The people, science and technology behind discovery

Globe Viewers: The New, Digital Frontier

Leonard Chan



Geology of Australia in Dapple.

The earth is a big place.

But within the confines of your desktop, and with the aid of free exploration software, you can now visit Kathmandu, Kinshasa, and Kansas without the need for lengthy security checks, plane cabin fever, or painful vaccinations.

The world of globe viewers

Globe viewers, downloadable virtual globe applications, are becoming a very important tool for visualizing the world’s spatial data. Google Earth, NASA’s World Wind, and newer ones like Geosoft’s Dapple are all available as free internet downloads. Google Earth requires you to purchase a license if you intend to use it for professional work. Although superficially similar, these globe viewers operate under different philosophies and have divergent target audiences. The way each application fits into the workflow of a geoscientist is vastly different as well.

The most horizontal application of the three, Google Earth targets a broad audience. Straight out of the box, Google Earth comes with a great deal of functionality that will appeal to a wide range of users, with virtual sight-seeing and route planning being two of the most common usages. Its interface is streamlined for ease and efficiency, which is unsurprising given its namesake.


The Eiffel Tower in Google Earth.


SRTM + LandSat 7: Mt. St. Helens, Washington in NASA World Wind.

Google Earth uses KML (Keyhole Markup Language) which is based on the XML standard. To view your data in the Google Earth environment, you need to create KML files with the Google Earth user interface or you can use an XML editor to enter ’raw’ KML. While many users are investing in converting their data to KML, as a developing language KML is known to have some limitations. It does not scale very well for big earth datasets, nor does it perform well for image data. This restricts its value, particularly for geoscientific applications.

World Wind is an open-source browser from NASA. Immediately after download, World Wind provides access to the 4.6 terabytes of high resolution DDS and JPEG satellite images available from NASA servers, and unlike Google Earth, there is flexibility in the image sets you can display. Users can choose from several layers including Landsat 7, USGS, and SRTM imagery, as well as animated data layers that include real-time weather.

Supported by a robust open-source community, World Wind has benefited from its plug-in architecture, with community-made add-ons such as additional planets (fictional or otherwise). An additional benefit to the open-source nature of World Wind is that, unlike Google Earth, corporate use of the software comes entirely free of charge.

There are, however, some limitations that World Wind shares with Google Earth. An important one is its limited support of Web Map Services (WMS). WMS is an internationally standardized method for producing maps of spatially referenced data from remote geographic information. There are hundreds of WMS server sites with thousands of layers that provide useful images of geospatial data. These servers are generally made available from government surveys, commercial providers, or enthusiastic end-users. Though both World Wind and Google Earth are able to connect to WMS servers, neither provides an intuitive or efficient interface with WMS.

World Wind’s interface is also nowhere near as user-friendly as that of Google Earth’s and requires users to tinker quite a bit in order to understand its oft-times esoteric features. It is this complexity that simultaneously makes World Wind less accessible to a larger audience but more useful to specific disciplines.

The next generation

More recently, Dapple appeared on the landscape as a new alternative for professional geoscientists. An offspring of World Wind, Dapple is an open source initiative sponsored by Geosoft specifically for the geoscience community. Like World Wind, Dapple is available to professional and corporate users free of charge. It employs a Google-type interface that provides the advantage of usability to its target user base while delivering more advanced features for exploring large, earth data. Most important, it was designed to provide geoscientists with a better way to work with the thousands of WMS data providers on the internet today, on a globe viewer.

The major difference between these globe viewers is the way in which they handle and present data. Google Earth is streamlined for one data layer, so while that one layer is visually spectacular, it is still only one layer. Using KML, it is possible to add additional layers, but image performance is generally poor and unresponsive. Although Google Earth can afford you a luxurious view of the car in your driveway, what geoscientists really want to see is the geology beneath the car, along with electromagnetic, remote sensing, and other earth data.

While World Wind can access a wider range of data and can handle multiple layers, its capabilities for viewing WMS sites are quite limited. WMS layers lack floor style browsing, layer ordering, and transparency control. Dapple was developed to deliver superior WMS capabilities, recognizing that much of the world’s public sources of geoscientific data reside on WMS servers. As one user, Brian Timoney wrote online, Dapple is a “nice spinning globe alternative that can be a user-friendly showcase of the utility of WMS.” According to Timoney, an advantage of working with Dapple is that it “handles WMS layers in a superior manner when compared to World Wind – both in terms of tiling/streaming as well as easy navigation/controlling transparency.”

Ian MacLeod, Chief Technology Officer at Geosoft, a geoscientist and one of the architects behind Dapple explains, “Dapple is different than Google and NASA because of its unique applicability to earth data and earth scientists. The geoscience community is very used to dealing with spatial data. Geoscientists work with spatial data on a daily basis. They’re used to GIS systems like ArcGIS or MapInfo and geoscientific software like Oasis montaj™. We are very much an image-based, spatial data industry.”

According to MacLeod, how the geoscientist wants to see and work with spatial data is also different than the mainstream. “Geososcientists need to be able to see a lot of different data from different sources within the same environment. They need to be able to see data that they retrieve from the internet and from their own servers. They want control over the order of the data layers as well as transparency, which is a critical function. Once they have done all that, they want to be able to put it all on a map.”

A globe viewer for geoscientists

Understanding the geoscientist workflow was why Geosoft took on the challenge of developing Dapple™. The focus from the start was making this powerful technology valuable in the context of earth data exploration. Technically, a lot of what the geoscience community needs is possible within both the Google Earth and World Wind environments, but it’s not intuitive and simple, often requiring tricky manoeuvring within the user interface. Dapple was designed to give geoscientists access to the features and data they need with one or two mouse clicks.

Making a globe viewer, like Dapple, valuable within a geoscience organization or exploration company meant tackling another challenge – the ability to search data available on private servers as well as public ones. Dapple’s support of Geosoft’s server technology, DAP, has delivered a whole new value to Geosoft’s enterprise customers, enabling them to search, find, and see data from their own massive data resources, as well as public sources in one viewing environment.

Geosoft’s DAP sever technology is also uniquely optimized for earth science, a discipline where one must wade through large swaths of data to pinpoint the relevant information useful to a specific project. One of the key concepts of DAP is the ability to store datasets in their native formats. Using WMS, this data can be easily accessed through Dapple, a visualization tool for the geoscience masses. This solves one of the biggest frustrations that geoscientists had with Google Earth and World Wind: the difficulty involved in seeing their own data.

Geosoft is continuing to integrate Dapple further into its earth data mapping applications to close the loop, and provide a whole data experience – from finding and viewing earth data, to working with and producing data outcomes, like maps, interpretations, and presentations and storing them on their own servers. Given the complexity of the geoscientist’s workflow, and the depth of knowledge they need to extract from their data, there is a lot of room for improvement – making the data experience simpler and more natural, so that outcomes and decisions are easier to arrive at.

Asked to summarize the globe viewer market, MacLeod concludes, “All these globe viewers have made an incredible contribution to opening up access and interest in spatial data. Google Earth is valuable. World Wind is valuable. They’ve led the way in proving out the power of viewing the world’s data on a globe.”

“The next generation of viewers, like Dapple” says MacLeod, “begins to harness this power in a way that’s useful to a community, in this case the geoscience community. Geoscientists needed more than what the other viewers offered, and that’s why we developed Dapple. It’s a viewer for us.”