Elsevier

Computers & Geosciences

Volume 109, December 2017, Pages 25-31
Computers & Geosciences

Research paper
TouchTerrain: A simple web-tool for creating 3D-printable topographic models

https://doi.org/10.1016/j.cageo.2017.07.005Get rights and content

Highlights

  • Web-tool makes 3D printable digital models from public elevation data.

  • Python code uses Google Earth Engine API to process elevation data.

  • 3D models use 3D printer constraints making Direct Digital Manufacturing possible.

  • 3D Printed models can be tiled to overcome size limitation of 3D printers.

Abstract

An open-source web-application, TouchTerrain, was developed to simplify the production of 3D-printable terrain models. Direct Digital Manufacturing (DDM) using 3D Printers can change how geoscientists, students, and stakeholders interact with 3D data, with the potential to improve geoscience communication and environmental literacy.

No other manufacturing technology can convert digital data into tangible objects quickly at relatively low cost; however, the expertise necessary to produce a 3D-printed terrain model can be a substantial burden: knowledge of geographical information systems, computer aided design (CAD) software, and 3D printers may all be required. Furthermore, printing models larger than the build volume of a 3D printer can pose further technical hurdles.

The TouchTerrain web-application simplifies DDM for elevation data by generating digital 3D models customized for a specific 3D printer's capabilities. The only required user input is the selection of a region-of-interest using the provided web-application with a Google Maps-style interface. Publically available digital elevation data is processed via the Google Earth Engine API. To allow the manufacture of 3D terrain models larger than a 3D printer's build volume the selected area can be split into multiple tiles without third-party software. This application significantly reduces the time and effort required for a non-expert like an educator to obtain 3D terrain models for use in class. The web application is deployed at http://touchterrain.geol.iastate.edu, while source code and installation instructions for a server and a stand-alone version are available at Github: https://github.com/ChHarding/TouchTerrain_for_CAGEO.

Introduction

Terrain has a profound influence on many Earth processes and human activities, such that a thorough understanding of it is vital to many geoscience and engineering disciplines. Despite this importance, the nature and scale of terrain often places it outside simple comprehension, which leads to difficulty in the classroom when students are asked to make qualitative and quantitative measurements using traditional topographic maps (Tversky, 2003, Taylor et al., 2004, Ishikawa and Kastens, 2005, Rapp et al., 2007). 3D-printed models can overcome this problem by putting data directly into the hands of students, educators, citizens, and stakeholders (Hasiuk, 2014, Hasiuk and Harding, 2016). The goal of the TouchTerrain project is to overcome the most technically challenging barriers to more widespread adoption in the classroom by providing a web application for easily generating 3D-printable terrain model files of any area on Earth.

Elevation data is widely available in digital elevation models (DEMs) derived from remote sensing techniques with meter-scale accuracy or better (Bellian et al., 2005). DEMs can be visualized in a variety of ways (Buckley et al., 2004; Mach and Petschek, 2007; Mitasova et al., 2012). Traditional 2D visualizations include contour lines, color sequences/ramps, and hillshading. To trained geoscientists, the spacing between the lines also suggest the slope, i.e., smaller gaps indicate a steeper hill; however, students often find it difficult to make the leap from reading a contour map to visualizing a terrain's 3D shape.

Visualizing terrain data in 3D leads to additional visualization techniques (Johnson et al., 2006, Mach and Petschek, 2007). 3D viewers, such as ESRI's ArcScene, and digital globes, such as Google Earth, combine visualization of terrain properties in 2D space with interactive viewpoint navigation to enable users to explore terrain data in ways that they cannot in the real world. However, it is still not clear for what use-cases 3D maps are best suited (Schobesberger and Patterson, 2007, Popelka and Brychtova, 2013). Augmented reality sandboxes allow students to move sand and witness the resulting effects on topographic maps digitally superimposed on the sand and updated in real-time (e.g., Woods et al., 2016).

The intuitive and material nature of 3D-printed terrain models give them advantages over 2D maps and 3D computer visualizations. Actions such as zooming and rotating are accomplished via hand positioning of the model, and surface details are easily discerned. The models can be directly annotated with pens and can help visually-impaired users to comprehend terrain (Wild et al., 2013). Although the use of 3D-printed terrain models as instructional material is still in its infancy, early research has shown that such models have value, either on their own, or in concert with 2D and 3D terrain visualization methods (Rule, 2011, Williams et al., 2013, Horowitz and Schultz, 2014, Hasiuk and Harding, 2016).

As the equipment, software, and material costs for printing 3D models have come down, the greatest cost lies in generating a 3D model file of the chosen area that reliably prints well on a specific type of 3D printer. The expertise and time required to do this, along with the specialized software which may be required, is a hurdle to widespread use of 3D terrain models. The TouchTerrain project aims to remove this barrier, empowering educators to use 3D-printed terrain models from any area on the Earth as a basis for novel teaching methods in the classroom and the field.

Section snippets

3D printers

A 3D printer is designed to take information from any digital 3D model and make a tangible 3D model (Pham and Gault, 1998). “Fused Filament Fabrication” (FFF) is one 3D printing method that uses plastic filament with a small circular cross-section (often 1.75 mm or 3 mm in diameter). The filament is heated to a semi-molten state and then extruded through a nozzle with an orifice smaller than the original filament diameter (e.g., 0.4 mm). After the filament is added to a model, it quickly cools

TouchTerrain architecture and Google Earth Engine

TouchTerrain has a client-server architecture (Fig. 3). The server is written in Python and, in conjunction with Google Earth Engine (GEE), performs heavy computations that would not be feasible to run on the frontend, in the client's browser. The client is a webpage written with JavaScript which communicates with both the server and GEE.

We use Google Earth Engine (GEE) to access and process a variety of DEM rasters. Unrelated to Google Earth, Google Earth Engine is a development environment

Conclusions

We explored creating of digital 3D terrain models suitable for 3D printing on personal 3D printers. After initially hand-crafting the digital models via a complex, manual workflow utilizing several software tools, we created a web-application that hides much of the complexity from the end-user. As result, the user receives 3D-printable, multi-tiled model files that cover the requested area.

The TouchTerrain server can be used at http://touchterrain.geol.iastate.edu. Open-source code can be

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