What is GIS

Geographical Information System or GIS, is an organized collection of computer hardware, software, spatial and non-spatial data, and users, designed to efficiently capture, store, update, manipulate, analyze and display all forms of geographically referenced information. [after: Understanding GIS, P.xxx, ESRI, 1991]

GIS enables one to ask two key questions

WHERE IS WHAT ?

&

WHAT IS WHERE ?

The "WHAT" may be defined in terms of phyisical descripion or by any combintion of characteristics that are attributed to compliment the spatial layout. The "WHERE" may de defined in terms of space and time. This broad concept of geographically referenced information manifest itself in complex processes such as temporal analyses (trends) and modelling.

Although the range of actual queries and analyses is unlimited, there are several broad types of questions that are commonly used with GIS. Some of these general queries are the following:

Where is object A ? e.g. Where is the University of Haifa ?

Where is A in relation to place B ? e.g What is the distance between Haifa and Jerusalem ?

What exists in place X ? e.g. Which hotels are located at the city center ?

What if ? e.g. How will the water drainage change if we pave a road ?

What has changed since ? e.g. "What types of vegetation have regenrated after the fire ?

What is Remote Sensing

Remote sensing is the measurement and analysis of electromagnetic radiation reflected from, transmitted through, or absorbed and scattered by the atmosphere, the hydrosphere and by material at or near the land surface, for the purpose of understanding and managing the Earth's resources and environment.

Remote sensing may be broadly defined as the collection of information about an object without being in physical contact with the object. Aircrafts and satellites are the common platforms from which remote sensing observations are made. The term remote sensing is restricted to methods that employ electromagnetic energy as the means of detecting and measuring target characteristics.