Comparison of Vector and Raster Based Data Analysis (Especially for GATE-Geospatial 2022)

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Vector

In a GIS, geographical features are often expressed as vector, by considering those features as geometrical shapes.

Image Shows Vector Data Model

Raster

A raster data types is any type of digital image. Anyone who is familiar with digital photography will recognize the pixel as the smallest individual unit of an image.

Image Shows Raster Data Model

Comparison of Vector and Raster Operations

Figure Shows Comparison of Vector and Raster Data Analysis

Vector data analysis and raster data analysis represent the two basic types of GIS analyses. They are treated separately because a GIS package cannot run them together in the same operation. Although some GIS packages allow the use of vector data in some raster data operations, the data are converted into raster data before the operation starts.

The general guideline is to choose the type of data analysis that is efficient and appropriate for a project. Each GIS project is different in terms of data sources and objectives. We must therefore choose the type of data analysis that is efficient and appropriate. In the following, overlay and buffering, the two most common operations in GIS, are used as examples to compare vector- and raster-based operations.

Overlay

A local operation with multiple rasters is often compared to a vector-based overlay operation. The two operations are similar in that they both use multiple data sets as inputs. But important differences exist between them.

First, to combine the geometries and attributes from the input layers, a vector-based overlay operation must compute intersections between features and insert points at the intersections. This type of computation is not necessary for a raster-based local operation because the input rasters have the same cell size and area extent.

Buffering

A vector-based buffering operation and a raster-based physical distance measure operation are similar in that they both measure distance from select features. But they differ in at least two aspects. First, a buffering operation uses x- and y- coordinates in measuring distance, whereas a raster-based operation uses cells in measuring physical distances. A buffering operation can therefore create more accurate buffer zones than a raster-based operation can. Second, a buffering operation is more flexible and offers more options. For example, a buffering operation can create multiple rings, whereas a raster-based operation creates continuous distance measures.

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