Sections describing raster data models, tin data models, and data structure then follow. The raster data model is widely used by nongis technologies such as digital cameraspictures and lcd monitors. Many people use raster data as a backdrop to be used behind vector layers in order to provide more meaning to the vector information. Dengan demikian, secara konseptual, model data raster merupakan model data spasial yang paling sederhana. For raster positions, its simple to understand cell size. For example, you can process data through a geoprocessing model to create a raster dataset that maps suitability for a specific activity. Rasters have a new home in the geodatabase since arcgis 9. Raster data models present information through a grid of cells raster grids are usually made up of square or rectangular cells. Raster grids are usually made up of square or rectangular cells. The raster data model is a widely used method of storing geographic data. Data structures and data models raster and vector refer to a particular data model a data structure refers to a particular implementation of either the raster or vector model 4 topology the spatial relationships between things an important distinction between data models and data structures.
Index introduction components of gis data types in gis data representation raster data model vector data model differences between raster and vector triangulated irregular network tin digital elevation model dem conclusion reference. For the love of physics walter lewin may 16, 2011 duration. Data is represented at original resolution and form without generalization. Raster data model makes use of regular array or matrix of cells of uniform size and shape for representing data. Data can be represented at its original resolution and form without generalization. Length encoding quad tree used when values change continuously cell. There are two broad categories of spatial data models. The raster data model jackson school of geosciences. These are vector data model and raster data models. Most likely, you are already very familiar with this. Raster data structure refers to the method or format for storing raster data so that it can be used efficiently. Raster data models are used to represent a wide variety of phenomena, including continuous data like surface temperature or elevation.
Raster data model represents phenomena as occupying the cells of a predefined, grid shaped tessellation. In this course, the second in the geographic information systems gis specialization, you will go indepth with common data types such as raster and vector data, structures, quality and storage during four weeklong modules. This parameter is useful when the z units differ from the x and y units, for example feet and meters. This value can be interpreted to mean several different things. Raster model through georeferencing we calculate the parameters used in the equation to transform between a coordinate system and cell pixel location in the image a point is described by the position of a single pixel. But this is really just a guideline to get us started. The raster data model is widely used in applications ranging far beyond geographic information systems giss. The position of each cell is defined by a row and column number. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. The human eye is very good at interpreting images and so using an image behind vector layers, results in maps with a lot more meaning. Digital photography is the best example of raster data type model, anyone who is familiar with digital photography can recognize the pixels as the smallest individual unit of an image, where each pixel value in the image corresponds to a.
It is unnecessary to store the coordinates of each cell as the. Unlike the vector data model, there are many more types of raster data. To begin, i want to show you, the kind of raster data supported in arcmap. These pixels are used as building blocks for creating points, lines, areas, networks, and surfaces chapter 2 map anatomy, figure 2. All cells in a raster must be the same size, determining the resolution. A raster is an array of cells, where each cell has a value representing a specific portion of an object or a feature. The figure represents vector left versus raster right data. Raster grid format is data model for satellite data and other remote sensing data.
Raster models are useful for storing data that varies continuously, as in an aerial photograph, a satellite image, a surface of chemical concentrations, or an elevation surface. Each layer of grid cells in a raster model records a separate attribute. Below is an image in arcgis showing the attributes that provide the meaning for each of the codes in the pixels in the raster. The model most commonly takes the form of a gridlike. The digital photographs we see in our everyday life, satellite imagery, aerial photographs etc. Satellite imagery remotely sensed satellite data are recorded in raster format. What is the difference between vector and raster data. Pdf the raster data model is a widely used method of storing geographic data. For raster data, this is the size of the individual cell or pixel. Map algebra with raster data is usually quick and easy to perform. Maidment, introduction to spatial hydrology esri campus continuous surfaces can be represented using the grid or raster data model in which a mesh of square cells is laid over the landscape and the. When pdf import isnt an option autocad raster design.
In contrast, within the raster data model, a representation of the world is created as a surface divided into a regular grid of cells. Raster data has issue while overlaying multiple images. Raster data model each grid cell in a raster data layer is one unit the minimum amount of information in the raster data model every cell has a value, even if it is a special value to indicate that there is no data or that data is missing at that location the values are numbers, either. The raster data model consists of rows and columns of equally sized pixels interconnected to form a planar surface. The model most commonly takes the form of a gridlike structure that holds values at regularly spaced intervals over the. Data models in geographical information systemgis 1.
In contrast to the raster data model is the vector data model. Data raster, data vektor dan pengelolaannya gedbinlinks weblog. The data base concept is central to a gis and is the main difference between a. There are several advantages and disadvantages for using either the vector or raster data model to store spatial data. 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. Care should be taken to determine whether the raster or vector data model is best suited for your data andor analytical needs. Raster data is less expensive to create computationally compare to vector graphics.
Raster data representations cell value measurement, average, majority, significance cellbased vs. Raster data storage uses square cells to model points, lines, or areas continuously. Types of raster data model advantages, disadvantages just. For example, a table is a very simple example of a data model, and in the way in which tables are often used in gis, the rows of the table correspond to a group or class of. Raster data models present information through a grid of cells. Resolution depends on real world area represented by each grid cell. Raster data model za raster represents a continuous surface, but for data storage and analysis, a raster is divided into rows, columns, and cells. A raster data type is made up of pixel or cells and each pixel has an associated value.
Thematic maps can also result from geoprocessing operations that combine data from various sources, such as vector, raster, and terrain data. As with all rasters, remember that what is in the pixel does not correspond exactly to what is on the ground, there is always uncertainty in our data. Check out my previous post for tips on identifying vector. The cells pixels, picture elements are constant in size and are generally square. To see what kinds of raster data are supported in arcmap. Integrated with the geoprocessing framework, arcgis spatial analyst offers easy access to numerous functions in modelbuilder, a graphic modeling tool. What is the difference between vector and raster data models. Discuss components of spatial data centers for disease. In this model, space is not quantized into discrete grid cells like the raster model. Gridcell systems are very compatible with raster based output devices, e. The raster data model, has a simple and elegant structure. Pendahuluan model dunia nyata memudahkan manusia di dalam studi area aplikasi yang dipilih dengan cara mereduksi sejumlah kompleksitas yang sebenarnya hadir.
Each of these units is composed simply as a series of one or more coordinate points, for example, a line is a. Di luar area aplikasi yang dipilih diasumsikan tidak penting. Unlike vector data models, which show geographic data through points, lines, or polygons, raster data is displays one value in each cell. Dengan model data raster, data geografi ditandai oleb nilainilai elemen matriks persegi panjang dari suatu objek. When a gis data set is created by digitizing a paper map, it is helpful to. A raster dataset is the same type of image that is produced when recording an image with a digital camera. Raster data model data model user group join the data model user group if you are an existing arcgis customer and want to learn more about design and architecture of personal or enterprise geodatabase and become a part of esris growing data model community. Overall, quantitative analysis is intuitive with discrete or continuous rasters. A point may be represented by a single cell, a line by a sequence of neighbouring cells and a polygon by a collection of contiguous cells. Simple data structures overlay and combination of maps and remote sensed images easy some spatial analysis methods simple to perform simulation easy, because cells have the same size technology is cheap disadvantages of raster data structures. Each grid cell is filled with the measured attribute values. With the vector and raster data model, a very basic guideline just to get started with is that, discrete objects are easily represented with the vector data model. Searching for supported, raster data set file format,will give us. Raster data model record value of all the points of the area covered which required more data storage than model represented by the vector model.
Raster terrain analysis qgis documentation documentation. Learn about data models and formats, including a full understanding of vector data and raster concepts. A point may be represented by a single cell, a line by a sequence of neighbouring cells and a polygon by a collection of contiguous cells all cells in a raster must be the same size, determining the resolution. Lecture 1 intro to gis and gis vector and raster data models. It needs 10,000 rows x 10,000 columns or 100,000,000 pixels. Lines are represented by strings of connected pixels the spatial resolution of a raster is the. Continuous surfaces can be represented using the grid or raster data model in which a mesh of square cells is laid over the landscape and the value of the. Graphic output is usually more aesthetically pleasing traditional cartographic representation. If the area is 100 km x 100 km and cell size is 10 m. Below is an example of a classified raster dataset showing land use. Raster data models and comparisons with vector youtube. The most common raster with codes is the national land cover database. Sep 03, 2016 raster data model and comparisons with vector. One of the most common types of raster data is land cover derived from satellite imagery.
The vector model uses points and line segments to identify locations on the earth while the raster model uses a series of cells to represent locations on the earth. Vector data are easily overlaid, for example overlaying. In vector data, the basic units of spatial information are points, lines arcs and polygons. Raster data is focused on modeling continuous phenomena and images of the earth. If one byte is used per pixel, it requires 100 mb storage ags 722 types of raster data 1. The cells contain values or attributes for showing the variation of features. The basic spatial data model is known as arcnode topology.
Raster file size file size rows x columns x bitdepth 27 bit depth. Difference between vector and raster data model vector data model. Vector data model representations of the real world source. Jun 06, 2017 data models in geographical information systemgis 1. Raster model spatial data of different types can be overlaid without the need for the complex geometric calculations. Data raster dapat dikonversi ke sistem koordinat georeferensi dengan cara meregistrasi sistem grid raster ke sistem. Vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. The model most commonly takes the form of a gridlike structure that holds values at. Types of raster data model advantages, disadvantages. Simple data structures overlay and combination of maps and remote sensed images easy some spatial analysis methods simple to perform simulation easy, because cells have the same size technology is cheap. Walaupun demikian, jika model dunia nyata yang bersangkuan akan. The gis spatial data model university of washington. One of the strengths of the vector data model is that it can be used to render geographic features with great precision however, this comes at the cost of greater complexity in data structures, which sometimes translates to slow processing speed.
316 240 1139 166 1151 270 1355 501 45 495 1434 1054 1198 522 94 482 1030 408 893 1155 127 1210 1320 332 1084 825 50 609 1478 301 560 1387 1284 792 731 162 24 7 522 738 1270 551 985 896 1335 1096