To begin, i want to show you, the kind of raster data supported in arcmap. Technical specifications for raster dataset formats esri. A geographic information system gis is an organized integration designed to store, manipulate, analyze, and display geographically referenced information. In some gis packages, the dbms is based in an existing software, i. Point, polyline and polygon features work well for representing some features. Mar 11, 2020 raster data model is a very efficient representation inside digital computers. A common use of raster data in a gis is as a background display for other feature layers.
Raster data models present information through a grid of cells raster grids are usually made up of square or rectangular cells. A simple raster data set is a regular grid of cells divided into rows and columns. Representation of the real world and showing differences in how a. Representation of the real world and showing differences in how a vector and a raster gis will represent this real world. High or fine resolution rasters have comparatively closer spacing. The major format now for cartographic production is adobe acrobat pdf, which has. The model most commonly takes the form of a gridlike structure that holds values at regularly spaced intervals over the. You will know the difference between raster and vector data in gis you will know when each data model is the best choice for a particular analysis or map. Jun 06, 2017 gis data represents real objects which can be stored under two broad types known as vector data and raster data vector data the vector data is made up of points, lines and polygons.
The raster data model consists of rows and columns of equally sized pixels interconnected to form a planar surface. Although vector data can look like raster data on a map, the two are fundamentally different for analysis. Unlike vector data models, which show geographic data through points, lines, or polygons, raster data is displays one value in each cell. Care should be taken to determine whether the raster or vector data model is best suited for your data andor analytical needs. Pdf the raster data model is a widely used method of storing geographic data. Geographic information systems an overview sciencedirect. Model based on scale of original data commonly a raster dataset. When comparing rasters with different cell size, some rasters get wrong min, max and std values. Alain lamarche, in oil spill science and technology, 2011. The book is also made available as an electronic pdf document. Raster data in detail raster data is used in a gis application when we want to display information that is continuous across an area and cannot easily be divided into vector features.
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. The raster data model is the most suitable format for arithmetic operations among cells. Raster data is made up of pixels or cells, and each pixel has an associated value. 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. What is the difference between vector and raster data.
Raster data models present information through a grid of cells. About analyzing imagery and raster datahelp arcgis for. Because the volume of spatial data is so high, it is particularly important for the geographic information systems to have efficient data storage formats and associated optimal algorithms. To learn about these tools and others, see the following. Standardization of high voltage electric transmission line siting methodologies, by using. Lecture 1 intro to gis and gis vector and raster data models. The raster data model, has a simple and elegant structure. Nations have a clear need for accurate framework data in a spatial data infrastructure. A raster dataset is the same type of image that is produced when recording an image with a digital camera.
Giss have traditionally used either raster or vector for maps. Rasters as basemaps a common use of raster data in a gis is as a background display for other feature layers. Raster data models incorporate the use of a gridcell data structure where the geographic area is divided into cells identified by row and column. Searching for supported, raster data set file format,will give us the. Elevation, as a continuous land field characteristic, is usually stored in a vector file for easier data management, but is more suitable to be represented by a raster data model. 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. The raster data model is widely used by nongis technologies such as digital cameraspictures and lcd monitors. Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates.
The raster data model jackson school of geosciences. So if you consider creating a data structure for rastor it would be a 2d array, each x,y coordinate refer a square in the are and it can have a certain predefined characteristic e. In this model, space is not quantized into discrete grid cells like the raster model. About analyzing imagery and raster datahelp arcgis for desktop. In particular, the quadtree data structure has found some. Principles of geographic information systemsan introductory. If the area is 100 km x 100 km and cell size is 10 m. The use of large cells to reduce data volumes structures can be lost and there can be a serious loss of information crude raster maps are considerably less beautiful than line maps network linkages are difficult to establish projection transformations are time consuming.
In vector data, the basic units of spatial information are points, lines and polygons. Satellite imagery remotely sensed satellite data are recorded in raster format. High voltage transmission lines deliver generated power. Aug 08, 2017 the structure of raster data is simple, it is exceptionally useful for a wide range of applications. The proof lies in considering some basic capabilities. The spatial resolution of a raster dataset represents a measure of the accuracy or detail of the displayed information. What are raster and vector data in gis and when to use.
The data model a logical data model is how data are organized for use by the gis. Arcgis is able to read an alpha band from an existing png. All cells in a raster appear to be the same size in a gis application but may represent an area on the ground that has a different width than height. Chapter 1 gis and modeling overview uc santa barbara geography. What is the difference between vector and raster data models. From the basics of map algebra and its natural language interface to complex hydrological modeling techniques. While the term raster implies a regularly spaced grid other tessellated data structures do exist in grid based gis systems. A raster data model can be a grid, a raster map, a surface cover, or an image in gis. Learn the latest gis technology through free live training seminars, selfpaced courses, or classes taught by esri experts.
Gis integrated with high resolution remote sensing data and field survey data for. A raster catalog can be used to manage tiles of raster data or time series raster datasets. Raster to vector is harder decisions needed, sometime scalesensitive. The differences between raster and vector graphics, as detailed below, effect the level of detail, visual appeal, speed of manipulating graphics and data storage space required. Raster model s 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. Spires occur when a very high elevation, relative to surrounding cells, is entered. In contrast to the raster data model is the vector data model. Geospatial modeling of electricity distribution network. A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data. Each of these units is composed simply as a series of one or more coordinate points, for example, a line is a collection of related points. The raster data model is a widely used method of storing geographic data. It needs 10,000 rows x 10,000 columns or 100,000,000 pixels. To see what kinds of raster data are supported in arcmap.
However, the distinction between vector and raster data types is not unique to gis. Images reflect pictures or photographs of the landscape. Raster model vector model points, lines, polygons features and maps a gis map is a scaleddown digital representation of point, line, area, and volume. Aerial photographs and satellite images are generally in a raster format and are used in gis to view a detailed map at a given extent or for the purpose of digitizing. Discrete objects legal boundaries versus natural gradients many natural features are very hard logically to delineate because consequence of continuous processes raster data model. A raster is an array of cells, where each cell has a value representing a specific portion of an object or a feature. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. The use of gis in high voltage transmission line routing in kenya. The use of gis in high voltage transmission line routing. The raster data model is widely used by non gis technologies such as digital cameraspictures and lcd monitors. The tension method tunes the stiffness of the surface according. These pixels are used as building blocks for creating points, lines, areas, networks, and surfaces chapter 2 map anatomy, figure 2. Integration of these two data model types is essential to a successful gis project. Gis spatial analysis tools, has great potential in helping predict and defend new optimal.
Raster data model the raster data is made up of a matrix of grids. 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 value of the variable defined for each cell. Unlike the vector data model, there are many more types of raster data. While the structure of raster data is simple, it is exceptionally useful for a wide range of applications. For example, the vector data model represents geography as collections of points, lines, and polygons. This value can be interpreted to mean several different things. Raster grids are usually made up of square or rectangular cells. Simplifying slightly, a digital photograph is an example of a raster. The closely mimics the manual drafting process by representing map features discrete spatial objects as a set of lines which, in turn, are stores as a series. A mathematical procedure called topology is used for representing spatial relationships among the objects. In rastor, the area under consideration is divided into equal squares and a characteristic assigned to it. Certain analytical procedures require raster data while others are better suited to vector data. The selection of a particular data model, vector or raster, is dependent on the source and type of data, as well as the intended use of the data. In vector data, the basic units of spatial information are points, lines arcs and polygons.
Geographic information systems have requirements for high volume spatial data handling. This conversion technique is also demonstrated in the select layer by area model found in gp service example. Raster band statistics works so far, but i dont know how to compute the significance of the results with arcgis. A data type of any value is a generic data type that can be connected to any tool parameter.
Each of these units is composed simply as a series of one or more coordinate points, for example, a line is a collection of related points, and a polygon is a collection of related lines. They are actually stored on disk and can be accessed through the personal, file, or enterprise geodatabase as either a raster dataset or a raster catalog. Rasters have a new home in the geodatabase since arcgis 9. The structure of raster data is simple, it is exceptionally useful for a wide range of applications. Gis data represents real objects which can be stored under two broad types known as vector data and raster data vector data the vector data is made up of points, lines and polygons. The darker red areas show locations predicting the highest level of drug traffic while the yellow dots.
Is it possible to calculate correlation and significance maybe with spss for grids. Raster data sets record a value for all points in the area covered which may require more storage space than representing data in a vector format that can store data only where needed. Resources are available for professionals, educators, and students. In gis, vector and raster are two different ways of representing spatial data. Arcgis displays raster and vector data simultaneously and can convert one to the other.
Image data utilizes techniques very similar to raster data, however typically lacks the internal formats required for analysis and modeling of the data. The raster data model is widely used by nongis technologies such as digital cameras pictures and lcd monitors. Easy to use importance of terrain in hydrology and environmental modeling visualization of landscapes. More than a classroom text this book is a longterm resource for the raster gis modeling professional. Except the digital elevation model dem, all the other data sets were in vector formats and neededrasterization. If one byte is used per pixel, it requires 100 mb storage ags 722 types of raster data 1. Vector data model representations of the real world source. Within a gis, the uses of raster data fall under four main categories. Convert data as necessary for analyses, including vector to raster. Implementing a gis methodology for siting high voltage electric. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. Also note that while the cells are always rectangular the original pixels when the data was remotely sensed was probably larger and more of an ellipse.
Representing discrete phenomena data redundancy no topology for discrete data spatial accuracy 16 raster data structures method by which raster model is implemented in a particular gis software application typically,user is unaware of how data structure works 17 cell by cell 18. Esri, the esri globe logo, arcgis, arceditor, arcinfo, arcpad, arccatalog, 3d analyst. There are additional tools in arcmap to help you in your analysis of raster data, such as the pixel inspector tool, which is used to view an area of pixel values in your raster dataset, or the swipe layer tool, which is used to interactively reveal layers beneath the layer being swiped. Locate gis data representing the modellocate gis data representing the model variables at the desired scale 5. In the vector based model figure 4, geospatial data is represented in the form of coordinates. Define objectives and purpose to create a model for potential habitat for the coeur dalene salamander 2. Raster data are derived from a gridbased system of contiguous cells containing specific attribute information.
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