Animated chorem-based summaries of geographic data streams from sensors in real time

https://doi.org/10.1016/j.jvlc.2017.03.002Get rights and content

Highlights

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    On-the-fly generation of visual summaries from geo-data coming from the sensors.

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    New approach about the use of chorems for automated data processing applications.

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    We define chorem as a semantic and a geometric generalization of a territory.

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    Our interest was not to represent the entire information, but the most relevant aspects.

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    We address cartographic generalization and spatial conflict resolution problems.

Abstract

This paper describes a new visualization approach for the automatic generation of visual summaries dealing with cartographic visualization methods and modeling of real time data coming from sensors. Indeed the concept of chorems seems an interesting candidate to visualize real time geographic database summaries. Chorems have been defined by Roger Brunet as schematized visual representations of territories. However, the time information is not yet handled in existing chorematic map approaches, that is the issue been discussed in this paper in which geodata are coming regularly from sensors distributed along some territory. Our approach is based on spatial analysis by interpolating the values recorded at the same time, so we have a number of distributed observations on areas of study. To get a better visual overview of the entire sensor geodata at a given time, we use spatial statistics formulas on the fly, and so it is possible to extract important spatiotemporal patterns and detect trends over time as geographic rules. Then, those spatiotemporal patterns are visualized as animated chorems. An example is taken from meteorology.

Introduction

In today's society, the shared amount of information and data is significantly increasing, requiring a strong need for understanding. A direct projection of the geodata on a display surface does not make sense to mapping viewpoint. For this, methods and techniques for the representation and visualization grew into a new scientific discipline known as “Visual Analytics” [28] and more precisely in our case “Geovisualization”; this discipline utilizes intelligent tools that can help find needles in a big data haystack, using spatial relationships to filter relevant data. Geovisualization is defined by Kraak [30] and MacEachren and Kraak [39] as it “Incorporates methods and the development of decision making techniques through spatial thinking, visualization, statistic analytics, analytical reasoning, synthesis and presentation of spatial data”. In addition, when it comes to real time data coming from sensors, here the complexity increases further. As visual presentation and analysis of these data are currently a very promising research topic [3], the scope will be not to determine the mapping once at all, but more especially to calculate it in real time in order to schematize evolution and to understand the structures in space and time. In this paper, our challenge is twofold:

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    Synthesized map: essential information is displayed in a layout layer, which requires prior analysis to extract relevant information. The solution presented in this paper is called a chorematic map [13] in which both geometry and semantics are generalized; this solution has shown several successes as an efficient communication tool. In addition, for extracting salient features, a novel method based on importance functions is presented.

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    Animated real-time map: a single map which shows changes discretely over time in accordance with the modification of the data results in motion or perceived changes in the object's appearance. In the presented work, as data streams come from sensors, it is necessary to implement an automatic and efficient solution for chorematic cartography without any expert editing.

In this paper, we are concerned with the concept of chorems as inspiration to propose a new approach for allowing the generation of animated chorematic maps, using the methods able to take into account the spatial and temporal distribution of structured data provided by sensors.

After briefly introducing the related works necessary for the understanding of our research, the proposed approach is detailed, followed by the implementation process. Along the paper, an example is used, based on meteorological data. Then we conclude with a discussion of the results and finally suggest some further perspectives.

Section snippets

Related works

In this section, we briefly discuss related works required to understand the background of our research, i.e. some reminders concerning sensor networks, data streams, geovisualization time, and chorems.

Proposed approach for generating real-time chorems

In order to explain our approach, an example will be taken from meteorology. It should have been interesting to work with very time-critical applications such as in the monitoring of nuclear plants, but in geography usually phenomena are slow (it is not necessary to measure temperature every second!). In other words, processing time is not very decisive, but anyway time constraints must be followed. In this section, first the application domain will be detailed. Then the global methodology of

Design of a prototype and discussions

We underline our idea and in order to check the validity of our approach, a prototype was made with an application example, describing the whole process; the system accomplishes the construction of one of the animated chorematic maps necessary to represent the important situations meteorological of Algeria. In particular, details about the different steps and the modules involved are described as follows.

Conclusion and future works

In this paper, we have presented our early efforts for a new approach to define mapping solutions that adequately represent information from a geographic database in real time based on animated chorematic maps defined as cartographic and semantic generalization of a map.

Because our primary interest was not to represent the entire available information, but rather a general overview of a visual summary, a novel solution was proposed based on the concept of the animated chorematic map and its

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