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78-718: While latitude and longitude are well suited to describing locations over large areas of the Earth's surface, most practical land navigation situations occur within much smaller, local areas. As such, they are often better served by a local Cartesian coordinate system , in which the coordinates represent actual distance units on the ground, using the same units of measurement from two perpendicular coordinate axes. This can improve human comprehension by providing reference of scale, as well as making actual distance computations more efficient. Paper maps often are published with overlaid rectangular (as opposed to latitude/longitude) grids to provide

156-505: A tan ⁡ ϕ {\displaystyle \textstyle {\tan \beta ={\frac {b}{a}}\tan \phi }\,\!} ; for the GRS   80 and WGS   84 spheroids, b a = 0.99664719 {\textstyle {\tfrac {b}{a}}=0.99664719} . ( β {\displaystyle \textstyle {\beta }\,\!} is known as the reduced (or parametric) latitude ). Aside from rounding, this

234-408: A datum transformation such as a Helmert transformation , although in certain situations a simple translation may be sufficient. Datums may be global, meaning that they represent the whole Earth, or they may be local, meaning that they represent an ellipsoid best-fit to only a portion of the Earth. Examples of global datums include World Geodetic System (WGS   84, also known as EPSG:4326 ),

312-435: A 0.9996 scale factor at the central meridian, growing to 1.0000 at two meridians offset from the center, and increasing toward the zone boundaries, so as to minimize the overall effect of scale distortion across the zone breadth.) The USNG is not intended for surveying, for which a higher-precision (lower-distortion) coordinate system such as SPCS would be more appropriate. Also, since USNG north-south grid lines are (by design)

390-570: A UTM zone and a latitude band is (normally) a 6° × 8° polygon called a grid zone , whose designation in MGRS is formed by the zone number (one or two digits – the number for zones 1 to 9 is just a single digit, according to the example in DMA TM 8358.1, Section 3-2, Figure 7), followed by the latitude band letter (uppercase). This same notation is used in both UTM and MGRS, i.e. the UTM grid reference system;

468-650: A choice of geodetic datum (including an Earth ellipsoid ), as different datums will yield different latitude and longitude values for the same location. The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene , who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC. A century later, Hipparchus of Nicaea improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of lunar eclipses , rather than dead reckoning . In

546-519: A column letter (A–Z, omitting I and O) followed by a row letter (A–V, omitting I and O). Near the equator, the columns of UTM zone 1 have the letters A–H, the columns of UTM zone 2 have the letters J–R (omitting O), and the columns of UTM zone 3 have the letters S–Z. At zone 4, the column letters start over from A, and so on around the world. For the row letters, there are actually two alternative lettering schemes within MGRS: If an MGRS coordinate

624-500: A fixed distance from the zone central meridian, only the central meridian itself will be aligned with "true north". Other grid lines establish a local " grid north ", which will differ from true north by a small amount. The amount of this deviation, which is indicated on USGS topographic maps, is typically much less than the magnetic declination (between true north and magnetic north), and is small enough that it can be disregarded in most land navigation situations. Since its adoption as

702-414: A grid that is universal, interoperable, non-proprietary, works across all jurisdictions, and can readily be used with GPS receivers and other location service applications. In addition to providing a convenient means to identify and communicate specific locations (points and areas), an overlaid USNG grid also provides an orientation, and—because it is distance based—a scale of distance that is present across

780-626: A known regional or local area. For example: Thus in practical usage, USNG references are typically very succinct and compact, making them convenient (and less error prone) for communication. Rectangular, distance-based ( Cartesian ) coordinate systems have long been recognized for their practical utility for land measurement and geolocation over local areas. In the United States, the Public Land Survey System (PLSS), created in 1785 in order to survey land newly ceded to

858-441: A local discontinuity along each of the 'seam' meridians between zones. However, every point continues to have a well-defined, unique geoaddress, and there are established conventions to minimize confusion near zone intersections. The six-degree zone width of UTM strikes a balance between the frequency of these discontinuities versus distortion of scale, which would increase unacceptably if the zones were made wider. (UTM further uses

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936-479: A manual to guide GIS users and others through the practical steps of naming assets using the USNG. Geographic coordinate system This is an accepted version of this page A geographic coordinate system ( GCS ) is a spherical or geodetic coordinate system for measuring and communicating positions directly on Earth as latitude and longitude . It is the simplest, oldest and most widely used of

1014-592: A national standard in 2001, the USNG has itself been incorporated into standards and operating procedures of other organizations: " POLICY STATEMENT: FEMA will use the United States National Grid (USNG) as its standard geographic reference system for land-based operations and will encourage use of the USNG among whole community partners." The utility of almost every large or medium scale map (paper or electronic) can be greatly enhanced by having an overlaid coordinate grid. The USNG provides such

1092-608: A point on Earth's surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses (often called great circles ), which converge at the North and South Poles. The meridian of the British Royal Observatory in Greenwich , in southeast London, England, is the international prime meridian , although some organizations—such as

1170-1086: A prefix code to identify the type of asset. Organizations have successfully fielded this type of USNG-based asset naming recently: "The Mohawk Valley Water Authority serves 40,000 customers in the Greater Utica Area in Central New York. We have 700+ miles of pipe, 28 storage tanks, 21 pump stations, and numerous fire hydrants. We communicate hydrant status information internally and with many fire departments. We need to name these items meaningfully. We have tried several naming conventions—both sequential and hierarchical—with confusing and disappointing results. We converted to USNG asset naming and have used this successfully for over 4 years!" -- Elisabetta T. DeGeronimo, Watershed/GIS Coordinator at Mohawk Valley Water Authority, Utica, New York -- "Hundreds of thousands of roadside assets—culverts, drains, signs on ground mounts, signs on overhead support structures, signs on span wires, and guide rails—are found along

1248-448: A reference to identify locations. However, these grids, if non-standard or proprietary (such as so-called "bingo" grids with references such as "B-4"), are typically not interoperable with each other, nor can they usually be used with GPS. The goal of the USNG is to provide a uniform, nationally consistent rectangular grid system that is interoperable across maps at different scales, as well as with GPS and other location based systems. It

1326-473: A region of the surface of the Earth. Some newer datums are bound to the center of mass of the Earth. This combination of mathematical model and physical binding mean that anyone using the same datum will obtain the same location measurement for the same physical location. However, two different datums will usually yield different location measurements for the same physical location, which may appear to differ by as much as several hundred meters; this not because

1404-594: A single one-meter grid square out of the entire surface of the earth. It consists of three parts (each of which follows a "read-right-then-up" paradigm familiar with other "X,Y" coordinates): In addition to truncating references (on the right) when less precision is required, another powerful feature of USNG is the ability to omit (on the left) the Grid Zone Designation, and possibly even the 100 km Square Identification, when one or both of these are unambiguously understood; that is, when operating within

1482-411: Is 6,367,449 m . Since the Earth is an oblate spheroid , not spherical, that result can be off by several tenths of a percent; a better approximation of a longitudinal degree at latitude ϕ {\displaystyle \phi } is where Earth's equatorial radius a {\displaystyle a} equals 6,378,137 m and tan ⁡ β = b

1560-480: Is 110.6 km. The circles of longitude, meridians, meet at the geographical poles, with the west–east width of a second naturally decreasing as latitude increases. On the Equator at sea level, one longitudinal second measures 30.92 m, a longitudinal minute is 1855 m and a longitudinal degree is 111.3 km. At 30° a longitudinal second is 26.76 m, at Greenwich (51°28′38″N) 19.22 m, and at 60° it

1638-522: Is 15.42 m. On the WGS   84 spheroid, the length in meters of a degree of latitude at latitude ϕ (that is, the number of meters you would have to travel along a north–south line to move 1 degree in latitude, when at latitude ϕ ), is about The returned measure of meters per degree latitude varies continuously with latitude. Similarly, the length in meters of a degree of longitude can be calculated as (Those coefficients can be improved, but as they stand

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1716-431: Is a common method for identifying and referencing particular assets.  A strategically assigned asset identifier can include location information, thereby assuring both that the name is unique and that the location of the asset is always known. The USNG offers a method to locate any place or any object in the world with a brief alphanumeric code, which can be shortened depending on the known service area, and enhanced with

1794-406: Is a point reference system. When the term 'grid square' is used, it can refer to a square with a side length of 10 km (6 mi), 1 km, 100 m (328 ft), 10 m or 1 m, depending on the precision of the coordinates provided. (In some cases, squares adjacent to a Grid Zone Junction (GZJ) are clipped, so polygon is a better descriptor of these areas.) The number of digits in

1872-708: Is by no means limited to those fields. The USNG is an alpha-numeric reference system that overlays the UTM coordinate system . A number of brief tutorial references explain the system in detail, with examples. . Briefly, an example of a full USNG spatial address (grid reference) is: 18S UJ 23371 06519 (This example used by the FGDC is the full one-meter grid reference of the Jefferson Pier in Washington DC.) This full form (15 characters) uniquely identifies

1950-420: Is complete (with both a grid zone designation and a 100,000 meter square identification), and is valid in one lettering scheme, then it is usually invalid in the other scheme, which will have no such 100,000 meter square in the grid zone. (Latitude band X is the exception to this rule.) Therefore, a position reported in a modern datum usually cannot be misunderstood as using an old datum, and vice versa – provided

2028-705: Is intended to provide a frame of reference for describing and communicating locations that is easier to use than latitude/longitude for many practical applications, works across jurisdictional boundaries, and is simple to learn, teach, and use. It is also designed to be both flexible and scalable so that location references are as compact and concise as possible. The USNG is intended to supplement —not to replace—other location systems such as street addresses. It can be applied to printed maps and to computer mapping and other (GIS) applications. It has found increasing acceptance especially in emergency management, search and rescue, and other public safety applications; yet, its utility

2106-456: Is known as a graticule . The origin/zero point of this system is located in the Gulf of Guinea about 625 km (390 mi) south of Tema , Ghana , a location often facetiously called Null Island . In order to use the theoretical definitions of latitude, longitude, and height to precisely measure actual locations on the physical earth, a geodetic datum must be used. A horizonal datum

2184-675: Is the exact distance along a parallel of latitude; getting the distance along the shortest route will be more work, but those two distances are always within 0.6 m of each other if the two points are one degree of longitude apart. Like any series of multiple-digit numbers, latitude-longitude pairs can be challenging to communicate and remember. Therefore, alternative schemes have been developed for encoding GCS coordinates into alphanumeric strings or words: These are not distinct coordinate systems, only alternative methods for expressing latitude and longitude measurements. Military Grid Reference System The Military Grid Reference System ( MGRS )

2262-669: Is the geocoordinate standard used by NATO militaries for locating points on Earth. The MGRS is derived from the Universal Transverse Mercator (UTM) grid system and the Universal Polar Stereographic (UPS) grid system, but uses a different labeling convention. The MGRS is used as geocode for the entire Earth. It’s also referred as 10-digit coordinates. An example of an MGRS coordinate , or grid reference , would be 4QFJ12345678 , which consists of three parts: An MGRS grid reference

2340-428: Is used instead of a UTM projection. The west half-circle forms a grid zone with designation A; the east half-circle forms one with designation B; see figure 3. North of 84°N, UPS North is used, and the west half-circle is Y, the east one is Z; see figure 4. Since the letters A, B, Y, and Z are not used for any latitude bands of UTM, their presence in an MGRS coordinate, with the omission of a zone number, indicates that

2418-465: Is used to precisely measure latitude and longitude, while a vertical datum is used to measure elevation or altitude. Both types of datum bind a mathematical model of the shape of the earth (usually a reference ellipsoid for a horizontal datum, and a more precise geoid for a vertical datum) to the earth. Traditionally, this binding was created by a network of control points , surveyed locations at which monuments are installed, and were only accurate for

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2496-534: Is used to reduce confusion and improve efficiency in response to wildfires, floods and hurricanes and other events. As noted above, In 2015, the Federal Emergency Management Agency (FEMA) issued FEMA Directive 092–5, "Use of the United States National Grid (USNG)": " POLICY STATEMENT: FEMA will use the United States National Grid (USNG) as its standard geographic reference system for land-based operations and will encourage use of

2574-402: Is used, the first 5 digits give the easting in meters, measured from the left edge of the square, and the last 5 digits give the northing in meters, measured from the bottom edge of the square. The resolution in this case is 1 meter, so the MGRS coordinate would represent a 1-meter square, where the easting and northing are measured to its southwest corner. If a resolution of 10 meters is enough,

2652-481: The International Date Line , which diverges from it in several places for political and convenience reasons, including between far eastern Russia and the far western Aleutian Islands . The combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The visual grid on a map formed by lines of latitude and longitude

2730-717: The 100 km Grid Square ID(s) covering the area of the particular map. USNG can now be found on various pre-printed and custom-printed maps available for purchase, or generated from various mapping software packages. A growing number of software applications incorporate or refer to the US National Grid. See the External Links section below for links to some of these, including The National Map (USGS). These applications include conventional mapping applications with overlaid USNG grid and/or coordinate readouts, and several 'you-are-here' mobile applications which give

2808-526: The 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles , off the coast of western Africa around the Canary or Cape Verde Islands , and measured north or south of the island of Rhodes off Asia Minor . Ptolemy credited him with

2886-496: The Army. This truncation can put them on the wrong side of a latitude zone boundary, causing the truncated MGRS string to be considered invalid. The correction causes truncated strings to be considered valid if any part of the square which they denote lies within the latitude zone specified by the third letter of the string. In the polar regions, a different convention is used. South of 80°S, UPS South ( Universal Polar Stereographic )

2964-506: The Earth's surface move relative to each other due to continental plate motion, subsidence, and diurnal Earth tidal movement caused by the Moon and the Sun. This daily movement can be as much as a meter. Continental movement can be up to 10 cm a year, or 10 m in a century. A weather system high-pressure area can cause a sinking of 5 mm . Scandinavia is rising by 1 cm a year as a result of

3042-729: The European ED50 , and the British OSGB36 . Given a location, the datum provides the latitude ϕ {\displaystyle \phi } and longitude λ {\displaystyle \lambda } . In the United Kingdom there are three common latitude, longitude, and height systems in use. WGS   84 differs at Greenwich from the one used on published maps OSGB36 by approximately 112   m. The military system ED50 , used by NATO , differs from about 120   m to 180   m. Points on

3120-536: The French Institut national de l'information géographique et forestière —continue to use other meridians for internal purposes. The prime meridian determines the proper Eastern and Western Hemispheres , although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E. This is not to be conflated with

3198-631: The US further refined UTM for ease of use (and combined it with the Universal Polar Stereographic system covering polar areas) to create the Military Grid Reference System (MGRS), which remains the geocoordinate standard used across the militaries of NATO counties. In the 1990s, a US grass-roots citizen effort led to the Public X-Y Mapping Project, a not-for-profit organization created specifically to promote

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3276-685: The US. (Latitude and longitude [DMM variant] may be used as the secondary system for land responders; especially when coordinating with air and sea based responders who may use it as their primary system, and USNG as secondary.) The National Association for Search and Rescue (NASAR) is moving its education and certification testing programming towards USNG. Other organizations such as the National Alliance for Public Safety GIS (NAPSG) also provide USNG SAR training. FEMA Urban Search and Rescue (USAR) task forces including Florida Task Force 4 (FL-TF4) and Iowa Task Force 1 (IA-TF1) have incorporated

3354-545: The USNG among whole community partners." "Lessons learned from several large-scale disasters within the past three decades highlight the need for a common, geographic reference system in order to anticipate resource requirements, facilitate decision-making, and accurately deploy resources. ... Decision support tools that apply the USNG enable emergency managers to locate positions and identify areas of interest or operations where traditional references (i.e., landmarks or street signs) may be destroyed, damaged, or missing due to

3432-471: The USNG into their training and operations. Responders are often faced with significant geolocation issues when a responding to an emergency without a street address. This is particularly true in the recreational trail environment: In response to these issues, in 2009, a project funded by the nonprofit SharedGeo and University of Minnesota/Minnesota Department of Transportation Local Operational Research Assistance (OPERA) grant program got underway which had

3510-417: The USNG provides: This format ambiguity has led to confusion with potentially serious consequences, particularly in emergency situations. All of the above also lead to USNG references being typically very succinct and compact, with flexibility to convey precise location information in a short sequence of characters that is easily relayed in writing or by voice. As with any projection that seeks to represent

3588-575: The USNG was adopted by the FGDC as standard FGDC-STD-011-2001 in December 2001. Since then, the USNG has seen gradual but steadily increasing adoption both in formal standards and in practical use and applications, in public safety and in other fields. Users encountering the USNG (or similar grid reference systems) sometimes question why they are used instead of latitude and longitude coordinates, with which they may be more familiar. Proponents note that, in contrast to latitude and longitude coordinates,

3666-550: The acceptance of a national grid for the United States. The Public XY Mapping Project developed the idea, conducting informal tests and surveys to determine which coordinate reference system best met the requirements of national consistency and ease of human use. Based on its findings, a standard based on the MGRS was adopted and brought to the Federal Geographic Data Committee (FGDC) in 1998. After an iterative review process and public comment period,

3744-458: The article on Universal Transverse Mercator shows many maps of these grid zones, including the irregularities for Svalbard and southwest Norway. As Figure 1 illustrates, Honolulu is in grid zone 4Q. The second part of an MGRS coordinate is the 100,000-meter square identification . Each UTM zone is divided into 100,000 meter squares, so that their corners have UTM-coordinates that are multiples of 100,000 meters. The identification consists of

3822-461: The boundaries of the 100,000-meter squares (blue lines in figure 1). For example, at the boundary between grid zones 1P and 1Q, we find a 100,000-meter square BT, of which about two thirds is south of latitude 16° and therefore in grid zone 1P, while one third is north of 16° and therefore in 1Q. So, an MGRS grid reference for a position in BT should begin with 1PBT in the south part of BT, and with 1QBT in

3900-577: The center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels , as they are parallel to the Equator and to each other. The North Pole is 90° N; the South Pole is 90° S. The 0° parallel of latitude is designated the Equator , the fundamental plane of all geographic coordinate systems. The Equator divides the globe into Northern and Southern Hemispheres . The longitude λ of

3978-597: The coordinates are in the UPS system. The lettering scheme for 100,000 m squares is slightly different in the polar regions. The column letters use a more restricted alphabet, going from A to Z but omitting D, E, I, M, N, O, V, W; the columns are arranged so that the rightmost column in grid zone A and Y has column letter Z, and the next column in grid zone B or Z starts over with column letter A. The row letters go from A to Z, omitting I and O. The restricted column alphabet for UPS ensures that no UPS square will be adjacent to

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4056-697: The coordinates, not round. This has been controversial in the past, since the oldest specification, TM8358.1, used rounding, as did GEOTRANS before version 3.0. However, truncation is used in GEOTRANS since version 3.0, and in NGA Military Map Reading 201 (page 5) and in the US Army Field Manual 3-25.26. The civilian version of MGRS, USNG , also uses truncation. The boundaries of the latitude bands are parallel circles (dashed black lines in figure 1), which do not coincide with

4134-402: The curved Earth as a flat surface, distortions and tradeoffs will inevitably occur. The USNG attempts to balance and minimize these, consistent with making the grid as useful as possible for its intended purpose of efficiently communicating practical locations. Since the UTM (the basis for USNG) is not a single projection, but rather a set of 6-degree longitudinal zones, there will necessarily be

4212-453: The datums use different MGRS lettering schemes. In the map (figure 1), which uses the AA scheme, we see that Honolulu is in grid zone 4Q, and square FJ. To give the position of Honolulu with 100 km resolution, we write 4QFJ. The third part of an MGRS coordinate is the numerical location within a 100,000 meter square, given as n + n digits, where n is 1, 2, 3, 4, or 5. If 5 + 5 digits

4290-649: The default datum used for the Global Positioning System , and the International Terrestrial Reference System and Frame (ITRF), used for estimating continental drift and crustal deformation . The distance to Earth's center can be used both for very deep positions and for positions in space. Local datums chosen by a national cartographical organization include the North American Datum ,

4368-490: The distance they give is correct within a centimeter.) The formulae both return units of meters per degree. An alternative method to estimate the length of a longitudinal degree at latitude ϕ {\displaystyle \phi } is to assume a spherical Earth (to get the width per minute and second, divide by 60 and 3600, respectively): where Earth's average meridional radius M r {\displaystyle \textstyle {M_{r}}\,\!}

4446-748: The effectiveness of all types of emergency response, ranging from missing persons searches to off-road medical responses. In Lake County MN, with 900 miles of recreational trails, dispatchers and first responders have been provided the tools and training to use USNG as their primary means of geo-location. The goal of this education for responders and the public is to "Take the 'Search' out of 'Search and Rescue.'" In addition to ELM signs, notices at trailheads encourage hikers and off-road vehicle operators to "Download this USNG App" on their cell phones. Trail maps including USNG grid lines allow responders to interpolate locations from 911 callers who give their coordinates from ELMs or GPS apps. Cell phones also provide responders

4524-761: The effects of a disaster." The USNG is also seen as a tool for enhancing situational awareness and facilitating a common operating picture in emergency scenarios. The Department of Defense also has recognized the role of the civil USNG standard for the Armed Forces in support of homeland security and homeland defense. Organizations such as public utilities, transportation departments, emergency responders, and others own or rely upon fixed, field-based assets which they need to track, inventory, maintain, and locate efficiently when needed.  Examples include fire hydrants, overhead utility poles, storm drains, roadside signs, and many others. Assigning unique identifiers

4602-526: The final digit of the easting and northing can be dropped, so that only 4 + 4 digits are used, representing a 10-meter square. If a 100-meter resolution is enough, 3 + 3 digits suffice; if a 1 km resolution is enough, 2 + 2 digits suffice; if 10 km resolution is enough, 1 + 1 digits suffice. 10 meter resolution (4 + 4 digits) is sufficient for many purposes, and is the NATO standard for specifying coordinates. If we zoom in on Hawaii (figure 2), we see that

4680-844: The following objectives: After three years of field research and vetting by multiple focus groups of trail users, responders, and geospatial experts, a design based on USNG was adopted. This format, which can be used anywhere in the United States, was originally offered in three sizes to conform to federal, state and local signage standards: In the years since introduction, the USNG ELM program now includes vertical ELM versions for breakaway scenarios (e.g. mountain bike trails), ELM information signs, ELM stickers to retrofit trail posts, and corresponding apps such as USNGapp.org . USNG ELM implementations can be found in Minnesota, Florida, Georgia, Hawaii, Michigan, and other states. The USNG can increase

4758-474: The full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day. Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. After their work was translated into Arabic in the 9th century, Al-Khwārizmī 's Book of the Description of the Earth corrected Marinus' and Ptolemy's errors regarding

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4836-781: The length of the Mediterranean Sea , causing medieval Arabic cartography to use a prime meridian around 10° east of Ptolemy's line. Mathematical cartography resumed in Europe following Maximus Planudes ' recovery of Ptolemy's text a little before 1300; the text was translated into Latin at Florence by Jacopo d'Angelo around 1407. In 1884, the United States hosted the International Meridian Conference , attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt

4914-461: The location has moved, but because the reference system used to measure it has shifted. Because any spatial reference system or map projection is ultimately calculated from latitude and longitude, it is crucial that they clearly state the datum on which they are based. For example, a UTM coordinate based on WGS84 will be different than a UTM coordinate based on NAD27 for the same location. Converting coordinates from one datum to another requires

4992-595: The longitude of the Royal Observatory in Greenwich , England as the zero-reference line. The Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911. The latitude ϕ of a point on Earth's surface is the angle between the equatorial plane and the straight line that passes through that point and through (or close to)

5070-543: The map. USGS topographic maps have for decades been published with 1000-meter UTM tick marks in the map collar, and sometimes with full grid lines across the map. Recent editions of these maps (those referenced to the North American datum of 1983, or NAD83) are compatible with USNG, and current editions also contain a standard USNG information box in the collar which identifies the GZD(s) (Grid Zone Designator(s) and

5148-463: The melting of the ice sheets of the last ice age , but neighboring Scotland is rising by only 0.2 cm . These changes are insignificant if a local datum is used, but are statistically significant if a global datum is used. On the GRS   80 or WGS   84 spheroid at sea level at the Equator, one latitudinal second measures 30.715 m , one latitudinal minute is 1843 m and one latitudinal degree

5226-537: The nation, introduced a rectangular coordinate system to improve on the earlier metes-and-bounds survey basis used earlier in the original colonies. In the first half of the 20th century, State Plane Coordinate Systems (SPCS) brought the simplicity and convenience of Cartesian coordinates to state-level areas, providing high accuracy (low distortion) survey-grade coordinates for use primarily by state and local governments. (Both of these planar systems remain in use today for specialized purposes.) Internationally, during

5304-510: The north part of BT. At least, this is possible if the precision of the grid reference is enough to place the denoted area completely inside either 1P or 1Q. But an MGRS grid reference can denote an area that crosses a latitude band boundary. For example, when describing the entire square BT, should it be called 1PBT or 1QBT? Or when describing the 1000-meter square BT8569, should it be called 1PBT8569 or 1QBT8569? In these cases, software that interprets an MGRS grid reference should accept both of

5382-445: The numerical location must be even: 0, 2, 4, 6, 8 or 10, depending on the desired precision. When changing precision levels, it is important to truncate rather than round the easting and northing values to ensure the more precise polygon will remain within the boundaries of the less precise polygon. Related to this is the primacy of the southwest corner of the polygon being the labeling point for an entire polygon. In instances where

5460-475: The opportunity to counsel lost or injured persons to determine their location by downloading USNG apps on the spot. This saves time and effort for responders and patients alike who are not on roads or addressed locations. When multiple teams of responders are working in close vicinity, such as during woods searches for lost individuals, communicating with USNG allows them to truncate their coordinate string to eight digits, giving their location within 10 meters without

5538-521: The period between World Wars I and II, several European nations mapped their territory with national-scale grid systems optimized for the geography of each country, such as the Ordnance Survey National Grid (British National Grid). Near the end of World War II, the Universal Transverse Mercator (UTM) coordinate system extended this grid concept around the globe, dividing it into 60 zones of 6 degrees longitude each. Circa 1949,

5616-424: The polygon is not a square and has been clipped by a grid zone junction, the polygon keeps the label of the southwest corner as if it had not been clipped. The first part of an MGRS coordinate is the grid-zone designation . The 6° wide UTM zones, numbered 1–60, are intersected by latitude bands that are normally 8° high, lettered C–X (omitting I and O). The northmost latitude band, X, is 12° high. The intersection of

5694-492: The possible latitude band letters. A practical motivation was given in the release notes for GEOTRANS, Release 2.0.2, 1999: The MGRS module was changed to make the final latitude check on MGRS to UTM conversions sensitive to the precision of the input MGRS coordinate string. The lower the input precision, the more "slop" is allowed in the final check on the latitude zone letter. This is to handle an issue raised by some F-16 pilots, who truncate MGRS strings that they receive from

5772-680: The routes maintained by the New York State Department of Transportation. In the past, the existence of these assets was only recorded in construction plans and the minds and memories of dedicated career staff. Our new asset naming convention, based upon the U.S. National Grid, benefits the entire department and particularly the field forces." -- Mary Susan Knauss, Senior Transportation Analyst, Office of Transportation Management, New York State Department of Transportation, Albany, New York These and other contributors at Florida State University and elsewhere have collaborated to produce

5850-622: The square that contains Honolulu, if we use 10 km resolution, would be written 4QFJ15. If the grid zone or 100,000-meter square are clear from context, they can be dropped, and only the numerical location is specified. For example: One always reads map coordinates from west to east first (easting), then from south to north (northing). Common mnemonics include "in the house, up the stairs", "left-to-right, bottom-to-top" and "Read Right Up". As mentioned above, when converting UTM coordinates to an MGRS grid reference, or when abbreviating an MGRS grid reference to lower precision, one should truncate

5928-408: The use of decimals, special symbols or unit descriptors, and intuitively estimate the distance and direction between teams for better coordination. Emergency managers coordinate response to and recovery from all types of natural hazards and man-made threats. In large scale events, where responders may be imported from many jurisdictions, coordination of geo-location formats is mandatory. The USNG

6006-539: The user's current USNG coordinates, such as USNGapp.org and FindMeSAR.com . Mission Manager , the most widely used incident management software tool for first responders, integrates the USNG in its functionality. As noted above under Standards, since 2011 the USNG has been designated by the US Government's National Search and Rescue Committee (NSARC) as the primary coordinate reference system to be used for all land-based search and rescue (SAR) activities in

6084-461: The various spatial reference systems that are in use, and forms the basis for most others. Although latitude and longitude form a coordinate tuple like a cartesian coordinate system , the geographic coordinate system is not cartesian because the measurements are angles and are not on a planar surface. A full GCS specification, such as those listed in the EPSG and ISO 19111 standards, also includes

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