More and more industries have already realized and explored the benefits of 3D data for their day-to-day routines beyond just visualization purposes. The aviation industry is no exception to this. Technological advancements in the field of 3D graphics on the Web as well as streaming services have opened new possibilities for data visualizations of large amounts of weather-related aviation data. Commercial airline pilots are using a range of weather products for flight planning and to avoid severe turbulence areas whilst in the air. Most of those weather products are still displaying weather information in 2D to the pilots, including turbulence forecast data (e.g., 2D Significant Weather Charts, see figure 1). While severe aircraft accidents have reduced significantly in the last decades, the number of injuries and fatalities caused by turbulence is still rising.
The circumstance of turbulence still being a major threat in commercial aviation and the lack of 3D visualizations for turbulence forecast data has motivated researchers in the Institute for Cartography and Geoinformation at ETH Zurich to develop a 3D Web-Based Aviation Weather Visualizer. Over 4 months and in the scope of a master thesis, a prototype was designed, implemented and eventually evaluated in a user study in which 64 pilots participated.
The underlying turbulence forecast data used for the prototype are so-called Significant Weather Charts (SWC). These are issued four times a day by the World Area Forecast Center (WAFC) located in London and Washington. The 2D black-and white maps depict elements such as jet streams, areas of moderate or severe turbulence in cloud or clear-air, cumulonimbus clouds associated with thunderstorms and other weather phenomena related to aviation.
The 2D elements were first digitized using ArcGIS Pro (since the source data was not available) and annotated and joined with several attributes representing altitude and additional information (e.g., minimum and maximum height). Some of the layers needed further processing steps, such as a 3D intersection of the flight route with the turbulence areas or the determination of jet stream directions on equally distributed points along the stream. In a next step, all data layers were published to an ArcGIS Portal, to which the Web Application had access for the 3D visualization. This workflow, which is depicted in figure 3, was then used to come up with an initial proposal for the application which was subsequently reviewed in a pilot study.
One of the major challenges concerning the visualization of aviation weather data is the fact that most weather products are maintained and created by meteorologists and are not designed for pilots. To implement a prototype with a high level of usability, it was crucial to do a pilot study where an optimal design was identified based on feedback from subject matter experts, namely experienced pilots. The motivation to do a pilot study originated from the requirement of implementing a 3D representation that aligns as much as possible with the pilots’ mental perception of weather objects.
The pilot study was performed with three subject matter experts that were brought in for on-site interviews. They were able to choose several design parameters in a first draft of the application. The parameters included vertical exaggeration (thickness), offset from the ground, colors of elements and basemaps, as well as different types of renderers. For the night mode of the application, the subject matter experts came up with different 3D designs which can be reviewed in figure 4. They were also able to dynamically choose parameters for the day mode of the application which has brighter colors. The dual mode was implemented since most aviation displays have a day-night mode switch due to frequently changing lighting conditions in the cockpit.
The inputs from the pilot study as well as an additional review of all three designs by the subject matter experts were then used to implement the actual prototype.
The direction of the jet streams was visualized by using an ObjectSymbol3DLayer with a white cone symbol (width = 75 km, height = 150 km). The rotation of the cone was adapted for each point along the stream by using visual variables on the heading property of the object. Additionally, the cone had to be tilted by 270° to have it lying down as well as the correct initial position. The renderer for the cones was constructed as follows:
Transparency, like color and shape, has proven to be a useful visual variable in 3D visualizations, especially for data overlays. However, correct transparency sorting is still one of the challenges in displaying 3D graphics on the web and is not supported by WebGL. Since some weather objects were rendered in a transparent style e.g., to make objects that they enclose visible, an order-dependent transparency sorting was manually established in the prototype. The implementation was achieved by using a promise for each layer which waits until the LayerView of the previous FeatureLayer is loaded. Afterwards, the next layer or group of layers is loaded. The result of the transparency sorting can be seen in figure 6.
The following shows how this was implemented in the code assuming that layer 1 is enclosed by layer 2, as well as that layer 2 potentially represents the outline of layer 3 and therefore needs to be loaded first:
Spatial awareness was assessed by a drawing task for the participants in which they had to draw four categories of weather objects (jet streams, clouds, CBs, CAT areas) with the flight path and a basemap as reference. Sketch maps were used for the evaluation of cognitive maps and mental representation and have proven to be a reliable source of information to assess the internal representation of an environment which correlates to the sense of direction and therefore spatial awareness. Participants of the user study were asked to look at either a 2D or a 3D representation of the data and were then required to draw what they remembered in a second step. The drawing was implemented in the user study with a map and the drawing widgets. The features which participants drew were saved as new features in a result layer. A drawing from one of the participants can be seen in figure 8 in comparison with what the participant was presented in the 2D or 3D condition.
The research project showed great potential and promising results for the use of a 3D web-based visualization for aviation weather and will therefore be continued at ETH Zurich in collaboration with the international airline. Additionally, the project also contributes to the research community around user interfaces and has been published to an international conference. Further information can be found in the research paper about this project.