Global Positioning System and GIS

IN WHICH you are introduced to facts and concepts relating to the NAVSTAR Global Positioning System and have your first experience using a GPS receiver. OVERVIEW A sports club in Seattle decided to mount a hunting expedition. They employed a guide who came well recommended, and whose own views of his abilities were greater still. […]

Basic Concepts (GPS and GIS) Part 2

HOW WE KNOW WHERE SOMETHING IS First, a disclaimer: This text does not pretend to cover issues such as geodetic datums, projections, coordinate systems, and other terms from the fields of geodesy and surveying. In fact, I am going to make it a point not even to define most of these terms, because simply knowing […]

Basic Concepts (GPS and GIS) Part 3

Understanding the Screens and Controls The process of giving commands to the GeoExplorer consists of selecting choices from a "Main Menu" and its submenus, and then pressing the CMD key. In other words, you may freely press the arrow keys without changing anything but the display. And you may "escape" from whatever menu you are […]

Basic Concepts (GPS and GIS) Part 4

Preparing to Correlate GPS Data with Map Data {_} Take out the USGS topographic quadrangle (a topo map, usual scale 1:24,000) of the appropriate general area. The receiver can display a geographic position in several coordinate systems. Under "Configuration ~ Coordinates" you will find • Degrees, Minutes, and decimal fractions of minutes (Deg &Min) • […]

Basic Concepts (GPS and GIS) Part 5

Set Your Watch {_} The GPS receiver’s clock has been correctly set by the exposure to the satellites. It now has a very accurate idea of the time. So you may set your watch by it and be correct to the nearest second.21 With the recording of the geographic coordinates and the setting of your […]

Automated Data Collection (GPS and GIS) Part 1

IN WHICH you learn the basic theoretical framework of  GPS position finding, and practice using a GPS receiver tocollect computer-readable data. OVERVIEW How’d They Do That? By now you have determined that GPS really works. That little gadget can actually tell you where you are! How?! The fundamentals of the system are not hard to […]

Automated Data Collection (GPS and GIS) Part 2

Position Accuracy and DOP Prior to the end of 1993, GPS had less than the full complement of 24 satellites operating. In earlier years, there were periods during the day when there were not enough satellites in view from a particular point on the ground to provide a position fix. Now a data collector can […]

Automated Data Collection (GPS and GIS) Part 3

PROJECT 2B Taking Data Along a Path In this project you will again use the receiver to take fixes and record the coordinates in the datalogger. The difference between this and the previous project (2A) is that you will move the receiver antenna through space in order to record data points along a track. This […]

Examining GPS Data (GPS and GIS) Part 1

IN WHICH we continue our discussion of the theoretical framework of GPS position finding, and you practice using PC software to investigate files collected by GPS receivers. OVERVIEW Some Questions Answered As you read the last two topics some questions may have occurred to you. And the answers to these questions may generate other questions. […]

Examining GPS Data (GPS and GIS) Part 2

PROJECT 3A—Volcano We begin by looking at a file generated by a GPS receiver that circum-navigated Kilauea Caldera, the active volcano on the island of Hawaii. Before you can see or analyze the data, however, several parameters must be set up. (Right. Just as when you used the GPS receiver. It turns out that, when […]