GeoPlanes. Interactive Analysis of Virtual Geological Outcrops. Alpha Version January 2016

Transcription

1 GeoPlanes Interactive Analysis of Virtual Geological Outcrops Alpha Version January Introduction Geoplanes is an application for interactive structural interpretation and annotation of 3D texture rendered virtual models derived from terrestrial or UAV photogrammetry. Geoplanes allows measurement of the orientation of planar and linear features, stores these measurements in a data table and plots features automatically on a stereonet. The software has been developed at The University of Tasmania using the Unity platform and is available for both Windows and Macintosh systems. 2. Software Installation Geoplanes does not require installation on either Windows or Macintosh hardware. Simply unzip the application folder onto your hard drive and double click the application to run. 3. File Formats Geoplanes currently only reads input 3D model files in Google KMZ format as exported by the Photoscan photogrammetry software. Models should be fully georeferenced in Photoscan prior to export in KMZ format. Geoplanes session files are stored as ASCII XML text files. Structural data can be exported as a CSV file for input into other applications. 4. Start Up After starting Geoplanes you will be prompted to define the graphics settings (Figure 1). Figure 1. Geoplanes configuration window. Select the desired window size (in pixels) and whether the application will run in windowed mode or in full screen mode. It is usually best to run the application at the highest available resolution and in full screen mode to maximize image quality and the area for model display. On a PC use Alt+Tab to toggle between Geoplanes and other applications (Cmd+Tab on a Mac)

2 GeoPlanes Guide Alpha Version, January On the Geoplanes start-up screen (Figure 2), select New Session to load a KMZ file without any pre-existing measurements or annotation or select Load Session to load a KMZ file and with its associated measurements and annotations from a pre-existing XML file (*.gpx). 5. Program Operation Figure 2. Geoplanes start-up window. The elements of the main Geoplanes display are shown in Figure 3. Figure 3. Geoplanes main interface with the interface components annotated. 5.1 Model Display The 3D model viewport displays the texture-rendered 3D model. The current orientation of the viewport is displayed on the bottom banner (View) and also shown by the camera icon in the stereonet. The orientation of the surface of the model at the mouse cursor position is shown in real time as the mouse

3 GeoPlanes Guide Alpha Version, January moves across the model (Hover). The small white dot at the centre of the model viewport shows the model rotation point. Model display controls are: Zoom in or out on the current position of the rotation point by rolling the mouse wheel or by pressing the A and Q keys on the keyboard Rotate - around the rotation point by depressing the left mouse button and dragging the mouse Pan move the model left, right, up or down by depressing the right mouse button and dragging the mouse or using the arrow keys. 5.2 Measurement Modes Measurement options are selected from the pull-down menu in the lower left corner of the display. Current measurement options are: Point This allows measurement of the orientation of the external surface of the model at the location of the mouse cursor. The orientation reported is the normal to the triangle face in the model at exactly this location. Double left click or shift+ left click to make a measurement and assign the data point to a category (S0, S1, Joint, Fault etc). The feature is marked on the model as a small plane with a short normal extending outward from the surface (Figure 4). The colour is determined by the chosen geological category. The point is automatically plotted on the stereonet in the same colour and recorded in the feature table. Multiple This option is similar to the Point selection mode and is used to measureme the orientation of the external surface of the model at the location of the mouse cursor. In Multiple mode the orientation is determined from the vector average of normals at the cursor position and eight surrounding locations. This provides a mechanism to smooth small irregularities in the surface. Double left click or shift+ left click to make a measurement and assign the data point to a category (S0, S1, Joint, Fault etc). The feature is marked on the model as a small plane with a short normal extending outward from the surface (Figure 4). The colour is determined by the chosen surface category. The point is automatically plotted on the stereonet in the same colour and recorded in the feature table. Neighbour This option is similar to the Point and Multiple selection modes and is used to measure the orientation of the external surface of the model at the location of the mouse cursor. In Neighbour mode orientation is determined from the vector average of normals at the closest vertex to the cursor position and all connected vertices. This provides a mechanism to smooth small irregularities in the surface. Double left click or shift+ left click to make a measurement and assign the data point to a category (S0, S1, Joint, Fault etc). The feature is marked on the model as a small plane with a short normal extending outward from the surface (Figure 4). The colour is determined by the chosen surface category. The point is automatically plotted on the stereonet in the same colour and recorded in the feature table. Lineation This allows measurement of a lineation by digitising two successive points on the model surface. Double left click or shift+ left click to indicate the position of these points (keep shift depressed until you have digitised both points). When the second point is digitised, assign the lineation to a geological category. The trend and plunge of the lineation are recorded in the feature table and plotted on the stereonet in the appropriate colour. The lineation is marked in the model

4 GeoPlanes Guide Alpha Version, January view by a vector (Figure 4). It does not matter which order the points are digitised, the plunge direction is automatically determined from the elevation of the points. Best Fit Plane This mode enables measurement of the orientation of planes that intersect the model. Double left click or shift+ left click to digitise a series of points on the model surface where the geological feature intersects the surface. When a minimum of three points have been digitised, a plane is shown intersecting the model surface. Points on the trace of the plane can be digitised in any order. During digitising, the colour of the plane varies depending on the misfit of the points and also the colinearity of the points. For close fitting points that are not co-linear the plane will be green. More poorly fitting or co-linear point selections will result in yellow, orange or red planes to warn the user to reconsider the selection of points. It is useful to realign the model to look along the plane to visually assess the accuracy of the selected plane prior to selecting Finish. Then assign the plane to a geological category. The dip and dip direction of the plane are recorded in the feature table and the pole to the plane is plotted on the stereonet. The plane is shown as a semi-transparent feature in the model view. Multi-Line This mode enables annotation of the model surface with 3D connected line segments that are shown in the model as traces of different colour. Line segments are drawn as straight lines between successive digitised points and may intersect the model if the surface is complex and the points are widely spaced. Double left click or shift+ left click to digitise a series of points on the model surface. Select Finish to end the multi-line and then select a colour for display. Multi-lines do not represent structural measurements and don t plot on the stereonet but do appear as records in the feature table. Figure 4. Geoplanes interface showing: bedding planes and normals (red), a fold axis depicted as a green vector, a fold axial plane as a blue semi-transparent plane, a joint as a purple semitransparent plane and a multi-line annotation that follows layering as a green polyline. 5.3 Feature Links

5 GeoPlanes Guide Alpha Version, January Structural measurements are depicted as planes, normals and vectors in the model viewport, as points (poles or lineations) on the stereonet and as text records in the feature table. Features in these three representations are linked so that selection of a feature in any part of the interface will automatically highlight the same feature in all views. In the model view the selected feature is repositioned to the centre of the display (white dot). The selected feature in the stereonet is marked by a larger circle. In the table, the selected feature is highlighted. 5.4 Deleting Features In the current implementation, features can only be deleted when they already exist and are then selected. It is not possible to delete a feature during digitisation. So if you make an error while digitising a point in Best Fit Plane or Multi-Line modes, you need to finish the object and then delete it. 5.5 Saving, Restoring and Ending Sessions The Geoplanes main menu can be accessed at any time by pressing the Esc key. To exit the menu and return to the main interface, also press Esc. Figure 5. The Geoplanes main menu is accessed by pressing Esc and provides options to load and save sessions. The New Session option will load a new KMZ file and delete all existing measurements and annotation. The Save Session option will store application settings and data in an XML file (.gpx extension). All information necessary to completely restore the current session is recorded in the XML file, including feature types, display colours etc. The Load Session option loads a.gpx XML file to restore a previous session. The Quit option will close the application without saving any data or settings. 5.6 Exporting Data The Export button below the data table writes the structural data into an ASCII text file in CSV format for import into other software. The export file includes fields that specify the orientation and relative position of the structural feature, the feature type and the feature selection mode. Multi-line annotation features are listed in the feature table but are not exported in the CSV file (they are saved when you save a session). An example of the CSV data export file for the measurements depicted in Figure 5 is shown in Figure 6.

6 GeoPlanes Guide Alpha Version, January longitude latitude altitude altitude absolute dip/plunge dipdirection/trend featuretype sampletype eastoffset(m) northoffset(m) altitudeoffset(m) OTHER BESTFITPLANE S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT S0 POINT FOLDAXIS LINEATION JOINT BESTFITPLANE Figure 6. The CSV export file for the measurements depicted in Figure 5 after import into Microsoft Excel. 6. Acknowledgements and Contacts The GeoPlanes application has been developed at The University of Tasmania with funding from an Innovation and Development Grant from the Australian Government Office for Learning and Teaching with additional support from Australian universities and government geoscience agencies. 3D model data files for GeoPlanes can be accessed from the AusGeol website (ausgeol.org) in Google Earth KMZ format or can be created using Agisoft Photoscan. The current Alpha version of the application is available for restricted distribution for testing purposes. A Beta version will be released in February 2016 for free distribution as an Open Educational Resource. Michael Roach and Robert Scott are responsible for concept development and project direction. Programming has been undertaken in the Unity environment by Alex Grace and Jen Ralph. Please direct any comments or suggestions regarding this application to Michael Roach (Michael.roach@utas.edu.au).