Glossary of Terms - D

Data Layer

A set of related information on a GIS map. A map can have many layers to present different types of information. For example, the first layer of a map may be a satellite image of an area. The next layer may have only lines that represent roads or highways. The next layer may contain topographic information.

Data Logger

Used to store electronic data sent by a measurement device. A yield monitor is an example of a data logging device.

Data Mining

The process of gathering relevant data for the area of interest, generate a model to find patterns and relationships amongst the data, and present the derived information in appropriate and useful form.

Data Wrangling

The process of acquiring data from multiple sources, cleaning the data (removing/replacing missing/redundant data), combining the data to acquire only required fields and entries, and preparing the data for easy access and analysis.

Database

A collection of different pieces of georeferenced information (yield, soil type, fertility) that can be manipulated (layered) in a GIS model.

Datum

A set of parameters and control points used to accurately define the three-dimensional shape of the earth. The datum defines part of a geographic coordinate system that is the basis for a planar coordinate system. For example, the North American Datum for 1983 (NAD83) is the datum for map projections and coordinates within the United States and throughout North America.

Dead reckoning

A method of estimating field position based on forward speed, time of operation, implement width and number of passes.

Decision Tree

A supervised learning algorithm that models a tree where every branch represents a set of alternatives and leaves represent the decisions. By taking a series of decisions along the branches, we ultimately reach the desired result at one of the leaves. 

DEM (Digital Elevation Model)

A digital representation of the elevation of locations on the land surface. A DEM is often used in reference to a set of elevation values representing the elevations at points in a rectangular grid on the Earth's surface. Some definitions expand DEM to include any digital representation of the land surface.

Dependent variable

A variable that is under test and changes with respect to the change in an independent variable. In a housing price example, change in area results in change in price. Here, price is a dependent variable which depends on the independent variable area.

Differential correction

Modification of GPS signal information to increase accuracy. Correction of a signal is done from a second GPS receiver/transmitter at a known fixed location. The signal is then transmitted to the tractor, combine or other equipment that corrects the proper location through differential processing. Differential correction signals can be transmitted from satellites, on AM or FM radio, or through other means.

Digital agriculture

The realm in which our physical and social world is fused through digital devices. Integrated characterization and modeling improve decision making using modern data-intensive technologies that collect, connect, curate, communicate, and compute.

Dithering

The introduction of digital noise. This is the process the Department of Defense uses to add inaccuracy to GPS signals to induce Selective Availability.

DOP (Dilution Of Precision)

Describes fluctuations in the level of precision that a GPS receiver can have in a short period of time.

Drone

An aircraft without a human pilot.