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They were built and used between the 18th and 20th centuries, particularly in the region of Coxilha Rica. The main objective of this research is to develop a method for decision-making applied to the territorial landscape management in the Coxilha Rica.
After data processing, the information was entered into the cartographic database; the data were cross-checked and analysis was made of the visibility of the surrounding farms and stone-walled corridors.
Quality assessments showed that, with the visibility polygons, and through the use of cartographic tools, we could cross-check between different levels of information and analyze landscape intervention alternatives in order to minimize environmental impacts.
When applying the method in the Coxilha Rica it was possible mapping the visibility polygon, taking human visual acuity into consideration, based on historical farms and stone-walled corridors; and making spatial analyses to explore alternatives to intervention installation of power transmission systems in order to preserve the scenic environment of the region.
In the end, the decision was by does not construct the system. Coxilha Rica has some of the main rivers that form the springs of the Uruguay River, with large areas of fields and enclosed valleys that drain a large volume of water and offer high hydroelectric potential. IPHAN, concerned about the preservation of the scenic environment, and taking into account the significant number of hydroelectric projects under analysis, requested that the companies involved in the projects should work together to develop a method to minimize a negative impact on the area in the future.
Such concern was relevant, not only because of environmental damage that could be caused, but also because of the visual impact resulting from the installation of transmission systems in the scenic environment. For this reason, this research has become scientifically relevant, mainly for developing a support method, a tool and cartographic products for decision-making in territorial landscape management.
In view of the need to preserve this important heritage, and in compliance with environmental constraints, historical research and other studies were started, aimed at minimizing possible visual impact on the power transmission system to drain the energy generated by hydroelectric dams on the landscape, caused by structures and cables for carrying electricity to the consuming centers. Right at the beginning of the research work, there was a clear need to delimit the area of the polygons that were to be generated.
For this purpose, specific studies were developed to estimate the human visual range and to delimit the coverage area of subsequent studies and applications. The aim of this paper is to develop a method for decision-making applied to territorial landscape management. Particularly, the objectives are:.
Studying a landscape, such as the landscape of a path used by animal, military, and human troops, requires understanding that this is a theoretical cultural construction made in the present about relationships and a society and an environment from the past .
Discussions and reflections concerning the landscape and the relationship between man and the environment were developed in the United States and gained emphasis in Europe. They should be selected on the basis both of their outstanding universal value and of their representativity in terms of a clearly defined geo-cultural region and also for their capacity to illustrate the essential and distinct cultural elements of such regions .
The author sought to understand the transformations that occurred not in the sense of physical modifications, but rather from a historical perspective of a process of conquest and occupation of a territory through an old road, which formed part of what is currently referred to as droving landscape.
According to , droving was an economic cycle that left marks in the past, and built an environment that formed the current notion of a droving landscape, which needs to be understood in contemporary times. Thus, we sought to understand human conduct in the past by analyzing maps and their spatial relations in the present, combining logic, perception and cognition in the same geographical and timeless space.
It is important to preserve this cultural identity, because Brazil is a new Country, with little more than years of the history. When preserving the landscape, human subjective factors must be taken into account and how much one wishes to maintain the preserved environment for the future. At this moment, it is important to considerate the human visual acuity. As far as human visual acuity is concerned,  argued that some factors inherent in nature may interfere with the correct capture and perception of images by humans.
The greater the amount of light and the shorter the viewing distance, the better the image will be formed, the lesser the influence of atmospheric effects and their consequent changes in radiation velocity, wavelength, intensity and spectral distribution. One of the phenomena that most interferes with image capture and perception is atmospheric refraction.
Another factor that must be considered is earth curvature. It is necessary to consider both factors in analyses that evolve the landscape. According to , earth curvature and the different densities in the atmosphere layers affect observations, especially with high viewing angles. To reduce the effects of curvature and atmospheric refraction, Gaussian refraction coefficient was used.
Details of the development of the equation can be seen in . According to , visual perception can be described through logical phenomena, provided that some criteria are taken into account, such as scale, location, height of observation, logical schemes and etc.
According to , visual perception is a process of reconstruction of outer reality, carried out by the cerebral cortex, based on fragmented information captured by the eyes. Through the optic nerve that leads the nerve impulses to the cerebral cortex, located in the occipital region, a mental image is formed and the third dimension is recovered.
According to , Visual Acuity VA is the ability to discriminate the details of objects in the field of view, determined by the minimum dimension of some spatial aspects of visual stimuli, referring to the spatial limit of visual discrimination.
In quantitative and measurable terms, visual acuity refers to the subject's ability to detect, separate or discriminate an object in space. These capabilities correspond, respectively, to the smallest detectable object detection acuity , the shortest distance between two objects for them to be detected as separate objects separation or resolution acuity and the smallest discriminable or recognized object discrimination or recognition acuity .
According to the , acuity can also be understood as being a characteristic of the eye to recognize two very close points either as the clarity or sharpness of the eyesight or the ability of the eyes to see fine details. In simple terms, acuity is the clarity of view of details and is divided into qualitative ability to see objects close together and quantitative reciprocal angular value of separation between two neighboring objects that the eyes can see apart.
For quantification of acuity, the stimulus of visual perception of the human eye is nonlinear. For this reason, the Weber-Fechner Law was established, which is based on a logarithmic model of subjective perception of stimuli, for which only differences in brightness are noticeable , as shown in Figure 1. Based on this law,  determined that human visual acuity is proportional to the logarithm of stimulus intensity, and this stimulus must grow exponentially so that human sight can differentiate it with increased distance from the object being observed.
Some of our senses operate logarithmically, which makes the use of logarithmic scales appropriate for determining distances, what allowed the development of the method presented in this research, relating human visual acuity and the distances that objects could be inserted in the landscape, without carrying out concrete interventions in the region.
Figure 1. Visual acuity is influenced by brightness, color and contrast, and it can be measured using Snellen charts, which are widely used by ophthalmologists. Humans see objects in a predefined visual field, which corresponds to the total area or visible space in peripheral vision with the eye looking straight ahead. Visual fields can be measured by perimetry and can be analogous to the visual axes used in mapping. It extends over an area around km 2.
It stands out for its natural beauty and rich architectural heritage see Figure 2. They were built by the Portuguese crown in the eighteenth and nineteenth centuries with different objectives, for example:. The main reason for the creation of these corridors was to facilitate transportation and avoid the dispersal of animals, which were mostly mules. The domestic market needed a supply of goods and Minas Gerais state needed strong and resilient animals to transport gold.
Horses did not adapt to the rugged terrain and were automatically replaced by mules, because they are more resilient, withstand heavy loads and travel well on difficult terrains over long distances. In the following centuries, during the coffee cycle, mule trains were also used. Over time, several branches were created. The route was generally determined by the conditions of the terrain, the march of the animals and the places of.
Figure 2. Study area. Along the Path, stations were created for such stays, determining the settlement of these sites, either through the construction of farms or commercial establishments. Stays sometimes lasted many months, because drovers needed to gain weight and recover physically, because they felt very weak as a result of the distance and the challenges posed by the journey. Also, drovers had to wait for the level of the rivers to go down so that they could cross the animals over more safely.
The construction of the first roads and farms usually used slave labor and was sponsored by landowners. The ground was stony, mostly made of basalt stones. They were laid tight together, eliminating the need for any kind of mortar joints Figure 3.
In Coxilha Rica, many of these stone-walled corridors are still preserved, and so are many farms over years old, which eventually created a set of historical, cultural, architectural and landscape remnants, nonexistent in other regions of Brazil where animal drovers were also present. Many parts of these paths and farms are still in a good state of conservation and deserve to be preserved.
Figure 3. Stone-walled corridors. This chapter describes the materials used to conduct the research, as well as the method to achieve the proposed objectives. The following materials were used:. The main starting point to develop the method was, in principle, to define a value for human linear visual acuity Ai , taking into consideration a 24 m high power transmission tower, was defined as the object of study, and then delimit the area of visibility of the observer.
Logarithmic scales and adaptations of the Snellen table with a horizontal distance of 6 m were used. Horizontal distances between the observer and the transmission tower were determined.
The height of the tower was reduced, for each distance, by lowering the Gauss :. Through trigonometric relations, the heights at the corresponding distances observed in the bulkhead were determined, resulting in the following equation:. The angular intervals for the height of the tower were also determined, in relation to the projection to the bulkhead, for each calculated distance, according to the following equation:.
Visual acuity was used as the tangent angle formed by the distance from the bulkhead and the vertical distance of the human visual acuity projected on the bulkhead, so that the value returned was compatible with the linear acuity, relative to the established limit of one minute of degree 1' :. After determining the new height perceived by the view of the tower, the respective height projected on the bulkhead was calculated.
Thus, the remainder of the method consisted of generating reproducible criteria on how to map the visibility spot reached from the main points chosen to the limit of m that involved the following procedures:.
The results presented that, at a distance of m or further, the projection of the view of a 24 m tower in the shield is smaller than the determined value of 0. Starting at the main house of the historical farms see example in Figure 4 , reference points see Figure 5 were determined in the field, which allowed the generation of visibility polygons for each case. The reference point was carefully defined: prominent position, rising, near the main house, with a good view of the surroundings and representative of each farm.
After data processing for each farm and each quadrant , the resulting information was input into the cartographic database to cross-check the data and analyze the visibility of the surrounding farms and stone-walled corridors together. Figure 4. Location and main house of Santa Cecilia farm. Figure 5. Reference pointo for Santa Cecilia farm. Figure 6. Poligonal visibility for the first quadrant of the Santa Cecilia farm.
After the survey of the coordinates of each flag through the Total Station, a camera was installed at the same point for taking photographs and making videos. The parameters considered in the field in the method validation were the same as those used in the GIS environment; the footage and photographs were used to compare the simulation results and perform detailed analyses.
Figure 7 shows the validation scheme of the method for the generation of visibility polygons. The scheme also shows the radii of distance from the reference point ranging from 1 to 15 km in Figure 7 and from 1 to 8 km in Figure 8. When compared to the field footage and photographs, they allowed the analysis of each sector separately and also enabled the observation and identification of elements not represented by the DEM. These elements correspond mostly to the vegetation and buildings that exist around the reference points and which represent an obstacle to the horizon view.
However, the results. Figure 7. Method validation Scheme.
Curso de Topografia-Lelis Espartel 9ed-1987