A New Tool for Producing 3D Orientation Symbology for Google Earth

Abstract

Modern methods for creating geologic maps feature a digital workflow, with dedicated mapping apps for mobile devices (e.g., ArcGIS Collector, FieldMove, StraboSpot), cloud storage of data in public repositories (e.g., strabospot.org), and preparation and presentation of maps and other deliverable products via geographic information systems (GIS), such as ArcGIS, QGIS, and Google Earth. Recently, the StraboSpot field data system (Walker et al., 2019) has provided a new standard for digital data collection and curation, and the StraboSpot app is increasingly used to collect field data. Data archived at strabospot.org can be downloaded in a variety of formats, including GIS shapefiles, KMZ files, XLS files, and image JPEGs. Mapping platforms, such as ArcGIS, FieldMove, and StraboSpot, can export field data in a variety of formats, including KMZ files that can be displayed in virtual 3D terrains. Viewing field data in a virtual 3D terrain can aid in the interpretation of planar and linear features, such as lithologic contacts, faults, and fold axes. However, field data points with orientation measurements are often not satisfactorily rendered when draped or positioned over a 3D surface that has notable topographic relief. Preferable is the depiction of orientation data as symbols in the correct 3D orientation at the virtual location equivalent to where it was mapped in the field. The depiction of 3D orientation symbols for bedding, foliation, lineation, etc. (Fig. 1), can now be easily achieved with a web-based tool called Symbols. Our initial version of Symbols uploads generic CSV files of field data to produce 3D orientation symbols as a KML file for Google Earth (Whitmeyer and Dordevic, 2020). Recently, in order to interface more seamlessly with the StraboSpot field mapping system, we developed a new version: Symbols2 (https://educ.jmu.edu/~whitmesj/ GEODE/symbols2/), which uploads an XLS file of field data. XLS files produced by the StraboSpot app or other sources will often include more columns of data than are necessary for creating 3D orientation symbols. Data columns that are relevant for generating orientation symbols include: Latitude and Longitude (to position a symbol in the correct virtual location in Google Earth), Strike, Dip, Planar Feature Type, Facing (upright or overturned), Trend, Plunge, Linear Feature Type, Name (for a field data point), Date (when the field data was collected) and Notes (field notes as recorded by the geologist). Symbols2 can handle an XLS file of field data from any source by assigning column headers to the type of data in the column. Field data is included within pop-up balloons in Google Earth, which are displayed by clicking on a symbol (Fig. 1). StraboSpot records lithologic units for field data points as Tags, and thus a StraboSpot XLS file will include several columns with headers as Tag:unit name. Symbols2 assigns a nominal color to each of these unit Tags, so that the orientation symbols generated will be color coded. The user can change a unit Tag color using a graphical color selector or color hex code. If preferred, a user can select a master color for all unit Tags. Other adjustable parameters for the orientation symbols include Symbol length (size of the symbols), Symbol height (height of the symbols above the Google Earth ground surface or the specified Altitude), Symbol line thickness (thickness of the symbol lines), and the Filename for the KML file that the Symbols2 tool exports. Users can group data symbols in KML folders by Unit/Formation and/or by field Location (useful if some field locations have both planar and linear data recorded). A detailed instructions file is available via a button at the upper right side A New Tool for Producing 3D Orientation Symbology for Google Earth