Vector and raster data in gis pdf
File Name: vector and raster data in gis .zip
- What is the difference between raster and vector data?
- Vector vs Raster: What’s the Difference Between GIS Spatial Data Types?
- GIS Introduction by David J. Buckey
- GIS Data Formats and Data Conversion
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.
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.
What is the difference between raster and vector data?
There are two types of formats, those that preserve and use the actual ground coordinates of the data and those that use alternative page coordinate description of the map. Page Coordinates are used when a map is being drafted for display in a computer mapping program or in the data display module. In the late s, programs came out that were device independent. Each line of the file contains one move command, so a line segment connects two successive lines or points. It is unstructured and does not store or use topology.
A GIS file format is a standard of encoding geographical information into a computer file. A raster data type is, in essence, any type of digital image represented by reducible and enlargeable grids. Anyone who is familiar with digital photography will recognize the Raster graphics pixel as the smallest individual grid unit building block of an image, usually not readily identified as an artifact shape until an image is produced on a very large scale. A combination of the pixels making up an image color formation scheme will compose details of an image, as is distinct from the commonly used points, lines, and polygon area location symbols of scalable vector graphics as the basis of the vector model of area attribute rendering. While a digital image is concerned with its output blending together its grid based details as an identifiable representation of reality, in a photograph or art image transferred into a computer, the raster data type will reflect a digitized abstraction of reality dealt with by grid populating tones or objects, quantities, cojoined or open boundaries, and map relief schemas. Aerial photos are one commonly used form of raster data, with one primary purpose in mind: to display a detailed image on a map area, or for the purposes of rendering its identifiable objects by digitization.
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. A raster dataset is composed of rows running across and columns running down of pixels also know as cells. Each pixel represents a geographical region, and the value in that pixel represents some characteristic of that region. Raster data is used in a GIS application when we want to display information that is continuous across an area and cannot easily be divided into vector features. Point, polyline and polygon features work well for representing some features on this landscape, such as trees, roads and building footprints.
Vector vs Raster: What’s the Difference Between GIS Spatial Data Types?
In contrast to the raster data model is the vector data model. In this model, space is not quantized into discrete grid cells like the raster 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 Aronoff, S. The data attributes of these features are then stored in a separate database management system. The spatial information and the attribute information for these models are linked via a simple identification number that is given to each feature in a map.
GIS Introduction by David J. Buckey
Every house, every tree, every city has its own unique latitude and longitude coordinates. The two primary types of spatial data are vector and raster data in GIS. But what is the difference between raster and vector data? When should we use raster and when should we use vector features? Find out more on the spatial data models commonly used.
GIS Data Formats and Data Conversion
There are several advantages and disadvantages for using either the vector or raster data model to store spatial data. These are summarized below. It is often difficult to compare or rate GIS software that use different data models. Some personal computer PC packages utilize vector structures for data input, editing, and display but convert to raster structures for any analysis.
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.
PDF | GIS-based measurements that combine native raster and native vector data are commonly used in environmental assessments. Most of these | Find.