Additionally, storage of rasters can be small due to the way it handles and stores its geographic location. The coordinates of each cell is inferred by its position within the grid network. The grid surface is ideally suited for presenting and storing continuous values. Due to the fact that raster surfaces represent one attribute or value, calculations, algorithms and quantitative processing can be very quick and simple to run. Raster data is more suited to mathematical modelling and analyses. Elevation can be depicted via spot heights, contour lines or polygon fills, but presented as a flowing surface, vector data can be mismatched. Ultimately, with more features or points of data, the lengthier any edits can be and the more complex processes and algorithms become. Continuous type data is not efficiently presented and stored in vector format. Dependant on size and number of features, the editing and processing of vector data, either as a topology, or other format, can be quite time-consuming. Topology representations can be useful in vector data, however it can often be processing intensive. Added to this, each point, or collections of points, can have associated data, which can add to vector storage and processing times.
Advantages of raster images series#
Due to the fact that vector data is stored as a series of points, each item needs to be stored and listed.
However the processing and storage of vector data can be intensive.
Data is stored without any loss or generalisation and accurate geolocation information is preserved.įigure 1: Highlighting the different way vector (left side) and raster (right side) represents data for point, line and areaĪdditionally, multiple attributes and data fields can be stored in vector features. Also it is more visually aesthetically pleasing. Vector data is considered to be a more traditional method for cartographic representation, it delivers a representation that is sharp, clean and scalable. In comparison between the two forms of data, there are particular advantages and disadvantages of use. In this vein, raster representation are more closely linked with representing physical properties or phenomena found on the globe. Raster datasets are useful in the storage a presentation of continuous data, such as weather events and climate projections, or elevation surfaces. But provide a geographical context and now we can position this correctly on a globe and then run analyses off the cell values which can be considered colour wavelength bands. At a simple level, satellite imagery can be considered a digital photograph of the surface of the globe, each cell indicates a particular colour. Satellite imagery provides a perfect context example of this image vs. The main point of difference between the digital photograph and the GIS representation is that in the GIS there is accompanying data detailing where the cells can be found on a globe and how big these cells can be. Here each cell, which in this instance is referred to as a pixel, corresponds to a particular colour value. When transferred into a GIS setting, the cells in a raster grid can potentially represent other data values, such as temperature, rainfall or elevation. In an alternate sense, we can consider a digital photograph as an example of a raster dataset.
Raster data provides a representation of the world as a surface divided up into a regular grid array, or cells, where each of these cells has an associated value. Ubiquitous online mapping portals, such as Google Maps and Open Street Maps, present data in this format. Vector data is extremely useful for storing and representing data that has discrete boundaries, such as borders or building footprints, streets and other transport links, and location points. These points can be joined, in a particular order, to form lines or joined into closed areas to form polygons. At its simplest level, vector data comprises of individual points stored as coordinate pairs that indicate a physical location in the world. Data in this format consists of points, lines or polygons. Vector data is what most people think of when they consider spatial data. Both of these methods present data in their own format, with their own advantages and disadvantages. 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.
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