Aerial photography is the taking of photographs of the ground from an elevated/direct-down position. Usually the camera is not supported by a ground-based structure, mounted cameras may be triggered remotely or automatically, hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that chase, Aerial photography was first practiced by the French photographer and balloonist Gaspard-Félix Tournachon, known as Nadar, in 1858 over Paris, France. However, the photographs he produced no longer exist and therefore the earliest surviving aerial photograph is titled Boston, as the Eagle, taken by James Wallace Black and Samuel Archer King on October 13,1860, it depicts Boston from a height of 630m. Kite aerial photography was pioneered by British meteorologist E. D. Archibald in 1882 and he used an explosive charge on a timer to take photographs from the air. Frenchman Arthur Batut began using kites for photography in 1888, Samuel Franklin Cody developed his advanced Man-lifter War Kite and succeeded in interesting the British War Office with its capabilities.
The first use of a motion picture camera mounted to an aircraft took place on April 24,1909 over Rome in the 3,28 silent film short. The use of aerial photography rapidly matured during the war, as aircraft were equipped with cameras to record enemy movements. At the start of the conflict, the usefulness of aerial photography was not fully appreciated, germany adopted the first aerial camera, a Görz, in 1913. The French began the war with several squadrons of Blériot observation aircraft equipped with cameras for reconnaissance, the French Army developed procedures for getting prints into the hands of field commanders in record time. Frederick Charles Victor Laws started aerial photography experiments in 1912 with No.1 Squadron of the Royal Flying Corps, in 1916 the Austro-Hungarian Monarchy made vertical camera axis aerial photos above Italy for map-making. The camera was inserted into the floor of the aircraft and could be triggered by the pilot at intervals. In January 1918, General Allenby used five Australian pilots from No.1 Squadron AFC to photograph a 624 square miles area in Palestine as an aid to correcting and improving maps of the Turkish front and this was a pioneering use of aerial photography as an aid for cartography.
Beginning 5 January, they flew with an escort to ward off enemy fighters. The first commercial aerial photography company in the UK was Aerofilms Ltd, founded by World War I veterans Francis Wills, the company soon expanded into a business with major contracts in Africa and Asia as well as in the UK. Operations began from the Stag Lane Aerodrome at Edgware, using the aircraft of the London Flying School, the Aircraft Manufacturing Company, hired an Airco DH.9 along with pilot entrepreneur Alan Cobham. From 1921, Aerofilms carried out vertical photography for survey and mapping purposes, during the 1930s, the company pioneered the science of photogrammetry, with the Ordnance Survey amongst the companys clients. One Fairchild aerial survey aircraft in 1935 carried unit that combined two synchronized cameras, and each camera having five six inch lenses with a ten-inch lenses, each photo covered two hundred and twenty five square miles
Surveying or land surveying is the technique and science of determining the terrestrial or three-dimensional position of points and the distances and angles between them. A land surveying professional is called a land surveyor, Surveyors work with elements of geometry, regression analysis, engineering, programming languages and the law. Surveying has been an element in the development of the environment since the beginning of recorded history. The planning and execution of most forms of construction require it and it is used in transport, communications and the definition of legal boundaries for land ownership. It is an important tool for research in other scientific disciplines. Basic surveyance has occurred since humans built the first large structures, the prehistoric monument at Stonehenge was set out by prehistoric surveyors using peg and rope geometry. In ancient Egypt, a rope stretcher would use simple geometry to re-establish boundaries after the floods of the Nile River. The almost perfect squareness and north-south orientation of the Great Pyramid of Giza, built c.2700 BC, the Groma instrument originated in Mesopotamia.
The mathematician Liu Hui described ways of measuring distant objects in his work Haidao Suanjing or The Sea Island Mathematical Manual, the Romans recognized land surveyors as a profession. They established the basic measurements under which the Roman Empire was divided, Roman surveyors were known as Gromatici. In medieval Europe, beating the bounds maintained the boundaries of a village or parish and this was the practice of gathering a group of residents and walking around the parish or village to establish a communal memory of the boundaries. Young boys were included to ensure the memory lasted as long as possible, in England, William the Conqueror commissioned the Domesday Book in 1086. It recorded the names of all the owners, the area of land they owned, the quality of the land. It did not include maps showing exact locations, abel Foullon described a plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument. Gunters chain was introduced in 1620 by English mathematician Edmund Gunter and it enabled plots of land to be accurately surveyed and plotted for legal and commercial purposes.
Leonard Digges described a Theodolite that measured horizontal angles in his book A geometric practice named Pantometria, joshua Habermel created a theodolite with a compass and tripod in 1576. Johnathon Sission was the first to incorporate a telescope on a theodolite in 1725, in the 18th century, modern techniques and instruments for surveying began to be used. Jesse Ramsden introduced the first precision theodolite in 1787 and it was an instrument for measuring angles in the horizontal and vertical planes
A town is a human settlement larger than a village but smaller than a city. The size definition for what constitutes a town varies considerably in different parts of the world, the word town shares an origin with the German word Zaun, the Dutch word tuin, and the Old Norse tun. The German word Zaun comes closest to the meaning of the word. An early borrowing from Celtic *dunom, in English and Dutch, the meaning of the word took on the sense of the space which these fences enclosed. In England, a town was a community that could not afford or was not allowed to build walls or other larger fortifications. In the Netherlands, this space was a garden, more specifically those of the wealthy, in Old Norse tun means a place between farmhouses, and is still used in a similar meaning in modern Norwegian. If there was any distinction between toun and burgh as claimed by some, it did not last in practice as burghs, for example, Edina Burgh or Edinburgh was built around a fort and eventually came to have a defensive wall.
In some cases, town is a name for city or village. Sometimes, the town is short for township. A places population size is not a determinant of urban character. In many areas of the world, as in India at least until recent times, in the United Kingdom, there are historical cities that are far smaller than the larger towns. Some forms of settlement, such as temporary mining locations, may be clearly non-rural. Towns often exist as governmental units, with legally defined borders. In the United States these are referred to as incorporated towns, in other cases the town lacks its own governance and is said to be unincorporated. Note that the existence of a town may be legally set forth through other means. In the case of planned communities, the town exists legally in the form of covenants on the properties within the town. Australian geographer Thomas Griffith Taylor proposed a classification of towns based on their age, although there is no official use of the term for any settlement. In Albanian qytezë means small city or new city, while in ancient times small residential center within the walls of a castle
The foot is a unit of length in the imperial and US customary systems of measurement. Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly, in both systems, the foot comprises 12 inches and three feet compose a yard. Historically the foot was a part of local systems of units, including the Greek, Chinese, French. It varied in length from country to country, from city to city and its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits. The United States is the industrialized nation that uses the international foot and the survey foot in preference to the meter in its commercial, engineering. The foot is legally recognized in the United Kingdom, road signs must use imperial units, the measurement of altitude in international aviation is one of the few areas where the foot is widely used outside the English-speaking world. The length of the international foot corresponds to a foot with shoe size of 13,14,15.5 or 46.
Historically the human body has been used to provide the basis for units of length. The foot of a male is typically about 15. 3% of his height, giving a person of 160 cm a foot of 245 mm. These figures are less than the used in most cities over time. Archeologists believe that the Egyptians, Ancient Indians and Mesopotamians preferred the cubit while the Romans, under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 13.2 inches and a cubit of 20.8 inches. The Egyptian equivalent of the measure of four palms or 16 digits—was known as the djeser and has been reconstructed as about 30 cm. The Greek foot had a length of 1⁄600 of a stadion, one stadion being about 181.2 m, the standard Roman foot was normally about 295.7 mm, but in the provinces, the pes Drusianus was used, with a length of about 334 mm. Originally both the Greeks and the Romans subdivided the foot into 16 digits, but in years, after the fall of the Roman Empire, some Roman traditions were continued but others fell into disuse.
In AD790 Charlemagne attempted to reform the units of measure in his domains and his units of length were based on the toise and in particular the toise de lÉcritoire, the distance between the fingertips of the outstretched arms of a man. The toise has 6 pieds each of 326.6 mm, at the same time, monastic buildings used the Carolingian foot of 340 mm. The procedure for verification of the foot as described in the 16th century by Jacob Koebel in his book Geometrei, the measures of Iron Age Britain are uncertain and proposed reconstructions such as the Megalithic Yard are controversial. Later Welsh legend credited Dyfnwal Moelmud with the establishment of their units, the Belgic or North German foot of 335 mm was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the Anglo-Saxons in the 5th & 6th century
Atmospheric pressure, sometimes called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth. In most circumstances atmospheric pressure is approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimetre in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kilograms and that force is a pressure of 10.1 N/cm2 or 101 kN/m2. A column 1 square inch in cross-section would have a weight of about 14.7 lb or about 65.4 N and it is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The standard atmosphere is a unit of pressure defined as 101325 Pa, the mean sea level pressure is the average atmospheric pressure at sea level.
This is the pressure normally given in weather reports on radio, television. When barometers in the home are set to match the weather reports, they measure pressure adjusted to sea level. The altimeter setting in aviation, is an atmospheric pressure adjustment, average sea-level pressure is 1013.25 mbar. In aviation weather reports, QNH is transmitted around the world in millibars or hectopascals, except in the United States, however, in Canadas public weather reports, sea level pressure is instead reported in kilopascals. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar, the lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar. Pressure varies smoothly from the Earths surface to the top of the mesosphere, although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases, one can calculate the atmospheric pressure at a given altitude.
Temperature and humidity affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C, at low altitudes above the sea level, the pressure decreases by about 1.2 kPa for every 100 meters. See pressure system for the effects of air pressure variations on weather, Atmospheric pressure shows a diurnal or semidiurnal cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars and these variations have two superimposed cycles, a circadian cycle and semi-circadian cycle. The highest adjusted-to-sea level barometric pressure recorded on Earth was 1085.7 hPa measured in Tosontsengel
Levelling is a branch of surveying, the object of which is to Find the elevation of a given point with respect to the given or assumed datum. Establish a point at an elevation with respect to the given or assumed datum. Levelling is the measurement of geodetic height using an optical levelling instrument, common levelling instruments include the spirit level, the dumpy level, the digital level, and the laser level. Spirit levelling employs a spirit level, an instrument consisting of a telescope with a crosshair, when the bubble in the tube level is centered the telescopes line of sight is supposed to be horizontal. The spirit level is on a tripod with sight lines to the two points whose height difference is to be determined, a graduated leveling staff or rod is held vertical on each point, the rod may be graduated in centimetres and fractions or tenths and hundredths of a foot. The observer focuses in turn on each rod and reads the value, subtracting the back and forward value provides the height difference.
If the instrument is placed equidistant from the two points to be measured, any errors in its adjustment and the effects of earth curvature. A typical procedure is to set up the instrument within 100 metres of a point of known or assumed elevation, a rod or staff is held vertical on that point and the instrument is used manually or automatically to read the rod scale. This gives the height of the instrument above the starting point, the rod is held on an unknown point and a reading is taken in the same manner, allowing the elevation of the new point to be computed. The procedure is repeated until the point is reached. It is usual practice to either a complete loop back to the starting point or else close the traverse on a second point whose elevation is already known. The closure check guards against blunders in the operation, and allows residual error to be distributed in the most likely manner among the stations, some instruments provide three crosshairs which allow stadia measurement of the foresight and backsight distances.
These allow use of the average of the three readings as a check against blunders and for averaging out the error of interpolation between marks on the rod scale, the two main types of levelling are single-levelling as already described, and double-levelling. Double-levelling costs twice as much as single-levelling, the curvature of the earth means that a line of sight that is horizontal at the instrument will be higher and higher above a spheroid at greater distances. The effect may be significant for some work at distances under 100 meters, the line of sight is horizontal at the instrument, but is not a straight line because of refraction in the air. The change of air density with elevation causes the line of sight to bend toward the earth, for most work it is sufficient to keep the foresight and backsight distances approximately equal so that the refraction and curvature effects cancel out. Refraction is generally the greatest source of error in leveling, for short level lines the effects of temperature and pressure are generally insignificant, but the effect of the temperature gradient dT / dh can lead to errors.
Assuming error-free measurements, if the Earths gravity field were completely regular and gravity constant, leveling loops would always close precisely, ∑ i =0 n Δ h i =0 around a loop
Height above average terrain
Height above average terrain is a measure of how high an antenna site is above the surrounding landscape. HAAT is used extensively in FM radio and television, as it is more important than effective radiated power in determining the range of broadcasts. Stations that want to increase above a certain HAAT must reduce their power accordingly, the entire radial graph could be rotated to achieve the best effect for the station. The altitude of the site, minus the average altitude of all the specified points, was the HAAT. This can create some unusual cases, particularly in mountainous regions—it is possible to have a number for HAAT. The FCC has divided the Contiguous United States into three zones for the determination of spacing between FM and TV stations using the same frequencies, FM and TV stations are assigned maximum ERP and HAAT values, depending on their assigned zones, to prevent co-channel interference. The FCC regulations for ERP and HAAT are listed under Title 47, Maximum HAAT,150 meters Maximum ERP,50 kW Minimum co-channel separation,241 km Maximum HAAT,600 meters Maximum ERP,100 kW Minimum co-channel separation,290 km.
In addition, Zone I-A consists of all of California south of 40° north latitude, Puerto Rico, zones I and I-A have the most grandfathered overpowered stations, which are allowed the same extended coverage areas that they had before the zones were established. One of the most powerful of these stations is WBCT in Grand Rapids, Zone III consists of all of Florida and the areas of Alabama, Louisiana and Texas within approximately 241.4 kilometers of the Gulf of Mexico. Zone II is all the rest of the Continental United States and Hawaii
GIS or geographic information system is a computer system that allows for visualizing, manipulating and storage of data with associated attributes. GIS offers better understanding of patterns and relationships of the landscape at different scales, tools inside the GIS allow for manipulation of data for spatial analysis or cartography. A topographical map is the type of map used to depict elevation. In a Geographic Information System, digital models are commonly used to represent the surface of a place. Digital terrain models are another way to represent terrain in GIS, USGS is developing a 3D Elevation Program to keep up with growing needs for high quality topographic data. 3DEP is a collection of enhanced elevation data in the form of high quality LiDAR data over the conterminous United States, there are three bare earth DEM layers in 3DEP which are nationally seamless at the resolution of 1/3,1, and 2 arcseconds. This map is derived from GTOPO30 data that describes the elevation of Earths terrain at intervals of 30 arcseconds and it uses color and shading instead of contour lines to indicate elevation.
Hypsography is the study of the distribution of elevations on the surface of the Earth, the term originates from the Greek word ὕψος hypsos meaning height. Most often it is used only in reference to elevation of land, related to the term hypsometry, the measurement of these elevations of a planets solid surface are taken relative to mean datum, except for Earth which is taken relative to the sea level. In the troposphere, temperatures decrease with altitude and this lapse rate is approximately 6.5 °C/km. S
Global Positioning System
The Global Positioning System is a space-based radionavigation system owned by the United States government and operated by the United States Air Force. The GPS system operates independently of any telephonic or internet reception, the GPS system provides critical positioning capabilities to military and commercial users around the world. The United States government created the system, maintains it, the US government can selectively deny access to the system, as happened to the Indian military in 1999 during the Kargil War. The U. S. Department of Defense developed the system and it became fully operational in 1995. Roger L. Easton of the Naval Research Laboratory, Ivan A, getting of The Aerospace Corporation, and Bradford Parkinson of the Applied Physics Laboratory are credited with inventing it. Announcements from Vice President Al Gore and the White House in 1998 initiated these changes, in 2000, the U. S. Congress authorized the modernization effort, GPS III. In addition to GPS, other systems are in use or under development, mainly because of a denial of access.
The Russian Global Navigation Satellite System was developed contemporaneously with GPS, GLONASS can be added to GPS devices, making more satellites available and enabling positions to be fixed more quickly and accurately, to within two meters. There are the European Union Galileo positioning system and Chinas BeiDou Navigation Satellite System and general relativity predict that the clocks on the GPS satellites would be seen by the Earths observers to run 38 microseconds faster per day than the clocks on the Earth. The GPS calculated positions would quickly drift into error, accumulating to 10 kilometers per day, the relativistic time effect of the GPS clocks running faster than the clocks on earth was corrected for in the design of GPS. The Soviet Union launched the first man-made satellite, Sputnik 1, two American physicists, William Guier and George Weiffenbach, at Johns Hopkinss Applied Physics Laboratory, decided to monitor Sputniks radio transmissions. Within hours they realized that, because of the Doppler effect, the Director of the APL gave them access to their UNIVAC to do the heavy calculations required.
The next spring, Frank McClure, the deputy director of the APL, asked Guier and Weiffenbach to investigate the inverse problem — pinpointing the users location and this led them and APL to develop the TRANSIT system. In 1959, ARPA played a role in TRANSIT, the first satellite navigation system, TRANSIT, used by the United States Navy, was first successfully tested in 1960. It used a constellation of five satellites and could provide a navigational fix approximately once per hour, in 1967, the U. S. Navy developed the Timation satellite, which proved the feasibility of placing accurate clocks in space, a technology required by GPS. In the 1970s, the ground-based OMEGA navigation system, based on comparison of signal transmission from pairs of stations. Limitations of these systems drove the need for a more universal navigation solution with greater accuracy, during the Cold War arms race, the nuclear threat to the existence of the United States was the one need that did justify this cost in the view of the United States Congress.
This deterrent effect is why GPS was funded and it is the reason for the ultra secrecy at that time
A building or edifice is a structure with a roof and walls standing more or less permanently in one place, such as a house or factory. To better understand the term building compare the list of nonbuilding structures, Buildings serve several needs of society – primarily as shelter from weather, living space, privacy, to store belongings, and to comfortably live and work. A building as a shelter represents a division of the human habitat. Ever since the first cave paintings, buildings have become objects or canvasses of much artistic expression. In recent years, interest in planning and building practices has become an intentional part of the design process of many new buildings. The word building is both a noun and a verb an adverb, the structure itself and the act of making it. As a noun, a building is a structure that has a roof and walls and stands more or less permanently in one place, there was a building on the corner. In the broadest interpretation a fence or wall is a building, the word structure is used more broadly than building including natural and man-made formations and does not necessarily have walls.
Structure is more likely to be used for a fence, as a verb, building is the act of construction. Structural height in technical usage is the height to the highest architectural detail on building from street-level, depending on how they are classified and masts may or may not be included in this height. Spires and masts used as antennas are not generally included, the definition of a low-rise vs. a high-rise building is a matter of debate, but generally three storeys or less is considered low-rise. A report by Shinichi Fujimura of a shelter built 500000 years ago is doubtful since Fujimura was found to have faked many of his findings. Supposed remains of huts found at the Terra Amata site in Nice purportedly dating from 200000 to 400000 years ago have called into question. There is clear evidence of homebuilding from around 18000 BC, Buildings became common during the Neolithic. Single-family residential buildings are most often called houses or homes, residential buildings containing more than one dwelling unit are called a duplex, apartment building to differentiate them from individual houses. A condominium is an apartment that the occupant owns rather than rents, houses which were built as a single dwelling may be divided into apartments or bedsitters, they may be converted to another use e. g. an office or a shop.
Building types may range from huts to multimillion-dollar high-rise apartment blocks able to house thousands of people, increasing settlement density in buildings is usually a response to high ground prices resulting from many people wanting to live close to work or similar attractors. Other common building materials are brick, concrete or combinations of either of these with stone, if the residents are in need of special care such as a nursing home, orphanage or prison, or in group housing like barracks or dormitories
The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures.
In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are called artificial satellites to distinguish them from natural satellites such as Earths Moon. In 1957 the Soviet Union launched the worlds first artificial satellite, since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate,3,600 remained in orbit, of those, about 1,000 were operational, the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in orbit,50 are in medium-Earth orbit. A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Venus, Jupiter, Saturn, a few asteroids, Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, Space stations and human spacecraft in orbit are satellites.
Satellite orbits vary greatly, depending on the purpose of the satellite, well-known classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that throws a satellite into orbit, usually it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, attitude control, the first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Vernes The Begums Fortune, in 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the speed required for a minimal orbit. In 1928, Herman Potočnik published his book, The Problem of Space Travel — The Rocket Motor.
He described the use of orbiting spacecraft for observation of the ground, in a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet, the first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4,1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the Soviet Union and the United States, Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere