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MAPLE: Portable Laser Equipment for Shallow Water Reflectance Measurement

Introducing MAPLE, a multi-beam autonomous portable laser equipment that measures the reflectance of shallow water facies and habitats. It is a new tool to calibrate airborne laser bathymetry instruments.

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MAPLE: Portable Laser Equipment for Shallow Water Reflectance Measurement

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  1. Shallow Survey 2008, Portsmouth NH USE OF A MULTI-BEAM AUTONOMOUS PORTABLE LASER EQUIPMENT (MAPLE) TO MEASURE THE REFLECTANCE OF SHALLOW WATER FACIES AND HABITATS a new tool to calibrate airborne laser bathymetry instruments BERNARD LONG & VALERIE ROBITAILLE INSTITUT NATIONAL DE LA RECHERCHE SCIENTIFIQUE - ETE QUÉBEC, CANADA

  2. INTRODUCTION MATERIAL LAB TESTS CALIBRATION FIELD WORK CONCLUSIONS Shallow Water Environments Airborne Laser Bathymetry • Uses laser pulses time of flight • (532 nm and 1064 nm) and the • speed of light, to determine the • water columnheight. • Is precise, economical and • efficient. • The intensity of the lasers • signal return is a function of • the target’sreflectance… • giving information about the • differentsedimentary facies • and biologicalenvironments. http://www.aeromapss.com/airbor84.jpg http://www.encora.eu Shallow Survey 2008, Portsmouth NH

  3. INTRODUCTION MATERIAL LAB TESTS CALIBRATION FIELD WORK CONCLUSIONS Post-treated SHOALS-3000T Laser Pulse Challenges Environmental Parameters: - water column turbidity, - atmospheric conditions, - seabed morphology, - waves, currents and tides - biodiversity - sedimentary facies origin surface peak bottom peak water column Difficulties: - air/water boundary identification - seabed localization - water column characterization - sedimentary facies identification - biological habitats identification - investigation of shallow water ecosystems Bonavanture River mouth, Quebec Other Technical Problems: - laser beam incident angle - laser beam expansion - small object detection - accuracy standards - relative temperature changes author: Antoine Cottin Shallow Survey 2008, Portsmouth NH

  4. INTRODUCTION MATERIAL LAB TESTS CALIBRATION FIELD WORK CONCLUSIONS constant needs for the calibration of airborne laser bathymetry systems ONE SOLUTION Develop a Multi-beam Autonomous Portable Laser Equipment (MAPLE) that simulates the functions of airborne laser bathymetry systems TO Conduct tests in controlled (laboratory) and semi-controlled (field) environments to solve issues specific to the airborne laser bathymetry system surveying techniques Shallow Survey 2008, Portsmouth NH

  5. MAPLE Components MATERIAL INTRODUCTION LAB TESTS CALIBRATION FIELD WORK CONCLUSIONS ** the signal emitted by this laser system is countinuous ** Stainless Steel Splashproof Casing thermal sensor humidity sensor dataview screen distance meter 532 nm return lens 1064 nm return lens 532 nm output 1064 nm output Records: CR1000 Datalogger Campbell Scientific • 532nm output (mV) • 532nm input (mV) • 1064nm output (mV) • 1064nm input (mV) • distance (cm) • beam inclination (angle) • external temperature (C°) • internal temperature (C°) • system voltage (V) • time stamp (h:m:s) Tripod: min 1.3 m max 4.0 m The datalogger is integrated in the casing on which a built-in serial port enables communication Shallow Survey 2008, Portsmouth NH

  6. MATERIAL INTRODUCTION LAB TESTS CALIBRATION FIELD WORK CONCLUSIONS MAPLE Components Thermoelectrically Cooled Modulated Green and Infrared Laser Systems Same specs for 1064 nm Shallow Survey 2008, Portsmouth NH

  7. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Mission of MAPLE in Laboratory • To measure the reflectance of different • specimens and isolate their specific • characteristics such as: • - pigmentation, • - rugosity, • - porosity, • - grain shape and size (sediments), • - water content… • To study the influence of external variables • on the intensity of blue-green and infrared • laser beam return signals : • - system’s internal temperature, • - beam inclination, • - distance traveled by the laser beam, • - water column attenuation… Shallow Survey 2008, Portsmouth NH

  8. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Specimensvs. DifferentMineral Composition Sand REFLECTANCE (normalized with a white target) NEW HAMPSHIRE - quartz - feldspar - biotite - muscovite BERMUDA - coral reef • ILLINOIS • Ottawa Sand • (99.44% silica) • MAINE • - shells • - quartz • feldspar • rock fragments QUEBEC - Old Red Sandstone (detritus from warm climate) • CANARIES • Basalt and other • ferro-magnetic • minerals INspecimen/OUTspecimen INtarget/OUTtarget X100 Rsand = Shallow Survey 2008, Portsmouth NH

  9. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Specimens vs. Different Mineral Composition Igneous Rocks • Obsidian • (1st side) • Volcanic • glass • Intrusive • Diorite • - Granite Intrusive oxidized - Gabbro • Gneiss • Quartz • Feldspar • Tourmaline • Orthopyroxen • Gneiss • Grenat • - Biotite • Gneiss • Quartz • Feldspar • (ribbons) • Tourmalinite • Tourmaline • - Quartz • Gneiss • Quartz • Feldspar • Biotite Basalt porous • Obsidian • (2nd side) • Volcanic • glass Shallow Survey 2008, Portsmouth NH

  10. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Specimens vs. Different Mineral Composition Sedimentary Rocks Dolomite Shale Limestone Calcite Rippled limestone Polished limestone Breccia Calcarenite Altered shale Sand Stone (Old Red) Shallow Survey 2008, Portsmouth NH

  11. Reflectance Ratio 1064nm / 532 nm Altered polished rocks Gneiss group Oxidized and carbonate rocks Old Red sand stone formation Shallow Survey 2008, Portsmouth NH

  12. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Sand vs. Different Pigments (532 nm) white yellow green blue red purple orange black natural sand with pigment = Reflectance normalized with a white target = pigment only Reflectance of Sand vs. different Pigments (1064 nm) white yellow green blue red purple orange black natural Shallow Survey 2008, Portsmouth NH

  13. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Sand vs. its Grain Size < 63 µm 2 different populations Shallow Survey 2008, Portsmouth NH

  14. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Reflectance of Sand vs. its Moisture Content nm nm dry sand 99.4% Quartz Sand nm nm Sand Beach Sample (Acadia National Park, Maine) Shallow Survey 2008, Portsmouth NH

  15. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Attenuation of the Laser Beams in the Water Column Due to the Nature and Concentration of Suspended Sediments 532 nm Laser Beam concentration of suspended sediments (g/L) concentration of suspended sediments (g/L) Reflectance (input signal/output signal) Portsmouth beach sand Terrigenous sediments Quartz sand 1064 nm Laser Beam Shallow Survey 2008, Portsmouth NH concentration of suspended sediments (g/L)

  16. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Interaction of Distinct Facies in a Heterogeneous Environment 0,77% 0,54% 0,19% 0,17% all within 5 % error from theoretical value Reflectance normalized with a white target 12,91% 23,50% 13,72% 16,40% 32,67% 21,91% 17,26% 19,34% 14,34% error 12,25 % error 6,20 % error 4,82 % Sandstone fine grains/conglomerate Unconsolidated Sediments fine sand/pebbles Gneiss quartz (white)/biotite(black) Shallow Survey 2008, Portsmouth NH

  17. LAB TESTS INTRODUCTION CALIBRATION FIELD WORK CONCLUSIONS MATERIAL Incident Angle Effect on the Reflectance of Submerged Surfaces Reflectance (input signal/output signal) Incident Angle (degree) Porcelain Bowl various grain size populations Coral Sand 63 - 125 µm Quartz Sand 250 - 500 µm Quartz Sand Pebbles Shallow Survey 2008, Portsmouth NH

  18. CALIBRATION OF THE EXTERNAL VALUES I. Internal Temperature II. Distance III. Incident Angle

  19. CALIBRATION INTRODUCTION FIELD WORK CONCLUSIONS MATERIAL LAB TESTS Signals' Ratio vs. MAPLE’s Internal Temperature 1064nm : y = 0.0077575 x2 - 0.41602 x + 8.9729 Peltier Element Fan Signals Ratio (input signal/output signal) 532 nm 1064 nm 532nm : y = -0.0018919 x + 1.936 Internal Temperature of MAPLE (C°) Shallow Survey 2008, Portsmouth NH

  20. CALIBRATION INTRODUCTION FIELD WORK CONCLUSIONS MATERIAL LAB TESTS Signals’ Ratio vs. Distance of Specimen from MAPLE Laser Sources 1064nm : y = 0.00000082332 x3 - 0.00068693x2 + 0.1727 x - 9.739 532 nm 1064 nm Optimal distances: 532 nm 139 cm 1064 nm 186 cm Signals Ratio input signal/output signal) 532 nm : y = 0.0000014908 x3 - 0.00086847 x2 + 0.15286 x - 6.606 Distance (cm) Shallow Survey 2008, Portsmouth NH

  21. CALIBRATION INTRODUCTION FIELD WORK CONCLUSIONS MATERIAL LAB TESTS Signals’ Ratio vs. Incident Angle of MAPLE Laser Beams 532 nm 1064 nm 1064nm : y = - 0.00058089 x2 – 0.0013119 x + 4.1035 Signals Ratio input signal/output signal) B. LONG & V.ROBITAILLE INRS-ETE, QUÉBEC 532nm : y = - 0.0002243 x2 + 0.0010963 x + 1.8749 Beam Inclination (degree) Shallow Survey 2008, Portsmouth NH

  22. FIELD WORK COMPLETED AND FUTURE FIELD APPLICATIONS

  23. FIELD WORK INTRODUCTION CALIBRATION CONCLUSIONS MATERIAL LAB TESTS Reflectance Measurements; samples from New Castle Beach, NH 12 14 13 Station 6 9 fine sand New Castle, New Hampshire 8 pebbles mixed with fine sand field laboratory cobbles granules 7 6 3 2 5 1 Shallow Survey 2008, Portsmouth NH

  24. FIELD WORK INTRODUCTION CALIBRATION CONCLUSIONS MATERIAL LAB TESTS ON THE FIELD CALIBRATION MAPLE measures reflectances on the field Ratios between the different environments Integration of ratios to post treatment of ALB data More precise and efficient classification of environments from ALB techniques GPS Example with 2 distinct facies found on New Castle beach, NH (measured in lab with MAPLE) Alimentation cable polyvalent support Digital camera Long lasting batteries (14 V) reflectances normalized with white target Next step: integrate the calibration equations into datalogger program to automatically correct reflectance measurements on the field… no white target needed Shallow Survey 2008, Portsmouth NH

  25. FIELD WORK INTRODUCTION CALIBRATION CONCLUSIONS MATERIAL LAB TESTS Shallow Survey 2008, Portsmouth NH

  26. Shallow Survey 2008, Portsmouth NH CONCLUSIONS • Right now MAPLE is a good laboratory tool to study green and • infrared laser beam behaviors to shallow water facies and habitats • MAPLE has the potential to improve and develop new algorithms • relevant to airborne laser bathymetry systems NEXT STEPS • Use MAPLE as an in situ calibration tool to increase the environmental • classification precision of airborne laser bathymetry surveys • Develop another calibration tool (pulsed and submarine)

  27. Shallow Survey 2008, Portsmouth NH To be continued… Thank you! Questions?

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