Integrating 3D Optical Imagery with Thermal Remote Sensing for Evaluating Bridge Deck Conditions

Transcription

1 Integrating 3D Optical Imagery with Thermal Remote Sensing for Evaluating Bridge Deck Conditions Richard Dobson

2 Project History 3D Optical Bridge-evaluation System (3DOBS) Proof-of-Concept developed under the USDOT-RITA project Assessing Bridge Condition Though the Use of Remote Sensors Used to asses spalling and cracking BridgeGuard Thermal imaging system used to asses delaminations Currently a commercially operated by GS Infrastructure MDOT Project Improve 3DOBS Near highway speed version (45mph) High resolution version Combine both systems on the same vehicle 2

3 3DOBS: Proof of Concept The vehicle mount was built for a 12.3-mp Nikon D5000 with a lens that had a focal length of 18 mm. A vehicle mount was constructed to elevated the camera to 9 ft above the bridge deck. This enabled the collection of a full lane width per pass. The vehicle maintained a speed of about 2 mph to ensure a 60% overlap of the photos. We are adapting this to operate for speeds of at least 45 mph ( near highway speed ) using a faster camera setup Proved concept worked for USDOT Bridge Condition project 3

4 Agisoft Process (Structure from Motion) Automatically aligns photos Reference points were needed to generate DEM 4

5 3DOBS Results Generated overview images of all four bridges 2mm resolution Generated Digital Elevation Model (DEMs) of all four bridges a high-res bridge surface representation 5mm horizontal resolution 2mm vertical resolution 5

6 Bridge Overview Close Up Spall on Willow Rd. Bridge: 2 mm resolution 6

7 Bridge DEM Close Up Spall on Willow Rd. Bridge: 5 mm resolution 7

8 Automated Spall Detection Algorithm Programmed in Python Uses ArcPy to utilize ArcGIS geospatial tools Uses DEM as the input raster Creates a GIS shapefile of detected spalls Generates a table of spall sizes and volumes 8

9 Detected spalls overview 9

10 Restrictions on Minimum Spall Size 10

11 3DOBS High-Res Crack Detection Body type Nikon D800 full-sized (FX) sensor, 36.3 Mp, 2 fps Weight prime lens, weights ~1.5 kg max 5 mph speed $2,800 ($480 Lens) Body type Mid-size SLR Body material Magnesium alloy Sensor Max resolution 7360 x 4912 (px) Effective pixels 36.3 megapixels Sensor photo 36.8 megapixels detectors Other resolutions 6144 x 4912, 6144 x 4080, 5520 x 3680, 4800 x 3200, 4608 x 3680, 4608 x 3056, 3680 x 2456, 3600 x 2400, 3072 x 2456, 3072 x 2040, 2400 x 1600 Image ratio w:h 5:4, 3:2 Sensor size Full frame (35.9 x 24 mm) Sensor type CMOS Processor Expeed 3 Color space srgb, Adobe RGB Color filter array Primary Color Filter Image ISO in 1, 1/2 or 1/3 EV steps ( with boost) White balance presets Custom white balance Image stabilization Uncompressed format 12 Yes (5) No.NEF (RAW) JPEG quality levels Fine, Normal, Basic File format NEF (RAW): 12 or 14 bit, lossless compressed, compressed or uncompressed TIFF (RGB) JPEG Optics & Focus Autofocus Phase Detect Multi-area Selective single-point Tracking Single Continuous Face Detection Live View 11

12 3DOBS High-Res Data Output 0.5 mm resolution imagery produced from 3DOBS- High Res Ortho Imagery (top), hill shade representation of the DEM (middle) and the location of each on the bridge (bottom) 12

13 3DOBS High-Res Results With imagery resolution of 0.5 mm, cracks down to 1 mm (just over 1/32nd inch) can be mapped while travelling at speeds up to 5 mph Maryland Ave cracks: 35 Cracks were digitized Total crack length in 13

14 Detail of a 1 mm Crack 14

15 3DOBS Highway Speed Spall Detection Red-EPIC camera system 13.8 MP up to 60 frames per second Capable of collecting data at vehicle speeds of 45 mph with the current setup $30,000 15

16 3DOBS Near Highway-Speed Data 16

17 Spall Detection Algorithm Able to locate and characterize spalls by area, volume and depth. Able to limit the minimum size of spalls detected. US-131 NB spall detection results 9.9 ft2 spalled 1 % of bridge spalled 17

18 Passive IR Thermography To detect concrete bridge deck delaminations using thermal imagery and the natural thermal transition within the structure due to normal diurnal environmental exposure, while traveling at highway speed 18

19 Passive IR Thermography (BridgeGuard) Delamination Sun provides thermal impulse Heat transfers from surface to concrete interior Delaminations restrict heat transfer and appear as hot spots on thermal images during daytime hours Maximum contrast occurs during specific testing time window 19

20 US131 NB over White Creek Ave Tested 8/9/13 at 3:45 pm 20

21 Passive IR Thermal into GIS Thermal Infrared data provided by BridgeGuard Using ArcGIS software, MTRI georeferenced and mosaicked these data. These data can now be combined with other geospatial datasets (spall detection from 3DOBS). Data collected for north and south bound US-131 shown to the left. 21

22 Maryland Ave. Thermal Layer Mosaicked thermal layer of Maryland Ave. 22

23 NDE Technology Integration for Top of Bridge Deck All collected data and results are either GIS raster or shape files and can be easily displayed and overlaid in a GIS. Data and Results Output: Orthoimage DEM Hillshade Thermal Image Mosaic Detected Spalls Layer Detected Delaminations Layer` (Can also create.las point cloud) 23

24 Combined 3DOBS and BridgeGuard System 24

25 Maryland Ave. Datasets Orthoimage DEM Hillshade Thermal Spalls Delaminations 25

26 Maryland Ave. Datasets Orthoimage Spall Area: 1.5 sq ft Percent Spalled: < 1% Potential delaminated area: 31.7 sq ft Thermal 26

27 Conclusions The RED Epic enabled 3DOBS Near Highway Speed to be driven along side the BridgeGuard thermal camera at vehicle speeds of 45 mph for spall, crack and delamination detection. 3DOBS High-Res allows for visualizing cracking down to roughly 1/32nd inch. A vehicle mount was built allows for both optical and thermal data to be collected simultaneously. Both datasets and results are referenced on top of each other in a GIS to allow for a more complete understanding of surface and subsurface conditions. 27

28 Thank You! Contact Info Richard Dobson Desk: Michigan Tech Research Institute, MTRI 3600 Green Court, Suite 100 Ann Arbor, MI