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36-542: The elevation models are arranged into tiles, each covering one degree of latitude and one degree of longitude, named according to their south western corners. For example, "n45e006" stretches from 45°N 6°E to 46°N 7°E and "s45w006" from 45°S 6°W to 44°S 5°W . The resolution of the raw data is one arcsecond (30 m along the equator) and coverage includes Africa, Europe, North America, South America, Asia, and Australia. A derived one arcsecond dataset with trees and other non-terrain features removed covering Australia

72-410: A " prime " (minute of arc), 1 for a second , 1 for a third , 1 for a fourth , etc. Hence, the modern symbols for the minute and second of arc, and the word "second" also refer to this system. SI prefixes can also be applied as in, e.g., millidegree , microdegree , etc. In most mathematical work beyond practical geometry, angles are typically measured in radians rather than degrees. This

108-452: A cycle or revolution) is equal to 360°. With the invention of the metric system , based on powers of ten, there was an attempt to replace degrees by decimal "degrees" in France and nearby countries, where the number in a right angle is equal to 100 gon with 400 gon in a full circle (1° = 10 ⁄ 9 gon). This was called grade (nouveau) or grad . Due to confusion with

144-453: Is 1 nautical mile . The example above would be given as 40° 11.25′ (commonly written as 11′25 or 11′.25). The older system of thirds , fourths , etc., which continues the sexagesimal unit subdivision, was used by al-Kashi and other ancient astronomers, but is rarely used today. These subdivisions were denoted by writing the Roman numeral for the number of sixtieths in superscript: 1 for

180-422: Is a glyph or symbol that is used, among other things, to represent degrees of arc (e.g. in geographic coordinate systems ), hours (in the medical field), degrees of temperature or alcohol proof . The symbol consists of a small superscript circle. The word degree is equivalent to Latin gradus which, since the medieval period, could refer to any stage in a graded system of ranks or steps. The number of

216-511: Is approximately 365 because of the apparent movement of the sun against the celestial sphere, and that it was rounded to 360 for some of the mathematical reasons cited above. For many practical purposes, a degree is a small enough angle that whole degrees provide sufficient precision. When this is not the case, as in astronomy or for geographic coordinates ( latitude and longitude ), degree measurements may be written using decimal degrees ( DD notation ); for example, 40.1875°. Alternatively,

252-527: Is approximately equal to one milliradian ( c. 1 ⁄ 6,283 ). A mil measuring 1 ⁄ 6,000 of a revolution originated in the imperial Russian army , where an equilateral chord was divided into tenths to give a circle of 600 units. This may be seen on a lining plane (an early device for aiming indirect fire artillery) dating from about 1900 in the St. Petersburg Museum of Artillery. Degree symbol The degree symbol or degree sign , ° ,

288-474: Is equivalent to ⁠ π / 180 ⁠ radians. The original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is related to the fact that 360 is approximately the number of days in a year. Ancient astronomers noticed that the sun, which follows through the ecliptic path over the course of the year, seems to advance in its path by approximately one degree each day. Some ancient calendars , such as

324-442: Is for a variety of reasons; for example, the trigonometric functions have simpler and more "natural" properties when their arguments are expressed in radians. These considerations outweigh the convenient divisibility of the number 360. One complete turn (360°) is equal to 2 π radians, so 180° is equal to π radians, or equivalently, the degree is a mathematical constant : 1° = π ⁄ 180 . One turn (corresponding to

360-603: Is now "kelvin", in lower case, and no longer "degrees Kelvin". In photography , the symbol is used to denote logarithmic film speed grades. In this usage, it follows the number without spacing as in 21° DIN , 5° ASA or ISO 100/21° . The degree symbol is included in Unicode as U+00B0 ° DEGREE SIGN ( ° ). For use with wide character fonts , there are also code points for U+2103 ℃ DEGREE CELSIUS and U+2109 ℉ DEGREE FAHRENHEIT . The degree sign

396-549: The Babylonian astronomers and their Greek successors, was based on chords of a circle. A chord of length equal to the radius made a natural base quantity. One sixtieth of this, using their standard sexagesimal divisions, was a degree. Aristarchus of Samos and Hipparchus seem to have been among the first Greek scientists to exploit Babylonian astronomical knowledge and techniques systematically. Timocharis , Aristarchus, Aristillus , Archimedes , and Hipparchus were

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432-627: The EGM96 geoid separation values were added to convert to heights relative to the geoid for all the released products. The elevation models derived from the SRTM data are used in geographic information systems . They can be downloaded freely over the Internet, and their file format (.hgt) is widely supported. The Shuttle Radar Topography Mission is an international project spearheaded by the U.S. National Geospatial-Intelligence Agency ( NGA ), an agency of

468-552: The International Organization for Standardization and the U.S. Government Printing Office ) prescribe printing temperatures with a space between the number and the degree symbol, e.g. 10   °C . However, in many works with professional typesetting, including scientific works published by the University of Chicago Press or Oxford University Press , the degree symbol is printed with no spaces between

504-457: The OEIS ). Furthermore, it is divisible by every number from 1 to 10 except 7. This property has many useful applications, such as dividing the world into 24 time zones , each of which is nominally 15° of longitude , to correlate with the established 24-hour day convention. Finally, it may be the case that more than one of these factors has come into play. According to that theory, the number

540-542: The Persian calendar and the Babylonian calendar , used 360 days for a year. The use of a calendar with 360 days may be related to the use of sexagesimal numbers. Another theory is that the Babylonians subdivided the circle using the angle of an equilateral triangle as the basic unit, and further subdivided the latter into 60 parts following their sexagesimal numeric system. The earliest trigonometry , used by

576-622: The U.S. Department of Defense , and the U.S. National Aeronautics and Space Administration ( NASA ). NASA transferred the SRTM payload to the Smithsonian National Air and Space Museum in 2003; the canister, mast, and antenna are now on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia . The USGS SRTM data is based on NASA's SIR-C instrument. It is available in at the following versions: The SRTM also carries

612-405: The 1570s, with a borderline example by Jacques Pelletier du Mans in 1569, and was popularized by, among others, Tycho Brahe and Johannes Kepler , but didn't become universal. Similarly, the introduction of the temperature scales with degrees in the 18th century was at first without such symbols, but with the word "gradus" spelled out. Use of the degree symbol was introduced for temperature in

648-588: The United States (except Alaska) and northernmost Mexico according to the announcement. 1-arc second global digital elevation model (30 meters) is available from the United States Geological Survey web site. The United States Government announced on September 23, 2014 over a United Nations Climate Summit that the highest possible resolution of global topographic data derived from the SRTM mission will be released to public. Before

684-597: The X-SAR instrument operated by the German Aerospace Center (DLR) and Italian Space Agency (ASI). The resulting dataset is usually called SRTM/X-SAR, or SRTMX for short. The grid resolution is high at 25 meters, but it has many gaps. The data was made public in May 2011. The terminology regarding versions and resolutions can be confusing. "SRTM1" and "SRTM3" refers to the resolutions in 1 and 3 arc-seconds, not

720-599: The case of degrees of angular arc , the degree symbol follows the number without any intervening space , e.g. 30° . The addition of minute and second of arc follows the degree units, with intervening spaces (optionally, non-breaking space ) between the sexagesimal degree subdivisions but no spaces between the numbers and units, for example 30°   12 ′   5″ . In the case of degrees of temperature , three scientific and engineering standards bodies (the International Bureau of Weights and Measures ,

756-709: The degree sign at the same code point, 0xB0. The code point in the older DOS Code Page 437 was 0xF8 (248 decimal); therefore, the Alt code used to enter the symbol directly from the keyboard is Alt + 2 4 8 . Other characters with similar appearance but different meanings include: Some computer keyboard layouts, such as the QWERTY layout as used in Italy, the QWERTZ layout as used in Germany, Austria and Switzerland, and

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792-541: The end of the same year, a 1-arc second global digital elevation model (30 meters) was released. Most parts of the world have been covered by this dataset ranging from 54°S to 60°N latitude except for the Middle East and North Africa area. Missing coverage of the Middle East was completed in August 2015. In early June 2011, there were 750,000 confirmed users of SRTM topography dataset. Users in 221 countries have accessed

828-573: The existing term grad(e) in some northern European countries (meaning a standard degree, ⁠ 1 / 360 ⁠ of a turn), the new unit was called Neugrad in German (whereas the "old" degree was referred to as Altgrad ), likewise nygrad in Danish , Swedish and Norwegian (also gradian ), and nýgráða in Icelandic . To end the confusion, the name gon was later adopted for

864-403: The first Greeks known to divide the circle in 360 degrees of 60 arc minutes . Eratosthenes used a simpler sexagesimal system dividing a circle into 60 parts. Another motivation for choosing the number 360 may have been that it is readily divisible : 360 has 24 divisors , making it one of only 7 numbers such that no number less than twice as much has more divisors (sequence A072938 in

900-427: The later 18th century and became widespread in the early 19th century. Antoine Lavoisier in his "Opuscules physiques et chymiques" (1774) used the ordinal indicator with Arabic numerals – for example, when he wrote in the introduction: The 1 . is to be read as primo meaning "in the first place", followed by 2 . ("in the second place"), etc. In the same work, when Lavoisier gives a temperature, he spells out

936-481: The new unit. Although this idea of metrification was abandoned by Napoleon, grades continued to be used in several fields and many scientific calculators support them. Decigrades ( 1 ⁄ 4,000 ) were used with French artillery sights in World War I. An angular mil , which is most used in military applications, has at least three specific variants, ranging from 1 ⁄ 6,400 to 1 ⁄ 6,000 . It

972-600: The number, the symbol, and the Latin letters "C" or "F" representing Celsius or Fahrenheit , respectively, e.g. 10°C . This is also the practice of the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research. Both ASTM International and NIST , the official US entities related to the standardization of the use of units, require a space between

1008-465: The numerical value and the unit designator, except when the degree symbol alone is used to denote an angular value. Use of the degree symbol to refer to temperatures measured in kelvins (symbol: K) was abolished in 1967 by the 13th General Conference on Weights and Measures ( CGPM ). Therefore, the triple point of water, for instance, is written simply as 273.16 K. The name of the SI unit of temperature

1044-447: The rank in question was indicated by ordinal numbers , in abbreviation with the ordinal indicator (a superscript o ). Use of "degree" specifically for the degrees of arc, used in conjunction with Arabic numerals, became common in the 16th century, but this was initially without the use of an ordinal marker or degree symbol: instead, various abbreviation of gradus (e.g., Gra., Gr., gr., G.). The modern notation appears in print in

1080-480: The site. Degree (angle) A degree (in full, a degree of arc , arc degree , or arcdegree ), usually denoted by ° (the degree symbol ), is a measurement of a plane angle in which one full rotation is 360 degrees. It is not an SI unit —the SI unit of angular measure is the radian —but it is mentioned in the SI brochure as an accepted unit . Because a full rotation equals 2 π radians, one degree

1116-588: The traditional sexagesimal unit subdivisions can be used: one degree is divided into 60 minutes (of arc) , and one minute into 60 seconds (of arc) . Use of degrees-minutes-seconds is also called DMS notation . These subdivisions, also called the arcminute and arcsecond , are represented by a single prime (′) and double prime (″) respectively. For example, 40.1875° = 40° 11′ 15″ . Additional precision can be provided using decimal fractions of an arcsecond. Maritime charts are marked in degrees and decimal minutes to facilitate measurement; 1 minute of latitude

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1152-704: The versions of the format. On the other hand, "SRTM4.1" refers to a specific filled version by CGIAR-CSI. It is recommended to add a "v" in front of the version number to disambiguate. The elevation datasets are affected by mountain and desert no-data areas. These amount to no more than 0.2% of the total area surveyed, but can be a problem in areas of very high relief. They affect all summits over 8,000 meters, most summits over 7,000 meters, many Alpine and similar summits and ridges, and many gorges and canyons. There are some SRTM data sources which have filled these data voids, but some of these have used only interpolation from surrounding data, and may therefore be very inaccurate. If

1188-699: The voids are large, or completely cover summit or ridge areas, no interpolation algorithms will give satisfactory results. Groups of scientists have worked on algorithms to fill the voids of the original SRTM (v2.1) data. Three datasets offer global coverage void-filled SRTM data at full (3-arcsecond) resolution: In November 2013, LP DAAC released the NASA Shuttle Radar Topography Mission (SRTM) Version 3.0 (SRTM Plus) Product collection with all voids eliminated. Voids were filled primarily from ASTER GDEM2 , and secondarily from USGS GMTED2010 – or USGS National Elevation Dataset (NED) for

1224-547: The word "degree" explicitly, for example (p.  206 ): une température de 16 à 17 dégrés du thermomètre ("a temperature of 16 to 17 degrees of the thermometer") - notice the old spelling for degré in the citation. An early use of the degree symbol for temperature is that by Henry Cavendish in 1776 for degrees of the Fahrenheit scale . The symbol is also declared as a notation for degrees of arc as early as 1831, in an American mathematics textbook for schools. In

1260-526: Was made available in November 2011; the raw data are restricted for government use. For the rest of the world, only three arcsecond (90 m along the equator) data are available. Each one arcsecond tile has 3,601 rows, each consisting of 3,601 16 bit bigendian cells. The dimensions of the three arcsecond tiles are 1201 x 1201. The original SRTM elevations were calculated relative to the WGS84 ellipsoid and then

1296-628: Was not included in the basic 7-bit ASCII set of 1963. In 1987, the ISO/IEC 8859 standard introduced it at position 0xB0 (176 decimal) in all variants except Part 5 (Cyrillic), 6 (Arabic), 7 (Greek) and 11 (Thai). In 1991, the Unicode standard incorporated all of the ISO/IEC 8859 code points and thus included the degree sign (at U+00B0).. The Windows Code Page 1252 was an extension of ISO/IEC 8859-1 (8859 Part 1 or "ISO Latin-1") standard, so it had

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