Surface Modeling and Analysis Using the TIN Model
The Surface Modeling and Analysis Using the TIN Model is tasks foe this assignment that we interested in/considerate on the modeling functionality of 3D analyst and the TIN surface model and also looking in the Surfer girding software package that we have to deal with one of the study areas discussed in class so, up to us to selected an area that we desire. We will be responsible for preparing the data that we need for this assignment. The objective of this assignment is to investigate and present landscape characteristics of the study area you are working with, which this is the main object as well as is important. Statistical as well as qualitative assessments are required as part of this assignment for the two interpolation algorithm (TIN and any one of the many available interpolators within Surfer). However, we will gain experience in data conversion procedures and utilities (ArcView grid-Surfer grid-ArcView grid) as well.
The following elements will form the basis of the comparison
We are required to generate a
TIN surface via 3D analyst and a raster surface in the Surfer girding package.
Available input data:
TIN
(Triangulated Irregular Network)
What is a TIN? The TIN data structure is base on two basic elements: points with x, y, z values, and a series of edges joining these points to form triangles. This triangular mosaic forms a continuous faceted surface, much like a jewel. TIN�s triangulation method satisfies the Delaunay criterion, which Delaunay triangulation is a proximal method that satisfies the requirement that a circle drawn through the three nodes of a triangle will contain no other point. Restated, this means that all sample points are connected with their two nearest neighbors to form triangles. A circle drawn through the three nodes of a Delaunay triangle contains no other point from the data distribution.
Delaunay triangulation has several advantages over other triangulation methods:
Component of a TIN, a TIN data model is composed of nodes, edges, triangles, hull polygons, and topology.
Notes are the fundamental building blocks of the TIN. The nodes originate from the points and arc vertices contained in the input data sources. Every node is incorporated in the TIN triangulation. Every node in the TIN surface model must have a z value. As we will learn later, the CREATE TIN command can interpolate node z values for some input features that are without z values
Every node is joined with its nearest neighbors by edges to form triangles, which satisfy the Delaunay criterion. Each edge has two nodes, but a node may have two or more edges. Because edges have a node with a z value at each end, it is possible to calculate a slope along the edge from one node to the other.
Each feature in the data source used to build the TIN is processed in accordance with its surface feature type. Break line
The Triangular Irregular Network (TIN), we can see the elevation data such as spot elevation at summits and depressions and break lines can also be included in the TIN model. Break lines represent significant terrain feature like a lake or cliff that cause a change in slope; TIN triangles do not cross break lines. TIN is a data structure that defines geographic space as a set of contiguous non-overlapping triangles, which vary in size and angular proportion. Like grids, TIN is used to represent surface such as elevation, and can be created directly from files of previously saw displayed with a grid? In fact, the surface looks quite similar. The button graphic shows the internal triangular structure of the TIN, which Tins represent surface using continuous non-overlapping triangle facets. One can estimate a surface value any where in the triangulation by averaging node values of nearby triangles. Giving more weight and influence to those that are closer. The resolution of TINs can vary; they can be more detailed in areas where the surface is more complex and less detailed in areas where surface is simple. (3D Analyst, ESRI)
Digital
Elevation Model (DEM)
Digital elevation model (DEM) represents the heights at discrete, the elevation points extracted from the stereo model can also be used to create a raster (Grid) model of terrain elevation. A land surface represent in the raster domain is called a digital elevation model (DEM). From here, we can say Grid and DEM are same. Grids represent surfaces using mesh of regularly spaced points. One can estimate a surface value anywhere within the mesh by averaging nearly mesh point values, giving more weight and influence to those that are closer. The smaller the distance between points (the finer resolution) the more details the model picks up. The grid model is simple and processes on them tend to be more efficient. Grids are used more regional, small-scale application, while TINS use for more detailed, large-scale application (3D analyst Arc View)
Applications of digital terrain modeling abound in civil engineering, landscape planning, military planning, aircraft simulation, visibility analysis, hydrological modeling, and more traditional cartographic, such as the production of contour, hill-shaded, slope and aspect maps. In all such applications, the fundamental requirement of the digital elevation model (DEM) is to represent the terrain surface such that elevation can be retrieved for any given location. As it is often unlikely that the sampled locations will coincide with the user�s queried location, elevation must be interpolated from the DEM (ESRI, Virtual campus)
Virtual
Reality Modeling Language (VRML)
VRML (Virtual Reality Modeling Language) is a language specifically used to make graphical, 3-D image, and interactive worlds, with VRML 2.0, we can incorporate sound, animations and movie. In the VRML language, everything is made up of basic shapes, cubes, spheres, triangles and cones. The shapes are defined and given their size by specific commands. Then with that one object, you can stretch it to any size, add color, texture and sound.
VRML Export Users can export three-dimensional scenes to an exchange format for three-dimensional data called VRML. Because VRML browsers and plug-ins are inexpensive and widely available, the three-dimensional virtual worlds that users make from existing geographic data will be accessible to a wide audience. (3D analyst Arc View)
The 3D Analyst extension to Arc View GIS software turns conventional two-dimensional flat maps into dynamic, interactive three-dimensional views. Users can create and display surface data in three dimensions for analysis and visualization.
Arc View 3D Analyst
supports three primary data types for modeling three-dimensional
features�grids, triangulated irregular networks (TINs), and shapefiles (2D and
3D).
Grids and TINs are
used to model continuous data or surfaces. Three-dimensional vector features,
where X, Y, and Z values are stored for every vertex, let users capture and
precisely represent geographic features. Both two-dimensional and
three-dimensional data can be viewed in perspective using the Arc View 3D
Analyst 3D Scene Viewer. With the viewer, a user can rotate, zoom in and out,
and pan the data from any angle in a scene. With Arc View 3D Analyst, users can
perform a wide range of activities. Create realistic surface models from
multiple input sources. Determine height at any location on a surface. Find what
is visible from an observation point. Calculate the surface area and volume
between surfaces. Work with three-dimensional vector features to make realistic
models of the three-dimensional world. Visualize data in three dimensions. View
in pan and zoom mode as well as interactively tilt and rotate data, featuring
fly-through simulation. Turn maps into Web-viewable VRML files. Allow creation
of TINs from any combination of point, line, and polygon feature types or from
grids. Import girded elevation models including U.S. Geological Survey (USGS)
digital elevation models (DEMs).
The Arc View 3D Analyst extension enables users to
create, analyze, and display surface data. This generic surface-modeling package
is ideal for both of the novice and the advanced user, its functionality
answering the needs of those performing tasks related to surface analyst and
display. Unique features of Arc View 3D analyst include support for triangulated
irregular networks (TIN) and simple three-dimensional vector geometry, as well
as interactive perspective viewing. With 3D Analyst we can create and modify
surface models, created 3D shapefile themes, simple editing of TIN and plan
metric display of surfaces. (ESRI, Virtual campus)
Slope and Aspect
Arc View 3D
Analyst calculates the steepness and direction of surfaces, which is commonly
referred to as slope and aspect. Slope identifies the incline of a surface. This
feature is often used to find low slopes for potential construction sites and
high slopes that may be prone to erosion or landslides. Slope values are output
in degrees. Aspect is the direction the surface faces. It is often used to
determine how much sun a hill will receive or the direction of runoff. The
values of the output theme are in degrees. (ESRI, Virtual campus)
Contour
Contour
maps are frequently used to represent surfaces. Contouring produces an output
line theme from an input grid or TIN theme. Each line represents all contiguous
locations with the same height, magnitude, or concentration of values in the
input grid or TIN theme. (ESRI, Virtual campus)
Profile
Selecting three-dimensional lines from either the graphic or the active theme, users can create profile graphs to see and measure height along those lines. Profile graphs are used for things such as evaluating the difficulty of mountain trails or assessing a corridor for rail lines. (ESRI, Virtual campus)
Surface Area
Surface area is measured along the slope of a surface, taking height into consideration. The area calculated will always be greater than simply using the two-dimensional planimetric extent of the model. When compared to planmetric area, surface area provides information about surface roughness. The larger the difference between the two values, the rougher the surface. (ESRI, Virtual campus)
Hill Shade
Hill shade display brings out the relief of a surface. Users can display TIN faces with single color hill shading. The faces will all display with the same hue, but brightness will vary depending on which way they face and how steep they are. Grids can be shaded using a categorical grid with a brightness theme. Visibility determining what is visible on a surface from one or more locations is useful for a wide range of applications ranging from estimating real estate value to locating communication towers or placing military troops. (ESRI, Virtual campus)
View Shed
Areas on a surface those are visible from one or more observation points are known as view sheds. For any visible position, users can discover how many observers can see that position. In addition to controlling the height of an observer, the view-shed function can provide constraints on how far, how high, and which direction an observer can look. (ESRI, Virtual campus)
Line of Sigh
Line of sight determines whether a given target is visible from a point of observation. If the target is obscured, the coordinates of the first obstruction are given. Users can also find out what is visible along the line of sight. (ESRI, Virtual campus)
