A digital image is a numeric representation binary, of a two-dimensional image. Depending on whether the image resolution is fixed, it may be of raster type. By itself, the term "digital image" refers to raster images or bitmapped images. Raster images called picture elements or pixels; the digital image contains a fixed number of columns of pixels. Pixels are the smallest individual element in an image, holding antiquated values that represent the brightness of a given color at any specific point; the pixels are stored in computer memory as a raster image or raster map, a two-dimensional array of small integers. These values are transmitted or stored in a compressed form. Raster images can be created by a variety of input devices and techniques, such as digital cameras, coordinate-measuring machines, seismographic profiling, airborne radar, more, they can be synthesized from arbitrary non-image data, such as mathematical functions or three-dimensional geometric models. The field of digital image processing is the study of algorithms for their transformation.
Most users come into contact with raster images through digital cameras, which use any of several image file formats. Some digital cameras give access to all the data captured by the camera, using a raw image format; the Universal Photographic Imaging Guidelines suggests these formats be used when possible since raw files produce the best quality images. These file formats allow the photographer and the processing agent the greatest level of control and accuracy for output, their use is inhibited by the prevalence of proprietary information for some camera makers, but there have been initiatives such as OpenRAW to influence manufacturers to release these records publicly. An alternative may be Digital Negative, a proprietary Adobe product described as "the public, archival format for digital camera raw data". Although this format is not yet universally accepted, support for the product is growing, professional archivists and conservationists, working for respectable organizations, variously suggest or recommend DNG for archival purposes.
Vector images resulted from mathematical geometry. In mathematical terms, a vector consists of point that has both length. Both raster and vector elements will be combined in one image. Image viewer software displays images. Web browsers can display standard internet image formats including GIF, JPEG, PNG; some can show SVG format, a standard W3C format. In the past, when Internet was still slow, it was common to provide "preview" image that would load and appear on the web site before being replaced by the main image. Now Internet is fast enough and this preview image is used; some scientific images can be large. Such images are difficult to download and are browsed online through more complex web interfaces; some viewers offer a slideshow utility to display a sequence of images. Early Digital fax machines such as the Bartlane cable picture transmission system preceded digital cameras and computers by decades; the first picture to be scanned and recreated in digital pixels was displayed on the Standards Eastern Automatic Computer at NIST.
The advancement of digital imagery continued in the early 1960s, alongside development of the space program and in medical research. Projects at the Jet Propulsion Laboratory, MIT, Bell Labs and the University of Maryland, among others, used digital images to advance satellite imagery, wirephoto standards conversion, medical imaging, videophone technology, character recognition, photo enhancement. Rapid advances in digital imaging began with the introduction of microprocessors in the early 1970s, alongside progress in related storage and display technologies; the invention of computerized axial tomography, using x-rays to produce a digital image of a "slice" through a three-dimensional object, was of great importance to medical diagnostics. As well as origination of digital images, digitization of analog images allowed the enhancement and restoration of archaeological artifacts and began to be used in fields as diverse as nuclear medicine, law enforcement and industry. Advances in microprocessor technology paved the way for the development and marketing of charge-coupled devices for use in a wide range of image capture devices and displaced the use of analog film and tape in photography and videography towards the end of the 20th century.
The computing power necessary to process digital image capture allowed computer-generated digital images to achieve a level of refinement close to photorealism. Computer printer Digital image editing Digital geometry Digital photography Geocoded photo Optical character recognition Signal processing Digital image correlation DICOM
Classified information is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to know, intentional mishandling of the material can incur criminal penalties. A formal security clearance is required to view or handle classified documents or to access classified data; the clearance process requires a satisfactory background investigation. Documents and other information must be properly marked "by the author" with one of several levels of sensitivity—e.g. Restricted, confidential and top secret; the choice of level is based on an impact assessment. This includes security clearances for personnel handling the information. Although "classified information" refers to the formal categorization and marking of material by level of sensitivity, it has developed a sense synonymous with "censored" in US English. A distinction is made between formal security classification and privacy markings such as "commercial in confidence".
Classifications can be used with additional keywords that give more detailed instructions on how data should be used or protected. Some corporations and non-government organizations assign levels of protection to their private information, either from a desire to protect trade secrets, or because of laws and regulations governing various matters such as personal privacy, sealed legal proceedings and the timing of financial information releases. With the passage of time much classified information can become a bit less sensitive, or becomes much less sensitive, may be declassified and made public. Since the late twentieth century there has been freedom of information legislation in some countries, whereby the public is deemed to have the right to all information, not considered to be damaging if released. Sometimes documents are released with information still considered confidential obscured, as in the example at right; the purpose of classification is to protect information. Higher classifications protect information.
Classification formalises what constitutes a "state secret" and accords different levels of protection based on the expected damage the information might cause in the wrong hands. However, classified information is "leaked" to reporters by officials for political purposes. Several U. S. presidents have leaked sensitive information to get their point across to the public. Although the classification systems vary from country to country, most have levels corresponding to the following British definitions. Top Secret is the highest level of classified information. Information is further compartmented so that specific access using a code word after top secret is a legal way to hide collective and important information; such material would cause "exceptionally grave damage" to national security if made publicly available. Prior to 1942, the United Kingdom and other members of the British Empire used Most Secret, but this was changed to match the United States' category name of Top Secret in order to simplify Allied interoperability.
The Washington Post reports in an investigation entitled Top Secret America, that per 2010 "An estimated 854,000 people... hold top-secret security clearances" in the United States. Secret material would cause "serious damage" to national security. In the United States, operational "Secret" information can be marked with an additional "LIMDIS", to limit distribution. Confidential material would cause "damage" or be prejudicial to national security if publicly available. Restricted material would cause "undesirable effects"; some countries do not have such a classification. Such a level is known as "Private Information". Official material forms the generality of government business, public service delivery and commercial activity; this includes a diverse range of information, of varying sensitivities, with differing consequences resulting from compromise or loss. OFFICIAL information must be secured against a threat model, broadly similar to that faced by a large private company; the OFFICIAL classification replaced the Confidential and Restricted classifications in April 2014 in the UK.
Unclassified is technically not a classification level, but this is a feature of some classification schemes, used for government documents that do not merit a particular classification or which have been declassified. This is because the information is low-impact, therefore does not require any special protection, such as vetting of personnel. A plethora of pseudo-classifications exist under this category. Clearance is a general classification, that comprises a variety of rules controlling the level of permission required to view some classified information, how it must be stored and destroyed. Additionally, access is restricted on a "need to know" basis. Possessing a clearance does not automatically authorize the individual to view all material classified at that level or below that level; the individual must present a legitimate "need to know" in addition to the proper level of clearance. In addition to the general risk-based classification levels, additional compartmented constraints on access exist, such as Special Intelligence, which protects intelligence sources and methods, No Foreign dissemination, which restricts dissemi
National Geospatial-Intelligence Agency
The National Geospatial-Intelligence Agency is a combat support agency under the United States Department of Defense and a member of the United States Intelligence Community, with the primary mission of collecting and distributing geospatial intelligence in support of national security. NGA was known as the National Imagery and Mapping Agency until 2003. NGA headquarters known as NGA Campus East, is located at Fort Belvoir North Area in Virginia; the agency operates major facilities in the St. Louis, Missouri area, as well as support and liaison offices worldwide; the NGA headquarters, at 2.3 million square feet, is the third-largest government building in the Washington metropolitan area after The Pentagon and the Ronald Reagan Building. In addition to using GEOINT for U. S. military and intelligence efforts, the NGA provides assistance during natural and man-made disasters, security planning for major events such as the Olympic Games. In September 2018, researchers at the National Geospatial-Intelligence Agency released a high resolution terrain map of Antarctica, named the "Reference Elevation Model of Antarctica".
U. S. mapping and charting efforts remained unchanged until World War I, when aerial photography became a major contributor to battlefield intelligence. Using stereo viewers, photo-interpreters reviewed thousands of images. Many of these were of the same target at different angles and times, giving rise to what became modern imagery analysis and mapmaking; the Engineer Reproduction Plant was the Army Corps of Engineers's first attempt to centralize mapping production and distribution. It was located on the grounds of the Army War College in Washington, D. C. Topographic mapping had been a function of individual field engineer units using field surveying techniques or copying existing or captured products. In addition, ERP assumed the "supervision and maintenance" of the War Department Map Collection, effective April 1, 1939. With the advent of the Second World War aviation, field surveys began giving way to photogrammetry, photo interpretation, geodesy. During wartime, it became possible to compile maps with minimal field work.
Out of this emerged AMS, which absorbed the existing ERP in May 1942. It was located at the Dalecarlia Site on MacArthur Blvd. just outside Washington, D. C. in Montgomery County and adjacent to the Dalecarlia Reservoir. AMS was designated as an Engineer field activity, effective July 1, 1942, by General Order 22, OCE, June 19, 1942; the Army Map Service combined many of the Army's remaining geographic intelligence organizations and the Engineer Technical Intelligence Division. AMS was redesignated the U. S. Army Topographic Command on September 1, 1968, continued as an independent organization until 1972, when it was merged into the new Defense Mapping Agency and redesignated as the DMA Topographic Center; the agency's credit union, Constellation Federal Credit Union, was chartered during the Army Map Service era, in 1944. It has continued to serve all successive legacy their families. After the war, as airplane capacity and range improved, the need for charts grew; the Army Air Corps established its map unit, renamed ACP in 1943 and was located in St. Louis, Missouri.
ACP was known as the U. S. Air Force Aeronautical Chart and Information Center from 1952 to 1972. A credit union was chartered for the ACP in 1948, called Aero Chart Credit Union, it was renamed Arsenal Credit Union in 1952, a nod to the St. Louis site's Civil War-era use as an arsenal. Shortly before leaving office in January 1961, President Dwight D. Eisenhower authorized the creation of the National Photographic Interpretation Center, a joint project of the CIA and US DoD. NPIC was a component of the CIA's Directorate of Science and Technology and its primary function was imagery analysis. NPIC became part of the National Imagery and Mapping Agency in 1996. NPIC first identified the Soviet Union's basing of missiles in Cuba in 1962. By exploiting images from U-2 overflights and film from canisters ejected by orbiting Corona s, NPIC analysts developed the information necessary to inform U. S. influence operations during the Cuban Missile Crisis. Their analysis garnered worldwide attention when the Kennedy Administration declassified and made public a portion of the images depicting the Soviet missiles on Cuban soil.
The Defense Mapping Agency was created on January 1, 1972, to consolidate all U. S. military mapping activities. DMA's "birth certificate", DoD Directive 5105.40, resulted from a classified Presidential directive, "Organization and Management of the U. S. Foreign Intelligence Community", which directed the consolidation of mapping functions dispersed among the military services. DMA became operational on July 1, 1972, pursuant to General Order 3, DMA. On Oct. 1, 1996, DMA was folded into the National Imagery and Mapping Agency – which became NGA. DMA was first headquartered at the United States Naval Observatory in Washington, D. C at Falls Church, Virginia, its civilian workforce was concentrated at production sites in Bethesda, Northern Virginia, St. Louis, Missouri. DMA was formed from the Mapping and Geodesy Division, Defense Intelligence Agency, from various mapping-related organizations of the military services. DMA Hydrographic Center DMAHC was formed in