MidTerm Flashcards
What are the three keys to success in Precision Ag?
Information, technology and management
Precision ag is defined as:
A system designed to optimize ag production through crop information, technology and management practices
One of the most common starting points for farmers entering precision ag:
Swath Guidance
The 5 objectives of precision ag are:
Energy Conservation Soil/Ground Protection Efficient Chemical Use Improved product Quality Increased Production Efficiency
What is Postharvest Control?
aspect that addresses the control/protection of product quality shortly after harvest but before delivery
What is site specific management?
Management of the field by recognizing differences across the field and breaking it into smaller zones
What is the farmers most valuable resource?
Information
What are the 2 tools that make precision ag feasible?
GPS and GIS
What is Spatial Variability?
Changes in measured properties over distance or depth
What is active remote sensing?
A remote sensing system that generates it’s own signal and monitors for a response
What is an embedded computer?
Computer designed for a specific purpose, has limited flexibility and software for it’s task
What is spatial resolution?
The smallest object that can be detected
What is temporal variability?
Changes in measured properties over time
What is physical variability?
Changes in measured physical/chemical properties
What is Feedback Analysis?
Input –> Analyzer –> Output
^ – Feedback ———-|
Continuous improvement due to feedback
What is a measurand?
Physical parameter of interest in a information system
What is a sensor designed to do?
Detect change in a quantity and convert it into signal
What is a transducer used for?
Convert signals into a more useable form
What do we use to transport information between systems?
USB drives, Wireless transfer, PCMCIA cards
What is a coordinate system?
A frame of reference from which measurements are made
Specifies units of measure on an axis from an origin
What is a geoid?
A mathematical model of the earth’s grav field, it is a reference for determining elevation. It roughly corresponds to mean sea level
What is georeferencing?
The act of turning an image into a map by linking points in the image to coordinates. Need 3 or more points
What is GNSS?
A space and land based system that allows a receiver to determine location based on the known position of space vehicles
What is the highest accuracy GPS?
RTK
What are L1, L2 and L5
GPS Frequencies
Position System Requirements:
Available at any point
Available any time
Should interface with equipment
How many satellites are needed to get a GPS fix?
4
GPS for civilians is called
SPS, standard point positioning
What is a C/A code?
Civilian receivers code
What is PPS?
Military GPS, precise point positioning
What is trilateration?
Determines the location of the receiver based on estimated distance for the satellite
The distance between a sat and a receiver can never be measured exactly
True/False?
True
NMEA 0183
Standard that defines GPS serial communications. Includes a baud rate specification (speed of transmission)
Most common GPS sentences are?
GLL
GGA
VTG
What is ‘true range’?
Distance between satellite and antenna
What is the unique identifier that a GPS receiver uses to identify which psuedorandom code it is tracking?
PRN
The use of 2 frequencies in a receiver allows for correction of:
Ionospheric effects
2DRMS means:
95% probability that observations will fall within 2 standard deviations
What is PDOP?
Position of Dilution of Precision, a type of error estimate. Less than 4 is excellent, over 8 is bad
What position of accuracy is needed for variable rate herbicide?
1 meter
What’s a good task for Point Guidance?
Locating a drain tile discharge point
Recommended accuracy for row crop planting?
10 cm
Recommended accuracy for seed bed formation?
5 cm
Recommended accuracy for Yield Mapping?
10 meters
Recommended accuracy for fertilizer?
30 meters
2 types of guidance systems
Light bar and Map Screen
2 Modes for GPS Guidance
Error (inches off from line) or Correction (inches to adjust)
2 types of steering systems
Universal and Fully Integrated
Advantages of GPS Guidance:
High accuracy reduced swath errors works any time easy to use works in any weather works well with spinner spreaders
Definition of precision agriculture
a management system that is tech based, site specific, uses data to reach optimum profitability
How to get started in precision ag
Review existing info Add more Data Research tech Add tech that fits (yield monitor, swath guidance, soil sampling) Examine Results Develop a strategy
FMIS
GIS
Database,
Analytics
Business management
Office system can include book keeping, field management, decision support system
Why do we need information on a field?
Spatial variability (chg over distance) Temporal variability (chg over time)
Ways to acquire data
Real Time - sensors - yield sensor, crop sensor, temp control
Lab Analysis - soil tests. Predictive or Diagnostic
Field Observations - yield history, scout reports
Real Time Data
Measurand - physical parameter of interest
Sensor - device that detects change as a signal
Transducer - converts signal to useable form
Processor - analyzes it
Output Display - user interface readout
Direct Sensor - needs physical contact
Remote sensor - no contact, maybe EM
Rate Sensor - tachometer, speed
Proximity Sensor - magnetic displacement
Force/Pressure sensor - strain, load, displacement
Flow Sensor - turbines, ultrasonic, electromagnetic
Temp Sensor - infrared bimetallic, thermocouplers
Chemical Property Sensors - PH, conductivity
Electromagentic - radiometers, measure reflected infrared
In-field sensing
direct contact or proximity, but while in the field itself
make sure sensors are calibrated
identify measureable property
Remote Sensing
Aerial, Satellite, drone
measures EM energy, UV, infrared, visible
Active (RADAR) or Passive (camera)
Spectral resolution - wavelengths detected
Coverage frequency - how often is data collected/repeated
Rules about information
Must be managed by type/application Must be searchable Must be formatted for analysis Must be readily available Must be understandable
Field Computer
has GNSS receiver, has CAN interface, runs apps or control algorithms
Function of cell modems and wifi on the farm
Track location Track service hours Create auto steer guidelines geofencing Transfer sensor data Send prescription maps Upload yield data
GIS
Computer system designed to collect, store and manipulate data
Georeferenced Data
Spatial Data can be vector or raster (tiff, gif, bmp)
Raster Data
array of cells
Each cell is georeferenced
each cell has a fixed resolution
each cell is a single attribute
Aerial Images
zoom factor is tied to pixel count
one pixel = 1 meter or 10
Coord System
framework used to define position of points
Lat/Long/evelation
datum
a reference from which measurements are made
geomatic datum - uses ellipsoid (horizontal or vertical)
horizontal datum - NAD83, WGS84
vertical datum - used for elevation, tides
State Plane
Cartesian coords. northing, easting, elevation N | | _ _ _ _ _ _ _ E 0,0
Different Feet
survey ft - 0.30480061 meter
international ft 0.3048 meter
Geodetic height
height above ellipsoid
elevation
height above sea level h = H + N
ellipsoid height = ortho height + geoid height
Georeferencing photos
Input control points choose coord system minimize residuals (difference between actual control points and coords predicted)
normalized map
starts with 100, and then shows deviation from that (high/low)
FMIS Analysis
Comparison Analysis
Correlation - -1 to 1, statistics
profit/loss, expense/income estimates
Files need for shapefile
shp
shx
dbf
projection optional
PNT
Position, navigation and timing system 'aid in determination of location, provide guidance, and precise coordination of time' 1) provide location 2) available on demand 3) available anywhere 4) must interface w/ equipment
Types of PNT
Dead Reckoning - orienteering, uses bearings
Laser Systems - transmitters/reflectors. Uses triangulation with 2+ transmitters, need line of sight
GNSS - GPS, GLONASS, Galileo, Beidou
GNSS
Space and land based system for location, guidance and timing
GPS: Space - 24 satellites plus backups. In medium earth orbit., orbit earth twice a day
Shifts west a bit every day. 6 orbital planes, broadcast 2 frequencies L1 and L2, plus new L5
Control - monitors satellites, position of each is maintained
User - receiver interprets signal
GPS Signal contents
Pseudorandom Nosie (uniquely identifies satellite), C/A Code (C for civies, P for military) NAV data message: ephemeris (broadcast by all satellites, provides precise location of satellite) and almanac (where each satellite should be) inside
Limits of GPS
Line of sight
low power signals - not go through solid objects
tree cover a problem
Pseudorandom Range
Estimate of distance from satellite
Carrier phase
time difference between when signal was sent and received
trilateration
determine position from known points
4 satellites needed for a unique point
plus reduces clock error
autonomous GPS
based on only GPS
Single Point Positioning
horizontal accurate to 8m
vertical accurate to 13m
Types of Augmented GNSS
Differential (DGNSS)
Precise Point (PPP)
Real Time Kinematic (RTK)
Can improve GPS error by:
Averaging multiple observations
applying differential correction by a reference receiver (known other locations)
applying correction by predictive modeling of error (PPP)
DGNSS
references receivers at known locations to transmit a correction signal which is picked up by a differential receiver
removes clock error and orbital error
reduces ionosphere error and troposphere error
1) signal to receiver and fixed reference at same time
2) fixed receiver calculates error in position
3) fixed receiver transmits error out to diff receiver
4) mobile receiver calculates more precise location
Diff signals can come from land or space
Coast Guard or DOT, private stations, commercial (Omnistar, Terrastar)
WAAS (US) - wide area augmentation system
EGNOSE
MSAS (Asia)
PPP
correction in real time w/o base stations
uses predicted model of orbit and atmosphere
correction/model from the satellitte
have to wait for it to converge - sometimes 5 minutes
RTK
position from carrier phase
number of wavelengths between sat and receiver
accurate to 2 cm horizontal, 3 cm vertical
high speed/low latency
need 5 satellites
uses local base station good for 12 miles
RTK base station
fixed or portable
or subscription to a tower cluster
CORS covers whole state, NC realtime network
NTRIP
access via cell or dsl or sat. multi-base or single
NMEA Sentences
GGA - fix data - 4 = RTK GLL - lat long RMC VTG - ground/speed ZDA - time/date, UTC plus a checksum
Baud Rate
needs to be fast enough to transfer data, but too slow garbles it
excess speed uses too much processor
rate = (bytes per sentence) x upload rate (Hertz) X 8 bits/byte
max 82 bytes per sentence
9600, 19200, 38400
Pass to PAss accuracy
paralell swatsh, repeatability accuracy within 15 minutes
Lightbar setup
Needs clear antenna view
Set swath width
set sensitivity and error vs correction mode
universal auto steer
turns the steering wheel via a motor
can retrofit for any tractor
fully integrated steering
interfaces with hydraulics and electrical. Kits are model specific
Universal motor install
Install support bracket
install motor
install terrain compensator - needs no vibrations, parallel to rear axle (may or may not be on top of it)
wheelbase
center of axle to center of axle
antenna height
use manufactorer reference point
angle per turn
one full turn of the wheel = number of degrees axle rotates (can self-calculate)
override sensitivity
how much you need to touch wheel before auto steer disengages
online aggressiveness
how crisp it engages/stays on target
maximum angle
must be with X degrees of guidline before auto steer engages
accuracy check
Program A-B line stop and flag tires turn around drive back to flags should go between flags
Advantages of GPS
high accuracy works well w/ spinner spreaders less chemical use/more efficient any weather any time
Implement setup
hitch type - draw bar or 3 pt width - rows x row spacing overlap/skip (skip aka alley) left/right offset from tractor front/back offset referenced to antenna
Section Control
on-off control for planters, sprayers, spreaders
switching triggered by field location
each sprayer has a clutch and can disengage/engage on its own. indivduals or groups
Spreaders have no granular control
Application Record Map
‘as applied’ map, good record for fertilizer application
