points with known elevation.

DEM

Digital Elevation Model; a representation of the terrain surface, created by measuring a set of equally spaced elevation values

DSM

Digital Surface Model; a measurement of the heights of ground elevations as well as the objects on top of the ground, as captured by lidar

Lidar

a process in which a series of laser beams fired at the ground from an aircraft is used both to create highly accurate elevation models and also to measure the elevation of objects from the ground

Point Cloud

the name given to the massive number of elevation data measurements collected by lidar

LAS File

the industry standard data format used for lidar data

Bathymetric Lidar

a lidar process that uses a green laser beam for measuring underwater terrain heights

Slope

Hillshade (Azimuth, Altitude)

a shaded relief map of the terrain created by modeling the position of the Sun in the sky relative to the landscape

perspective View

the oblique angle view of a digital terrain model from which the model takes on a three-dimensional appearance

Draping

a process in which an image is given z-values to match the heights in a digital terrain model (draping a 2D image over a 3D one)

Base Heights

a z-value of a digital terrain model that can then be applied to an image in the process of draping

Z-Scale

The ratio between the vertical scale and the horizontal scale in a perspective view. Also called the vertical exaggeration factor.

Cloud

a technology wherein data, resources, or applications are kept in a remote location and made available to users over the internet

Webmap

an interactive online representation of geospatial data, which can be accessed via a web browser

Basemap

an image layer that serves as a backdrop for the other layers that are available on a web map

Mashup

the combination of two or more map layers that result in a combination