Geographical data are typically visualized using various information layers that are displayed over a map. Interactive exploration by zooming and panning actions needs real-time re-calculation. A common operation in calculating with multidimensional data is the computation of aggregates. For layers containing aggregated information derived from voluminous data sets, such real-time exploration is impossible using standard database technology. Calculations require too much time.
The University of Twente has developed “Stairwalker‿: database technology that accurately aggregates data so that they can geographically be explored in real-time. The technology is a plug-in to common open source technology.
Its core is the pre-aggregate index: a database index that cleverly precalculates aggregation values such that it can obtain exact aggregation results from voluminous data with high performance. A fast calculation allows to fully recalculate the result for even the slightest movement of the map, such as a panning or zooming action, without loss of accuracy. Thanks to this indexing mechanism, we can provide a scalable real-time calculation: an order of magnitude larger dataset requires only one additional aggregation level.
In geo data visualization, the ability to quickly develop new information layers is important. Although many solutions exist, there is a niche: the combination of visualizing aggregation information, interactive data exploration in real-time, Big Data, calculating exact numbers instead of approximations, and doing so with common open source technology. Our technology for the first time integrates all these features.
Our research partners are the companies Arcadis and Nspyre. They both have struggled with this combination of requirements in many of their projects. Our database index technology is not specific to geographical data. It can be used with all types of multidimensional data. Visualization in business intelligence or eScience can also benefit from it.
The company Arcadis developed an application for the DCMR Milieudienst Rijnmond based on the Stairwalk technology to investigate whether people send tweets about unpleasant odors as a possible signal of danger. This turns out not to be the case, probably because people think that nobody reads the tweets anyway. But if people have the idea that their complaining tweets are read, then tweets might be much more convenient than the reporting of unpleasant odors by telephone.
This manual explains how to use Stairwalker. We first explain in Section 2 how to install the required components in order to have a basic running system. We then explain in Section 3 how to add databases and different kinds of datatypes to Geoserver, an open source server for sharing geospatial data.1 It is explained how to show and customize layers and views, but also how to adjust the system, for example, how to add dimensions or use different dimension types such as median. Finally, Section 4 explains how to extend the system.
|Name||CTIT technical report|
|Publisher||University of Twente, Centre for Telematics and Information Technology (CTIT)|