ND 
CES 
om 
ond 
ion 
age 
AM 
ion 
ga 
del, 
ital 
ing 
ion 
etri 
age 
VII 
99- 
oor 
nce 
ion 
| of 
ing 
gh- 
ing 
OF 
AL 
nal 
sed 
of 
fa 
on, 
a a 
ror, 
on, 
1Z 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
OPENWEBGLOBE - AN OPEN SOURCE SDK FOR CREATING 
LARGE-SCALE VIRTUAL GLOBES ON A WEBGL BASIS 
B. Loesch, M. Christen, S. Nebiker 
Institute of Geomatics Engineering, FHNW University of Applied Sciences and Arts Northwestern Switzerland 
3 
Muttenz, Switzerland — (benjamin.loesch, martin.christen, stephan.nebiker)@fhnw.ch 
Commission IV, WG IV/4 
KEY WORDS: Visualization, Algorithms, Virtual Reality, Web based, Point Cloud, Three-dimensional, Triangulation 
ABSTRACT: 
This paper introduces the OpenWebGlobe project (www.openwebglobe.org) and the OpenWebGlobe SDK (Software Development 
Kit) — an open source virtual globe environment using WebGL. 
toolkits, the OpenWebGlobe SDK not only supports the conte 
Unlike other (web-based) 3d geovisualisation technologies and 
nt authoring and web visualization aspects, but also the data 
processing functionality for generating multi-terabyte terrain, image, map and 3d point cloud data sets in high-performance and 
cloud-based parallel computing environments. The OpenWebGlobe architecture is described and the paper outlines the processing 
and the viewer functionality provided by the OpenWebGlobe SDK. It then discusses the generation and updating of a global 3d base 
map using OpenStreetMap data and finally presents two show cases employing the technology a) for implementing an interactive 
national 3d geoportal incorporating high resolution national geodata sets and b) for implementing a 3d geoinformation service 
supporting the real-time incorporation of 3d point cloud data. 
1. INTRODUCTION 
In recent years virtual globes have become an important tool for 
interactively visualizing and investigating geo-referenced 
content. Virtual globes are capable of streaming terabytes of 
imagery, elevation data and other geospatial contents over the 
Internet. Emerging Internet technologies, such as HTMLS and 
WebGL, offer new possibilities to develop virtual globes 
running in web-browsers without a need for browser extensions 
or plugins. 
WebGL is a cross-platform, royalty-free web standard for a 
low-level 3d graphics API based on OpenGL ES 2.0 (WebGL, 
2011). It is exposed through the HTMLS Canvas element as 
Document Object Model interface. WebGL is a shader-based 
API using the OpenGL Shading Language (GLSL), with 
constructs that are semantically similar to those of the 
underlying OpenGL ES 2.0 API. In March 2011 version 1.0 of 
the WebGL specification was released. Today WebGL runs in 
desktop and mobile web-browsers like Mozilla Firefox, Google 
Chrome, Safari, and Opera. In the Internet Explorer WebGL 
can currently only be used through plugins. 
Many different JavaScript 3d engines such as three.js (Three.js, 
2012) or SceneJS (SceneJS, 2012) were created to ease the 
implementation of different 3d web applications or games using 
WebGL. It is no surprise that also in the field of virtual globes 
WebGL is a hot topic and used for several virtual globe web 
applications. Projects like WebGL Earth (WebGL Earth, 2012) 
the ReadyMap SDK (Pelican Mapping, 2012) and our 
OpenWebGlobe SDK were initiated to provide a base for the 
implementation of new 3d virtual globe applications using 
WebGL. Also Google is currently working on a WebGL 
version of Google Maps (Google Maps, 2012). 
Apart from the discussion about the advantages or 
disadvantages of a plugin free virtual globe (VG) browser 
application, today's VGs also have a number of shortcomings 
such as a lack of extensibility in terms of large , complex user- 
generated or third-party geospatial contents (c.g. own high- 
resolution DTMs or large to very large customized map or 
orthoimage data sets). Other potentially more serious 
shortcomings are the lacking extensibility in terms of 
functionality and the lacking ease of integration into third party 
applications and into operational environments which might not 
be compatible with data and IP right policies of large 
commercial VG operators. The strive for new applications of 
VGs together with the above mentioned limitations of the main 
commercial VGs have been the motivation for developing our 
own VG technology at the FHNW. 
In this paper we discuss the evolution of and research activities 
in Internet- and web-based interactive 3d technologies. We then 
present the OpenWebGlobe project and architecture. The paper 
first focuses on the OpenWebGlobe viewer component, which 
is fully based on HTMLS and WebGL, as well as some of its 
key features. This is followed by a short discussion of the 
OpenWebGlobe processing functionality. In the later sections 
of this paper we present two applications which were built 
using the OpenWebGlobe SDK. First a pilot national 3d 
geoportal of Switzerland using high resolution imagery and 
elevation data is described. Second an application in which 
OpenWebGlobe is used for visualizing continuously generated 
point cloud data for rapid mapping and inspection of unknown 
buildings or industry-sites. 
2. RELATED WORK 
Different mechanisms for an interactive visualization of 3d 
contents in the web are available and frequently used. Early 
formats and standards such as the Virtual Reality Modeling 
Language (VRML) (Bell, 1995) were defined in the mid 90ies 
and permitted the authoring and delivery of 3d contents over the 
web but required applications or browser plugins. VRML was 
185