When should we use raster and when should we use vector. Images reflect pictures or photographs of the landscape. Within the spatial referenced data group, the gis data can be further classified into two different types. Spatial data are of two types according to the storing technique, namely, raster data and vector data. There are several advantages and disadvantages for using either the vector or raster data model to store spatial 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 spatial resolution of a raster dataset represents a measure of the accuracy or detail of the displayed information. What is the difference between vector and raster data. While the structure of raster data is simple, it is exceptionally useful for a wide range of applications. In gis, vector and raster are two different ways of representing spatial data. Vector data models for gis up to now vector data models model boundaries of spatial features vector feature types. Spatial data comprise the relative geographic information about the earth and its features. 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. 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.
The process of defining and organizing data about the. The spatial resolution the smallest distance between two adjacent features that can be detected in an image. Besides increased processing requirements this may introduce data integrity concerns due to generalization and choice of inappropriate cell size. 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. And vector model will be investigated in more detail. Vector data can have quality issues such as undershoots, overshoots and slivers which you need to be aware of. As well as employing the raster and vector spatial data models1 we are required to provide the computer with further information to reconstruct these models in digital format. In this unit, we will discuss the basic concepts of raster and vector data models in gis. The content of the lecture are the following, comparison of object view and field view, and related vector model and raster model will be discussed.
A common use of raster data in a gis is as a background display for other feature layers. In this model, space is not quantized into discrete grid cells like the raster model. Spatial data models representation of data vector point, line, polygon raster cells or pixels triangulated irregular network tin source. Within a gis, the uses of raster data fall under four main categories. 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. Vector data can be used for spatial analysis in a gis application, for example to find the nearest hospital to a school. Built from at least two points at the ends of the line. Vector data, in contrast, consist of arcs, nodes, and polygons.
However, the distinction between vector and raster data types is not unique to gis. Apr 15, 2016 since most input data is in vector form, data must undergo vector to raster conversion. In vector data, the basic units of spatial information are points, lines and polygons. 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. Maidment, introduction to spatial hydrology esri campus. What are raster and vector data in gis and when to use. What is the difference between vector and raster data models. Vector and raster data models university of maryland. 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 is made up of pixels or cells, and each pixel has an associated value. 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. A gis can facilitate the organization, analysis, and mapping of landuse and landcover data.
Vector data models for gis vector model boundaries of spatial features our focus so far vector feature types. Spatial data models geographic information system gis. Find out more on the spatial data models commonly used. There are two broad categories of spatial data models. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. Digitising is the process of creating digital vector data by drawing it in a gis application. The gis spatial data model university of washington. It is often difficult to compare or rate gis software that use different data models.
Raster data are derived from a gridbased system of contiguous cells containing specific attribute information. Vector data models will be described in the next section, including commonly found variants. Jun 06, 2017 spatial data models the traditionally spatial data are stored in the form of digital databases and presented them in the form of maps. There are many analysis that make use of both data models i. Vector data model represents phenomena in terms of the spatial primitives, or components, consisting of point, line, polygon, surfaces and volumes. The raster data model is widely used by nongis technologies such as digital cameraspictures and lcd monitors. Mapping, and spatial analysis, youll learn about what a gis is, how to get started with the software yourself, how things we find.
The two primary types of spatial data are vector and raster data in gis. 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. The components of the model are spatial objects, approximating spatial entities of the real world. 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.
These are vector data model and raster data models. Mrr removes the barriers to working with large and complex raster files, and enables the highest quality visualization and processing of raster data at any scale and for rasters of any size. A map is a symbolic model, because it is a simplified representation of part of the real world. Spatial data models and structures semantic scholar. Instead, vector graphics are comprised of vertices. Raster data are gridcell surfaces comprised of hundreds, thousands, or, with large data sets, millions of cells.
Lecture 1 intro to gis and gis vector and raster data models. Sep 03, 2016 raster data model and comparisons with vector. But what is the difference between raster and vector data. Spatial analysis ii raster models 26 october 2005 joseph ferreira raster vs.
These features are the basic features in a vector based gis, such as arcgis 9. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. There are a great number of spatial data structures, specific to either the raster or vector spatial data models, used by commercial gis. There are two types of data models namely, vector and raster data models. Raster data processing is efficient in neighbourhood query, filtering, overlay operations for combining two or more images. Two basic types of spatial data models have been evolved for storing geographic data digitally. 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.
Data can be represented at its original resolution and form without generalization. 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. 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. In contrast to the raster data model is the vector data model. It unifies the storage of multiple raster data types, including satellite imagery, gridded data e. Raster data are composed of grid cells identified by row and column. Simplifying slightly, a digital photograph is an example of a raster. It is one of the two main types of gis data models, the other being the raster data model.
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 vector data model is a strategy for describing distinct features in a gis. A pair of latitude and longitude coordinates defines a specific location on earth. Gis refers to those spatial information systems that are used for processing and analyzing geospatial data. Jun 06, 2017 data models in geographical information systemgis 1. In rastor, the area under consideration is divided into equal squares and a characteristic assigned to it. Vector model in a vector model the position of each spatial feature is defined by a series of x and y coordinates.
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