Data Fusion

Using Active Structure

Interactive Engineering

Data Fusion combines the outputs of sensors of different types to build a better picture of the object being sensed

Simultaneous Sensing

The sensors may be dynamically configurable (or even dynamically manoeuvrable), and may produce ranges with error estimates.The knowledge will certainly be dynamically configurable, depending on the state of the system, and some connections will be both input and output

Simultaneous Sensing is very much like Constraint Reasoning, except that pruning of alternatives needs to be more general

Cutting continues until the sensing system settles, with ranges of numbers, probability spectra, sets of objects and even existence being shuttled backwards and forwards along the connections.

Example

Sensing a Tsunami

Causal Sensing

The tsunami example is more complicated than simultaneous sensing, in that there is considerable delay between the two sensings and a decision has been made after information from the first sensor has been received.

Information from the second type of sensor may validate the decision, leave room for doubt, or negate it.

As with all Data Fusion applications, the sensors may not be in the best possible position to sense what is desired, or to sense anything at all

This needs to be built in to the knowledge wrapped around the sensor to transform to the sensed object

Sensor Types

Seismometerto sense earthquakes

Tide Gaugeto measure wave height near land

Dart Buoyto measure deep ocean wave amplitude

Single Sensor - Multiple Sensings

The seismometer is an example of a sensor that senses four different types of seismic wave - P-Wave, S-Wave, Rayleigh wave, Love wave - in three orthogonal directions, so joining together all the information is already a Data Fusion application (but one that has been automated for the last 20 years) where data from multiple sensors of the same type may not agree. The complexity of the resulting information makes it especially hard to integrate with information from other phenomena.

A network of seismometers senses an earthquakeFrom theses sensors can be deduced the magnitude and the location of the quakeA worst case scenario is created of the resulting tsunami and a decision will be made on this partial information

Later, the shape of the rupture may be available by inverting the seismometer signals to estimate the size, type and orientation of the source

Tsunami System

There is information of doubtful validity at every stage- it needs to be reconciled backwards and forwards

Chimera

Building a chimera by mixing sightings - a typical problem of knowledge-poor algorithms - circulating detailed knowledge about the detections would help prevent such mistakes

Variables

The seismometer signals are predicting the latitude, longitude, rupture type, length, width, uplift and angle of rupture. From those variables, the wave distance L2 and heights H2 and H3 are estimated. A different rupture type would have the wave at 90 degrees to that shown.

DART Buoy Has Different Value

Uneven uplift changes beam angle

Wrong rupture location

A variety of reasons why a particular value is not foundEach reason has a calculable probability

Wrong magnitude or uplift

Wrong rupture type

Tide Gauge Has Different Value

Tide gauge protected

Aside from the same reasons as the DART buoy, the location of the tide gauge relative to an island or mainland is important in terms of measured wave amplitude

Full energy and shoaling

Deep ocean amplitude

Dynamic Assembly of System

The seismometer/tide gauge example of Data Fusion requires a system to be dynamically (and automatically) assembled and analysed - while the sensor locations are fixed, the beam heading affects which sensors can be used and their sensitivity, and the heading can only be known within the event being detected

Active Structure allows this dynamic assembly and analysis during Data Fusion