Geol-4165_Subsurface_Geology-ch2-Gridding_algorithms

# Geol-4165_Subsurface_Geology-ch2-Gridding_algorithms -...

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Click to edit Master subtitle style 3/14/11 Gridding Algorithms What is the right solution for a good computer map? Hannes E. Leetaru, Ills. Survey

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3/14/11 Deterministic or Geostatistical Deterministic use mathematical function for interpolation Geostatistics use both statistical and mathematical methods for interpolation Geostatistical packages have better data analysis tools Hannes E. Leetaru, Ills. Survey
3/14/11 Grid or TIN Gridding uses an array of x and y values TIN (Triangulated Network) uses the points themselves Gridding is more commonly used Gridding is only contouring method available in some software packages There are advantages and disadvantages to both methods Hannes E. Leetaru, Ills. Survey

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3/14/11 Triangulated Network Also known as polyhedron surface fitting The surface is modeled through a system of triangular plates Contour lines are drawn between points through the sides of the triangles Hannes E. Leetaru, Ills. Survey
3/14/11 TIN Generate a series of triangles based on input points Estimate a value anywhere in a triangulation by averaging nearby triangle node values The triangles are as close to equilateral in shape as possible (Delhaney triangles) Hannes E. Leetaru, Ills. Survey

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3/14/11 Triangulated Network Hannes E. Leetaru, Ills. Survey
3/14/11 Advantages of TIN All locations are honored, no smoothing or interpolation is necessary The contouring is not degraded by changes in spatial density of the values The triangles get smaller in high density areas This means that you can have higher resolution in areas where the surface is highly variable and lower resolution is areas that are less variable There are no interpolated grid nodes Hannes E. Leetaru, Ills. Survey

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3/14/11 Disadvantages of TIN Maps limited to areas with data, no extrapolation is possible Cannot project trends into less densely sampled areas Difficult to do conformable mapping because isopach values have no constant xy Surfaces cannot readily be input into other packages such as 3D visualization or reservoir simulation software Hannes E. Leetaru, Ills. Survey
3/14/11 Reality of TIN Many programs will use TIN and then force it into a grid for manipulation purposes Hannes E. Leetaru, Ills. Survey

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Triangulation Hannes E. Leetaru, Ills. Survey
3/14/11 Gridded Data and Rasters A cell is a pixel element of a raster and can represent various types of data Photography (color) Thematic attribute (vegetative type) Surface value (elevation) Hannes E. Leetaru, Ills. Survey

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3/14/11 What is Gridding Gridding is a mathematically method of interpolating intermediate locations between control points and using them to create contour lines Hannes E. Leetaru, Ills. Survey
3/14/11 Gridding Assumptions All gridding algorithms are based on the following assumptions: The function is continuous within the region to be gridded The function to be gridded is single-valued at any point

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## This note was uploaded on 03/14/2011 for the course GEOL 4165 taught by Professor Alanbrown during the Spring '11 term at LSU.

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Geol-4165_Subsurface_Geology-ch2-Gridding_algorithms -...

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