What is a GIS - Why is it important for farm management

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There are several definitions for a Geographic Information System (GIS).

This definition from the USGS is fairly straightforward: A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.

This type of system provides a systematic approach to managing large amounts of data, along with the tools necessary for analysis and interpretation. This is specifically important in agriculture because the collection and management of data from site-specific crop and soil management systems generates amounts of data impossible to be managed by standard farm record systems.

Thus, a GIS can help organize and manage the data so that they can be more effectively used in various management decisions.

To name a few of the most usual applications in Agriculture:

  • Precision agriculture is based on the existence of in-field variability, and requires the use of various new technologies, such as global positioning (GPS and DGPS), sensors, satellites or aerial images, and (GIS) to assess and understand variations.
  • Thematic maps are a simple way of understanding different aspects of agricultural activity, at the farm or regional levels. thematic maps serve three primary purposes.
    - First, they provide specific information about particular locations (What are the areas with drainage problems?) 
    - Second, they provide general information about spatial patterns (Which areas of my farm had yield above average last year?)
    - Third, they can be used to compare patterns on two or more maps (Which areas of my farm have consistently performed with yields above average in the last 5 years?)

The following figures illustrate a couple of use examples of thematic maps at the regional level:

Thematic map depicting types of landcover

Layered map depicting Common Land Units over a classified satellite image

Representation – how is data stored?

Data are stored in a GIS in two main formats—vector and raster.

Vector representation of data is more precise, defining objects as points, connected points (lines) or areas enclosed by lines (polygons).

In a Raster representation, each area is divided into rows and columns, which form a regular grid structure. It has advantages, but is somewhat less precise because the entire cell has to be identified with the same representation. Precision depends upon the relative size of the grid cells.
Points, lines and Areas are represented in a different way, in vector and raster datasets:

  • Points Points are stored as individual (x,y) coordinates in vector format, or as individual column, row (col,row) matrix cells in a raster format.
  • Lines Lines are stored as a set of mathematically connected points in vector format, or as connected cells in raster format.
  • Areas (or polygons) Areas (or polygons) are stored as a mathematically connected set of points defining the boundary (vector) or as a set of contiguous cells classified as equals defining the interior (raster).

For a discussion on advantages and disadvantages of both data structures, please review this article

GeoAgro GIS works mainly with Vector data, stored in a shapefile format. Raster data is used mainly as background imagery (e.g.: aerials, satellite images, topographic maps), and is not used for Spatial analysis purposes.




Desktop, Mobile and Web GIS

Also, a farm GIS can be used in different environments, through a web browser, in local GIS desktop software, or through mobile devices and tools:

Desktop GIS

  • Create, edit, and analyze geographic data on your desktop computer.
  • See your data on a map.
  • Analyze your data to reveal patterns, relationships, and trends that are not readily apparent in tabular format.
  • Create publication quality, professional maps.

Mobile GIS

Enables field based personnel to capture, store, update, manipulate, analyze, and display geographic information. Mobile GIS integrates one or more of the following technologies:

  • Mobile devices
  • Global Positioning Systems (GPS)
  • Wireless communications for Internet GIS access

Web GIS

  • Access 2D maps, 3D globes, reference layers, and functional tasks via the Web to support your GIS work.
  • Multiple users can add data to a single map.