Presented by: Mike Catalano GEONICS LIMITED

Transcription

1 What s In The Ground: A Non-Invasive Soil Mapping Tool! Presented by: Mike Catalano GEONICS LIMITED

2 INTRODUCTION Measuring Soil Conductivity with Geonics Limited Electromagnetic Geophysical Instrumentation This presentation will briefly discuss the principles of operation and the practical applications of electromagnetic (EM) systems manufactured by Geonics Limited as they relate to agricultural investigations. A review of all soil conductivity models currently available through Geonics will also be made.

3 Soil conductivity is now widely accepted across the Precision Agriculture industry as one of the primary properties of soil to be mapped. The technique has grown in use in part due to the increasing efficiencies of accessories used to collect data and the drive by farmers to become more productive. The intention of this talk is to introduce the southern Alberta farming community to the Geonics EM38-MK2.

4 History & What is it? Mining & Exploration industries adopted technology 50 years ago. It s a light-weight geophysical instrument revolutionizing Precision Ag industry with usefulness for mapping by means of a noninvasive, non-destructive principle of operation called electromagnetic induction

5 What Does Current Model Look like?

6 WHAT CAN IT MAP? Crop Yield Soluble Salts Nitrates Soil Moisture Top Soil Depth in Claypan soils Organics Soil Textural Changes Compaction Clay Content Magnetic Susceptibility

7 A Look at some Historical Electromagnetic Induction Systems Manufactured by Geonics Limited

8 EM15 & EM15-MK2 (Compact Personal Electromagnetic Detector) EM15 produced in 1963 & EM15-MK2 in 1965 Operating Frequency 15 khz Coil separation 83 cm, null coupled by being parallel at 35 degrees from vertical Depth penetration 15m for large good conductor Used to distinguish between a conductor (sulphide minerals, metals) and magnetically permeable bodies (magnetite, pyrrhotite) Meter would display +ve (Red) for conductor and ve (Blue) magnetic permeable body

9 The Canada Agriculture Museum is featuring this electromagnetic detector in celebration of National Science and Technology Week, October 14 to 23, 2011.

10 Old & New?

11

12 Electromagentic systems Frequency Domain The transmitter current varies sinusoidally with time at a fixed frequency

13 What do we measure directly? An electromagnetic field may be defined in terms of four vector functions E, D, H and B, where: E is the electrical field in V/m. D is the dielectric displacement in Coulomb/m². H is the magnetic field intensity in A/m. B is the magnetic induction in Tesla. J is the current in A The operation of all Geonics instrumentation is controlled by the Following two Laws of Physics which form part of Maxwell s Equations. Maxwell s Equations 1. Faraday s Law An Electric Field (Voltage) can be generated by a time varying magnetic field E = -db/dt 2. Ampere s Law An Electric current or a time varying electric field can generate a magnetic field H = J + dd/dt

14 INTRODUCTION A magnetic field can be used to induce, or create, an electromotive force (emf). This emf can drive an electric current. Electromagnetic induction is the basis for the generation of most of the electricity that is produced in the world today. Electromagnetic induction can also be used to change or transform an emf (a voltage). It is used in devices called transformers that increase or decrease the voltage, of an alternating current power supply. The direction of the force on a positively-charged particle is defined by a right hand rule, illustrated in the diagram above. Note that the magnetic field in the illustration is oriented parallel to the screen and the velocity is downward so that we can show the thumb and fingers clearly

15 An Electric Field (Voltage) can be generated by a time varying magnetic field Graphical animations of Maxwell s circulation, time-varying, curl equations Ampere s Law An Electric current or a time varying electric field can generate a magnetic field

16 Principle of Operation Control panel Tx Rx, Receiver H s Reinforced magnetic field H p +H i H p, Primary magnetic field H i, Induced secondary magnetic Current loops in the ground created by H p (Corwin 2011) Where the subsurface is homogeneous there is no difference between the fields propagated above the surface and through the ground (only slight reduction in amplitude). If a conductive anomaly is present, the magnetic component of the incident EM wave induces alternating currents (Eddy currents) within the conductor. The eddy currents generate their own secondary EM field which travels to the receiver.

17 Principle of Operation (Understanding Terminology of Data Output for Conductivity Meters) Receiver detects the primary field which travels through the air. Receiver responds then to the resultant of the arriving primary and secondary fields. Consequently, the measured response will differ in both Phase and Amplitude relative to the unmodulated primary field. Differences between the transmitted and received electromagnetic fields reveal the presence of the conductor and provide information on its geometry and electrical properties. Two components measured are : Quad-phase = Quadrature component = Conductivity (ms/m) In-phase = In-phase component = Magnetic Susceptibility (ppt)

18 GROUND CONDUCTIVITY METERS EM31-MK2 EM31-SH EM38 EM38-DD EM38-MK2 EM34-3 EM34-3XL

19 Factors that affect Soil Conductivity Porosity; shape and size of pores, number, size and shape of interconnecting passages Extent pores are filled by Water (i.e. Moisture content) Concentration of dissolved electrolytes in contained moisture = Salinity Temperature & Phase state of pore water Presence of Clays with moderate to high Cation Exchange Capacity (CEC) Presence of Conductive minerals (i.e. magnetite, hematite, pyrite )

20 Factors that affect Soil Conductivity In general the Conductivity is electrolytic and takes place through the moisture filled pores and passages which are contained within the insulating matrix. The conductivity is determined for both rocks and soils by the following: Soil Particles (Insulators) Soil Moisture (Conductive) Lines of Current flow

21 Two Properties measured by All EM Soil Conductivity Meters Apparent Conductivity (ms/m) = Quadrature Component of EM Field Magnetic Susceptibility (ppt) = Inphase Component of EM Field

22 Understanding the Measurement Conductivity is measured in millisiemens/metre (ms/m) which is equivalent to millimohs/metre (mmhos/m) The displayed reading of the EM38 is in ms/m which can be converted to the following as well: Symbol most often used for Conductivity is the Greek letter Sigma = Symbol most often used for Resistivity is the Greek letter Rho = r s s r (ms/m) = 1000/ (Ohm*m) 1 ms/m = 0.01mS/cm and 1 ds/m = 0.01 x (ms/m)

23 Depth Control of EM Soil Conductivity Meters Changing coil separation distance Changing the dipole mode or rotating of coils Changing frequencies

24 Vertical Distribution of EM Response VDM Old EM38 Model HDM Depth = 1.5 x coil separation Depth = 0.75 x coil separation

25

26 EM38-MK2 Coil Schematic and Depth of Exploration in V-mode Tx 0.5m 1m Rx1 Rx m Surface 1.5 m Coil Separation = 1m and 0.5m Operating Frequency = 14.5 khz V-mode Depth Exploration = 1.5m and 0.75m

27 EM38-MK2 Coil Schematic and Depth of Exploration in H-mode Tx 0.5m 1m Rx1 Rx m Surface 0.75 m Coil Separation = 1m and 0.5m Operating Frequency = 14.5 khz H-mode Depth Exploration = 0.75m and 0.38m

28

29

30

31

32 Back to Shallow EM & our most popular Agricultural Product Line

33 Old Style EM38 Models

34

35 The new EM38-MK2 Ground Conductivity Meter effectively combines the performance features of all previous EM38 models in a single instrument: The EM38-MK2 provides measurement of both the quadphase (conductivity) and in-phase (magnetic susceptibility) components, within two distinct depth ranges, to a maximum effective depth of 1.5 m, all simultaneously.

36 In addition, new standard features and options each provide additional benefits: integrated Bluetooth functionality provides the option of wireless data transmission; a power input connector allows for the use of external power sources; a rechargeable external battery pack extends the duration of instrument operation; and a portable calibration stand provides the convenience of an automated calibration.

37 Geonics Standard Logging and Processing Software (DAT38MK2) XF101 DGPS Receiver for the Archer Field PC

38 A Look at some Third Party Data logging and mapping Software

39 Ag Leader & SMS Mobile

40 Farm Works Mobile Software

41 StarPal & HGIS PRO Software with Sensor Track

42 Use your iphone & ipad with WiSnap software App to collect data by Wifi-RS232 Serial module

43 SST Management Software Direct Geonics Data Import

44 Mobile EM38 Sleds & Trailers

45 Mobile EM38 Sleds & Trailers

46 Mobile EM38 Sleds & Trailers

47 Salinity Lab EMI rig Sled w/ Dual-dipole EM-38

48 EM Applications Groundwater Exploration & Contamination Precision Agriculture/Soil Salinity Environmental hazards (ie drums, waste containers, UST s, and UXO s) Pipelines, Utilities & Landfill Boundaries Buried trenches & pits Historical structures and artifacts Turfgrass

49 THE APPARENT CONDUCTIVITY OF SOILS WILL INCREASE WITH INCREASING: Water content, Clay content, Soluble salt content.

50 EM Applications The quadrature component is used to measure the apparent conductivity (ECa) of earthen materials. The in-phase component can be used to detect objects of high conductivity (metals) and assess differences in magnetic susceptibility Pipe

51 Salinity Mapping & Management Zones

52 Management of Saline Soils

53 Salinity Mapping & Management Zones EM38 in sled 50cm depth of investigation (Anning-Landline Geophysics) EM31 on outrigger. 4m depth of investigation.

54 Salinity Mapping Irrigated Pasture Deep Shallow Dryland Pasture

55 Salinity Mapping in Australia 200m

56 Salinity Mapping in Australia EM31-MK2 data to depth of 6m

57 Salinity Mapping in Australia EM38 data to depth of 1.5 m Chemical attributes with profile depth at location DeB01

58 Mapping soil and soil map unit inclusions Renshaw Fine-loamy over sandy or sandyskeletal, mixed, superactive, frigid Calcic Hapludolls Svea Fine-loamy, mixed, superactive, frigid Pachic Hapludolls (Doolittle-USDA)

59 Identifying soilhydrologic-landscape units

60 Spatiotemporal variations in EC a associated with changes in soil moisture Spring 2006 Fall 2005

61 EM38 Turf Grass Applications EM38 Soil Conductivity Survey HOLE FAIRWAY GREEN FAIRWAY GREEN Oak Hill Country Club Golf Course Conductivity (ms/m) Conductivity (ms/m) (Vertical dipole) (Vertical dipole) HOLE

62 Hole 18 Conductivity (ms/m) Elevation (feet) Very conductive and wet due to drainage of water toward Tee Box

63 Conductivity maps of Drainage Patterns for Turf in Stadiums CRICKET STADIUM SOCCER STADIUM

64 Relating Soil Water Content, Conductivity and Crop Yield Conductivity Yield Purple Yellow Green Red Barley Field

65 Relating Soil Water Content, Conductivity and Crop Yield Conductivity Soil Water Content

66 In Conclusion..EM Conductivity Helps Any time of year No ground contact Any kind of weather Light weight, Low power Multiple Field correlations Low maintenance No moving parts Integration with existing Precision Software

67