Misplaced Pages

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99-523: The mile marker 0 is posted in Hilo on the traffic signal at the intersection of Waiānuenue Avenue, Kamehameha Avenue and Bayfront Highway at coordinates 19°43′36″N 155°5′12″W  /  19.72667°N 155.08667°W  / 19.72667; -155.08667 . The route continues mauka along Waiānuenue Avenue to a little over a half-mile past the mile 1 where it veers left onto Kaūmana Drive near Gilbert Carvalho Park. Further along Waiānuenue Avenue

198-449: A ( ρ ) {\displaystyle D_{\phi _{a}}\left({\mathbf {\rho } }\right)} is the atmospherically induced variance between the phase at two parts of the wavefront separated by a distance ρ {\displaystyle {\boldsymbol {\rho }}} in the aperture plane, and ⟨ ⋅ ⟩ {\displaystyle \langle \cdot \rangle } represents

297-550: A ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} describe the effect of the Earth's atmosphere, and the timescales for any changes in these functions will be set by the speed of refractive index fluctuations in the atmosphere. A description of the nature of the wavefront perturbations introduced by the atmosphere is provided by the Kolmogorov model developed by Tatarski, based partly on

396-413: A ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} , but any amplitude fluctuations are only brought about as a second-order effect while the perturbed wavefronts propagate from the perturbing atmospheric layer to the telescope. For all reasonable models of the Earth's atmosphere at optical and infrared wavelengths the instantaneous imaging performance is dominated by

495-480: A ( r ) e i ϕ a ( r ) ) ψ 0 ( r ) {\displaystyle \psi _{p}\left(\mathbf {r} \right)=\left(\chi _{a}\left(\mathbf {r} \right)e^{i\phi _{a}\left(\mathbf {r} \right)}\right)\psi _{0}\left(\mathbf {r} \right)} where χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} represents

594-469: A ( r ) {\displaystyle \phi _{a}(\mathbf {r} )} is the optical phase error introduced by atmospheric turbulence, R (k) is a two-dimensional square array of independent random complex numbers which have a Gaussian distribution about zero and white noise spectrum, K (k) is the (real) Fourier amplitude expected from the Kolmogorov (or Von Karman) spectrum, Re[] represents taking

693-419: A ( r ) = Re ⁡ [ FT [ ( R ( k ) ⊗ I ( k ) ) K ( k ) ] ] {\displaystyle \phi _{a}(\mathbf {r} )=\operatorname {Re} [{\mbox{FT}}[(R(\mathbf {k} )\otimes I(\mathbf {k} ))K(\mathbf {k} )]]} where I ( k ) is a two-dimensional array which represents the spectrum of intermittency, with

792-769: A commonly used definition for r 0 {\displaystyle r_{0}} , a parameter frequently used to describe the atmospheric conditions at astronomical observatories. r 0 {\displaystyle r_{0}} can be determined from a measured C N profile (described below) as follows: r 0 = ( 16.7 λ − 2 ( cos ⁡ γ ) − 1 ∫ 0 ∞ C N 2 ( h ) d h ) − 3 / 5 {\displaystyle r_{0}=\left(16.7\lambda ^{-2}(\cos \gamma )^{-1}\int _{0}^{\infty }C_{N}^{2}(h)dh\right)^{-3/5}} where

891-408: A destination. Such references are also used by maintenance engineers and emergency services to direct them to specific points where their presence is required. This term is sometimes used to denote a location on a road even if no physical sign is present. This is useful for accident reporting and other record keeping (e.g., "an accident occurred at the 13-mile mark" even if the road is only marked with

990-447: A fair degree of precision; in the UK, the chain (equal to 1 ⁄ 80 mile or 20 metres) is the usual accuracy. In the U.S. and Canada, miles are "decimalized", so that, for example, there may be a "milepost 4.83" to mark a junction, crossing, bridge or tunnel. In metricated areas, the equivalent is the kilometric point . Surveyors place milestones to mark the boundaries between

1089-407: A filled disc called the "seeing disc". The diameter of the seeing disk, most often defined as the full width at half maximum (FWHM), is a measure of the astronomical seeing conditions. It follows from this definition that seeing is always a variable quantity, different from place to place, from night to night, and even variable on a scale of minutes. Astronomers often talk about "good" nights with

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1188-457: A lava tube. Just past mile 6 (coordinates 19°40′51″N 155°9′23″W  /  19.68083°N 155.15639°W  / 19.68083; -155.15639  ( Hawaii Route 2000 ) ) is the junction with Pūʻainakō Street Extension , (Hawaii Route 2000), completed in September 2004 as a bypass of the above-mentioned windy sections. The intersection with Ua Nahele Street at mile 8 marks

1287-475: A low average seeing disc diameter, and "bad" nights where the seeing diameter was so high that all observations were worthless. The FWHM of the seeing disc (or just "seeing") is usually measured in arcseconds , abbreviated with the symbol (″). A 1.0″ seeing is a good one for average astronomical sites. The seeing of an urban environment is usually much worse. Good seeing nights tend to be clear, cold nights without wind gusts. Warm air rises ( convection ), degrading

1386-508: A masonry platform built with bricks and plastered over with lime. Though not architecturally very impressive, being milestones, they were an important part of communication and travel in a large empire. Kos is an ancient Indian unit of distance. It can represent either a distance of approximately 1.8 kilometres (1.1 mi) or 3.2 kilometres (2.0 mi). Minar is a Persian word for tower. Abul Fazl recorded in Akbar Nama that in

1485-460: A means of determining the distance travelled (fares were set by distance at this time). Section 94 states: "The company shall cause the length of the railway to be measured, and milestones, posts, or other conspicuous objects to be set up and maintained along the whole line thereof, at the distance of one quarter of a mile from each other, with numbers or marks inscribed thereon denoting such distances." Similar laws were passed in other countries. On

1584-478: A road directly between the two population centers of the Island of Hawaiʻi . Using prison labor, it started near Holualoa Bay at 19°35′57″N 155°58′26″W  /  19.59917°N 155.97389°W  / 19.59917; -155.97389  ( Judd Road west ) and proceeded in a straight line up to the plateau south of Hualālai . After ten years only about 12 miles (19 km) were completed, when work

1683-456: A stone once every 10 miles). Miliarium ( Classical Latin : [miːllɪˈaːrɪ.ũː ˈau̯rɛ.ũː] ) were originally stone obelisks – made from granite , marble , or whatever local stone was available – and later concrete posts. They were widely used by Roman Empire road builders and were an important part of any Roman road network: the distance travelled per day was only a few miles in some cases. Many Roman milestones only record

1782-472: A system mirroring that of the Interstate System, other states, such as Illinois , California , and Kentucky , use the county line as the zero mile marker , while others, including Missouri , do not sign mile-markers at all (except on Interstates). Arizona has a rather unusual system, where a route's mileposts continue those from its original host. Often, the exits are numbered according to

1881-409: A telescope. The perturbed wavefront ψ p {\displaystyle \psi _{p}} may be related at any given instant to the original planar wavefront ψ 0 ( r ) {\displaystyle \psi _{0}\left(\mathbf {r} \right)} in the following way: ψ p ( r ) = ( χ

1980-424: A unique location number. The number is given without units but is the distance in kilometres from a designated datum location for the road. In the U.S. Interstate Highway System , the numbers usually measure the distance to the southern or western state line, or the route's terminus, if the national southern or western terminus lies in that state. The numbering system for other highways varies by state; most use

2079-509: A white background, written in black. On top is a large "K" (or "KM"), and a number, referencing the distance from the kilometre zero . While the national kilometre zero is in Rizal Park , each major island has its own kilometre zero. The milestones on the Luzon mainland reference Rizal Park's kilometre zero. The second label is a letter, standing for the first letter of the next town if one

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2178-530: Is Rainbow Falls Park (Wai means "water" (fresh) in the Hawaiian language ; ānuenue means "rainbow". Thus "Rainbow Falls" is rendered as Waiānuenue). Starting at the “ Y ” junction adjacent to Gilbert Carvalho Park, Highway 200 continues mauka (uphill) on Kaūmana Drive and provides access to neighborhoods overlooking Hilo. The road is quite narrow and windy with many blind corners, hidden driveways and open drainage ditches . Near mile 4 it passes Kaumana Cave,

2277-410: Is 10–20 cm at visible wavelengths under the best conditions) and this limits the resolution of telescopes to be about the same as given by a space-based 10–20 cm telescope. The distortion changes at a high rate, typically more frequently than 100 times a second. In a typical astronomical image of a star with an exposure time of seconds or even minutes, the different distortions average out as

2376-413: Is a commonly used measurement of the astronomical seeing at observatories. At visible wavelengths, r 0 {\displaystyle r_{0}} varies from 20 cm at the best locations to 5 cm at typical sea-level sites. In reality, the pattern of blobs ( speckles ) in the images changes very rapidly, so that long-exposure photographs would just show a single large blurred blob in

2475-401: Is a term used in metricated areas , where distances are commonly measured in kilometres instead of miles . " Distance marker " is a generic unit-agnostic term. Milestones are installed to provide linear referencing points along the road. This can be used to reassure travellers that the proper path is being followed, and to indicate either distance travelled or the remaining distance to

2574-549: Is assumed to occur on slow timescales, then the timescale t 0 is simply proportional to r 0 divided by the mean wind speed. The refractive index fluctuations caused by Gaussian random turbulence can be simulated using the following algorithm: ϕ a ( r ) = Re [ FT [ R ( k ) K ( k ) ] ] {\displaystyle \phi _{a}(\mathbf {r} )={\mbox{Re}}[{\mbox{FT}}[R(\mathbf {k} )K(\mathbf {k} )]]} where ϕ

2673-588: Is at Hawaii Route 11 (known as the Hawaii Belt Road) in Hilo where the Prince Kūhiō Plaza shopping center is located. Route 2000 is called Pūʻāinakō Street Extension, East Pūʻāinakō Street, and West Pūʻāinakō Street. The project was planned since 1995. Milestone A milestone is a numbered marker placed on a route such as a road , railway line , canal or boundary . They can indicate

2772-815: Is common for drivers to negotiate the center of the road to avoid the rough shoulders, moving back into the lane only when necessary to pass traffic proceeding in the opposite direction. The route is quite scenic with views of the coastline, the Hualālai and Kohala volcanoes, winding its way across Parker Ranch and through the development of Waikiʻi . The original western terminus of Route 200 comes at its junction with Māmalahoa Highway (state route 190) six miles (9.7 km) toward Kona of Waimea (coordinates 19°56′10″N 155°41′14″W  /  19.93611°N 155.68722°W  / 19.93611; -155.68722  ( western end of Saddle Road ) ). In May 1849, Minister of Finance Gerrit P. Judd proposed building

2871-518: Is now in the Malta at War Museum . The Kos Minars or Mile Pillars are medieval milestones that were made by the 16th-century Afghan Ruler Sher Shah Suri and later on by Mughal emperors. These Minars were erected by the Mughal Emperors on the main highways across the empire to mark the distance. The Kos Minar is a solid round pillar, around 30 feet (9.1 m) in height that stands on

2970-476: Is now well paved, and in the uphill sections there is a separate lane for trucks and slower cars. Eventual plans are to complete a section past Māmalahoa Highway down to the coast and intersecting the Queen Kaʻahumanu Highway (state route 19) to support cross-island commuting by tourists and resort employees. The route for the entirely new sections of the highway was changed after the 2006 expansion of

3069-457: Is often characterized by the angular diameter of the long-exposure image of a star ( seeing disk ) or by the Fried parameter r 0 . The diameter of the seeing disk is the full width at half maximum of its optical intensity. An exposure time of several tens of milliseconds can be considered long in this context. The Fried parameter describes the size of an imaginary telescope aperture for which

Hawaii Route 200 - Misplaced Pages Continue

3168-453: Is rapidly changing variations of the optical refractive index along the light path from the object to the detector. Seeing is a major limitation to the angular resolution in astronomical observations with telescopes that would otherwise be limited through diffraction by the size of the telescope aperture . Today, many large scientific ground-based optical telescopes include adaptive optics to overcome seeing. The strength of seeing

3267-462: Is the Dirac delta function . A more thorough description of the astronomical seeing at an observatory is given by producing a profile of the turbulence strength as a function of altitude, called a C n 2 {\displaystyle C_{n}^{2}} profile. C n 2 {\displaystyle C_{n}^{2}} profiles are generally performed when deciding on

3366-401: Is the complex field at position r {\displaystyle \mathbf {r} } and time t {\displaystyle t} , with real and imaginary parts corresponding to the electric and magnetic field components, ϕ u {\displaystyle \phi _{u}} represents a phase offset, ν {\displaystyle \nu } is

3465-519: Is traveling on that direction, then the distance in kilometers, from the town. In the example to the right, a milestone in Ortigas Avenue in Pasig says it is 14 kilometers (8.7 mi) from Rizal Park, and 3 kilometers (1.9 mi) from Cainta . On the other side, the milestone there says it is 2 kilometers (1.2 mi) from San Juan . Most milestones only have labels on one side, facing

3564-693: Is treated as an oscillation in a field ψ {\displaystyle \psi } . For monochromatic plane waves arriving from a distant point source with wave-vector k {\displaystyle \mathbf {k} } : ψ 0 ( r , t ) = A u e i ( ϕ u + 2 π ν t + k ⋅ r ) {\displaystyle \psi _{0}\left(\mathbf {r} ,t\right)=A_{u}e^{i\left(\phi _{u}+2\pi \nu t+\mathbf {k} \cdot \mathbf {r} \right)}} where ψ 0 {\displaystyle \psi _{0}}

3663-576: Is under the jurisdiction of the University of Hawaiʻi Institute for Astronomy . West and northwest of these turnoffs, the 6.5-mile (10.5 km) segment of Route 200 from milepost 28 to 35 was dedicated and opened to traffic on May 29, 2007, with Senator Daniel K. Inouye as the keynote speaker and other local dignitaries. The new section was constructed to full federal highway standards , with wide shoulders, rumble strips, good signage and emergency phones at regular intervals. From milepost 35 to 44

3762-553: The C n 2 {\displaystyle C_{n}^{2}} profile. Some are empirical fits from measured data and others attempt to incorporate elements of theory. One common model for continental land masses is known as Hufnagel-Valley after two workers in this subject. The first answer to this problem was speckle imaging , which allowed bright objects with simple morphology to be observed with diffraction-limited angular resolution. Later came space telescopes , such as NASA 's Hubble Space Telescope , working outside

3861-523: The Milliarium Aureum of Ancient Rome . The Milion survived intact until at least the late 15th century. Its fragments were discovered again in the late 1960s. A fragment is re-erected as a pillar. In Islamic civilisation, use of milestone began in the first Islamic century. The Umayyad caliph Abd al-Malik bin Marwan laid the milestones along the paths that travelers used, and some were found in

3960-709: The Overseas Highway of the Florida Keys – use mileposts to mark points of interest or (in the cases of many businesses along the Overseas Highway) as a portion of their address. In Myanmar , furlongs have been used at least until 2010 in conjunction with miles to indicate distances on highway signs, for example on the Yangon-Mandalay Expressway . Zimbabwean milestones are constructed of cast concrete painted white with

4059-660: The US Army Corps of Engineers in case of an invasion. Military vehicles of all types and treads traversed the Island for the next three years. Following the end of World War II in 1945, the Army turned over jurisdiction of the road to the Territory of Hawaiʻi and it was designated "State Route 20". However, the territorial government had few funds to maintain the road, let alone upgrade it to civilian standards. Much of

Hawaii Route 200 - Misplaced Pages Continue

4158-546: The mauka terminus of Kaūmana Drive. The official start of Saddle Road is at the “ T ” intersection of Ua Nahele Street at mile 8. This is the last neighborhood through which the route will pass. As it has from its beginning in Hilo, Route 200 continues to climb towards the Humuʻula Saddle between Mauna Kea and Mauna Loa . The rainforest of the Hilo Forest Reserve and Upper Waiākea Forest Reserve surround

4257-438: The strength of the phase fluctuations as it corresponds to the diameter of a circular telescope aperture at which atmospheric phase perturbations begin to seriously limit the image resolution. Typical r 0 {\displaystyle r_{0}} values for I band (900 nm wavelength) observations at good sites are 20–40 cm. r 0 {\displaystyle r_{0}} also corresponds to

4356-576: The 1990s, many telescopes have developed adaptive optics systems that partially solve the seeing problem. The best systems so far built, such as SPHERE on the ESO VLT and GPI on the Gemini telescope, achieve a Strehl ratio of 90% at a wavelength of 2.2 micrometers, but only within a very small region of the sky at a time. A wider field of view can be obtained by using multiple deformable mirrors conjugated to several atmospheric heights and measuring

4455-503: The UK, milestones are especially associated with former turnpike roads . The British built many milestones on the island of Malta . They consisted of large slabs of local hard rock and they were engraved with the distance to or from a particular location. Many of these were defaced in World War II to disorientate forces in a potential invasion . Despite this, a very small number of milestones still exist undefaced, and one of these

4554-703: The United States should be reckoned. Odometers were used to measure the Roman milestone spacing, most likely based on Ancient Greek technology . A mile-marker monument, the Milion , was erected in the early 4th century AD in Constantinople . It served as the starting point for measurement of distances for all the roads leading to the cities of the Byzantine Empire , and had the same function as

4653-436: The aperture diameter for which the variance σ 2 {\displaystyle \sigma ^{2}} of the wavefront phase averaged over the aperture comes approximately to unity: σ 2 = 1.0299 ( d r 0 ) 5 / 3 {\displaystyle \sigma ^{2}=1.0299\left({\frac {d}{r_{0}}}\right)^{5/3}} This equation represents

4752-638: The atmosphere and thus not having any seeing problems and allowing observations of faint targets for the first time (although with poorer resolution than speckle observations of bright sources from ground-based telescopes because of Hubble's smaller telescope diameter). The highest resolution visible and infrared images currently come from imaging optical interferometers such as the Navy Prototype Optical Interferometer or Cambridge Optical Aperture Synthesis Telescope , but those can only be used on very bright stars. Starting in

4851-535: The atmosphere. The parameters r 0 and t 0 vary with the wavelength used for the astronomical imaging, allowing slightly higher resolution imaging at longer wavelengths using large telescopes. The seeing parameter r 0 is often known as the Fried parameter , named after David L. Fried . The atmospheric time constant t 0 is often referred to as the Greenwood time constant , after Darryl Greenwood . Mathematical models can give an accurate model of

4950-416: The belief that there were canals on Mars . In viewing a bright object such as Mars, occasionally a still patch of air will come in front of the planet, resulting in a brief moment of clarity. Before the use of charge-coupled devices , there was no way of recording the image of the planet in the brief moment other than having the observer remember the image and draw it later. This had the effect of having

5049-404: The center for each telescope diameter. The diameter (FWHM) of the large blurred blob in long-exposure images is called the seeing disc diameter, and is independent of the telescope diameter used (as long as adaptive optics correction is not applied). It is first useful to give a brief overview of the basic theory of optical propagation through the atmosphere. In the standard classical theory, light

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5148-400: The changes in the dancing speckle patterns is substantially lower. There are three common descriptions of the astronomical seeing conditions at an observatory: These are described in the sub-sections below: Without an atmosphere, a small star would have an apparent size, an " Airy disk ", in a telescope image determined by diffraction and would be inversely proportional to the diameter of

5247-742: The city of Faiq in the Syrian Golan, which is, Faiq, one of the main road stations throughout the Islamic ages. The function of these stones was to guide travelers and introduce them to long distances, as the separation between one and the other was one mile. Many of these stones were found in more than one location, one in the Islamic Archeology Museum in Istanbul and another in the Jerusalem Museum. A translation of

5346-658: The diffraction limited angular resolution is equal to the resolution limited by seeing. Both the size of the seeing disc and the Fried parameter depend on the optical wavelength, but it is common to specify them for 500 nanometers. A seeing disk smaller than 0.4 arcseconds or a Fried parameter larger than 30 centimeters can be considered excellent seeing. The best conditions are typically found at high-altitude observatories on small islands, such as those at Mauna Kea or La Palma . Astronomical seeing has several effects: The effects of atmospheric seeing were indirectly responsible for

5445-409: The distance to towns, cities, and other places or landmarks like mileage signs ; or they can give their position on the route relative to some datum location. On roads they are typically located at the side or in a median or central reservation . They are alternatively known as mile markers (sometimes abbreviated MMs ), mileposts or mile posts (sometimes abbreviated MPs ). A " kilometric point "

5544-415: The driver. Others have labels on all four sides. In the UK, driver location signs are placed every 500 metres (550 yd) along each side of motorways , and along some other major roads. They were first introduced in 2003, and they complement distance marker posts, small roadside posts at 100 metres (110 yd) intervals, used for road maintenance and administrative purposes. Both types of sign display

5643-492: The effects of astronomical seeing on images taken through ground-based telescopes. Three simulated short-exposure images are shown at the right through three different telescope diameters (as negative images to highlight the fainter features more clearly—a common astronomical convention). The telescope diameters are quoted in terms of the Fried parameter r 0 {\displaystyle r_{0}} (defined below). r 0 {\displaystyle r_{0}}

5742-525: The effects of the atmosphere will be negligible, and hence by recording large numbers of images in real-time, a 'lucky' excellent image can be picked out. This happens more often when the number of r0-size patches over the telescope pupil is not too large, and the technique consequently breaks down for very large telescopes. It can nonetheless outperform adaptive optics in some cases and is accessible to amateurs. It does require very much longer observation times than adaptive optics for imaging faint targets, and

5841-682: The ensemble average. For the Gaussian random approximation, the structure function of Tatarski (1961) can be described in terms of a single parameter r 0 {\displaystyle r_{0}} : D ϕ a ( ρ ) = 6.88 ( | ρ | r 0 ) 5 / 3 {\displaystyle D_{\phi _{a}}\left({\mathbf {\rho } }\right)=6.88\left({\frac {\left|\mathbf {\rho } \right|}{r_{0}}}\right)^{5/3}} r 0 {\displaystyle r_{0}} indicates

5940-1037: The former mile markers to be gradually replaced with 10 km markers on highways and country roads, which are referred to as "kilometre plates". Kilometre plates have white text on a trapezoidal green background, and are generally located about a metre above the ground. They have a letter which indicates the town or city they are referring to, and a number, which is the distance in kilometres to that town or city. Kilometre plates are now generally 5 km apart on major highways and 10 or 20 km apart on less popular or rural highways, though there are many exceptions. Kilometre plates are supplemented by signboards, which display distances to several towns ahead. Some mile markers are retained as curiosities (see gallery). These include stone markers on Victoria's Glenelg Highway at Delacombe, Usage varies by province, as highways are under provincial jurisdiction. In Alberta, for example, kilometre markers are green metal signs with white lettering, and are generally placed every 4 km starting at

6039-417: The fractional change in wavefront amplitude and ϕ a ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} is the change in wavefront phase introduced by the atmosphere. It is important to emphasise that χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} and ϕ

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6138-442: The frequency of the light determined by ν = 1 π c | k | {\textstyle \nu ={\frac {1}{\pi }}c\left|\mathbf {k} \right|} , and A u {\displaystyle A_{u}} is the amplitude of the light. The photon flux in this case is proportional to the square of the amplitude A u {\displaystyle A_{u}} , and

6237-635: The high lava desert of the Humuʻula Saddle. Two roads intersect Saddle Road close to Puʻu Huluhulu at its crest near mile 28 at 6,632 feet (2,021 m) above sea level , the Mauna Loa Observatory Road to the south, and the Mauna Kea Summit Road to the north. The Mauna Loa Observatory Road is an unmarked 17.1 miles (27.5 km) long narrow rough (but paved) road which winds its way towards Mauna Loa Solar Observatory , Mauna Loa Atmospheric Observatory , and AMiBA on

6336-520: The highway was officially renamed the Daniel K. Inouye Highway in honor of the late senator from Hawaii. This new section avoids the old route, where from milepost 44, near Kilohana, to the Māmalahoa Highway the road retained its original character, a narrow ribbon of poorly maintained pavement with crumbling edges. On the old section, there are several one-lane bridges, blind curves and hills. It

6435-400: The image of the planet be dependent on the observer's memory and preconceptions which led the belief that Mars had linear features. The effects of atmospheric seeing are qualitatively similar throughout the visible and near infrared wavebands. At large telescopes the long exposure image resolution is generally slightly higher at longer wavelengths, and the timescale ( t 0 - see below) for

6534-574: The jurisdictions separated by borders. A series of such boundary markers exists at one mile (1.6 km) intervals along the borders of the District of Columbia in the United States . Astronomical seeing In astronomy , seeing is the degradation of the image of an astronomical object due to turbulence in the atmosphere of Earth that may become visible as blurring, twinkling or variable distortion . The origin of this effect

6633-655: The kilometre distance indented and painted black. There is no distinction between state and national road-sign markings. They were originally sited every 500 metres by the Rhodesian Ministry of Roads and Road Traffic, starting at zero from the largest town or city. In 1980, the Zimbabwean government began placing new markers 1 km apart and damaged or missing half kilometre markers were no longer replaced. The Railways Clauses Consolidation Act 1845 compels UK railway companies to provide their passengers with

6732-446: The last major intersection to the south or west, depending on whether the route runs north–south or east–west. Milestones on National highways of India typically have white backgrounds with yellow tops (on national highways) or green tops (on state highways). The names of cities and distances are painted in black. The names of the nearest towns and cities are written along with distance in kilometres. On undivided highways, both sides of

6831-403: The length-scale over which the turbulence becomes significant (10–20 cm at visible wavelengths at good observatories), and t 0 corresponds to the time-scale over which the changes in the turbulence become significant. r 0 determines the spacing of the actuators needed in an adaptive optics system, and t 0 determines the correction speed required to compensate for the effects of

6930-503: The milestones are used, telling the distance to the nearest cities in each direction. The highway number is written on the head of the milestone. The sum of the distances of two nearest cities in each direction from the milestone is listed on the side. Milestones in the Philippines are found in highways , one kilometer apart, and are found in pairs, one on each side of the road. These are short yellow concrete posts, with two labels on

7029-557: The military exercise areas. Completion of these projects represent a major realignment of island traffic patterns and conversion of this notorious roadway into a modern state highway. The entire route is in Hawaii County . Hawaii Route 2000 is a 6.2-mile (10.0 km) road on the island of Hawaii , in the state of Hawaii . The road's western terminus is at Hawaii Route 200 (known as the Saddle Road). The eastern terminus

7128-412: The modern railway, these historical markers are still used as infrastructure reference points. At many points, the distances shown on the markers are based upon points no longer on the network – for example, distances measured via a closed line or from a junction which has subsequently been moved. Whole mileposts are usually supplemented by half and quarter posts. Structure signs often include the mileage to

7227-580: The name of the reigning emperor without giving any placenames or distances. The first Roman milestones appeared on the Appian Way . At the centre of Rome, the " Golden Milestone " was erected to mark the presumed centre of the empire: this milestone has since been lost. The Golden Milestone inspired the Zero Milestone in Washington, D.C., intended as the point from which all road distances in

7326-604: The nearest milepost, known as the mile-log system. From the beginning of the Interstate system until the mid-2000s, most Interstate highways had markers every mile. Since that time, many states have installed more markers every 0.25 mile, every 0.2 mile, or in some metro areas, every 0.1 mile. Some historic and scenic routes – such as along the Blue Ridge Parkway in North Carolina and Virginia and

7425-407: The optical phase corresponds to the complex argument of ψ 0 {\displaystyle \psi _{0}} . As wavefronts pass through the Earth's atmosphere they may be perturbed by refractive index variations in the atmosphere. The diagram at the top-right of this page shows schematically a turbulent layer in the Earth's atmosphere perturbing planar wavefronts before they enter

7524-435: The paving dates from 1949. About the same time, Tom Vance, who had earlier supervised building a highway up Mauna Loa named for Governor Ingram Stainback , secretly used his prison laborers to start a more direct Hilo-Kona road. He started at a camp 19°38′12″N 155°28′52″W  /  19.63667°N 155.48111°W  / 19.63667; -155.48111  ( Vance ) (still called "Vance" on USGS maps) which

7623-421: The phase fluctuations ϕ a ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} . The amplitude fluctuations described by χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} have negligible effect on the structure of the images seen in the focus of a large telescope. For simplicity,

7722-759: The phase fluctuations in Tatarski's model are often assumed to have a Gaussian random distribution with the following second-order structure function: D ϕ a ( ρ ) = ⟨ | ϕ a ( r ) − ϕ a ( r + ρ ) | 2 ⟩ r {\displaystyle D_{\phi _{a}}\left(\mathbf {\rho } \right)=\left\langle \left|\phi _{a}\left(\mathbf {r} \right)-\phi _{a}\left(\mathbf {r} +\mathbf {\rho } \right)\right|^{2}\right\rangle _{\mathbf {r} }} where D ϕ

7821-624: The project was also abandoned. After islands became the State of Hawaii in 1959, Saddle Road was handed to the County of Hawaiʻi and for many years only minimal maintenance was performed, leading to generally poor conditions and the source of the road's notorious reputation. Since 1992, there has been increased attention on the road, with efforts to rebuild and renovate the highway into a practical cross-island route. This resulted in repaving some sections and complete rebuilding of others. The entire road

7920-419: The real part, and FT[] represents a discrete Fourier transform of the resulting two-dimensional square array (typically an FFT). The assumption that the phase fluctuations in Tatarski's model have a Gaussian random distribution is usually unrealistic. In reality, turbulence exhibits intermittency. These fluctuations in the turbulence strength can be straightforwardly simulated as follows: ϕ

8019-495: The resolution of long-exposure images is determined primarily by diffraction and the size of the Airy pattern and thus is inversely proportional to the telescope diameter. For telescopes with diameters larger than r 0 , the image resolution is determined primarily by the atmosphere and is independent of telescope diameter, remaining constant at the value given by a telescope of diameter equal to r 0 . r 0 also corresponds to

8118-411: The road passes the main gates of Pōhakuloa Training Area and Bradshaw Army Airfield before continuing across the military reservation. Military vehicles – including armored personnel carriers – occasionally cross or occupy the roadway. Artillery exercises, including live fire, are not uncommon. with batteries set up along the roadway firing towards Mauna Loa. This section of the road was repaved in

8217-545: The roadway and begin to thin as the elevation increases. Quality of the asphalt surface is quite good on this side of the crest but there are many curves and rises with limited visual distances. There are no tourist services or other infrastructure on the Saddle Road. Reconstruction of the sections from mileposts 11 to 19 and 19 to 28 was finished in November 2011 and October 2008, respectively. The terrain becomes

8316-606: The same dimensions as R ( k ) , and where ⊗ {\displaystyle \otimes } represents convolution . The intermittency is described in terms of fluctuations in the turbulence strength C n 2 {\displaystyle C_{n}^{2}} . It can be seen that the equation for the Gaussian random case above is just the special case from this equation with: I ( k ) = δ ( | k | ) {\displaystyle I(k)=\delta (|k|)} where δ ( ) {\displaystyle \delta ()}

8415-402: The seeing, as do wind and clouds. At the best high-altitude mountaintop observatories , the wind brings in stable air which has not previously been in contact with the ground, sometimes providing seeing as good as 0.4". The astronomical seeing conditions at an observatory can be conveniently described by the parameters r 0 and t 0 . For telescopes with diameters smaller than r 0 ,

8514-545: The slopes of Mauna Loa . It was connected in 1963 to the old Tom Vance road from 1950. The Mauna Kea Summit Road (known as John A. Burns Way) provides access to the Onizuka Center for International Astronomy (at elevation 9,300 ft (2,800 m) then climbs Mauna Kea past the Mauna Kea Ice Age Reserve to the height of 13,780 ft (4,200 m) at grades averaging 17% making this

8613-491: The studies of turbulence by the Russian mathematician Andrey Kolmogorov . This model is supported by a variety of experimental measurements and is widely used in simulations of astronomical imaging. The model assumes that the wavefront perturbations are brought about by variations in the refractive index of the atmosphere. These refractive index variations lead directly to phase fluctuations described by ϕ

8712-649: The summer of 2008, greatly improving the conditions. On August 18, 2009, the completely rebuilt section, from milepost 35 to 42, opened to public travel. The realignment relocated the highway north to the Mauna Kea side of the Army base and Bradshaw Army Airfield. A new section starting near mile marker 42 that bypasses Waikiʻi and connects to Māmalahoa Highway near mile marker 14, 19°50′39″N 155°44′53″W  /  19.84417°N 155.74806°W  / 19.84417; -155.74806  ( New western end of Saddle Road ) opened September 7, 2013. At this time,

8811-469: The telescope. However, when light enters the Earth's atmosphere , the different temperature layers and different wind speeds distort the light waves, leading to distortions in the image of a star. The effects of the atmosphere can be modeled as rotating cells of air moving turbulently. At most observatories, the turbulence is only significant on scales larger than r 0 (see below—the seeing parameter r 0

8910-832: The text written on the stone currently found in the Kasserine Museum in the Golan reads as follows: In the name of God, the Most Gracious, the Most Merciful. There is no god but God alone, and there is no partner for it. Muhammad is the Messenger of God. He ordered the making of these miles, Abdul Malik bin Marwan, Commander of the Faithful. At the hands of a consultant, the Lord of the Faithful. In Sha'ban from

9009-516: The third highest public road in the United States . The road is 14 miles (23 km) long, of which the first 6 miles (to the Onizuka Center) and the last 3 miles (4.8 km) are paved. Puʻu Wēkiu is the highest point in Hawaiʻi at 13,796 ft (4,205 m) and is home to Poliʻahu , Goddess of Snow . Mauna Kea Observatory on the summit, an ideal location for astronomical seeing ,

9108-401: The turbulence strength C N 2 ( h ) {\displaystyle C_{N}^{2}(h)} varies as a function of height h {\displaystyle h} above the telescope, and γ {\displaystyle \gamma } is the angular distance of the astronomical source from the zenith (from directly overhead). If turbulent evolution

9207-466: The type of adaptive optics system which will be needed at a particular telescope, or in deciding whether or not a particular location would be a good site for setting up a new astronomical observatory. Typically, several methods are used simultaneously for measuring the C n 2 {\displaystyle C_{n}^{2}} profile and then compared. Some of the most common methods include: There are also mathematical functions describing

9306-408: The vertical structure of the turbulence, in a technique known as Multiconjugate Adaptive Optics. Another cheaper technique, lucky imaging , has had good results on smaller telescopes. This idea dates back to pre-war naked-eye observations of moments of good seeing, which were followed by observations of the planets on cine film after World War II . The technique relies on the fact that every so often

9405-546: The wake of the attack on Pearl Harbor , the U. S. Army hastily built an access road in 1943 across the Humuʻula plateau of Parker Ranch at 19°41′44″N 155°29′8″W  /  19.69556°N 155.48556°W  / 19.69556; -155.48556  ( Humu‘ula Saddle ) . Since it was not intended as a civilian road, the simple gravel path was built by the Civilian Conservation Corps and

9504-585: The year 1575 AD, Akbar issued an order that at every Kos on the way from Agra to Ajmer, a pillar or a minar should be erected for the comfort of the travelers. The historical term milestone is still used today, even though the "stones" are typically metal highway location markers and in most countries use kilometres and metres rather than miles and yards. Also found today are more closely spaced signs containing fractional numbers, and signs along railways, beaches and canals. Metrication in Australia caused

9603-523: The year eighty-five, from Damascus to this stone fifty-three miles. In Europe , the distance measured typically starts at specified point within a city or town , as many roads were named for the towns at either end. For example, in London , United Kingdom , a plaque near the Eleanor cross at Charing Cross is the reference point from which distances from London to other towns and cities are measured. In

9702-468: Was abandoned at 19°38′38″N 155°45′12″W  /  19.64389°N 155.75333°W  / 19.64389; -155.75333  ( Judd Road east ) when the 1859 eruption of Mauna Loa blocked its path. Although destroyed at lower elevations due to residential development, it can still be seen on maps as the "Judd Trail". While planning for the defense of the Hawaiian Islands in

9801-458: Was exactly midway between Hilo and Kealakekua . The road extended in a straight line, heading for the pass between Hualālai and Mauna Loa. In 1950, the camp caught fire after construction reached 19°37′17″N 155°35′57″W  /  19.62139°N 155.59917°W  / 19.62139; -155.59917  ( Hilo-Kona Road ) . The public refused to allocate more funding when they discovered about US$ 1 million had already been spent, so

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