Within the spatial referenced data group, the gis data can be further classified into two different types. Raster to vector is harder decisions needed, sometime scalesensitive. Geography network, gis by esri, gis day, gis for everyone, gisdata server. Advanced gis spatial analysis using raster and vector data j8747 december 2001 4 visualize the data with advanced symbology and annotation options. A forest area stand is usually delineated and stored in a separate poly gis file, often called fri. The raster data model is a widely used method of storing geographic data. This is often processing intensive and usually requires extensive data cleaning. Each one of these things would be a feature when we represent them in a gis application. The accuracy of analysis results depends on the accuracy of these objects in terms of location and shape. The model most commonly takes the form of a gridlike structure that holds values at. As well, topology is static, and any updating or editing of the vector data requires rebuilding of the topology. These methods are indispensable for understanding the basic quantitative and qualitative trends of a dataset. However, they dont take particular advantage of the greatest.
Now that you have edited a few features, you must want to know what else one can do with them. A gis geographic information system is a powerful tool used for computerized mapping and spatial analysis. Having features with attributes is nice, but when all is said and done, this doesnt really tell you anything that a normal, non gis map cant. A feature is anything you can see on the landscape. For effective analysis, vector data must be converted into a topological structure. Furthermore, it gives higher geographic accuracy because data isnt dependent on grid size. This diagram shows how gis applications deal with vector data. This week we will also focus on what types of analyses we can do with discrete vector data e. Slr models pdf transportation infrastructure layers. The old gis adage raster is faster, but vector is corrector comes from the two different fundamental gis models. A common use of raster data in a gis is as a background display for other feature layers. The raster datasets also provide beautiful hillshade relief for your map.
A small pond might be stored as part of a wetlands gis file. Vector data analysis uses the geometric objects of point, line and polygon. In vector data, the basic units of spatial information are points, lines arcs and polygons. Gis concept data layers for infographic royalty free vector. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. Intersect is a tool which limits all the features in two layers to the places where they overlap. Locate gis data on the web and consider the merits of di. Implies some statistical analysis of attribute and location. 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. Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. The national hydrography dataset s, watershed boundary dataset, governmental. Introduction to gis basics, data, analysis case studies. In example 2, we will use point data to create a raster layer describing the spatial density of floridas springs.
Even with vector data, hydrologic inconsistencies between streams and sub. Information systems qgis, grass 7 and r before downloading and installation of qgis and other software in windows, check your windows system type 32 bit or 64 bit to assure compatibility. Unfortunately, the quappelle valley data you need for this assignment are not included in the collections list. What are raster and vector data in gis and when to use.
Spatial analysis example locating a shopping center. Convert data as necessary for analyses, including vector to raster. Introduction to basic gis and spatial analysis using qgis. Vector data can be used for spatial analysis in a gis application, for example to find the nearest hospital to a school. As sample data, a usgs quad sheet and one type of each shapefile are provided.
Why were covering it this class places more of an emphasis on rasterbased analyses andor analyses that combine vector and raster data sources. Information systems qgis, grass 7 and r before downloading and installation of qgis and other software in windows, check your windows system type 32 bit. The differences between rasters and vectors, properties and values, and the ways we can use gis for analysis. In vector data, the basic units of spatial information are points, lines and polygons. Gis system integrate data and convert it into maps. Natural earth data is number 2 on the list because it best suits the needs of cartographers. While the structure of raster data is simple, it is exceptionally useful for a wide range of applications. Each object is represented as a list of x,y coordinates examples tree, poles, roads, housing developments, zoning districts points polygons lines raster data cellbased representation of. Correct connectivity and topology are extremely important for the accuracy of network analysis results. Both vector and raster data can model discrete and continuous. Click on download directory, along the left side of the window. Overlay analysis in gis gathering information from multiple data layers vector data coordinatebased data structures commonly used to represent map objects. 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.
Understanding of vector data models as used in gis. A gis provides functionality to capture, store, query, analyze, display and output geographic information. The major differences between raster and vector modeling are dependent on the nature of the data models themselves. All gfw data is in the projection wgs84, which is a global projection that is good for displaying global webbased data. The raster data model, along with the vector data model.
Not only that, network analysis and proximity operations use. In chapter 6 data characteristics and visualization, we discussed different ways to query, classify, and summarize information in attribute tables. Raster analysis is similar in many ways to vector analysis. There are many feature classes included in each download up to 30, so please read the document below carefully. Topics in vector analysis gis and geocomputation for. Topology rules can help data integrity with vector data models. For more technical information, downloads, and developer scripts, please visit. Introduction to geography, gis, spatial data and use of gis in health. In this presentation, we will introduce types of geographic data in order to define them and differentiate between them. A vector data model uses points with their associated x and y coordinates to. There are many different analysisrelated functions in gis, so we wont go through them all. Vectorbased spatial analyses of discrete spatial data is one of the most power forms of geographic analysis. Within a gis, the uses of raster data fall under four main categories. Introduction to gis workbook university of maryland.
Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. Overview of different types of gis software tools and data. Geographic information system is a system intends to capture, store, manage, manipulate, analyze the data. A feature is anything you can see on the landscape such. The chapter discusses methods to calculate area, perimeter, length, and shapes of relevant geometric objects. By and large, all the key cultural and physical vector gis datasets are at a global scale conveniently for you to use. Map algebra map algebra is the analysis language for arcgis spatial analyst. Projections determine how 3d data are adjusted to a 2d map. Waternet is a gishydrologic application for the integration and analysis of stream and sub. The topographic maps and geographical information system gis data provided in the national map are pregenerated into downloadable products often available in multiple formats. Vector data provide a way to represent real world features within the gis environment. In that restricted area, the attribute table will have all of the information from both.
And as we know visuals are more powerful than words so it makes our understanding of data fast. For this seminar we will be using arcgis desktop 10. Creating vector data in arcgis in this workshop, you will learn how to derive vector features from a raster dataset. Topology can also be a factor for some vector data analyses such as buffering and overlay. Creating vector data in arcgis digital scholarship. Most gis software applications mainly focus on the usage and manipulation of vector geodatabases with added components. Pois or aois are usually vector data whereas background thematic datasets are often raster data.
However, when running an analysis that requires accurate distance measures, the data must be reprojected. Vector data represent geographic space that is intuitive and reminiscent of analog maps. Maps and gis data are available for digital download. This section explains how to download and unzip the data for use in the gis and qgis practical sessions. Introdution a geographic information system gis is a system designed to capture, store, manipulate, analyze, manage, and present all types of. Because vector data have vertices and paths, this means that the graphical output is generally more aestheticallypleasing. Lecture 1 intro to gis and gis vector and raster data models. Lakes would typically be stored in a polygon poly vector gis file, called, e.
Gis data modellinglessons from the analysis of dtms. Vector data structures the method of representing geographic features by the basic graphical elements of points, lines and polygon is said to be the vector method, or vector data model vector data represent geographic space that is intuitive and reminiscent of analog maps. 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. One of the most important topic in gisgeographic information system, which is types of data.
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