Geospatial Concepts: The Fundamentals of Geospatial Science


Preface

It was sometime after the implementation of the Geospatial Concepts course at Humboldt State University that a graduate student approached me. This student wanted to bypass the Geospatial Concepts course prerequisite and jump right into taking the Intermediate Geographic Information Science (GIS) course. This student had never completed a formal geospatial course before, though she asserted that someone in her workplace had shown her how to use “the GIS.” She assured me that she was “good with computers” and was confident that she could pass the course. I understood her situation. No graduate student wants to take a 100-level course. When I was a graduate student, I also had to do the same. I knew how she felt, so I considered her request.

However, I also wanted to gauge her understanding of basic geospatial science. After asking a few fundamental questions, it was clear that she just had no idea. This student did not understand how geospatial data is structured, how to use it appropriately, how to communicate effectively, or how to identify sources of error and uncertainty. Worse yet, she was utterly oblivious to the fact that there was a need to understand it. From her point of view, GIS was merely a matter of knowing how to use the software.

I explained that there was more to GIS than knowing how to operate the software. When entering a new scientific disciple, understanding the fundamental concepts is a reasonable expectation. She did not quite see it that way and argued that she did not need to know about “all that other stuff.” She just wanted to learn how to operate the software. In the end, I did not let her into the course and the student left, clearly upset. She had come with some preconceived notions about what GIS was.

Unfortunately, this was not the last time I encountered this situation. I have the same conversations every semester. Many people have certain expectations when it comes to the geospatial sciences, especially GIS. In part, this is because GIS software is one of the most ubiquitous tools used in the geospatial sciences but commonly used with little understanding about the nature of geospatial data. Throughout this course, we will be using GIS software, and later I will explain more about geographic information systems in more detail. However, it is important to realize that it is not enough to know how to operate a particular GIS software package. While GIS software is handy, all of its capabilities and features will not amount to much if you fail to understand the data that goes into it. This understanding requires knowing where data comes from and how it is measured, recorded, and represented. Most importantly, it requires an understanding of what its limitations are.

My goal is to provide you with the foundational material common to all geospatial science. I hope you find the information presented in the following chapters both thought-provoking and informative. Most importantly, I hope that by reading these chapters, you will come to see the value in having this knowledge, regardless of your interests, major, or career goals.

About the Chapters

Chapter 1: Understanding Geospatial Data

Chapter 1 introduces the primary and secondary geospatial sciences. These are the roots and branches of geospatial science and determine how we create, represent, manage, and display geospatial data. Geospatial data has particular properties, distinguishing it from other types of information. We use it to solve problems and answer questions related to geographic location, distribution, extent, changes over time, and geographic relationships. Commercial enterprises, governments, non-profits, and the average person on a day-to-day basis use geospatial data.

A phrase familiar to computer science that says, “Garbage in, garbage out.” It means that the results of your work depend upon the quality of data that goes into it. This phrase also applies to geospatial science. Understanding geospatial data will ensure that a project, analysis, or procedure will result in producing quality work. This Chapter covers the concepts, structure, data types, file types, and management of geospatial data.


Chapter 2: Communication and Design

Today everyone can be a mapmaker. However, not every mapmaker is a cartographer. Cartography is the art and science of making maps to communicate geospatial information efficiently. The difference between a lay mapmaker and a cartographer comes from an understanding of geospatial data, cartographic conventions, and in recognizing that a map’s primary role is to communicate information visually.

Chapter 2 presents the fundamental principles of cartographic design and communication. Maps are a medium for communication with a unique set of methods and techniques. Understanding how maps communicate will allow you to view maps in a new light and with a critical eye. You begin by learning the essential map elements and the visual variables of graphic communication.


Chapter 3: Geodesy and Transformation

Since ancient Greece, mathematicians and philosophers have speculated about the size and shape of Earth. The Greek mathematician Pythagoras was one of the first to advocate the idea of Earth as a sphere. Since then, there have been many estimates on the circumference of the earth by those that followed.

Chapter 3 presents the discipline at the root of geospatial science, geodesy. Geodesy is a branch of applied mathematics. It is the science of measuring and representing the size and shape of Earth, the exact position of points on the planet, and the study of Earth’s gravitational and magnetic fields as they change over time.


Chapter 4: Map Scale and Spatial Reference Systems

Most people have the idea that coordinate systems are static, unchanging definitions of where they are. You can log on to google maps and look up your latitude and longitude coordinates and feel confident that these numbers have a universal meaning that does not change. In reality, the numbers you see on google maps are just one of many versions of latitude and longitude coordinates that can define your location.

Chapter 4 presents how distance and location are defined and communicated using map scale and spatial reference systems. Determining a position on earth in a way that is meaningful to others is a difficult challenge. In part, the difficulty is due to the differences in map projections and datums used across the world, which can change longitude and latitude coordinates in different ways. It may seem like a trivial detail, yet boundary definitions and positional information can have significant legal, political, and military consequences.


Chapter 5: Mobile Mapping Fundamentals

Land survey is the direct application of geodesy, linking mathematical models of the earth to physical reality through precise field measurements. Land survey measures and defines positional information on Earth, which is a crucial element of geospatial science.  While you may not expect to achieve a surveyor’s level of precision, at some point, it is likely that geospatial fieldwork you do will involve some form of measurement related to position, elevation, perimeter, or area. This kind of mapping data in the field is what I refer to as mobile mapping.

Chapter 5 presents a series of methods and equipment for mapping data out in the field. This chapter differs from others due to the hands-on nature of field collection that is difficult to translate into a digital textbook. The activities included in this chapter have far less focus on software and incorporate some outdoor activities that you will have to perform.


Chapter 6: Image Acquisition and Interpretation

It is possible that many, if not most, of my students, were not alive before digital aerial imagery became commonplace. Most also have little direct experience with film-based photographs. Today, anyone with an internet connection and a web browser can view images from aircraft and space satellites. With imagery so commonplace and accessible, I find many students take it for granted.

However, there are still new frontiers emerging in the collection, application, and processing of images. The scientific and educational potential of civilian-operated unmanned aerial systems (UAS) is just one. Chapter 6 presents the phenomenon, concepts, equipment, and methods behind the science of Remote Sensing.


Chapter 7: Selection, Proximity, and Overlay

Too often a geospatial analysis is conducted without consideration for uncertainty and error, map projections, and datums. More often, there is little regard for cartographic convention and communication design goals.  A geospatial analysis should consider the properties of geospatial data before applying GIS software tools. Chapter 7 introduces the first steps in learning how to conduct a geospatial analysis. The topics presented within should help to prepare you for more complex uses of GIS and additional geospatial courses.