When should we use raster and when should we use vector. 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. Typically electrically created pdf originally from cad program, or publishedconverted from cad drawing files. Data model overview a data model is a set of constructs for representing objects and processes in the digital environment of the computer decisions about the type of data. What is the difference between vector and raster data.
Raster data model each grid cell in a raster data layer is one unit the minimum amount of information in the raster data model every cell has a value, even if it is a special value to indicate that there is no data or that data is missing at that location the values are numbers, either. 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. We will examine two of the more common data structures here vector data model. Whereas, vector data is a type of spatial data used for storing data that has discrete boundaries. They are more common in general such as jpg, gif, png, and are widely used on the web. One of the strengths of the vector data model is that it can be used to render geographic features with great precision. A comparison of vector and raster gis methods for calculating.
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. Instead, vector graphics are comprised of vertices and paths. Issues of data storage and retrieval are important. 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. It is one of the two main types of gis data models, the other being the raster data model. The basic spatial data model is known as arcnode topology. The mahomet sand is continuous in this area, and represents one occurrence of this unit in the data model. Raster grids are usually made up of square or rectangular cells. However, the lines od separation are sometimes crossed. Vector and raster data models university of maryland. A vector data model uses points with their associated x and y coordinates to construct. Thus, this is the main difference between raster and vector data. Pdf spatial data can be manipulated in different formats and patterns. Inaccurate vector data can occur when the instruments used to capture the data are not properly set up, when the people capturing the data arent being careful, when time or money dont allow for enough detail in the collection process, and so on.
Vector data also needs a lot of work and maintenance to ensure that it is accurate and reliable. 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. Vector representation vector representation of data in the vector based model figure 4, geospatial data is represented in the form of coordinates. Raster data models incorporate the use of a gridcell data structure where the geographic area is divided into cells identified by row and column. Raster data models have been updated mainly for data structure and data compression. Vector data is focused on modeling discrete features with precise shapes and boundaries. An emap that is based on raster tiles is inferior to vector tiles in. All topological data models have not been implemented in gis probably. 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. Using morton code to mark geographic information enables storage of data make full use of. In vector data, the basic units of spatial information are points, lines arcs and polygons.
Digital elevation models and different types of resolutions duration. Tiled vector data model for the geographical features of symbolized. These features are the basic features in a vector based gis, such as arcgis 9. While the term raster implies a regularly spaced grid other tessellated data structures do exist in grid based gis systems. In this model, space is not quantized into discrete grid cells like the raster model. Raster data are derived from a gridbased system of contiguous cells containing specific attribute information. In contrast to the raster data model is the vector data model. The spatial resolution of a raster dataset represents a measure of the accuracy or detail of the displayed information.
Raster data is a type of spatial data that consists of a matrix of cells organized into rows and columns in which each cell represents specific information. Generating pdf s best method raster vs vector vs sometihng else im still tyring to figure out what this is still an issue. For many people this question could be rephrased as whats the difference between adobe photoshop and illustrator. If the area is 100 km x 100 km and cell size is 10 m. In general, the vector data model is used to represent the former and the raster data model to represent the latter. Raster data models are used to represent a wide variety of phenomena, including continuous data like surface temperature or elevation. The raster data model jackson school of geosciences. Apr, 2016 a short and sweet description of the two data models and how they handle object versus discrete phenomena. Images reflect pictures or photographs of the landscape.
Historically, it has generally been accepted that raster calculations were faster, while vector methods gave higher accuracy kennedy and meyers, 1977. Raster data tend to require large amount of computer memory. The vector data model is a strategy for describing distinct features in a gis. Vector data models structures vector data models can be structured many different ways. Within the spatial referenced data group, the gis data can be further classified into two different types. Introduction to gis and spatial data vector and raster comparison vector raster compact data structure for homogenous areas. Raster data models present information through a grid of cells. A comparison of raster and vector data models developments in gis are now at a stage where all sophisticated gis packages are able to handle both raster and vector processing and it likely that the vast majority of data inputs in the future will be in raster format. Demers 1 the nature of geographic data most features or phenomena occur as either. Different types of vector data and concept of topology nptel. Raster twister model builder demo and data raster twister tools toolbox. A short and sweet description of the two data models and how they handle object versus discrete phenomena. In vector data, the basic units of spatial information are points, lines and polygons.
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. What is the difference between raster and vector 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 advantages and disadvantages of each data structure are shown here below. The following diagram reflects the two primary spatial data encoding techniques. This paper proposes a tiled vector data model for geographical. Id like to be able to print all of my sheets with one method. How to learn the difference between a vector and a raster image. Raster images are created with pixelbased programs or captured with a camera or scanner. 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. A raster is an array of cells, where each cell has a value representing a specific portion of an object or a feature. 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. What is the difference between vector and raster data models.
The raster data model, along with the vector data model, is one of the. Raster data models and comparisons with vector youtube. 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. As well, a typical gis process involves moving backandforth between the two models. It needs 10,000 rows x 10,000 columns or 100,000,000 pixels. The loss of map features from mark 1 and mark 3 is obvious, and. Vector representation of data in the vector based model, geospatial data is represented in the form of coordinates. Unlike vector data models, which show geographic data through points, lines, or polygons, raster data is displays one value in each cell. Raster data models 92016 geo327g386g, ut austin 3 92016 geo327g386g, ut austin9 30 m vs. Raster to vector conversion user guide convert rasterscanned pdfs to editable drawings how to identify the vector pdf and raster pdf. 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. The raster data model is widely used by nongis technologies such as digital cameraspictures and lcd monitors. Find out more on the spatial data models commonly used. There are many analysis that make use of both data models i.
Rasters are especially well suited for storing continuous data such as temperature and elevation values. This value can be interpreted to mean several different things. The raster data model is a widely used method of storing geographic data. Raster models are useful for storing data that varies continuously, as in an aerial photograph, a satellite image, a surface of chemical concentrations. Lecture 1 intro to gis and gis vector and raster data models. The three basic symbol types for vector data are points, lines and polygons areas. Pdf the raster data model is a widely used method of storing geographic data. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. One of the most important formats is vector data model which holds. Arcgis displays raster and vector data simultaneously and can convert one to the other. Discuss components of spatial data centers for disease. Sep 03, 2016 raster data model and comparisons with vector.
A raster dataset is the same type of image that is produced when recording an image with a digital camera. Tools for both raster and vector analysis will be examined in this module. If one byte is used per pixel, it requires 100 mb storage ags 722 types of raster data 1. The two primary types of spatial data are vector and raster data in gis. 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 and raster spatial data models are the based format for. Image data utilizes techniques very similar to raster data, however typically lacks the internal formats required for analysis and modeling of the data. Vector pdf uses math to draw shapes using points, lines and curves. Divides space into discrete features, usually points, lines or polygons. But what is the difference between raster and vector data. Satellite imagery remotely sensed satellite data are recorded in raster format. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The model most commonly takes the form of a gridlike structure that holds values at regularly spaced intervals over the extent of the raster.
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