In contrast to the raster data model is the vector data model. Discuss components of spatial data explain differences between the raster and vector spatial data models present common types of spatial data you may encounter and use introduce you to arccatalogas a means of organizing and managing your spatial data discuss best practices regarding the organization of spatial data, as. 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. These features are the basic features in a vector based gis, such as arcgis 9. Allows for efficient encoding of topology, and as a result more efficient operations that require topological information, e. Objects are represented as point, line, and polygon features with well. It is unnecessary to store the coordinates of each cell as the. 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. The raster format is more or less required for efficient manipulation and enhancement of digital images.
We will talk about it in detail in the next paragraphs. 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. Every house, every tree, every city has its own unique latitude and longitude coordinates. Sep 03, 2016 raster data model and comparisons with vector. Within the spatial referenced data group, the gis data can be further classified into two different types. 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. Historically, it has generally been accepted that raster calculations were faster, while vector methods gave higher accuracy kennedy and meyers, 1977. Vector data can be used for spatial analysis in a gis application, for example to find the nearest hospital to a school. Two common data models used to represent geographic data are the vector data model and the raster data model.
Jun 06, 2017 data models in geographical information systemgis 1. 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. 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. Pdf spatial data can be manipulated in different formats and patterns. 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. Instead, vector graphics are comprised of vertices and paths. In this model, space is not quantized into discrete grid cells like the raster model. It is often difficult to compare or rate gis software that use different data models. Each grid cell is filled with the measured attribute values. The gis spatial data model university of washington. 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. Whats the difference between gis spatial data types. There are two types of data models namely, vector and raster data models.
In vector data, the basic units of spatial information are points, lines and polygons. Case of multiple landuse in one cell raster and vector data models raster. Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. Apr 15, 2016 since most input data is in vector form, data must undergo vector to raster conversion. In raster data this delineation is defined by an arbitrary grid that is independent of the phenomena it is attempting to map. Features in a layer have the the same geometry type e. Besides increased processing requirements this may introduce data integrity concerns due to generalization and choice of inappropriate cell size. This value can be interpreted to mean several different things. Digitising is the process of creating digital vector data by drawing it in a gis application.
Introduction to gis basics, data, analysis case studies. What is the difference between raster and vector data. A comparison of vector and raster gis methods for calculating. Unlike vector data models, which show geographic data through points, lines, or polygons, raster data is displays one value in each cell. Jun 06, 2017 difference between vector and raster data model vector data model. The raster data model is widely used by nongis technologies such as digital cameraspictures and lcd monitors. Tin is a vector model that can represent continuous surfaces as a series of linked triangles. Raster data are derived from a gridbased system of contiguous cells containing specific attribute information. Overlay operations are easily and efficiently implemented. Data models are a set of rules and or constructs used to describe and represent aspects of the real world in a computer. Spatial analysis ii raster models march 11, 2020 based on materials by michael flaxman, joseph ferreira, thomas h. High spatial variability is efficiently represented in raster format. Difference between vector and raster data model vector data model.
Data models in geographical information systemgis 1. The figure represents vector left versus raster right data. Vector data can have quality issues such as undershoots, overshoots and slivers which you need to be aware of. A vector data model also known as discrete object model prepares data in two basic steps so that computer can process the data. Raster to vector conversion user guide convert rasterscanned pdfs to editable drawings how to identify the vector pdf and raster pdf. The main difference between raster and vector data is that the raster data represents data as a cell or a grid matrix while vector data represents data using sequential points or vertices geographic information system gis is a computerbased tool or technology to manage, analyze and display geographically referenced information. Each layer of grid cells in a raster model records a separate attribute. Resolution depends on real world area represented by each grid cell. In vector data, the basic units of spatial information are points, lines arcs and polygons. First, it uses points and their x,ycoordinates to represent discrete spatial features such as points, lines, and polygons over an empty space.
However, there are many other features such as points and measurements such as rainfall that could be stored as either a raster or a feature vector data type. In rastor, the area under consideration is divided into equal squares and a characteristic assigned to it. In general, the vector data model is used to represent the former and the raster data model to represent the latter. These features are the basic features in a vectorbased gis, such as arcgis 9. But what is the difference between raster and vector data. Generating pdfs best method raster vs vector vs sometihng else. 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. In this unit, we will discuss the basic concepts of raster and vector data models in gis. The raster data model, along with the vector data model, is one of the earliest and most.
Pdf the raster data model is a widely used method of storing geographic data. The spatial resolution of a raster dataset represents a measure of the accuracy or detail of the displayed information. Vector pdf uses math to draw shapes using points, lines and curves. Only print setting that was adjusted was switching to raster from vector. The three basic symbol types for vector data are points, lines and polygons areas. Raster model spatial data of different types can be overlaid without the need for the complex geometric calculations. So how do we make raster and vector clear seems important. Demers 1 the nature of geographic data most features or phenomena occur as either. In vector data the lines on the map are determined by a particular phenomena.
A database management system is a collection of software for storing, editing and retrieving data in. Download pdf and see representing fields in chapter 2. Instead, vector graphics are comprised of vertices. Data models are a set of rules andor constructs used to describe and represent aspects of the real world in a computer. What is the difference between vector and raster data. Typically electrically created pdf originally from cad program, or publishedconverted from cad drawing files. The cells pixels, picture elements are constant in size and are generally square.
One show the print with vector, one with raster and a screen shot. Sometimes you dont have the choice of storing your data as a raster. What is the difference between raster pdf file and vector pdf. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. Lecture 1 intro to gis and gis vector and raster data models. In order to visualize natural phenomena, one must first determine how to best represent geographic space. The vector data model is based on the assumption that the earths surface is composed of discrete objects such as trees, rivers, lakes, etc. What are raster and vector data in gis and when to use.
The vector model uses points and line segments to identify locations on the earth. Vector models are useful for storing data that has discrete boundaries. 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. Mrr is a completely new raster data format that reimagines how raster data is stored and what data can be stored as a raster. Vector vs raster data models there are two spatial models for storing geographic data the vector data model and the raster data model. One of the strengths of the vector data model is that it can be used to render geographic features with great precision. For example, the vector data model represents geography as collections of points, lines, and polygons.
Vector data model represents phenomena in terms of the spatial primitives, or components, consisting of point, line, polygon, surfaces and volumes. Raster data models present information through a grid of cells raster grids are usually made up of square or rectangular cells. Since most input data is in vector form, data must undergo vectortoraster conversion. Satellite imagery remotely sensed satellite data are recorded in raster format. 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. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. However, the lines od separation are sometimes crossed. Each of these models has its own advantages and disadvantages. If the area is 100 km x 100 km and cell size is 10 m. As well, a typical gis process involves moving backandforth between the two models. A surface can also be represented as a tin triangulated irregular network. Mar 01, 2019 the main difference between raster and vector data is that the raster data represents data as a cell or a grid matrix while vector data represents data using sequential points or vertices. The following diagram reflects the two primary spatial data encoding techniques.
If one byte is used per pixel, it requires 100 mb storage ags 722 types of raster data 1. Find out more on the spatial data models commonly used. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. It is better to think of raster data as a special type of vector data. Accurate geographic location of data is maintained. Image data utilizes techniques very similar to raster data, however typically lacks the internal formats required for analysis and modeling of the data. Raster data models and comparisons with vector youtube. It unifies the storage of multiple raster data types, including satellite imagery, gridded data e. 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.
The basic spatial data model is known as arcnode topology. 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. Geographic information system gis is a computerbased tool or technology to manage, analyze and display geographically referenced information. What is the difference between raster pdf file and vector. Most gis applications group vector features into layers.
Images reflect pictures or photographs of the landscape. What is the difference between vector and raster data models. Vector and raster data models university of maryland. The old gis adage raster is faster, but vector is corrector comes from the two different fundamental gis models. A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data.
A database is a collection of interrelated data and everything that is needed to maintain and use it. There are many analysis that make use of both data models i. Two primary data models are available to complete this task. When it comes to the difference between raster pdf file and vector pdf file,we may easily know the point is the difference between raster and vector.
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. It needs 10,000 rows x 10,000 columns or 100,000,000 pixels. Download pdf and see representing fields in chapter 2, section 2. Discuss components of spatial data centers for disease. 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. Comparison of raster and vector data models raster model advantage.