C4

• Geodesy


  The science that measures the shape and size of the earth as well as its gravitational and magnetic fields
• Basic Map Principles in Agriculture

  • Geodesy concept
  • Coordinate system
  • Projection
  • Datum
  • Scale
  • Types of Thematic Maps

  
• Types of Thematic Maps

  • Chloropleth maps
  • Isoline maps

  
• Map


  • Can show the physical location of each object
  • Can show the different levels of soil nutrients
  • Can show the area of high and low yield
  • Can show difference in topography

  
• Farmers are starting to use maps in a GIS because it brings value to data collection as well as to data analysis
• The ability to create maps that display spatial variability is fundamental to precision agriculture

  
• Precision Agriculture (PA)


  About collecting all of the data needed to create an accurate model of an agricultural crop field and using that model to keep accurate records, make informed decisions, and apply crop inputs at variable rates on a field
• Before computer and GIS, farmers just used an aerial photo of their farm and hand-drawn map of each their field
• Geography


  The earth science. Without geography, you are nowhere
• Applying geographical concepts is necessary in agriculture. No longer do farmers or agriculturists rely on hand-drawn maps
• Coordinate system


  Used for systematically identifying the location of an object on a map, usually with a grid

  
• Coordinate system


  • Spreadsheet with columns identified by letters and rows identified by numbers
• Geographic Coordinate System (GCS)


  A grid created on the surface of the earth using lines of latitude and longitude

  
• Latitude


  Lines that go around the earth horizontally (East/West), parallel to the equator. Used to measure how far north and south an object or feature is from the equator

  
• Longitude


  Lines that go north/south from North Pole to South Pole. Used to measure how far east or west an object is from the prime meridian

  
• Coordinate formats


  • Decimal degrees (DD)
  • Degree minutes (DM)
  • Degree minutes seconds (DMS)
• Universal Transverse Mercator (UTM) Coordinate System


  A coordinate system based on ease of use for navigational purposes. It creates 60 longitudinal north/south zones, each 6 degrees wide, and 16 latitudinal levels, 6 degrees wide. Coordinates are in meters

  
• Northings


  UTM coordinates that reference the number of meters north of a reference point

  
• Eastings


  UTM coordinates that reference the number of meters east of a reference point
• Projection


  The technique of transforming a spherical surface to a flat map with minimum distortion
• Changing a projection allows the user to convert GCS coordinates such as UTM that is designed for use on a flat surface such as a piece of paper or computer screen
• Datum


  A numerical representation of the center of the earth that latitude/longitude and other coordinates are based on

  
• Datum can cause problems when using multiple map layers, as different sources may use different datums causing the layers to not line up

  
• Scale


  Refers to the detail and size of the map that is displayed in the GIS

  
• Spatial


  Referring to space. Something that occupies space, such as a house or tree
• Aspatial data


  Data that does not have a connection to locational data
• Types of maps


  • Reference maps
  • Thematic maps

  
• Reference maps


  Provide a model of what a geographic area looks like, with features like roads, streams, and cities

  
• Thematic maps


  Focus on displaying information about attributes, usually using color

  
• Types of Thematic Maps

  • Chloropleth maps
  • Isoline maps

  
• Chloropleth maps


  Illustrate information about an attribute value by applying color to polygons, lines or points

  
• Isoline maps


  Provide information in a format similar to contour lines