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10.1 INTRODUCTION

Proper agricultural management decisions often require the integration and analysis of information from a number of different sources, including measurements obtained from one or more geophysical methods (resistivity, electromagnetic induction, ground-penetrating radar, etc.) along with other farm field geospatial data (topography, crop yields, soil properties, satellite remote sensing imagery, etc.). Integration and analysis of geophysical and nongeophysical information from multiple sources is especially important when employing precision agricultural techniques to separately manage different parts of a farm field. Geographic information systems (GISs) provide a set of tools that are particularly well suited for management, integration, and analysis of multiple geophysical and non-geophysical geospatial data sets. GIS software essentially allows geospatial data to be organized, stored, edited, displayed, and analyzed in an effective and efficient manner.

10.2 COMPONENTS OF A GIS

There are four basic components to a GIS: an input system, a database management system which includes data storage and editing, a data analysis system, and an output system (Figure 10.1). Basic functions within a GIS include data acquisition, data management, data manipulation, data analysis, modeling, and the display of spatial data. The input system to a GIS allows the user several different ways to incorporate data. Data input devices, such as digitizing tables and scanners, allow one to incorporate historical data from existing hard-copy maps. Software utilities are available to import data in various standard formats, such as ASCII, shapefiles, .tif, .img, and .dxf.

The database management system is the core of the GIS. The geospatial data will be in various computer formats in the database—vector data, raster data, shape files, and the attribute information. The database is typically in a standard format, depending on the GIS software. Data storage

Input

Management and Analytical Modules

Input

Management and Analytical Modules

Data Acquisition

- Geodetic positioning

- Remote sensing

- Field sampling Analog Data Conversion

- Digitize

Management

- Data storage

- Data retrieval, expand edit, and update

- Query

Data Acquisition

- Geodetic positioning

- Remote sensing

- Field sampling Analog Data Conversion

- Digitize

Management

- Data storage

- Data retrieval, expand edit, and update

- Query

Analytical Modules

- Data conversion

- Data manipulation

- Modeling

Components

Output

Components

Output

Data Output

- Visual presentation

- Analog map output

- Reports

Data Output

- Visual presentation

- Analog map output

- Reports

FIGURE 10.1 Components of a geographic information system (GIS).

and editing capabilities provide for a variety of software tools to store and maintain the digital representation of the data sets. The database needs to be kept up-to-date, so editing tools are available to correct and update the data layers. Procedures to join maps and to perform edge matching between adjacent map areas are also available.

Most GISs include a wide range of capabilities for analysis of geospatial data (geostatistics, numerical methods, etc.). The output system is used to create high-quality maps, charts, and statistical summaries from analysis of the data layers residing in the spatial database. There are several public domain and commercially available GIS software packages. These include ArcGIS, Geo-Media, Maplnfo, Idrisi, ERDAS, AUTOCAD MAP, Microimages, and Manifold. Bolstad (2005) provides a brief review of these software packages. There are several basic textbooks that provide excellent descriptions of GIS concepts. These include works by Bolstad (2005), Bernhardsen (2002), Bossler (2002), Chang (2002), Chrisman (2002), DeMers (2005), and Lo and Yeung (2002).

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