Human errors include mistakes, such as reading an instrument incorrectly, and judgments. In general, there are three sources of error in measurement: human beings, the environment in which they work, and the measurement instruments they use. Errors are also introduced when second- and third-generation data is produced, say, by scanning or digitizing a paper map. Errors are introduced in the original act of measuring locations on the Earth surface. All measurements contain some degree of error.
Positions are the products of measurements. These are fun, thought-provoking exercises to help you better understand the ideas presented in the chapter. Take a minute to complete any of the Try This activities that you encounter throughout the chapter. identify and explain methods used to improve the accuracy of GPS positioning.state the kinds and magnitude of error associated with uncorrected GPS positioning and.explain how radio signals broadcast by Global Positioning System satellites are used to calculate positions on the surface of the Earth.calculate plane coordinates by open traverse.list and explain the procedures land surveyors use to produce positional data, including traversing, triangulation, and trilateration.identify and define the key aspects of data quality, including resolution, precision, and accuracy.Students who successfully complete Chapter 5 should be able to: This chapter explores the technologies and procedures used to produce positional data, and the factors that determine its quality. Resolution and precision are two aspects of data quality. In practice, positions occupy 2- or 3-dimensional areas as a result of the limited resolution of measurement technologies and the limited precision of location coordinates. In theory, a single position is a "0-dimensional" feature: an infinitesimally small point from which 1-dimensional, 2-dimensional, and 3-dimensional features (lines, areas, and volumes) are formed.
A property boundary, for example, is made up of a set of positions connected by line segments. Like the letters that make up these words, positions are the building blocks from which features are constructed. Positions, then, are a fundamental element of geographic data. We defined "feature" as a set of positions that specifies the location and extent of an entity. As you recall from Chapter 1, geographic data represent spatial locations and non-spatial attributes measured at certain times.
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