Posted by: dmconroy | February 20, 2009

Mitchell Chapter 1

What is GIS Analysis?

Frame the question: it is important to be as specific as possible when considering your question. This will help decide how to approach the question, which method to use, and how to present the results.

Understand your data: the type of data you use will often determine that methods you use.  But, if you need to use a specifc method, you may need to obtain additional data. It is important to understand whta you have and what you need.

Choose a method: there is often more than one way to obtain your data and some methods may be quicker and give you more approximate data, while others will take longer and give you more specific information. The method you use may be dictated by the type of information you are trying to obtain.

Process the data:  once you have the data you need, you will need to use the appropriate steps in GIS.

Look at the results: the results may be displayed in a map and values in a table or chart. You will have to decide what information to display on your map and how to best present the information. It is also important to look at the results and then you can determine whether they are relevent or useful.

Types of Geographic Features represented on maps:

Discrete features: the location can be pinpointed. at any given location the feature is either present or not.

Continuous phenomena:  this type of feature is seen in precipitation or temperature maps. This feature often starts as sample points such as irregularly placed weather stations.

Features Summarized by Area: examples can be the number of businesses in a zip code, the total length of streams in each watershed or the number of households in each county.

Geographic features can be represented in the GIS using two models of the world: vector and raster.

Categories: groups of similar things that are put together to help the reader understand the data better.

Ranks: puts features in order from high to low or vise versa

Counts: this shows total numbers for each individual data points such as the amount of employees each company in a city employs.

Ratios: relationships between two quantities such as the average number of people per household.

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