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Peter Mann

Peter Mann. Radiodetection USA. Introduction. Welcome to the Radiodetection RD1000 Training Course. RD1000 Training Course. What is ground penetrating radar (GPR). Is a geophysical method that uses radar pulses to image the ground Non–destructive method

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Peter Mann

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  1. Peter Mann Radiodetection USA

  2. Introduction Welcome to the Radiodetection RD1000 Training Course RD1000 Training Course

  3. What is ground penetrating radar (GPR) • Is a geophysical method that uses radar pulses to image the ground • Non–destructive method • Uses microwave band in region of UHF/VHF • Typical frequency is 300 to 500 MHz • Detects reflected signals from subsurface objects • Uses transmitting and receiving antennas • Transmitting antenna radiates short pulses, of radio waves into ground. When the wave hits an object, the receiving antenna receives the deflected pulse • Can be used to locate non conductive materials RD1000 Training Course

  4. Characteristics • The most significant performance limitation is in high-conductivity materials such as clay soils that are salt contaminated. • As conductivity increases, the electromagnetic energy is more quickly dissipated into heat, causing loss in signal strength • Optimal depth is in ice where depth can be several hundred meters • Good penetration in dry sandy soils where depths of up to 15m • In moist and or clay laden soils penetration can be as low as a few centimetres • GPR effectiveness is thus site specific and varies greatly from place-to-place RD1000 Training Course

  5. Depth penetration • Can I predict exploration Depth ? - yes, provided you know the material • Can use radar range equation (RRE) - software available and numerous papers written - this can be difficult to understand • Can use a soil suitability chart RD1000 Training Course

  6. Soil suitability chart RD1000 Training Course

  7. Soil suitability chart for USA RD1000 Training Course

  8. Which frequency ? • Higher frequencies do not penetrate as far as lower frequencies but give better resolution. Ideal for detecting small, shallow objects such as pipes. • Use the lowest possible frequency - reasonably high penetration depths - if frequency is too small, the resolution will be too low, hence not able to detect small objects • 150MHz typical frequency – 300 to 500 MHz used for shallow high resolution probing

  9. Case Studies 3” parallel PE coated pipes RD1000 Training Course

  10. Case Studies Reinforcement bars in concrete RD1000 Training Course

  11. RD1000 Overview GPR: (Ground Probing Radar) • Simple to use • Affordable • Tough • Portable • Finds plastic and clay pipes • Walk over, look and see RD1000 Training Course

  12. RD1000 Overview Display unit Cabling Cart Power Sensor Odometer Main components RD1000 Training Course

  13. Sensor Features Tough moulded plastic shell Odometer connector Display connector Battery connector • Cutting edge GPR electronics • Emission approved for all major jurisdictions • Bandwidth 125 to 375 MHz, centre 250MHz Weight: < 5kg Power required: < 8 W Size: 630 x 410 x 230 (mm) High wear resistant skid plate RD1000 Training Course

  14. Data Display Unit Features Removable flash memory card Rugged aluminum extrusion housing • Upgradable embedded software • Low power <5W • Water proof enclosure Optimal sunlight visible screen Simple intuitive user interface Tough membrane keypad Image recording option RD1000 Training Course

  15. Embedded Software Upgrade from flash • Simple user interface • Selectable depth range to 8m • Signal enhance filtering Symbolic or selected language menus Option to record data images RD1000 Training Course

  16. Power Quick replace battery pack • Battery 9Ah standard (6 – 8 hours life) • Supply voltage 12V • Industry standard lead-acid gel cells • Charge time for empty battery is 12-14 hours • Below 10.2V – needs charging RD1000 Training Course

  17. Using the Display Unit • 8 buttons, Pause and Camera buttons as well as buttons to increase and decrease the screen Contrast and Brightness. • The menu option on the screen above the button indicates its function. RD1000 Training Course

  18. System Settings Screen Scan Press the Scan button to start scanning. Language Select the language for the menus. Current options are English or Icons. Units Units for the Position Axis, Depth Axis and Depth Indicator can be either Meters or Feet. RD1000 Training Course

  19. System Settings Screen Scale Scale toggles to four different options: • Lines: Plotted on the data image to assist with determining the depth of targets • Text: Depth Values plotted in the center of image every 8 metres • Both: Depth Lines and Values are plotted on image • Off: No Depth Lines and Values are plotted on the data image RD1000 Training Course

  20. System Settings Screen Date Opens the Date Screen to change the current date. Images are saved with this date. Time Opens the Time Screen to change the current date. Images are saved with this time. Power Off Opens a sub-menu to confirm powering off the system. There is also an option to restore the system to factory default settings. System Information The top of the Systems Setting Screen displays the serial number of the GPR sensor, the software version number, the GPR Sensor frequency (in MHz) and the current battery voltage. RD1000 Training Course

  21. Locating Screen GPR images can be displayed in colour, in general, stronger GPR signals appear in stronger colors. Some color palettes may show the target better than others. RD1000 Training Course

  22. Image Settings Screen Image Settings Pressing the Pause button opens the Image Settings Screen to change the current Color Palette, Depth, Filter and Gain. RD1000 Training Course

  23. Image Settings Screen Scan Since GPR signals are absorbed by the material being scanned, deeper targets have weaker signals. Gain acts like an audio volume control, amplifying the signals and making deeper targets appear stronger in the image. The Gain varies from 1 to 9 with 1 being no gain and 9 being the maximum gain. Gain setting 2 Gain setting 8 RD1000 Training Course

  24. Image Settings Screen Filter The filter has effect of removing flat-lying reflections in the image and enhancing the dipping reflections and arches usually caused by targets. Can also assist in identifying very shallow targets that might be masked by the strong signals at the top of the image. The Filter defaults to ON, so if you are looking for a layer or other flat-lying target, turn the Filter OFF. The image below shows the same scan with the Filter OFF and ON. RD1000 Training Course

  25. Image Settings Screen Depth The depth setting is an estimate of the total depth displayed on the Scanning Screen based on the current Soil Type setting. The depth setting ranges from 1 to 8 meters. RD1000 Training Course

  26. Locating Screen The Locating Screen is accessed by stopping and pulling the cart backwards while scanning. Locating Cursor • Position IndicatorVertical line indicating center of GPR • Depth IndicatorHorizontal line for indicating the depth. • Indicator ArchIdealized representation of a typical pipe-like target response observed on the GPR image. The width of the arch is controlled by soil type setting. The soil type setting is changed using the Arch buttons. Increasing the soil type makes the indicator arch wider while decreasing the soil type makes it narrower. RD1000 Training Course

  27. Depth calibration Soil Type To obtain an accurate depth axis and depth estimations of targets in the GPR image, a Soil Type Calibration must be performed. Soil Type Calibration can be done 3 ways: • Matching the shape of a target arch, • Using a target at a known depth, or, • Using the moisture level of the soil. RD1000 Training Course

  28. Depth calibration Matching a Target Arch Pipes, cables, buried artifacts, tree roots and rocks generate arch-shaped responses. Arches occur as GPR energy does not travel into the ground as a pencil-thin beam but like a 3D cone. Reflections can appear on the record even though the object is not directly below the GPR sensor. Thus, the GPR sensor “sees” the pipe before and after going over top of it and forms an arch-shaped response on the image. The depth estimation of a target will be incorrect if the soil type calibration is done on a target arch produced at an oblique angle (smaller that 90 degrees). RD1000 Training Course

  29. Depth calibration Use the Up and Down Arrowsto move the Indicator Arch shallower or deeper in the GPR image respectively, until it lies overtop of the target arch. RD1000 Training Course

  30. Depth calibration Press Soil Type button and toggle through the five different soil types to find the one that roughly fits the shape of the Indicator Arch to the shape of the Target Arch. Use the Wide and Narrow Arch buttons to change the shape of the Indicator Arch to match the shape of the Target Arch on the GPR image. The depth of the target is indicated on the bottom left. Press the Apply button to save the Soil Type and update the Depth Axis on the Scanning Screen. The Depth axis can now be used to estimate the depth of targets while scanning in the area. RD1000 Training Course

  31. Depth calibration Target at Known Depth If no suitable arches visible in the image to perform Target Arch Matching, there may be a target of known depth in scanning area. To determine the Soil Type using a target at known depth: • With target response visible on image, use Up and Down Arrows to move the Depth Indicator (and Indicator Arch) until it lies on top of the GPR response of the known target. • Use Wide and Narrow Arch buttons to change shape of Indicator Arch until depth of target, displayed in red above the menu, is correct. • Once depth is matched, save Soil Type value by pressing APPLY button. RD1000 Training Course

  32. Depth calibration Known soil conditions • If a good target arch or a target of known depth is not available, the user will have to estimate the Soil Type. • The soil type is most strongly affected by water so the soil type options relate to the amount of water in the soil. • Change the soil type by pressing the Soil Moisture button until the option that best describes the soil in the area is displayed. • The options are Very Dry, Dry, Moist, Wet and Very Wet Soil. RD1000 Training Course

  33. Locating Screen Identifying Air Wave Reflections Some arches in the image can be caused by objects that are not in the subsurface, such as posts, fences, overhead wires and even trees. An important part of understanding the data image is learning to recognize these unwanted “air” targets and differentiate them from the targets in the ground. Therefore, if the widest Indicator Arch is still not wide enough to match the target arch, the target arch is from on object in the air, not the ground. RD1000 Training Course

  34. Locating Screen Airwave Signals RD1000 Training Course

  35. Image Settings Screen Scan To exit Image Settings Screen and resume Scanning, press Scan button or Pause (||) button again (to resume). Scanning Screen returns at the current location with position information preserved. If, while paused in the Image Settings Screen, the cart has moved more than a few centimeters, when scanning is restarted, a gap called a Position Break will appear in the image. The position break is also indicated by a message on the bottom of the screen and the Position Axis along the top of the data image resetting to zero. RD1000 Training Course

  36. Scanning Screen Press Scan button, vertical depth scale will appear on the right side of the screen. A cross-sectional image of the ground scrolls onto the screen from the right to left. The position is displayed on the horizontal axis at the top while the depth is displayed on the vertical axis. RD1000 Training Course

  37. Scanning Screen Approximately 16 meters of data is displayed on one screen. If the survey line exceeds this distance the image will scroll off the left side of the screen. To save current screen image, press Camera button on Display Unit. Image number appears on the bottom of the screen. Pressing any of the number buttons on the Display Unit marked 1 to 8 while scanning adds a numbered marker at the current position. Pressing the Pause button opens the Image Settings Screen to change the current Color Palette, Depth, Filter and Gain. Stopping and pulling the cart backwards along the same path automatically opens the Locating Screen used to pinpoint the position and depth of a target. RD1000 Training Course

  38. Data Collection • System always collects data to a depth of 8 meters • Depth setting on menu determines how much data displayed on the screen. • Possible to scan a Depth setting of 2 meters, pause scanning and then increase the depth setting to re-display the image to look for deeper targets – very useful tool… RD1000 Training Course

  39. Saving images • To save image press camera button • Time, date and image number • Require viewing software - USB dongle RD1000 Training Course

  40. Surveying Techniques Most common method of locating is cross and mark as you go. This method works well in favorable soils and uncluttered settings. Cross and mark is very similar to the use of utility detectors. The Cart is moved along sweeps perpendicular to the anticipated utility axis (see figure below). When the GPR sensor crosses the utility, the image shows an arch. The top of the arch is the position of the utility. The depth to the top of the arch is an estimated depth. By moving the GPR back and forth and marking the ground where the top of the arch is observed, the alignment of the subsurface utility can be traced out as the X’s in the figure indicate. RD1000 Training Course

  41. GPR and Locator • The RD1000 can be further enhanced with use of a locator and transmitter • Useful for verifying • May locate where the RD1000 cannot • Soil conditions • Accuracy RD1000 Training Course

  42. Actual Results Power Cable under concrete RD1000 Training Course

  43. Actual Results Large area scan including very large manhole RD1000 Training Course

  44. Actual Results Recently completed excavation to lay new water pipe RD1000 Training Course

  45. RD1000 GPR Remember, GPR has limitations – Not a magic wand !! • Practice • Build up a portfolio • Use Internet for information Lets play !! RD1000 Training Course

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