Digital Close Range Photogrammetry of Soil Excavation Surfaces

Jared M. Shaffer

GIMS Specialist

Ohio Department of Agriculture

2015 Ohio GIS ConferenceSeptember 21 - 23, 2015 | Hyatt Regency Columbus| Columbus, Ohio

Digital Close Range Photogrammetry of Soil Excavation Surfaces for 3D Modeling

Jared M. Shaffer

GIMS Specialist

Ohio Department of Agriculture

2015 Ohio GIS ConferenceSeptember 21 - 23, 2015 | Hyatt Regency Columbus| Columbus, Ohio

Brian K. Slater, PhDAssistant Director and Associate Professor The Ohio State University, School of

Environment and Natural Resources

Tania D. Burgos-HernándezPhD StudentThe Ohio State University, School of

Environment and Natural Resources

Digital Close Range Photogrammetry• Photogrammetry

▫ “The art and science of obtaining precise mathematical measurements and three-dimensional (3D) data from two or more photographs”

• Digital Photogrammetry▫ Expanded EM spectrum, new operational scales▫ 3D Measurement and Modeling (3DMM) software

• Close Range Photogrammetry (CRP)▫ Object to sensor distance of < 300m

DCRP Approaches for Soil Images• Digital photogrammetry can be significantly simpler

and less expensive than laser scanning, and the quality of 3D models created has been shown to be comparable (Aguilar et al, 2009)

• Stereography▫ Multiple overlapping photos are taken at different

angles or orientations▫ 3D synthesized from parallax▫ depth relationships in the images can be accessed via

triangulation• Focus Stacking (Extended Depth of Field)

▫ multiple photographs taken at different focal distances from an object

▫ 3D synthesized from depth of field (using focal acuity contrasts between photographs)

Focus Stacking

Successive images are focused on object planes at different distances from image sensor, and exhibit narrow zones of in-focus pixels. Software identifies in-focus pixels from multiple images and combines them to reconstruct a fully focused image. 3D surface can be generated.

Berejnov, 2009

Some Applications

•Archeology•Architecture•Forensics•Stockpiles•Example application:

▫Soil excavation volume and bulk density

Bulk Density

• Fundamental soil physical property

• Proxy for other properties that may be less easily estimated (e.g. pore space)

• Commonly used to convert gravimetric measurements and concentrations to volumetric or areal quantities (e.g. soil carbon)

• Can be challenging to measure in some soils

Objective

•Compare bulk density measurements from soil pit horizons using conventional methods (core and clod), and from DCRP derived soil volume

•Site: Miamian silt loam, Madison Co., Ohio

DCRP Workflow• Photography

▫ Equipment: 35mm DSLR camera 24, 50, 60 mm macro

lenses Tripod and slider bar for

positioning

▫ Sequential overlapping photographs

DCRP Workflow

•Processing▫Software: EOS Systems Inc. Photomodeler▫Camera calibration▫DSM Model building 2-30 minutes▫Scaling & Editing▫Volume measurement

•To do▫More soils and situations, uncertainty▫Before and after models▫Measurements from focus-stacked models▫Printing

•Conclusions▫DCRP is a useful technique for soil profile

visualization▫Inexpensive alternative to laser scanning

for volume and shape-based measurements

Thank You

•Questions?