Simplifying slightly, a digital photograph is an example of a raster. Pdf spatial data can be manipulated in different formats and patterns. Data types the data model represents a set of guidelines to convert the real world called entity to the digitally and logically represented spatial objects consisting of the attributes and geometry. In gis, vector and raster are two different ways of representing spatial data. Digitising is the process of creating digital vector data by drawing it in a gis application. Gis data represents realworld objects such as roads, land use, elevation with digital data. Both vector and raster data can model discrete and continuous data, but vector data be er for discrete data raster data be er for con nuous data decision also depends on the scale or resolution of data, analysis workflow, and tools available. Vector data models for gis vector model boundaries of spatial features our focus so far vector feature types. Raster data models and comparisons with vector youtube.
These are vector data model and raster data models. Images reflect pictures or photographs of the landscape. Spatial analysis ii raster models march 11, 2020 based on materials by michael flaxman, joseph ferreira, thomas h. Vector model vector maps are point, segment, or polygon maps. There are two essential methods used to store information in a geographic information system gis for both reflections.
But what is the difference between raster and vector data. Vector and raster data difference between raster and. A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data. In contrast to the raster data model is the vector data model.
We do this by representing things with data and we have tools for transforming data and for exploring associations the way things that may be represented in different datasets may be related to each other. Gis at scholarly commons provide gis research services and consultation provide gis workshops and training manage the university library s geospatial data and gis software resources act as a central resource for the universitys gis community and promote the use of gis in research 3. One of the strengths of the vector data model is that it can be used to render geographic features with great precision. Vector data is focused on modeling discrete features with precise shapes and boundaries. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. The first is vector relational databases, and the second are raster models. Vector data structure can be grouped into four classes namely. Data models are a set of rules andor constructs used to describe and represent aspects of the real world in a computer. In the following, we assume that a multiresolution terrain model is used as georeference surface. Each raster, or pixel, on the mahomet sand surface has a set of map coordinates that are recorded in a gis in the data model bin that is labeled pixel coordinates, which is the raster corollary of the geometry bin for vector map data. A data model in gis is a mathematical construct for representing geographic objects or surfaces as data. It is one of the two main types of gis data models, the other being the raster data model. Data models for gis gis and geocomputation for water.
Raster data is made up of pixels or cells, and each pixel has an associated value. Spatial data introduction it uses points and their x,ycoordinates to geographical. Spatial databases and gis karl neumann, sarah tauscher ifis tu. In this post we are looking forward to see the list of vector data file formats in gis. Introduction to geographic information systems 19,552 views. For example, you can process data through a geoprocessing model to create a raster dataset that maps suitability for a specific activity. Gis refers to those spatial information systems that are used for processing and analyzing geospatial data. The gis spatial data model university of washington.
Gisbased measurements that combine native raster and native vector data are commonly used in environmental assessments. Download pdf and see representing fields in chapter 2, section 2. A comparison of vector and raster gis methods for calculating. Vector data can be used for spatial analysis in a gis application, for example to find the nearest hospital to a school. In some gis packages, the dbms is based in an existing software, i. Spatial analysis ii raster models 26 october 2005 joseph ferreira raster vs. The data base concept is central to a gis and is the main difference between a gis and drafting or computer mapping systems, which can produce only good graphic output. In this unit, we will discuss the basic concepts of raster and vector data models in gis. 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. Raster data models present information through a grid of cells. There are many types of vector formats used in gis, and even more raster formats. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. The basic spatial data model is known as arcnode topology. One of the most important formats is vector data model which holds.
Give two examples when it would be best to use raster data. Vector storage implies the use of vectors directional. The basic framework of the model is to describe each needed feature by its geometry location and shape and attributes also known as properties or characteristics. Vector maps require less disk storage space and are suitable for creating high quality outputs. Raster comparison geometric representation structured vs. Oct 19, 2015 both vector and raster data can be further classified based on the data content.
A later section of the chapter provides a more extended discussion of data model. Difference between vector and raster data model vector data model. They are less suitable for a number of gis operations, especially those dealing with map overlaying. Image data utilizes techniques very similar to raster data, however typically lacks the internal formats required for analysis and modeling of the data. Vector data models for gis up to now vector data models. Jun 06, 2017 conclusion geographic information system is a computer system for capturing, storing, checking, and displaying data related to positions on earths surface. Vector model vector model uses discrete points, lines andor areas corresponding to. Jun 06, 2017 difference between vector and raster data model vector data model. Sep 03, 2016 raster data model and comparisons with vector. Vector data models use points and their associated x, y coordinate pairs to represent the.
These features are the basic features in a vector based gis, such as arcgis 9. The raster data model is a widely used method of storing geographic data. Below is an example of a classified raster dataset showing land use. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. In gis, we require some data formats to express the geographical features, which mainly are of two types raster and vector data formats. However, the distinction between vector and raster data types is not unique to gis. It is less compact therefore data compression techniques can.
This value can be interpreted to mean several different things. Thematic maps can also result from geoprocessing operations that combine data from various sources, such as vector, raster, and terrain data. These data sources also has multiple file formats in them which are often used to express the geographical features. Both vector and raster data can be further classified based on the data content. Nov 26, 2017 there are two essential methods used to store information in a geographic information system gis for both reflections. The third lecture spatial data models will teach learners how to represent spatial reality in two spatial data models vector model and raster model. Vector model in a vector model the position of each spatial.
The gis data model represents a set of guidelines to convert the real world to the digitally and logically represented spatial objects consisting of the attributes and geometry. Mapping vector data to 3d requires 3d surfaces having the role of a georeference surface. In vector data, the basic units of spatial information are points, lines arcs and polygons. The raster data model, along with the vector data model, is one of the earliest and most wide ly used data models within geographic information systems tomlin, 1990. Vector data models structures vector data models can be structured many different ways. Aug 16, 2017 this tutorial is about vector and raster data in gis that how to understand the difference between vector and raster data structures. Raster grids are usually made up of square or rectangular cells. What is the difference between vector and raster data.
Gis based measurements that combine native raster and native vector data are commonly used in environmental assessments. The old gis adage raster is faster but vector is corrector comes from the two different fundamental gis models. Vector data can have quality issues such as undershoots, overshoots and slivers which you need to be aware of. The vector data model is based on the assumption that the earths surface is composed of discrete objects such as trees, rivers, lagoons, etc. The two basic data models of gis are raster and vector. Scribd is the worlds largest social reading and publishing site. When should we use raster and when should we use vector. One of the strengths of the vector data model is that it can be used to. Conclusion geographic information system is a computer system for capturing, storing, checking, and displaying data related to positions on earths surface. Rooted in the science of geography, gis integrates many types of data.
There are two types of data models namely, vector and raster data models. Vector data model attributes in gis vector files attributes are, in a simple form, stored in tables databases. Unstructured data topological data models from map to data store networks example polygon models topology in commercial gis example algorithms. Representation of the real world and showing differences in how a vector and a raster gis will represent. Spatial data can represent vector and raster data models realworld features that have discrete boundaries such as roads, buildings, lakes, rivers, administrative. A table consists of records rows representing individual features, fields columns representing a particular theme attribute describing the feature, and values an intersection between a record and a field. Complex data structures means that phenomenonologically recognizable combination of several vector polygon maps through overlay creates difficulties simulation is difficult because each unit has a different topological form display and plotting can be expensive, particularly for. Most of these measurements can be calculated using either raster or vector data formats and processing methods. It analyzes spatial location and organizes layers of information into visualizations using maps and 3d scenes.
In this model, space is not quantized into discrete grid cells like the raster model. Vector data can be used for spatial analysis in a gis application, for example to. Simple features, topological features, network data model tin data model, georelational data model and objectbased data model in which each has its spatial application. Two primary data models are available to complete this task. The objective of this section is to understand how vector data models are implemented in gis applications. Almost without exception, all gis users apply integrated raster layers as a fundamental data source in their gis. Vector data model represents phenomena in terms of the spatial primitives, or components, consisting of point, line, polygon, surfaces and volumes. The elements in a vector based gis are then the dbms data base management system for the attributes and the system that manages the topological data. All contemporary geographic information system incorporates a data base management system. Data are entered into a gis from various sources and using various methods. Most of the maps are obtained by digitizing or by importing them. Comparison of raster and vector data models raster model disadvantage. The model most commonly takes the form of a gridlike structure that holds values at regularly spaced intervals over the extent of the raster. Vector spatial data models and structures fundamental concepts of vectors.
The fourth lecture spatial data acquisition systems will cover topics on how and where to acquire spatial data and how to produce your own spatial data. Unlike vector data models, which show geographic data through points, lines, or polygons, raster data is displays one value in each cell. In order to visualize natural phenomena, one must first determine how to best represent geographic space. This tutorial is about vector and raster data in gis that how to understand the difference between vector and raster data structures. Gis and modeling overview the term modeling is used in several different contexts in the world of gis, so it would be wise to start with an effort to clarify its meaning, at least in the context of this book. Vector data models will be described in the next section, including commonly found variants. There are two major types of geometric data model a. What is the difference between vector and raster data models. 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. Lecture 1 intro to gis and gis vector and raster data models. True vector gis data formats are dlg and tiger, which has topology. Computers and gis cannot directly be applied to the real world. Vector data models use points and their associated x, y.
Hope you will find this tutorial best for learning. These features are the basic features in a vectorbased gis, such as arcgis 9. There are two major types of data model used in gis applications. The two primary types of spatial data are vector and raster data in gis. In vector data, the basic units of spatial information are points, lines and polygons. 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. Spatial data models geographic information system gis. 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 realworld phenomenafeatures that have nondiscrete boundaries such as precipitation and nutrient levels, terrain. It is fairly easy to exchange information from within these raster formats. Vector product format vpf is a standard format for a large geographic database based on georelational data models.
Rasters are especially well suited for storing continuous data such as temperature and elevation values. The vector data model is a strategy for describing distinct features in a gis. Each of these models has its own advantages and disadvantages. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. Raster processes are more commonly used because they can. It is often necessary to change between file formats, even if they are both raster, or both vector, to make data sets useable together. In essence, gis data models allow the user to create a representation of how the world looks. A geographic information system gis is a framework for gathering, managing, and analyzing data. Digital computers operate in numbers and characters held internally as binary digits. Divides space into discrete features, usually points, lines or polygons. Two data models commonly used to represent spatial data in gis are the raster and vector data models within the vector data model, a representation of the world is created using lines, points, and polygons. Introduction to gis basics, data, analysis case studies. Raster data models present information through a grid of cells raster grids are usually made up of square or rectangular cells. For example, the vector data model represents geography as collections of points, lines, and polygons. Discuss components of spatial data centers for disease. In many cases, users only think of the raster data as a static snapshot of information that builds compressed static catalogs of their imagery.