GIS Basics and Mathematical Operation of Threshold: Pixel Threshold, Scale Threshold (Especially for GATE-Geospatial 2022)

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GIS Basics

GIS contains various interrelated information for urban planners: cadastral maps, altitudes, urban plans, land use, economic development information, demographic information, and various statistical analyses.

Map of Bosnia and Herzegovina Made from Layers

GIS maps are layered, with each layer consisting of information related to the area contained in the map, such as spatial objects (roads, rivers, lakes, etc.) , population distribution, land division, etc.

GIS also has capability to show different kinds of objects by using simple geometric forms to represent them: dots, lines, and polygons.

One of the main benefits of GIS is improvements to the management of the organization and its resources by allowing for the sharing of data between various departments. A shared database allows one department to benefit from the work of another; data can be collected once and used many times.

Main Applications of GIS

In GIS are widely used in many government business and private activities, which fall into three major categories:

  1. Socio-economic applications (cadastral registration, natural resources, urban and regional planning)
  2. Environmental applications (forestry, fire, and epidemic control)
  3. Management applications (organization of pipeline networks and services such as electricity and telephones)

In these applications GIS provide decision makers with effective tools for solving the complex and usually not-at-all or semi-structured spatial problems.

What is Thresholding?

A threshold is a fixed location or value where an abrupt change is observed or is the starting point for a new state or experience. Thresholding is the simplest method of image segmentation. Individual pixels in a greyscale image are marked as ‘object’ pixels if their values are greater than some threshold value and as ‘background’ pixels otherwise. Typically, an object pixel is given a value of ‘1’ while a background pixel is given a value of ‘0’ .

Minimum Scale Threshold

When zoomed out beyond this scale, feature will not be visible. For example, tracts are not visible when zoomed to the USA

This Map Shows Minimum Scale Threshold

Maximum Scale Threshold

When zoomed in, feature will not be visible, for example, state population will disappear when zoomed in to a state

This Map Shows Maximum Scale Threshold

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