Soil erosion
Soil erosion is the displacement of upper layer of soil. The erosion of soil is a naturally occurring process on all land, the agents of soil erosion are water and wind, each contributing a significant amount of soil loss each year. Soil erosion may be a process that continues relatively unnoticed. The loss of soil from farmland may be reflected in reduced crop production potential, lower water quality. While erosion is a process, human activities have increased by 10–40 times the rate at which erosion is occurring globally. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils.
Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimeters or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers.
Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
Hoe (tool)
A hoe is an ancient and versatile agricultural and horticultural hand tool used to shape soil, remove weeds, clear soil, and harvest root crops. Shaping the soil includes piling soil around the base of plants, digging narrow furrows, weeding with a hoe includes agitating the surface of the soil or cutting foliage from roots, and clearing soil of old roots and crop residues. Hoes for digging and moving soil are used to harvest root crops such as potatoes, there are many kinds of hoes of varied appearances and purposes. Some have multiple functions while others have singular and specific functionality, there are two genera of hoe, draw hoes for shaping soil and scuffle hoes for weeding and aerating soil. A draw hoe has a set at approximately a right angle to the shaft. The user chops into the ground and pulls the blade towards them, altering the angle of the handle can cause the hoe to dig deeper or more shallowly as the hoe is pulled. A draw hoe can easily be used to cultivate soil to a depth of several inches, a typical design of draw hoe, the eye hoe, has a ring in the head through which the handle is fitted.
This design has been used since Roman times, a scuffle hoe is used to scrape the surface of the soil, loosen the top inch or so, and to cut the roots of, and disrupt the growth of weeds efficiently. These are primarily of two different designs, the Dutch Hoe and the Hoop Hoe, the term hand hoe most commonly refers to any type of light-weight, short-handled hoe, although it may be used simply to contrast hand-held tools against animal or machine pulled tools. The typical farming and gardening hoe with a heavy, broad blade, the Paxton hoe is similar to the Italian hoe, but with a more rounded rectangular blade. The hoedad, denominated the hoedag, is a tool used to plant trees. According to Hartzell, The hoedag originally called skindvic hoe, hans Rasmussen, legendary contractor and timber farm owner, is credited with having invented the curved, round-nosed hoedag blade which is widely used today. The mortar hoe is a specific to the manual mixing of mortar and concrete. The Dutch hoe is designed to be pushed or pulled through the soil to cut the roots of weeds just under the surface, a Dutch hoe has a blade sharp on every side so as to cut either forwards and backwards.
The blade must be set in a plane slightly upwardly inclined in relation to the axis of the shaft. The user pushes the handle to move the forward, forcing it below the surface of the soil. A scuffle hoe can easily cultivate soil and remove weeds from the surface layer. The hoop hoe, known as the hoe, hula, pendulum weeder
Precision agriculture
Precision agriculture or satellite farming or site specific crop management is a farming management concept based on observing and responding to inter and intra-field variability in crops. The goal of precision agriculture research is to define a decision support system for whole farm management with the goal of optimizing returns on inputs while preserving resources, among these many approaches is a phytogeomorphological approach which ties multi-year crop growth stability/characteristics to topological terrain attributes. The interest in the phytogeomorphological approach stems from the fact that the geomorphology component typically dictates the hydrology of the farm field, the practice of precision agriculture has been enabled by the advent of GPS and GNSS. The farmers and/or researchers ability to locate their position in a field allows for the creation of maps of the spatial variability of as many variables as can be measured. This data is used by variable rate technology including seeders, sprayers.
Precision agriculture has enabled by affordable unmanned aerial vehicles like the DJI Phantom that cost under $1000. It has been described as Big Data on the farm, monsanto, DuPont and others are launching this technology in the US. Geolocation is done in two ways, The field is delineated using an in-vehicle GPS receiver as the drives a tractor around the field. The field is delineated on a derived from aerial or satellite imagery. The base images must have the level of resolution and geometric quality to ensure that geolocation is sufficiently accurate. Intra and inter-field variability may result from a number of factors and these include climatic conditions, cropping practices and disease. Permanent indicators—chiefly soil indicators—provide farmers with information about the main environmental constants and this information may come from weather stations and other sensors. Soil resistivity measurements combined with soil analysis make it possible to measure moisture content, soil resistivity is a relatively simple and cheap measurement.
Using soil maps, farmers can pursue two strategies to adjust field inputs, Predictive approach, based on analysis of static indicators during the crop cycle, airborne instruments are able to measure the amount of plant cover and to distinguish between crops and weeds. Decisions may be based on models, but in the final analysis it is up to the farmer to decide in terms of business value. New information and communication technologies make field-level crop management more operational, the use of automated or robotic data gathering techniques is on the rise. ROS Agriculture - Software for agricultural robotics, the concept of precision agriculture first emerged in the United States in the early 1980s. In 1985, researchers at the University of Minnesota varied lime inputs in crop fields and it was at this time that the practice of grid sampling appeared
Working animal
A working animal is an animal, usually domesticated, that is kept by humans and trained to perform tasks. They may be members of the family, such as guide dogs or other assistance dogs, or they may be animals trained to provide tractive force. The latter types of animals are called animals or beasts of burden. Most working animals are either service animals or draft animals and they may be used for milking or herding, jobs that require human training to encourage the animal to cooperate. Some, at the end of their lives, may be used for meat or other products such as leather. The history of working animals may predate agriculture, with used by our hunter-gatherer ancestors. Around the world, millions of animals work in relationship with their owners, domesticated species are often bred to be suitable for different uses and conditions, especially horses and working dogs. Working animals are raised on farms, though some are still captured from the wild, such as dolphins. People have found uses for a variety of abilities found in animals.
The strength of horses and oxen is used in pulling carts, the keen sense of smell of dogs is used to search for drugs and explosives as well helping to find game while hunting and to search for missing or trapped people. Several animals including camels, donkeys and dogs are used for transport, either riding or to pull wagons, other animals including dogs and monkeys provide assistance to blind or disabled people. Conversely, not all domesticated animals are working animals, for example, while cats may perform work catching mice, it is an instinctive behavior, not one that can be trained by human intervention. Other domesticated animals, such as sheep, or rabbits, may have uses for meat and wool. Finally, small pets such as most birds or hamsters are generally incapable of performing work other than that of providing simple companionship. Some animals are used due to physical strength in tasks such as ploughing or logging. Such animals are grouped as a draught or draft animal, others may be used as pack animals, for animal-powered transport, the movement of people and goods.
People ride some animals directly as mounts, one or more animals in harness may be used to pull vehicles and they include equines such as horses, ponies and mules, elephants and camels. Dromedary camels in arid areas of Australia, North Africa and the Middle East, on occasion, though usually driven, may be ridden
Agriculture
Agriculture is the cultivation and breeding of animals and fungi for food, biofuel, medicinal plants and other products used to sustain and enhance human life. Agriculture was the key development in the rise of human civilization. The study of agriculture is known as agricultural science, the history of agriculture dates back thousands of years, and its development has been driven and defined by greatly different climates and technologies. Industrial agriculture based on large-scale monoculture farming has become the dominant agricultural methodology, genetically modified organisms are an increasing component of agriculture, although they are banned in several countries. Agricultural food production and water management are increasingly becoming global issues that are fostering debate on a number of fronts, the major agricultural products can be broadly grouped into foods, fibers and raw materials. Specific foods include cereals, fruits, meats, fibers include cotton, hemp and flax. Raw materials include lumber and bamboo, other useful materials are produced by plants, such as resins, drugs, perfumes and ornamental products such as cut flowers and nursery plants.
The word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, Agriculture usually refers to human activities, although it is observed in certain species of ant and ambrosia beetle. To practice agriculture means to use resources to produce commodities which maintain life, including food, forest products, horticultural crops. This definition includes arable farming or agronomy, and horticulture, all terms for the growing of plants, even then, it is acknowledged that there is a large amount of knowledge transfer and overlap between silviculture and agriculture. In traditional farming, the two are often combined even on small landholdings, leading to the term agroforestry, Agriculture began independently in different parts of the globe, and included a diverse range of taxa. At least 11 separate regions of the Old and New World were involved as independent centers of origin, wild grains were collected and eaten from at least 105,000 years ago. Pigs were domesticated in Mesopotamia around 15,000 years ago, rice was domesticated in China between 13,500 and 8,200 years ago, followed by mung and azuki beans.
Sheep were domesticated in Mesopotamia between 13,000 and 11,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops and einkorn wheat, hulled barley, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Cattle were domesticated from the aurochs in the areas of modern Turkey. In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, llamas, alpacas and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago, cotton was domesticated in Peru by 5,600 years ago, and was independently domesticated in Eurasia at an unknown time
Machine
A machine is a tool containing one or more parts that uses energy to perform an intended action. Machines are usually powered by chemical, thermal, or electrical means, historically, a power tool required moving parts to classify as a machine. However, the advent of electronics has led to the development of power tools without moving parts that are considered machines, a simple machine is a device that simply transforms the direction or magnitude of a force, but a large number of more complex machines exist. Examples include vehicles, electronic systems, molecular machines, television, the word machine derives from the Latin word machina, which in turn derives from the Greek. The word mechanical comes from the same Greek roots, the Ancient Greeks probably have borrowed the word mekhane from the ancient Hebrews. The ancient Greeks were familiar with the Hebrew Scriptures and language, a wider meaning of fabric, structure is found in classical Latin, but not in Greek usage. This meaning is found in late medieval French, and is adopted from the French into English in the mid-16th century, in the 17th century, the word could mean a scheme or plot, a meaning now expressed by the derived machination.
The modern meaning develops out of specialized application of the term to stage engines used in theater and to siege engines. Simple Machines are commonly reckoned to be Six in Number, viz. the Ballance, Pulley, Wedge, compound Machines, or Engines, are innumerable. The word engine used as a synonym both by Harris and in language derives ultimately from Latin ingenium ingenuity, an invention, perhaps the first example of a human made device designed to manage power is the hand axe, made by chipping flint to form a wedge. A wedge is a machine that transforms lateral force and movement of the tool into a transverse splitting force. The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines, pulley and he discovered the principle of mechanical advantage in the lever. Later Greek philosophers defined the five simple machines and were able to roughly calculate their mechanical advantage. Heron of Alexandria in his work Mechanics lists five mechanisms that can set a load in motion, windlass, pulley and screw, however the Greeks understanding was limited to statics and did not include dynamics or the concept of work.
In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, the complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche. He was the first to understand that simple machines do not create energy, the classic rules of sliding friction in machines were discovered by Leonardo da Vinci, but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons and were developed by Charles-Augustin de Coulomb. The word mechanical refers to the work that has produced by machines or the machinery
Woolbrook, New South Wales
Woolbrook is a village in the New England region of New South Wales, Australia. The nearest town, Walcha is 29 km to the east of Woolbrook, at the 2011 census, Woolbrook had a population of 248. The village straddles the Macdonald River which is in the headwater of the Namoi River, other parts of the Woolbrook area are within the Walcha Shire local government area. In 1836 Robert Rodd settled on the known as Surveyor’s Creek Run an area of 40,000 acres that covered the area of the future villages of Woolbrook. Amos Brothers erected the MacDonald River Private Hospital in 1879 to tend the men employed during the railway construction, the railway from Sydney to Woolbrook and onto Uralla was completed in 1882. Norm and Geoff Goodwin, started the Goodwin Brothers sawmill there in c.1950 and it was sold several times after Don died and finally closed in 2004. Macdonald River Post Office opened on 1 December 1889 and was renamed Woolbrook in 1891, a bakery was in operation at Woolbrook until around 1998.
A Weather Bureau site was opened in 1958 and is now monitored by the Watson family, remaining is a public school with about 20 pupils, a store, the AIF Memorial Hall and St John’s church which was built in 1929. The main industry in the area is sheep and beef cattle breeding, the population is now 220 persons, usually resident in the Woolbrook area. On 28 and 29 November 2008, Woolbrook received torrential rain caused severe flooding in the Macdonald River. Woolbrook hosts the annual Woolbrook Stampede each Easter, the horse sports include campdrafting, plus other sporting and novelty events. Woolbrook Spring Fair is held in October with draught horse events, goat racing, dog trials, the Macdonald River is a popular swimming and fishing spot and there are picnic facilities. Woolbrook has the cold winter, mild to warm summer climate of the Northern Tablelands. Although due to the location in a deep valley, it records some of the coldest temperatures in the region. Woolbrook is fairly sunny, recording 118 clear days on a yearly basis, on 19 June 1994, a temperature of −14.5 °C was recorded in the town, the coldest temperature observed anywhere in Australia outside of the Australian Alps.
Barnaby Joyce, an Australian politician, grew up at Woolbrook, Woolbrook station was opened on 2 Aug 1882 as Macdonald River. On 30 October 1891 it was renamed Woolbrook and closed at a date in the late 1990s/2000s. The nearest current station is Walcha Road, Woolbrook Tales Tall & True, Ruth Watson,2007, Walcha Telecottage, Walcha Inscription List for Woolbrook General Cemetery
Mule
A mule is the offspring of a male donkey and a female horse. Horses and donkeys are different species, with different numbers of chromosomes, of the two F1 hybrids between these two species, a mule is easier to obtain than a hinny, which is the offspring of a female donkey and a male horse. The size of a mule and work to which it is put depend largely on the breeding of the female parent. Mules can be lightweight, medium weight, or when produced from draft horse mares, Mules are more patient and long-lived than horses, and are less obstinate and more intelligent than donkeys. Mules tend to be more independent than most domesticated equines other than the donkey, the median weight range for a mule is between about 370 and 460 kg. While a few mules can carry live weight up to 160 kg, in general, a mule can be packed with dead weight of up to 20% of its body weight, or approximately 90 kg. Although it depends on the animal, it has been reported that mules trained by the Army of Pakistan can carry up to 72 kilograms.
The average equine in general can carry up to approximately 30% of its weight in live weight. A female mule that has estrus cycles and thus, in theory, could carry a fetus, is called a molly or Molly mule, pregnancy is rare, but can occasionally occur naturally as well as through embryo transfer. A male mule is called a horse mule, though often called a john mule. A young male mule is called a colt, and a young female is called a mule filly. With its short thick head, long ears, thin limbs, small narrow hooves, and short mane, in height and body, shape of neck and rump, uniformity of coat, and teeth, it appears horse-like. The mule comes in all sizes and conformations, there are mules that resemble huge draft horses, sturdy quarter horses, fine-boned racing horses, shaggy ponies and more. The mule is an example of hybrid vigor, charles Darwin wrote, The mule always appears to me a most surprising animal. The mule inherits from its sire the traits of intelligence, sure-footedness, endurance, from its dam it inherits speed and agility.
Mules exhibit a higher intelligence than their parent species. This is believed to be the result of hybrid vigor, similar to how mules acquire greater height and their hooves are harder than horses, and they show a natural resistance to disease and insects. Many North American farmers with clay soil found mules superior as plow animals, a mule does not sound exactly like a donkey or a horse
Pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants. Pollution is often classed as point source or nonpoint source pollution, Air pollution has always accompanied civilizations. Pollution started from prehistoric times when man created the first fires, metal forging appears to be a key turning point in the creation of significant air pollution levels outside the home. The burning of coal and wood, and the presence of horses in concentrated areas made the cities the cesspools of pollution. The Industrial Revolution brought an infusion of untreated chemicals and wastes into local streams that served as the water supply, king Edward I of England banned the burning of sea-coal by proclamation in London in 1272, after its smoke became a problem. But the fuel was so common in England that this earliest of names for it was acquired because it could be carted away from some shores by the wheelbarrow and it was the industrial revolution that gave birth to environmental pollution as we know it today.
London recorded one of the extreme cases of water quality problems with the Great Stink on the Thames of 1858. Pollution issues escalated as population growth far exceeded view ability of neighborhoods to handle their waste problem, reformers began to demand sewer systems, and clean water. In 1870, the conditions in Berlin were among the worst in Europe. There were no toilets in the streets or squares. Visitors, especially women, often became desperate when nature called, in the public buildings the sanitary facilities were unbelievably primitive. As a metropolis, Berlin did not emerge from a state of barbarism into civilization until after 1870. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881, as historian Martin Melosi notes, The generation that first saw automobiles replacing the horses saw cars as miracles of cleanliness. By the 1940s, automobile-caused smog was an issue in Los Angeles. Other cities followed around the country early in the 20th century.
Extreme smog events were experienced by the cities of Los Angeles and Donora, Pennsylvania in the late 1940s, Air pollution would continue to be a problem in England, especially during the industrial revolution, and extending into the recent past with the Great Smog of 1952. Awareness of atmospheric pollution spread widely after World War II, with fears triggered by reports of fallout from atomic warfare. Then a non-nuclear event, The Great Smog of 1952 in London and this prompted some of the first major modern environmental legislation, The Clean Air Act of 1956
Combine harvester
The combine harvester, or simply combine, is a machine that harvests grain crops. The name derives from its three separate operations comprising harvesting—reaping and winnowing—into a single process. Among the crops harvested with a combine are wheat, rye, corn, soybeans, flax and canola. Combine harvesters are one of the most economically important labour saving inventions, Scottish inventor Patrick Bell invented the reaper in 1826. The combine was invented in the United States by Hiram Moore in 1834, early versions were pulled by horse, mule or ox teams. In 1835, Moore built a version and by 1839. By 1860, combine harvesters with a cutting, or swathe, australian Hugh Victor McKay produced a commercially successful combine harvester in 1885, the Sunshine Harvester. Combines, some of them large, were drawn by mule or horse teams. Later, steam power was used, and George Stockton Berry integrated the combine with an engine using straw to heat the boiler. At the turn of the century, horse drawn combines were starting to be used on the American plains.
In 1911, the Holt Manufacturing Company of California produced a self-propelled harvester, in Australia in 1923, the patented Sunshine Auto Header was one of the first center-feeding self-propelled harvesters. In 1923 in Kansas, the Baldwin brothers and their Gleaner Manufacturing Company patented a self-propelled harvester that included several other improvements in grain handling. Both the Gleaner and the Sunshine used Fordson engines, early Gleaners used the entire Fordson chassis, in 1929 Alfredo Rotania of Argentina patented a self-propelled harvester. International Harvester started making horse-pulled combines in 1915, at the time horse powered binders and stand alone threshing machines were more common. In the 1920s Case Corporation and John Deere made combines and these were starting to be pulled with a second engine aboard the combine to power its workings. The world economic collapse in the 1930s stopped farm equipment purchases thus people largely retained the older method of harvesting, a few farms did invest and used Caterpillar tractors to move the outfits.
Tractor-drawn combines became common after World War II as many began to use tractors. An example was the All-Crop Harvester series and these combines used a shaker to separate the grain from the chaff and straw-walkers to eject the straw while retaining the grain
Manual labour
Manual labour or manual work is physical work done by people, most especially in contrast to that done by machines, and to that done by working animals. It is most literally work done with the hands, and, by figurative extension, for most of human prehistory and history, manual labour and its close cousin, animal labour, have been the primary ways that physical work has been accomplished. To be implemented, they require that sufficient technology exist and that its capital costs be justified by the amount of wages that they will obviate. Thus there is a partial but significant correlation between manual labour and unskilled or semiskilled workers, throughout human existence the latter has involved a spectrum of variants, from slavery, to caste or caste-like systems, to subtler forms of inequality. Economic competition often results in trying to buy labour at the lowest possible cost or to obviate it entirely. It has always been the case for humans that many workers begin their working lives lacking any special level of skill or experience and these conditions have assured the correlations strength and persistence.
The phrase hard labour has become a legal euphemism for penal labour. Throughout human existence, but most especially since the Age of Enlightenment, humans have not yet succeeded in instantiating any such utopia, but some social systems have been designed that go far enough toward the goal that hope yet remains for further improvement. Concepts such as the Three-fifths compromise and the Untermensch defined slaves as less than human, one interesting historical trend that is true of all of the systems above is that they began crumbling in the 20th century and have continued crumbling since. Todays forms of them are mostly greatly weakened compared to past generations versions, at the lowest extreme, such distortion produces subtler forms of racism and de facto inequality of opportunity. The more plausible the deniability, the easier the rationalisation and perpetuation, at such areas of the spectrum, it becomes ever harder to justify efforts that use de jure methods to fight de facto imbalances, because valid instances can be highlighted by all sides. A willingness to recognise that manual labour can involve skill and intelligence can take a variety of forms, in its healthier forms, it recognises the dignity and intelligence of blue-collar workers, and it recognises their civil equality with white-collar workers.
Yet it simultaneously leaves room in society for meritocracy, allowing both upward and downward social mobility. In its more pathological forms, it may admit that there can be a science of manual labour. Some people would have only the first, only the second, players usually should not be their own coaches. Whether Taylor was capable of predicting and preventing that problem is unclear, an example of the second pathology are 20th-century variants of communism, such as Leninism and Stalinism. Mechanisation and automation strive to reduce the amount of labour required for production. Automation helps to bring mechanisation to more complicated tasks that require dexterity, decision making based on visual input
Satellite imagery
Satellite imagery consists of images of Earth or other planets collected by satellites. Imaging satellites are operated by governments and businesses around the world, Satellite imaging companies sell images under licence. Images are licensed to governments and businesses such as Apple Maps, the first images from space were taken on sub-orbital flights. The U. S-launched V-2 flight on October 24,1946 took one image every 1.5 seconds. With an apogee of 65 miles, these photos were from five times higher than the previous record, the first satellite photographs of Earth were made on August 14,1959 by the U. S. The first satellite photographs of the Moon might have made on October 6,1959 by the Soviet satellite Luna 3. The Blue Marble photograph was taken from space in 1972, and has very popular in the media. Also in 1972 the United States started the Landsat program, the largest program for acquisition of imagery of Earth from space, Landsat Data Continuity Mission, the most recent Landsat satellite, was launched on 11 February 2013.
In 1977, the first real time satellite imagery was acquired by the United Statess KH-11 satellite system, all satellite images produced by NASA are published by NASA Earth Observatory and are freely available to the public. Several other countries have satellite imaging programs, and a collaborative European effort launched the ERS, there are private companies that provide commercial satellite imagery. Images can be in visible colours and in other spectra, there are elevation maps, usually made by radar images. Interpretation and analysis of imagery is conducted using specialized remote sensing applications. There are four types of resolution when discussing satellite imagery in remote sensing, spectral and radiometric. GSD is a term containing the optical and systemic noise sources and is useful for comparing how well one sensor can see an object on the ground within a single pixel. For example, the GSD of Landsat is ~30m, which means the smallest unit that maps to a single pixel within an image is ~30m x 30m, the latest commercial satellite has a GSD of 0.41 m.
This compares to a 0.3 m resolution obtained by some early military film based Reconnaissance satellite such as Corona, the resolution of satellite images varies depending on the instrument used and the altitude of the satellites orbit. For example, the Landsat archive offers repeated imagery at 30 meter resolution for the planet, Landsat 7 has an average return period of 16 days. For many smaller areas, images with resolution as high as 41 cm can be available, Satellite imagery is sometimes supplemented with aerial photography, which has higher resolution, but is more expensive per square meter
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