# Intro to Gis

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Intro to Gis
Introduction to Geographical Information Systems

1. Intro to GIS

1.1 What is a map?

A map is a two dimensional model of the real world. It can be regarded as a statistic geographical database printed on paper. real world.

1.2 What is the most important entity in a GIS?

Link. A link is required to connect attribute date to geometrical data. Without this the system will not operate properly

1.3 What is the difference between “spatial data” and “none spatial data”?

Spatial data are data that contain positional values (x and y coordinates). For example, spatial data can describe the positions for lakes, forests and roads. Non-spatial data have no defined spatial delimitation, and therefore represent events varying over space.

1.4 What kind of different geometrical objects are there in a GIS?

Point Objects, Polygons, and Lines.

1.5 Which are the four most important functions a GIS must be able to handle?

Input.
Data Management (storage and retrievel).
Manipulations and Analysis.
Output.

1.6 Describe the concept of spatial information.

Information is data that has been interpreted by a human being. People work with, and manipulate information. Perception and mental processing leads to information along with understanding and knowledge. Spatial information is a specific type of information that involves the interpretation of spatial data.

1.7 Describe some sort of an analysis which you can do with a GIS.

GIS analysis could be used in assessing crime rates of an area. Questions such as, where did most burglaries occur last week? What was the average age of the house occupants that have been burgled? Where has the lowest number of burglaries in the last year?
Questions such as these could help determine if specific areas are targeted by criminals.

1.8 Describe briefly how the “linking” in a GIS works.

Linking is used to indicate which objects belong to each other. Links are needed to join

Links: are established by allocating unique ID numbers for all objects within a map, and corresponding rows in a table are given corresponding ID numbers. It is important that no two objects have the same ID number. When a user then points at an object on a map, the ID number will be read by the computer, and the corresponding table entry will be displayed. This can also work in reverse, i.e. by selecting a row on a table, the corresponding object on the map will flash. 1.9 Describe the cycle of the GIS handling. Data is collected in the real world, digitised, and input into the database in a structured manner. Data can be retrieved by a number of users, combined and analysed with data from different sources. This data can be used for decision making. Such decisions will impact the real world, and as such new data will have to be collected from the real world to update the database. Therefore, a GIS will always require updating, and keeping the cycle going, as long as the real world keeps changing.

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