A gravel-bed stream's grain size distribution plays an important role in determining a river's depth, sediment transport rates, and stream bed stability as well as the survival rates of mussels and salmonids. Unfortunately, the material found in gravel-bed rivers exhibits vertical stratification as well as spatial variation in the horizontal direction and is difficult to sample. Previous research has largely dealt with the ability of grid, areal, and bulk sampling techniques to sample a single spot within a river. Little has been done in characterizing an entire river reach. Of the methods suggested, none is adequate because they are either inherently biased or are incapable of describing the spatial variations within a sampled region. The present research proposes a method that overcomes these problems. It shows that a single large grid sample, or composite grid sample, can be used to obtain an unbiased estimate of an area's overall grain size distribution at a known accuracy level. It then suggests that the arithmetic mean is a suitable parameter to characterize the coarseness of individual sediment deposits within a sampled area. Thus, by recording the size and location of each stone taken in the composite grid sample one can use statistical hypothesis testing to systematically analyze local means throughout the sampled area and locate sediment boundaries. Once the boundaries are located, stones from the composite grid sample falling within the boundaries of a particular deposit can be analyzed as separate grid samples representative of the individual deposits present and describe the local variability. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work is to present and discuss the Precision Farming in a simple way through the routines of the precision farming into the system Campeiro CR-7 and its performance in order to analyze the spatial variability of soil properties and productivity. Chapter I The Loop Sampling, provides a tutorial on developing a sampling plan for spatial assessment of physic-chemical properties of soil by means of geostatistical techniques, the sampling plan can contribute significantly to reducing the cost of collection of samples as well as quality of these samples. Chapter II Map of Fertility analyzes a tool that assists the user in the classification of levels of soil fertility, and the result presented in map form, where the final map is a cross between a map that contains phosphorus in the soil and map showing the clay making the recommendation to apply phosphorus fertilizer supplier to more precise areas where there is more than one class of clay. Chapter III Productivity Map filtering is performed on the data collection, making it possible to make a map of productivity consistent with the reality of the field with a greater reliability of the data, providing information relevant to agricultural management. / Este trabalho consiste em apresentar e discutir a Agricultura de Precisão de forma simples, através das rotinas de Agricultura de Precisão do Sistema CR-Campeiro 7, conjunto de programas elaborado no Departamento de Engenharia Rural da Universidade Federal de Santa Maria UFSM, Laboratório de Geomática, concebido e programado pelo Prof. Dr. Enio Giotto, e o desempenho desses programas, visando à análise da variabilidade espacial de propriedades químicas do solo e da produtividade. O Capítulo I Malha de Amostragem traz um tutorial sobre a elaboração de um plano de amostragem para avaliação espacial de propriedades físico-químicas de solo por meio de técnicas geoestatísticas; o plano de amostragem pode contribuir de forma relevante para diminuição do custo de coleta de amostras como também para a qualidade dessas amostras. O Capítulo II Mapa de Fertilidade analisa uma ferramenta que auxilia o usuário na classificação dos níveis de fertilidade do solo, sendo o resultado apresentado em forma cartográfica, onde o mapa final é a integração temática entre o mapa que contem os teores de Fósforo no solo e o mapa que apresenta os teores de Argila, tornando a recomendação para aplicação de fertilizantes fornecedores de Fósforo mais precisas para áreas onde ocorre mais de uma classe de Argila. No Capítulo III Mapa de Produtividade é realizada uma filtragem nos dados de colheita, tornando possível a confecção de um mapa de produtividade coerente com a realidade do campo, com uma confiabilidade maior dos dados, fornecendo informações relevantes ao gerenciamento agrícola.