Complex data structures means that phenomenonologically recognizable combination of several vector polygon maps through. Raster data models and comparisons with vector youtube. Vector field data model and operations xingong li department of geography, university of kansas, lawrence, kansas 66045 michael e. The objective of this section is to understand how raster data models are implemented in gis applications. Look closely at our maps and you will find coordinates. Raster data models present information through a grid of cells raster grids are usually made up of square or rectangular cells. Although web map services can display maps on screens. Tiled vector data model for the geographical features of symbolized. Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. The vector data model is based on the assumption that.
Image data utilizes techniques very similar to raster data, however typically. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Raster data models 262018 geo327g386g, ut austin 3 geo327g386g. In the vector based model figure 4, geospatial data is represented in the form of coordinates. Shapes and locations of features on maps need to be described in numbers so the information can be read by computers. Can overlay displays easily can easily manipulate data table can have many variables linked to one geographic file better suited for map output a simple data structure. When should we use raster and when should we use vector. Electronic maps emaps provide people with convenience in realworld space. Cee 468668 gis applications in civil engineering university of nevada las vegas. Each grid cell is filled with the measured attribute. Using the same graph as before, a grid showing how vertexes can be joined by edges lines would be represented as. In contrast to the raster data model is the vector data model. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas.
Lecture 1 intro to gis and gis vector and raster data models. Raster twister model builder demo and data raster twister tools toolbox. The raster data model is widely used in applications ranging far beyond. Currently used vector data models belong to any of the following types according to the complexity of the structure and the possibility of using topological. A data model is a way of defining and representing real world surfaces and characteristics in gis. Format description for vpf the vector product format vpf is a standard format, structure, and organization for large geographic databases based on a georelational data model intended. Vector data models structures vector data models can be structured many different ways. Unlike vector data models, which show geographic data through. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels.
You will know the difference between raster and vector data in gis you will know when. The raster data model jackson school of geosciences. Vector models are useful for storing data that has discrete boundaries, such as country. All topological data models have not been implemented in gis probably. The following diagram reflects the two primary spatial data encoding techniques. In vector data, the basic units of spatial information are points, lines. In vector data, the basic units of spatial information are points, lines and.
Spatial analysis using vectorbased data models taking advantage of gis to handle spatial operations spatial join issues. Can overlay displays easily can easily manipulate data. Two common data models used to represent geographic data are the vector data model and the raster data model. There are several advantages and disadvantages for using either the vector or raster data model to store spatial data. If you want to represent features with distinct boundaries, its probably better to use the vector data model and store. Vector data also needs a lot of work and maintenance to ensure that it is accurate and reliable. What is the difference between vector and raster data. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. Data model overview a data model is a set of constructs for representing objects and processes in the digital environment of the computer decisions about the type of data. Raster data tend to require large amount of computer memory.
The three basic symbol types for vector data are points, lines and polygons areas. There are two primary types of spatial data models. Inaccurate vector data can occur when the instruments used to capture the data are not. We will examine two of the more common data structures here. Layers representing two line and one polygon gis file. Rasters are especially well suited for storing continuous data such as temperature and elevation values. We will examine two of the more common data structures here vector data model. Instead, vector graphics are comprised of vertices. Gis data model set of constructsrules for describing or representing the real world within a computer two data models vector raster 3. For this purpose a hybrid data model is defined and extended. A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data.
Spatial data models vector data model points, lines, areas objectbased raster data model exhaustive regular or irregular partitioning of space locationbased the vector data model uses. In this model, space is not quantized into discrete grid cells like the raster model. Vector data model individual vector gis files point, line, polygon are in a typical gis software represented by layers, which are stacked on top of each other, creating chosen geographical content. Instead, vector graphics are comprised of vertices and paths. Vector data models use discrete elements such as points, lines, and polygons to represent the geometry of real world entities figure 26. In a vector data model, the computer stores points, lines and polygons as x and y locations a point feature would only have one x and y location associated with it. While deciding whether to use a vector data model or raster data model in your work it entirely depends on the data you have as input and what your goals are for displaying or analyzing the data. Difference between vector and raster data model vector data model. Different types of vector data and concept of topology nptel. These are vital for translating our maps into digital formats. But what is the difference between raster and vector data.
The two primary types of spatial data are vector and raster data in gis. Beyond the vector data model introduction collecting, managing, and analyzing data the raster world adding functionality with spatial analyst managing grid themes introduction. Vector data models use points and their associated x, y coordinate pairs to represent the vertices of spatial features, much as if they were being drawn on a map by hand aronoff 1989. Maidment, introduction to spatial hydrology esri campus continuous surfaces can be represented using the grid or raster data model in. Such a hybrid system can process raster data as well as vector data in an integrated manner taking uncertainty into account. When would you use the vector data model versus the raster data model. Raster data models have been updated mainly for data structure and data compression. Vector and raster data models university of maryland.
Digital elevation models and different types of resolutions. Vector data model a representation of the world using points, lines, and polygons. Spatial data can represent vector and raster data models realworld features that have discrete boundaries such as roads, buildings, lakes, rivers, administrative boundaries as well as real. Raster vector comparisons raster vector spatial location implicit explicit attributes explicit for each cell implicit within data layer in either case the challenge is to. The raster data model is a widely used method of storing geographic data. There are many analysis that make use of both data models i. Vector data models can be structured many different ways. The model most commonly takes the form of a gridlike structure that holds values at regularly spaced intervals over the extent of the raster.
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