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  2. Introduction to GIS
  3. Chapter Six
  4. Section One - Introduction

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Section One - Introduction

In GIS, we have two categories of data - primary and secondary data.  These are not unique terms to GIS, as many other sciences use these two categories, however, within GIS, the terms do have a unique meaning.  Primary data is created in one of two ways: either via digitizing from aerial and satellite images or collecting field data utilizing GPS-based collection devices, both methods of interacting with the Earth's surface in a very intimate and deliberate way.  Secondary data is any data which is produced as the output of a geoprocessing tool (the subject Chapter Seven).  Overall, primary data tends to carry a bit more weight, as it's not derived via a tool where error may be introduced through improper use of the tool, a misunderstanding of the tool or the data, or other similar errors (the topic of Chapter Eight).

In this chapter, we will look at the processes of manual and heads-up digitizing, a basic understanding of remote sensing, methods of taking paper maps and creating digital versions, converting postal addresses into geographic coordinates via geocoding, collecting data with smartphone based GPS apps and commercial GPS receivers, how to create data via crowdsourcing, and how to change existing data. The creation and correction of data are the two most common tasks a GIS technician does everyday, thus it is very necessary to have a solid understanding of the what and why of creating and editing data.