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Virtual Globes Museum 2.0 – Adding the Power
of Community
Mátyás Gede, Zsuzsanna Ungvári, László Zentai
Department of Cartography and Geoinformatics, Eötvös Loránd University
Abstract. The Virtual Globes Museum web page was opened in 2007 with
only five virtual globe models. Since then, the number of globes was raised
over one hundred. The amount and heterogeneity of data made it necessary
to rethink the underlying database structure. The new version of the web
site introduces several new functions such as the possibility of adding mul-
tiple descriptions to globes in various languages and creating collections
from a subset of globes. The most important improvement, however, is the
crowd sourcing of the site: registered users can add or update descriptions
and collections, which can fasten the growth of the database. Another nov-
elty is the replacement of the old VRML plug-in used for displaying the
globe models to a new WebGL or Flash-based visualization. This paper in-
troduces the technical details of the new version and sketches the further
plans of development.
Keywords: Virtual globes, Cartographic Heritage, Crowd sourcing, 3D
models
1. Introduction
Globes are a special group of cartographic objects. Being three-dimensional
models of our planet, they are very popular since the beginning of their his-
tory. Their nature of being spatial objects, however, also brings troubles:
globes are much more vulnerable than flat maps and their digital preserva-
tion is more complicated. The Virtual Globes Museum (VGM) project aimed
to present a cure to this problem. Cheap and quite simple methods were
developed for globe digitizing and visualization, and were used in a unique
website (http://vgm.elte.hu) offering realistic steerable-zoomable models of
old globes to the public. This enables the visitors to observe such details of
them that would be impossible in the museums where these objects are
usually exhibited in display cases or beyond security barriers. (Márton ed.
2008, Gede 2009)
The trilingual (Hungarian, English, German) website offered a simple
search engine, 3D visualization of globe models based on a VRML plug-in
or a Java VRML player applet (Figure 1).
Figure 1. The old website of Virtual Globes Museum
The project and the VGM website became quite popular soon. A new elec-
tive course, Globe Digitizing, was offered at our university department,
where students, after becoming familiar with the basic techniques, pro-
cessed the given materials (scanned globe prints or photo sets) and created
new virtual models. The content of the virtual exhibition grew to more than
a hundred globes in a few years. Some of the virtual globes were also pre-
sented on a real globe exhibition: after observing the original globes in
showcases, visitors of the exhibition were invited to computer kiosks, where
they were able to examine such details of globes that were impossible to see
on the originals: content on the back side, small details, etc. (Gede 2011)
With the growth of the collection new problems emerged. The English and
German translations of globe descriptions were made slowly as the few
people who had permission to the system did not have enough time to com-
plete them. Some attributes did not fit well in the database structure: globes
with uncertain creation date, multiple authors, etc. It was hard to select a
specific subset of globes if the selection was not based on the value of a da-
tabase field (e.g. globes that were displayed together at a specific exhibi-
tion). More and more problems occurred with the VRML plug-ins, which
made the website unstable.
To solve all these issues a brand new version was developed introducing
several technical changes and new features.
2. The Background Database
The background database of the new website consists of several tables (Fig-
ure 2). The most important ones are:
• The globes table contains the globes’ language-independent attributes
such as diameter, date etc., and the URLs of the X3D model files and the
KMZ superoverlays. Additionally, a thumbnail image is assigned to eve-
ry globe. These thumbnails appear in search results and in collections
where globes are referenced. This help users identifying globes.
• The descriptions table includes detailed globe descriptions. Each
globe can have several descriptions in various languages (not only the
currently available three languages of the user interface). Descriptions
have a predefined field structure to ensure that all important data are
included. These fields contain information about persons and compa-
nies related to the globe (authors, publishers), production technology,
the frame/support structure, the original material used for compiling
the virtual model, known occurrencies of the globe, its history, and a de-
tailed description of the map content.
• The collections table stores “article-like” texts describing a subset of
globes. The text can contain references to specific globes as hyperlinks.
Collections are a great possibility to describe a group of globes that are
somehow related to each other. Typical examples of collections are
globes of a specific author; celestial globes in the museum etc. A well-
composed collection is similar to an article in a magazine: it introduces
the given globe group, gives background information about the time pe-
riod or the authors, emphasizes the similarities and differences among
those globes – facts that are interesting and important, but cannot be
attached to one specific globe’s description.
Additional tables store static image URLs (each globe can have several im-
ages: portraits, scanned images of the printed gores etc.), user management
information and language codes.
Figure 2. Structure of the background database
3. 3D Visualization Using X3DOM and Novelties in the
User Interface
The old version of the globe museum visualized 3D globe models as VRML
scenes, using a VRML browser plug-in or Java applet (depending on the
user’s choice). Although several VRML plug-ins exist, none of them seemed
to work without any problems in every tested hardware+OS+browser com-
bination.
Luckily, a new technology, X3DOM emerged in the last few years, devel-
oped by the Fraunhofer Institute, Germany. X3DOM is a JavaScript frame-
work based on WebGL, enabling web-developers to include X3D codes in
HTML files (Fraunhofer 2011). While the first release of the system (in
2010) was rather unstable and less supported by web-browsers, current
versions are surprisingly good. In 2012, most of the current web-browsers
support WebGL, and the X3DOM framework has a fallback mechanism
using a Flash-based X3D viewer when it is necessary.
X3DOM not only facilitates the use of inline X3D codes in HTML, but the
X3D elements become an organic part of the Document Object Model
(DOM), which means that X3D nodes can be dynamically generated and
manipulated by JavaScript, and even styled using CSS rules.
globes
id
vrmlfile
kmzfile
author
date
diameter
...
added_by
descriptions
id
globe_id
lang_code
history
contents
...
added_by
reviewed_by
lang_codes
code
name
users
id
name
full_name
email
...
images
id
globe_id
url
collections
id
lang_code
globe_ids
text
...
added_by
reviewed_by
The 3D globe visualization in the new version of the VGM is based on this
technology. This solution makes the service more widely accessible as visi-
tors not able to install a plug-in (e.g. not having the appropriate rights on
their computer) also can enjoy the 3D view. (Figure 3)
Figure 3: X3DOM in use on the VGM website
The graphic performance of different PCs can show big differences. As the
authors did not want to exclude users with low-end graphic cards from
viewing virtual globe models, textures are stored in three different resolu-
tions. If a globe is not displayed correctly (usually due to insufficient
amount of memory on the graphic card), one must simply switch to lower
resolution. The smallest textures are rendered well even on 8-10 year-old
computers.
Further to the new background structure, the user interface of the website
also changed. A “What’s new” page greets the visitor first, where the latest
uploaded globes, descriptions and collections are listed. Naturally, it is pos-
sible to browse the globes using their full list or specifying search filters and
order criteria. After logging in, registered users can modify the content they
have created or add new content.
4. Adding the Power of Community
The title VGM 2.0 refers to the Web 2.0 phenomenon, as visitors of the new
website are no longer restricted to only view but also to add content (Zen-
tai, Guszlev 2006). Registered users can edit or add new globe descriptions
and collections.
Naturally, new content is not published uncontrolled. First of all, user regis-
tration is not automatic but done upon e-mail requests. This is mainly to
keep away robots and trolls from the site. Then, registered users can have
different permissions. All new or modified content is subject of a reviewing
process, and only materials reaching a certain quality are classified as “pub-
lic”. Non-public materials are visible only to their owners. The right of “giv-
ing publicity” is initially restricted to the developers of the site, but later any
user can achieve this right after generating a certain amount of high-quality
content.
In contrary to the previous version of the site, globe and collection pages
have unique URLs, so not only the museum’s website itself but any specific
content can be referenced, shared in social network community sites etc.
While users proudly present the latest content they added, at the same time
they popularize the museum itself, making it more widely known and visit-
ed.
5. Conclusion
Although the new system is still in “beta” (open to the public, but in testing
phase), the feedback is very positive. The introduced changes solved most of
the problems of the old system. The changes of the technical background
added even more possibilities to the future development, and made the use
of the VGM website easier.
The application of Web 2.0 principles (Gartner 2009) brought a kind of
cartographic communication to the site: it helps to collect further interest-
ing information about the globes and share it with the public. Furthermore,
thanks to the possibility of user-created collections, the museum can serve
much better the priorities in cartographic education with special thematic
collections such as an illustrated history of globes, or a collection following
the changes of geographical names etc.
6. Further plans
Currently, new globes can be added only by the system administrators. The
most important development plan is to add an online globe georeferencer.
The georeferencer will be able to deal with uploaded gore scans and globe
photographs, letting users create their own virtual globes. Naturally, a de-
tailed user manual and photographing guide will supplement the new sys-
tem, and quality checking will be even more important on user-created vir-
tual globes than on descriptions or collections.
This work is already in progress. The georeferencer user interface will rely
on the OpenLayers JavaScript framework (OpenLayers, 2012), while the
projection transformation will use the GDAL library (GDAL, 2012).
Another plan is adding a “WYSIWYG” text editor to the collection-creating
interface as currently text formatting can be done only by inserting HTML
tags to the description text.
References
Fraunhofer (2011) X3DOM Documentation. Fraunhofer IGD, VCST.
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Gartner G (2009) Applying Web Mapping 2.0 to Cartographic Heritage. In: e-
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05 November 2012
GDAL (2012) Geospatial Data Abstraction Library. http://www.gdal.org. Accessed
27 October 2012
Gede M (2009) Publishing Globes on the Internet. Acta Geodaetica and Geophysica
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