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