Tri-Closure Dr. Kotaro Yamafune (A.P.P.A.R.A.T.U.S. LLC) Daniel Bishop (The University of Alabama) Carolyn Kennedy (Texas A&M University)

Tri-Closure A new method to create a local coordinate system that is essential to create geo-referenced 1:1 scale-constrained photogrammetric models. Tri-Closure uses Photogrammetry to establish a local coordinate system It require only 2 dives to establish fairly accurate coordinate system!

GEO-REFERENCED 1:1 Scale-Constrained Photogrammetric Model To make 3D model into geo-referenced 1:1 scale-constrained model is essential if you need to use it as Archaeological data Measurable 3D models GIS Applications Site Plan AdriaS Project (Gnalic Shipwreck). Project Director Dr. Irena Radic Rossi

GEO-REFERENCED 1:1 Scale-Constrained Photogrammetric Model To make 3D model into geo-referenced 1:1 scale-constrained model is essential if you need to use it as Archaeological data Artifact Drawings Digital Analysis (Interactive Fragment Model) (Saveiro 1:10 wooden model) Section Profiles Point-Cloud-Based Deviation Analysis AdriaS Project (Gnalic Shipwreck). Project Director Dr. Irena Radic Rossi

GEO-REFERENCED 1:1 Scale-Constrained Photogrammetric Model Initial photogrammetry does NOT have any scale/accuracy! Accuracy of the photogrammetric model = Accuracy of coordinate system applied. NO MORE PRETTY PICTURES!!

Geo-referenced 1:1 scale-constrained Photogrammetric model Conventional Methods Create a local coordinate system separately (for examples, Total Station, Trilateration (DSMs).) Then apply created system into Photogrammetric models. Geo-referenced 1:1 scale-constrained Photogrammetric model Photogrammetric Model Local Coordinate System

Conventional Methods Total Station Direct Survey Methods (DSM) (Saveiro 1:10 wooden model) Total Station Direct Survey Methods (DSM)

Other Methods Scale Bars Direct Inputs Enclosure (Saveiro 1:10 wooden model) Scale Bars Direct Inputs Enclosure It scale-constrains photogrammetric models, but not make it geo-referenced.

Trilateration (DSM) (cm)   Control (cm) Trilateration (DSM) (cm) Enclosure (cm) Scale Bars (cm) Total Station (cm) R1 – R2 142.5 142.0 142.2 142.3 R1 – R3 51.2 51.3 51.1 51.0 50.7 R1 – R9 51.8 50.9 R1 – R6 63.4 63.9 63.2 62.9 R2 – R5 57.6 57.8 57.5 57.4 R2 – R11 50.4 50.5 50.3 R2 – R8 57.0 57.7 R3 – R5 44.9 44.6 45.2 45.1 45.5 R6 – R8 46.6 45.4 46.7 46.9 R3 – R6 54.2 53.9 54.4 54.3 54.0 R5 – R8 55.3 55.6 55.5 R4 – R7 57.2 57.1 56.7 R3 – R8 71.3 71.2 71.4 71.5 R6 – R5 71.0 70.4 71.8 71.7 Length of Keel 115.2 115.0 115.4 Average Error 0.39 0.20 0.19 0.33 Distances between reference points to compare different surveying methods to fix distortions and scales of the saveiro wooden ship models photogrammetric model

Assumptions 1 Direct Survey Methods (DSM) Time-consuming for short-term projects (DSM often requires more than 1oo measurements for one site) Not designed for Photogrammetric Recording (One positional error can distort the entire photogrammetric model) However, DSM provides a local coordinate system! (Enclosure, Scale Bars, Direct Input methods cannot provide this)

Assumption 2 Enclosure, Scale Bars, Direct Input methods Simple, fast, and many cases these are more accurate! It can provide Scale-constrained models (which is okay for individual artifacts), but it is impossible to create a local coordinate system, hence no geo- referenced models. Photogrammetric models of a site cannot be combined based on scientific data. Shelburne Shipyard Steamboat Graveyard Project Directors, Dr, Kevin Chrisman and Carolyn Kennedy

Tri-Closure 1. Create 1:1 Scale Model 2. Place this model on the ground plane (geo-referenced field) Mother Photogrammetric Model 3. Extract coordinates of reference points from the Mother Model, and use it for following photogrammetric recording (Child Models) 4. Merge Child Models to produce a Geo-referenced 1:1 Scale-constrained Photogrammetric Model

Tri-Closure Enclosure Mother Model Scale Bars

Tri-Closure 1. Place 3 control points (Example 1) ① ② ③

Tri-Closure 1. Place 3 control points (Example 2) ① ②

Tri-Closure 1. Place 3 control points As long as two edges keep same distance, it can be any distances.  Very Flexible 

Tri-Closure 2. Calculate X Y coordinates of the 3 control Points

Tri-Closure 3. Modify the 3 coordinates with depth (add Z coordinates)

Tri-Closure = Mother model 4. Input the modified coordinates to the initial photogrammetric model. (Also scale-constrain the model using the scale-bar method.) = Mother model

(1:1 Scale-Constrained model of the Site) Tri-Closure 5. Start photogrammetric recording (Child Models) Child Models Complete Model (1:1 Scale-Constrained model of the Site) Mother Model Local Coordinate System AdriaS Project (Gnalic Shipwreck). Project Director Dr. Irena Radic Rossi

Mother Model (Geo-referenced 3D model) Tri-Closure 6. Use Mother Model’s coordinate systems to scale-constrain the Child Models Mother Model (Geo-referenced 3D model) Child Model View Estimated Coordinates of the Reference Points Use Mother’s Coordinates Here Create markers (reference points) at mutual positions on both The Mother and the Child models Use Mother Model’s coordinates on Child models’ reference points (Geo-referenced Scale-Constrain) AdriaS Project (Gnalic Shipwreck). Project Director Dr. Irena Radic Rossi

Tri-Closure Geo-referenced 1:1 Scale-Constrained Photogrammetric Model Complete Model (Geo-referenced 1:1 Scale-Constrained model of the Site) Site Plan Digital Analysis (Interactive Fragment Model) Archaeological Applications Measurable 3D models Point-Cloud-Based Deviation Analysis GIS Applications AdriaS Project (Gnalic Shipwreck). Project Director Dr. Irena Radic Rossi

Tri-Closure Triangle can be added!

Comparison Tri-Closure Underwater Place 3 control points Apply Initial Photogrammetric Recording (Only 2 - 3 dives are required) On-land Calculate and modify 3 coordinates (Also scale constrain using Scale-bars) Create Mother Model Use Mother Model’s coordinate system (Unlimited numbers of reference points) Direct Survey Methods (DSM) Underwater Set-up Control Points (and Reference Points) Create Control Network Measure Control points to Reference Points 5-10 Days (50 to more than 100 of measurements are required) On-land Create Local Coordinates System (Statistical Adjustment of Trilateration) Use created local coordinate system for photogrammetric recording (Additional measurements are required for new reference points)

Conclusion Advantage of Tri-Closure Requires minimum amount of underwater working time Simple and fast Very flexible (Any distances can be used to set up 3 Control Points) (Positions and numbers of Reference points are not determined) Accurate (using Enclosure and Scale-bar methods to scale-constrain) Disadvantage Exclusively designed for Photogrammetric recording (Requires knowledge of Photogrammetry and CAD software)

 Thank you 