The Northern Territory Police Force is the police body that has legal jurisdiction over the Northern Territory of Australia. This police service has 1,537 police members made up of 79 senior sergeants, 228 sergeants, 839 constables, 208 auxiliaries, 73 Aboriginal Community Police Officers; the rest of the positions are members of inoperative positions. It has a civilian staff working across the NT Police and Emergency Services. Police in the Northern Territory are part of a Tri-Service: the Northern Territory Police and Emergency Services with the Commissioner of Police as the CEO of the Tri-Service. Sworn police officers can be required to serve anywhere where a police presence is required in the Northern Territory including remote Aboriginal communities in Arnhem Land and outback Northern Territory; the Northern Territory Police traces its roots back to the South Australian Mounted Police from 1870 when Inspector Paul Foelsche and six other police officers arrived in the Territory. A small rural constabulary was disbanded.
The Native Police Corps was formed in 1884. Their role was as a security force to protect the early inhabitants of the Northern Territory than as a police force; the current NTP came into existence in 1911. In 1931, the two Territories Central and Northern became the Northern Territory of Australia and the authority of the Commissioner of Police was established in the Administrator of the Northern Territory, in Darwin. In December 1869, the governor commissioned Paul Foelsche, a Corporal in the SA Mounted Police stationed at Strathalbyn, to be the first sub-inspector of police at Palmerston, he sailed for Darwin soon afterwards. The police uniform worn in the Territory was the same as that worn in South Australia, it consisted of a short cut-away blue serge tunic with nine regulation buttons, silver twisted cord shoulder knots, black braid on the sleeves and silver chevrons for non-commissioned officers. The riding breeches were dark blue corkscrew serge with a white stripe; the first firearms were a Schneider rifle or carbine, calibre.577.
These were the first breech loaded rifles used in the British Army, the original cartridges had a cardboard case. Martini-Henry rifles were used, Webley revolvers were issued. Like their predecessors, the Rural Constabulary at Escape Cliffs, the first detachment of police at Palmerston had as their first responsibility the maintenance of law and order in the community. With the discovery of gold near Pine Creek in 1872 the police found themselves with never a dull moment. Stations were established at Adelaide River, Yam Creek, Pine Creek, Roper River and at Daly River; the first police fatality occurred in 1872 when Mounted Constable Davis, a noted swimmer, disobeyed a local Standing Order and had a dip in the sea. He was killed by a crocodile. Darwin's first police station was constructed of poles and plaster measuring 6.1 metres by 3.7 metres. The inspector lived nearby in three rooms. A small stone building with two cells was the accommodation for those in custody; these are now incorporated in the Administrator's offices on the Esplanade.
In Central Australia the police were part of the South Australian Mounted Police. Mounted Constable Shirley was the first mounted trooper in charge at Alice Springs. At one time there were two Commissioners of Police in the Northern Territory: one for the Territory of North Australia and one for the Territory of Central Australia. In 1931, the two Territories became the Northern Territory of Australia and the authority of the Commissioner of Police was vested in the Administrator of the Northern Territory, in Darwin. On 1 July 1964, Clive William Graham, a police officer of long standing in the Territory, was appointed as Commissioner and the force as a whole was administered as part of the Public Service of the Northern Territory. In recent years, various cases have made national and international headlines: the end of the Petrov Affair occurred in Darwin. Events connected with search and rescue operations at sea, in swamps and the desert have made the news. Auxiliaries and Aboriginal Community Police Officers.
The Joint Emergency Services Communications Centre in Darwin has instant contact with all stations, vehicles and vessels and provides for the Police, Emergency Services and St John Ambulance Service. In 1955, there were 80 police officers; as of June 2011, the number of sworn Police and Aboriginal Community Police Officers in the service was 1,381. In 1989, the Northern Territory Police and Emergency Services were joined to become a Tri-Service; the Commissioner of Police becoming the Chief Executive Officer for the Fire and Rescue Service and the Emergency Services. In July 2019, Commissioner Reece Kershaw was appointed Commissioner of the Australian Federal Police, after being at the helm of NT Police for five years. Commissioner: Jamie Chalker Deputy Commissioner, Operations: Michael Murphy Deputy Commissioner and Capability: Michael White Assistant Commissioner and Integrity: Nick Anticich Assistant Commissioner and Support: Vacant Assistant Commissioner, Regional Operations: Narelle Beer Chief Fire Officer – NT Fire and Rescue Service: Mark Spain Chief Officer – NT Emergency Service: Fleur O’Connor Executive Director – NT Fire and Emergency Services: David Willing Chief of Staff: James J O'Brien The headquarters of the Northern Te
Underwater, things are less visible because of lower levels of natural illumination caused by rapid attenuation of light with distance passed through the water. They are blurred by scattering of light between the object and the viewer resulting in lower contrast; these effects vary with wavelength of the light, color and turbidity of the water. The vertebrate eye is either optimised for underwater vision or air vision, as is the case in the human eye; the visual acuity of the air-optimised eye is adversely affected by the difference in refractive index between air and water when immersed in direct contact. Provision of an airspace between the cornea and the water can compensate, but has the side effect of scale and distance distortion; the diver learns to compensate for these distortions. Artificial illumination is effective to improve illumination at short range. Stereoscopic acuity, the ability to judge relative distances of different objects, is reduced underwater, this is affected by the field of vision.
A narrow field of vision caused by a small viewport in a helmet results in reduced stereoacuity, associated loss of hand-eye coordination. At short range in clear water distance is underestimated, in accordance with magnification due to refraction through the flat lens of the mask, but at greater distances - greater than arm's reach, the distance tends to be overestimated to a degree influenced by turbidity. Both relative and absolute depth perception are reduced underwater. Loss of contrast results in overestimation, magnification effects account for underestimation at short range. Divers can to a large extent adapt with practice. Light rays bend. If one medium has a particular curved shape, it functions as a lens; the cornea and crystalline lens of the eye together form a lens that focuses images on the retina. The human eye is adapted for viewing in air. Water, has the same refractive index as the cornea eliminating the cornea's focusing properties; when immersed in water, instead of focusing images on the retina, they are focused behind the retina, resulting in an blurred image from hypermetropia.
Water has a different refractive index to air, this affects the focusing of the eye. Most animals' eyes are adapted to either underwater or air vision, do not focus properly when in the other environment; the crystalline lenses of fishes' eyes are convex spherical, their refractive indices are the highest of all the animals. These properties enable proper focusing of the light rays and in turn proper image formation on the retina; this convex lens gives the name to the fisheye lens in photography. By wearing a flat diving mask, humans can see underwater; the scuba mask's flat window separates the eyes from the surrounding water by a layer of air. Light rays entering from water into the flat parallel window change their direction minimally within the window material itself, but when these rays exit the window into the air space between the flat window and the eye, the refraction is quite noticeable. The view paths refract in a manner similar to viewing fish kept in an aquarium. Linear polarizing filters decrease visibility underwater by limiting ambient light and dimming artificial light sources.
While wearing a flat scuba mask or goggles, objects underwater will appear 33% bigger and 25% closer than they are. Pincushion distortion and lateral chromatic aberration are noticeable. Double-dome masks restore natural sized underwater vision and field of view, with certain limitations. Diving masks can be fitted with lenses for divers needing optical correction to improve vision. Corrective lenses are ground flat on one side and optically cemented to the inside face of the mask lens; this provides the same amount of correction below the surface of the water. Bifocal lenses are available for this application; some masks are made with removable lenses, a range of standard corrective lenses are available which can be fitted. Plastic self-adhesive lenses that can be applied to the inside of the mask may fall off if the mask is flooded for a significant period. Contact lenses may be worn under a mask or helmet, but there is some risk of losing them if the mask floods. Water attenuates light due to absorption.
In other words, as light passes through a greater distance of water color is selectively absorbed by the water. Color absorption is affected by turbidity of the water and dissolved material. Water preferentially absorbs red light, to a lesser extent, yellow and violet light, so the color, least absorbed by water is blue light. Particulates and dissolved materials may absorb different frequencies, this will affect the color at depth, with results such as the green color in many coastal waters, the dark red-brown color of many freshwater rivers and lakes due to dissolved organic matter. Fluorescent paints absorb higher frequency light to which the human eye is insensitive and emit lower frequencies, which are more detected; the emitted light and the reflected light combine and may be more visible than the original light. The most visible frequencies are those most attenuated in water, so the effect is for increased colour contrast over a short range, until the longer wavelengths are attenuated by the water.
The best colors to use for visibility in water was shown by Luria et al. and quoted from Adolfson and Berghage below: A. For murky, turbid water of low vis