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Glossary
A B C D E F G H  I  J K L M N O P Q R S T U V W X Y Z
A
Aerial Image
Images of the Earth's surface taken from the air with a camera, either hand held or mounted, in an aircraft, helicopter, balloon, rocket, kite, skydiver or similar vehicle. For the purposes of our site, we consider aerial images to be images taken by a craft that is not orbiting the Earth.
 
B
Basic Image
A TerraServer Basic Image contains an image in the JPEG format, along with a World File and a text file that gives basic information about the image such as the UTM zone and image date.
 
BBB
(Better Business Bureau)- The Better Business Bureau was founded in 1912 and has the stated mission to act as a mutually trusted intermediary between consumers and businesses to resolve disputes, to facilitate communication, and to provide information on ethical business practices.
 
BLM
(Bureau of Land Management)- An agency within the United States Department of the Interior which administers America's public lands, totaling approximately 258 million acres (1,060,000 km²) or one-eighth of the landmass of the country. The BLM has also modified USGS Topographic maps to show land under their management. These maps are available under our Maps tab. For a map of all of the lands under BLM management, please click here.
 
BMP
(Bitmap)- A graphics format used internally by the Microsoft Windows and OS/2 graphics subsystem (GDI), and used commonly as a simple graphics file format on those platforms. These files are usually not compressed.
 
Browser
A software application that enables a user to display and interact with text, images, and other information typically located on a web page at a website on the World Wide Web or a local area network. Web browsers format HTML information for display, so the appearance of a web page may differ between browsers. Common web browsers include Internet Explorer, Mozilla Firefox, Netscape, and Safari.
 
C
CAD
(Computer Aided Design)- The use of a wide range of computer-based tools that assist engineers, architects and other design professionals in their design activities. These programs can range from 2D vector modeling to 3D full surface modeling.
 
Canvas Paper
An extremely heavy duty fabric that is used as the medium for oil painting and some types of printing. Modern canvas is made from cotton. Our canvas prints are designed to resemble oil paintings in their finish. They will need to be stretched over a wood frame backing.
 
CD
(Compact Disc)- An optical disc used to store digital data.
 
Cloud Cover
The fraction of the sky covered by clouds in an aerial or satellite image.
 
Complete Image
A TerraServer Complete Image contains an image in the following formats: JPEG, Bitmap, PNG, TIFF, PSD, PDF, GIFF. The Complete File also includes a World File and basic information text file.
 
Compression
Applying data compression to an image to reduce redundancy in the image data in order to more efficiently transmit and store the image.
 
Cookies
Parcels of text sent by a web server to a browser and then sent back to the server unchanged any time that the browser accesses the server. Cookies are used for authenticating, tracking, and maintaining specific information about users, such as site preferences and the contents of their electronic shopping carts.
 
Coordinates
A set of numbers that define the position of some object in reference to a reference point or origin on coordinate plain. On the Earth, these numbers define the location of any point on Earth in reference to a geographical coordinate system.
 
D
Datum
A reference from which measurements are made. In georeferencing, a datum is a point on the Earth's surface from which surface measurements are made.
 
Degrees
A measurement of circular plane angle in reference to a meridian that indicates position along a great circle on a sphere. The Earth is divided into 360 degrees.
 
DEM
(Digital Elevation Model)- A digital representation of ground surface topography or terrain. DEMs are often used in GIS and are usually developed using remote sensing techniques. They are also known as Digital Terrain Models (DTM).
 
Domain Name
A name that identifies a computer on the internet and appears in the URL. The Domain name is often more memorable and stands in for the numeric IP address. They also allow mobility in that they do not have to change if the company moves and changes their IP address.
 
DOQ
(Digital Orthophoto Quadrangle)- A digital mapping product that combines the geometric qualities of a map with the detail of an aerial photograph. DOQs are digitally derived aerial photos that have been corrected so image distortion caused by perspective, camera tilt, and terrain relief are removed. Distances, bearings, and area calculations can all be measured on DOQs. Also known as Digital Orthophoto Quarter Quadrangle (DOQQ), which is one quarter of a standard DOQ
 
DVD
(Digital Video Disc)- An optical disc used to store digital files and media with a single layer capacity of 4.7 GB
 
E
Easting
A measurement used in the UTM coordinate system that measures the distance East of a point from the central meridian of a zone. The central meridian is given a false easting value of 500,000 so that there are no negative numbers. Any point west of the meridian will have a value less than 500,000 and any point east will be greater.
 
F
FAA
(Federal Aviation Administration)- An agency of the United States Department of Transportation with authority to regulate and oversee all aspects of civil aviation in the United States. Their tasks include regulating civil and commercial air traffic, operating a system of air traffic control, and carrying out programs to reduce noise and environmental pollution caused by aviation.
 
False Color
An image that depicts a subject in colors that differ from human perception of the same subject. This can include infrared thermal imagery.
 
FAQ
(Frequently Asked Questions)- An assembled list of questions and answers that are considered common about a certain topic.
 
Favorite
TerraServer uses a Favorite feature so that subscribers can store their favorite images to a page so that they can be accessed anytime. Subscribers can go to their Favorites page and access this imagery whenever they would like.
 
FEMA
(Federal Emergency Management Agency)- an agency of the United States Department of Homeland Security who purpose is to coordinate the response to a disaster which has occurred in the United States and which overwhelms the resources of local and state authorities. FEMA also keeps track and records natural disasters that occur within the United States. FEMA data is the basis for many of the overlays available to TerraServer subscribers
 
Flood Plain
A flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding. It includes the floodway, which consists of the stream channel and adjacent areas that carry flood flows, and the flood fringe, which are areas covered by the flood, but which do not experience a strong current.
 
G
Geo-reference
The process of defining the position of something in space with respect to Earth. This process is carried over to imagery in that the corner points and center point of the image must be defined with respect to the Earth.
 
Geographic Projection
A very simple map projection which is characterized by equidistant meridians and parallels. Also known as equarectangular projection.
 
Geospatial
A term widely used to describe the combination of spatial software and analytical methods with terrestrial or geographic datasets. The term is often used in conjunction with geographic information systems and geomatics. In the case of vector-based GIS this typically means operations such as map overlay (combining two or more maps or map layers according to predefined rules), simple buffering (identifying regions of a map within a specified distance of one or more features, such as towns, roads or rivers) and similar basic operations.
 
GIF
(Graphics Interchange Format)- An 8-bit-per pixel image format that is in wide use on the web and is used widely for basic animation. The 256 color palette for GIF images does not make it very good at reproducing photographs.
 
Gigabyte
A unit of computer storage equal to one billion bytes.
 
GIS
(Geographic Information System)- A computer system capable of allowing users to import, integrate, analyze, and display geo-referenced data. GIS is different from topography in that it can be used to depict and analyze geographically dependent phenomena.
 
Glossy Paper
A paper type that maintains a high ability to reflect light in the specular direction. This type of paper finish is similar to the finish on conventional photography.
 
GPS
(Global Positioning System)- The only fully functional Global Navigation Satellite System. GPS was developed by the United States Government and is a public good that is free for civilian use, despite an annual cost over $750 million. GPS coordinates are generally based on Latitude and Longitude. These coordinates are provided by receiving signals from at least three satellites and then using trilateration to determine a position.
 
H
Hyperspectral
The collection of imagery using a vast portion of the light spectrum, beyond visible light. Different elements within the image leave different marks in each of the various bands of the spectrum. By analyzing these marks, one can determine the identity of objects in the image that would not be possible with conventional imaging.
 
I
IKONOS
The first high resolution commercial satellite to make imagery of the Earth publicly available at 1 and 4 meter resolution.
 
Image Compression
The application of data compression on imagery. The object of compression is to reduce redundancy within the image file in order to make transmission and storage more efficient.
 
Image Date
The date or approximate date that an image was taken. Since images of a large area can occur over multiple days based on weather conditions and the size of the area, a group of images may all be assigned a specific date near to the date that they were taken.
 
Image Download
The transfer of image files from a host server onto a user's computer. Once the files are downloaded, they are contained on the computer's hard drive until they are removed by the user.
 
Infrared
Energy emission of a wave length longer than that of visible light. Infrared radiation can be used to determine the surface temperature of an object.
 
IP Address
(Internet Protocol Address)- A unique address that certain electronic devices utilize to communicate and identify each other when part of a computer network.
 
J
JPEG
(Joint Photographic Experts Group)- A commonly used standard method of compression for digital images. JPEG refers to both the file format and the codec, which defines how the image is broken down into bytes and then rebuilt into an image.
 
L
Laminated Paper
A process through which an image is printed and then covered with a thin plastic film. This film will allow wet and dry erase markers to be used on the image.
 
LandSat
The longest running enterprise for the acquisition of imagery of Earth from space. The first satellite was launched in 1972 while the most recent launch was in 1999. The resolution of LandSat images ranges from 60 meters to 15 meters.
 
Landscape
A page layout in which the horizontal edge is longer than the vertical edge.
 
Latitude
A number that gives the location of a place on Earth north or south of the Equator. This number is given in degrees. In some cases, this number is broken down into degrees, minutes, and seconds, where a minute is one sixtieth of a degree and one second is one sixtieth of a minute. A negative value for the degree indicates that the location is south of the Equator.
 
LIDAR
(Light Detection And Ranging)- An optical remote sensing technology in which light emission is measured and used to determine distance, shape, and other properties of a distant object. This can be done in a passive mode in which only output light from other objects is measured or in an active mode in which lasers or light are output by the apparatus and then the time delay between emission and reception of the reflected signal is used to calculate information about the target. This is very similar to RADAR except that RADAR uses sound where as LIDAR uses light.
 
Longitude
A number that gives the location of a place on Earth east or west of the Prime Meridian. This number is given in degrees. In some cases, this number is broken down into degrees, minutes, and seconds, where a minute is one sixtieth of a degree and one second is one sixtieth of a minute. A negative value for the degree indicates that the location is west of the Prime Meridian.
 
M
Matte Paper
A paper type that does not reflect a large amount of light. This finish is very similar to the finish found on common road maps.
 
Megabyte
A unit of computer storage equal to one million bytes.
 
Minutes
In the sense of geography, a subdivision of a degree that is equal to one sixtieth of a degree.
 
Multi-Spectral
An imaging technology that can capture light from frequencies beyond the visible light spectrum, such as infrared and electromagnetic.
 
N
NAD83
The North American Datum as established in 1983. This datum is the result of increases in technology in regards to remote sensing and is based on the GRS80 Ellipsoid.
 
NAIP
(National Agriculture Imagery Program)- Acquires imagery during the agricultural growing seasons (spring and summer months for leaf-on coverage) in the continental U.S. 
 
NAPP
(National Aerial Photography Program)- An interagency Federal effort coordinated by the USGS to obtain aerial imagery of the entire contiguous United States and Hawaii. These images are shot from 20,000 feet with a focal length of 6 inches.
 
Natural Color
Color as seen by the human eye. Composed of six unique colors and combinations of these colors.
 
NED
(National Elevation Dataset)- A seamless set of data giving the elevation of the entire United States and all island territories composed by the USGS.
 
NOAA
(National Oceanic and Atmospheric Administration)- A scientific agency under the Department of Commerce that focuses on the conditions of the of the ocean and the atmosphere. NOAA is responsible for charting both the sea and skies in addition to monitoring atmospheric and oceanic conditions.
 
Northing
The distance from the Equator when using UTM Coordinates. When in the northern hemisphere, the value at the Equator is zero and increases to 9,328,000 at the 84th Parallel. When in the southern hemisphere, the value at the Equator is given a false northing of 10,000,000 and anywhere south is a smaller number. This is done so that no northing coordinate is zero.
 
NWS
(National Weather Service)- One of the six agencies that makes up NOAA. The mission of the NWS is to provide "weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy."
 
O
Operating System
A set of computer programs that manage the hardware and software resources of a computer system. Common operating systems include Microsoft Windows, Linux, Unix, and Mac OS.
 
Orbit
The path of an object as it circles another object due to a centripetal force, usually gravity. The Laws of Planetary Motion state that these orbits are in fact elliptical, rather than circular.
 
OrbView
An imaging satellite operated by the GeoEye company.
 
Orthographic
The representation of a three dimensional object in two dimensions. A flat map is an orthographic projection of the world.
 
Orthorectified
The process of manipulating imagery that was taken at an angle other than perpendicular to the Earth's surface so that it appears as if it was taken at a right angle with respect to the surface in terms of the geographic information associated with the image. This process allows the images to be lined up and joined into one larger seamless image.
 
P
Panchromatic
A type of black and white imagery that is sensitive to all wavelengths of visible light. Panchromatic satellite image devices are generally able to take much higher resolution shots than their multispectral counterparts. Often times, high resolution color imagery is the result of a high resolution panchromatic image being colored in with color data from a lower resolution multispectral image collection.
 
Parcel
A contiguous area of land described in a single description by a deed or other instrument or as one of a number of lots on a plat or plan, separately owned and capable of being separately conveyed. In other words, a parcel is a unit of land under unified ownership.
 
PDF
(Portable Document Format)- A file format created by Adobe that has the ability to contain text, fonts, images, and 2D vector graphics that make up the file. PDF is used for representing two-dimensional documents in a device independent and display resolution independent fixed-layout document format. For use in Adobe Reader and Acrobat programs. PDF is considered to be the de facto file type for printing.
 
Pixel
A single point in a digital or graphic image. An image that is 1000 pixels by 1000 pixels is one megapixel.
 
PLSS
(Public Land Survey System)- A method used in the United States to survey and identify land parcels, particularly for titles and deeds of rural, wild or undeveloped land. Its basic units of area are the township and section. The system was created by the Land Ordinance of 1785 and is in place in most states that were created after this date.
 
PNG
(Portable Network Graphics)- A bitmapped image format that employs lossless image data compression. PNG was originally intended to replace GIF.
 
Portrait
A page layout in which the vertical edge is longer than the horizontal edge.
 
Principal
A north-south meridian that establishes the baseline off of which a PLSS system is based. In most cases, there is only one in each state and as such, the state can be used instead.
 
Print
A physical representation of an image, such as a photograph.
 
Projection
The process of representing a three dimensional object, such as the Earth, on a two dimensional surface.
 
Provider
The company that owns the rights to and has taken the images seen on the site. TerraServer does not own any aerial image equipment, we buy images from numerous providers in order to provide a site with many different images of a particular area.
 
PSD
(PhotoShop Document)- An image file type designed specifically to work in Adobe Photoshop.
 
Q
Quadrangle
An area defined by the USGS as containing 16 townships and hence being 24 miles on each side. This can also refer to USGS Quadrangle maps, which are usually named after a physiographic feature, such as a town or lake.
 
Quarter Section
A subdivision of a section into four equal parts, each measuring 0.25 square miles or 160 acres. There are 144 quarter-sections in a township.
 
QuickBird
The QuickBird satellite is the first in a constellation of spacecraft that DigitalGlobe® is developing that offers highly accurate, commercial high-resolution imagery of Earth.
 
R
Range
A part of the PLSS system that tells how far to the east or west of the principal meridian an area lies.
 
Remote Sensing
The collection of data using a method in which direct contact is not involved. A common example would be the use of ultrasound to monitor pregnancy. This term is more commonly used to describe the collection and analysis of satellite and aerial imagery. Imagery that is collected from space can be used to monitor an area on Earth without ever physically interacting with the environment.
 
Resolution
A number that describes the ability of an image to represent a certain area. The value for satellite images is given in meters per pixel, which means that each pixel in the image represents a certain distance on the ground. Once you surpass the native resolution when viewing an image, the image will begin to extrapolate and attempt to fill in the missing pixels. This causes the image to get blurry or block up.
 
RNC
(Raster Navigation Chart)- Geo-referenced, full-color images of NOAA’s paper nautical charts.
 
S
Sample
Preselected images of an area of interest. Samples eliminate the need to do a coordinate or address search on areas that are popular search topics. They can be found using the Samples button at the top of the page.
 
Satellite Image
An image taken from a vehicle that is in orbit around the Earth. In simpler terms, an image taken from an artificial satellite.
 
Seconds
In the sense of geography, a subdivision of a degree that is equal to 1/3600 of a degree. It is therefore one sixtieth of a geographic minute.
 
Section
A subdivision of a township into 36 equal parts, each equal to one square mile or 640 acres. Sections are numbered beginning with one in the northeast corner and then counting up to six going from east to west. The seventh section is directly south of the sixth and the eighth section is directly to the east of the seventh. The second row of section is then labeled seven to twelve going from west to east. This alternating pattern is continued until the 36th section, which lies at the southwest corner of the township.
 
Shape File
A digital geospatial vector storage format for storing geometric location and associated attribute information developed by ESRI to create compatibility between ESRI software packages and other software. This format lacks the capacity to store topological information.
 
Solution
A brief overview of how the TerraServer service can benefit certain industries.
 
Spectrum
A plot of light intensity or power as a function of frequency or wavelength. For example, the visible spectrum would be the wavelengths of light that would be visible to the human eye.
 
SPOT
(Satellite Pour l'Observation de la Terre)- A French Earth observation satellite operated by Spot Image, based in Toulouse, France. The satellite was developed by the French in cooperation with Belgian and Swedish agencies.
 
SSL
(Secure Sockets Layer)- Cryptographic protocol that provides for the secure transfer of data over the internet. This can be used to transfer customer information and billing information.
 
Subscription
Payment for access to a service or product for a certain period of time.
 
Sun-Synchronous
An orbit in which a satellite is lined up directly between the Sun and the Earth. This allows for good lighting and minimizes shadows when taking satellite images.
 
T
Terabyte
A unit of computer storage equal to one trillion bytes. This is equal to one thousand gigabytes and one million megabytes.
 
TIFF
(Tagged Image File Format)- An image file type that is popular for high color depth images and for its flexibility.
 
Topographic Map
A type of detailed map that displays geographic relief information about an area. Points of the same elevation are connected with contour lines. These contour lines each represent a constant elevation and there is a constant contour interval between these lines. Also known as topo maps, they also can show information such as water, vegetation, and even man made objects. Most of the topographic maps available for the United States were commissioned by the USGS.
 
Township
The main subdivision under the PLSS system in use in the United States. A township covers an area of thirty six square miles, which is equal to 23,040 acres. Township numbers define the north/south relation of the township to the baseline.
 
U
USDA
(United States Department of Agriculture)- A Cabinet level department of the United States Government whose purpose is to develop and execute policy on farming, agriculture, and food. The USDA commissioned the NAIP data that can be found on the site.
 
USGS
(United States Geological Survey)- A scientific agency within the Department of the Interior in the United States. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility.
 
UTM Coordinates
(Universal Transverse Mercator Coordinates)- A grid-based method of specifying locations on the surface of the Earth. The UTM system is not a single map projection. The system instead employs a series of sixty zones, each of which is based on a specifically defined Transverse Mercator projection.
 
W
Watermark
An image layer placed over another image with the intent of interfering with the copy or redistribution of the image without the permission of the image owner.
 
Waterproof Paper
A paper type and printing process that is immune to water damage and also resists tears.
 
WGS84
(World Geodetic System)- A geographic datum developed in 1984 as an update to previous WGS datums. The WGS 84 originally used the GRS 80 reference ellipsoid, but has undergone some minor refinements in later editions since its initial publication. Most of these refinements are important for high-precision orbital calculations for satellites, but have little practical effect on typical topographical uses.
 
World File
A plain text file used by GIS software to position and reference an image or map. The specification was developed by ESRI. The lines have the following representations:
Line 1: A, pixel size in the x-direction in map units/pixel
Line 2: D: rotation about y-axis (This is always zero)
Line 3: B: rotation about x-axis (This is always zero)
Line 4: E: pixel size in the y-direction in map units, almost always negative
Line 5: C: x-coordinate of the center of the upper left pixel (Easting UTM coordinate)
Line 6: F: y-coordinate of the center of the upper left pixel (Northing UTM coordinate)
 
Z
ZIP + 4
The conventional zip code used by the United States Postal Service with the addition of four digits that describe some feature about the address such as the fact that it is part of an apartment complex or on a specific hill.
 
Zone
A subdivision of the Earth's surface under the UTM Coordinate system. The UTM system divides the surface of the Earth between 80° S latitude and 84° N latitude into 60 zones, each 6° of longitude in width and centered over a meridian of longitude. Zones are numbered from 1 to 60. Zone 1 is bounded by longitude 180° to 174° W and is centered on the 177th West meridian. Zone numbering increases in an easterly direction.
 
 
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