Raster And Vector Data In Gis Pdf
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- What is Spatial Data?
- Vector vs Raster: What’s the Difference Between GIS Spatial Data Types?
- Types of GIS Data Explored: Vector and Raster
When we come to depict any spatial data in GIS, from physical assets and locations to real-world events and trends, there are two differing systems to display data; Raster and Vector representations. Both of these methods present data in their own format, with their own advantages and disadvantages. Vector data is what most people think of when they consider spatial data. Data in this format consists of points, lines or polygons. At its simplest level, vector data comprises of individual points stored as coordinate pairs that indicate a physical location in the world.
What is Spatial Data?
It only takes a minute to sign up. In general terms what applications, processes, or analysis are each suited for? Does anyone have some small, concise, effective pictures which convey and contrast these two fundamental data representations? Advantages : Data can be represented at its original resolution and form without generalization. Graphic output is usually more aesthetically pleasing traditional cartographic representation ; Since most data, e. Accurate geographic location of data is maintained.
In its simplest form, a raster consists of a matrix of cells or pixels organized into rows and columns or a grid where each cell contains a value representing information, such as temperature. Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps. Data stored in a raster format represents real-world phenomena:. Thematic and continuous rasters may be displayed as data layers along with other geographic data on your map but are often used as the source data for spatial analysis with the ArcGIS Spatial Analyst extension. Picture rasters are often used as attributes in tables—they can be displayed with your geographic data and are used to convey additional information about map features. Learn more about thematic and continuous data.
Raster and vector are two very different but common data formats used to store geospatial data. Vector data use X and Y coordinates to define the locations of points, lines, and areas polygons that correspond to map features such as fire hydrants, trails, and parcels. As such, vector data tend to define centers and edges of features. Raster data, on the other hand, use a matrix of square areas to define where features are located. These squares, also called pixels, cells, and grids, typically are of uniform size, and their size determines the detail that can be maintained in the dataset. Because raster data represent square areas, they describe interiors rather than boundaries as is the case with vector data. Vector data are excellent for capturing and storing spatial details, while raster data are well suited for capturing, storing, and analyzing data such as elevation, temperature, soil pH, etc.
Vector vs Raster: What’s the Difference Between GIS Spatial Data Types?
Vector data is comprised of lines or arcs, defined by beginning and end points, which meet at nodes. The locations of these nodes and the topological structure are usually stored explicitly. Features are defined by their boundaries only and curved lines are represented as a series of connecting arcs. Vector storage involves the storage of explicit topology, which raises overheads, however it only stores those points which define a feature and all space outside these features is 'non-existent'. A vector based GIS is defined by the vectorial representation of its geographic data. According with the characteristics of this data model, geographic objects are explicitly represented and, within the spatial characteristics, the thematic aspects are associated.
No matter what your interests are or what field you work in, spatial data is always being considered whether you know it or not. Spatial data can exist in a variety of formats and contains more than just location specific information. To properly understand and learn more about spatial data, there are a few key terms that will help you become more fluent in the language of spatial data. Vector data is best described as graphical representations of the real world. There are three main types of vector data: points, lines, and polygons. Connecting points create lines, and connecting lines that create an enclosed area create polygons.
Types of GIS Data Explored: Vector and Raster
A geodatabase is a database that is in some way referenced to locations on the earth. Coupled with this data is usually data known as attribute data. Attribute data generally defined as additional information, which can then be tied to spatial data. GIS data can be separated into two categories: spatially referenced data which is represented by vector and raster forms including imagery and attribute tables which is represented in tabular format. Within the spatial referenced data group, the GIS data can be further classified into two different types: vector and raster.
In the previous topics we have taken a closer look at vector data. While vector features use geometry points, polylines and polygons to represent the real world, raster data takes a different approach. In this topic we are going to take a closer look at raster data, when it is useful and when it makes more sense to use vector data.
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