An investigation into improving landmine detection by fusion and interpretation of data from a number of sensors as related sounds


Executive Summary


Research was conducted into enhancing current landmine detection methods using novel and intuitive techniques. The failures of previous technological methods for detecting landmines were noted and based on these two principles of the research were concluded:

  • Technological enhancements must integrate with the current demining toolkit available to deminers
  • It is not realistic to build a single device which can be used in all situations to detect all types of ERW (Explosive Remnants of War). Instead, a device should be made that a deminer can learn to make judgements on when its use is appropriate and can therefore be trusted.

One such device adhering to these principles was already in development at ERA Technologies. The device was a Vallon VMM3 pulse-induction metal detector fitted with a GPR (Ground Penetrating Radar) sensor. The device operated in two, switchable modes; the standard aural feedback from the metal detector and aural feedback of the GPR.

It was demonstrated that ERW could be located using standard demining procedures and the metal detector. The detector was then be switched to GPR mode which aurally provided feedback about the shape and depth of the buried object. It was hoped that the GPR could be used to help discriminate between metallic objects and landmines due to their shape, thus saving time excavating every metallic object.

The device was trialled at an MOD test site by Kjell Bjork, a landmine expert who was working with the York research group. His main conclusions were that while the use of GPR showed great promise, there was still much needed progress; most notably a means of combining the feedback from the metal detector and the GPR was needed to be able to more easily relate metallic content with depth and size of the buried object.

Basis of research

Based on this conclusion, the aim of the research summarised here was to develop a way to combine in real-time, signals from both a metal detector and GPR to produce an aural feedback which would help a deminer to discriminate between buried metallic objects and landmines, as well as improving the detection of minimum metal landmines in non-ideal conditions. (For example, a landmine is not easily located in ground contaminated with metallic fragments such as bullet casings. Using GPR to identify the shape of buried objects would enable the deminer to discriminate between small pieces of shrapnel and a firing pin inside a landmine.)

It was decided to meet this aim using the principle of sonification which may be briefly demonstrated by considering a car. When a car is running normally, one becomes less aware of the noise of the engine, almost to the point where it is not consciously noticed. However, if a fault were to develop, such as engine knocking – the brain would immediately recognise this sound as abnormal, even if the driver was unaware as to what caused change in the sound, their attention would be focussed on the source of the abnormal sound. This can be demonstrated in all manner of situations, even when there is loud background noise (such as a car radio).

It was hypothesised that by sonifying metal detector and GPR data, the same effect of listening to a car engine and aurally detecting and diagnosing problems as mentioned above could be applied to the ground. A deminer would be able to interact with the detector and the ground using their brain as data processor for the aural feedback. It was hoped that a deminer would be able to learn how the sounds of the detector correspond to the constituency of the ground and therefore make better judgements as to detecting and identifying buried objects. As the method of operation would be almost identical to that of a metal detector, the new technology would integrate seamlessly into existing demining toolkits as an addition and not as a replacement.


New sonification techniques were developed to produce aural feedback from both detectors. Most importantly, no filtering of the signals was done, instead the signals were synthesised into frequency modulated audio streams using different wave shapes and mixed together. Test results demonstrated the ability of a user to:

  • Identify discontinuities and abnormalities in the ground
  • Distinguish between metallic and non-metallic buried objects

The results clearly demonstrated that signal combination of data from multiple sensors using sonification vastly improves the detection and discrimination of buried mine and mine-like objects.

Future work

Due to the noted adaptive filtering of sound by the brain it was then hypothesised that results equally conclusive could be made in non-ideal soils such as gravel, compacted stones, ferrous and metal-contaminated soil. Quantitative tests need to be performed, as well as trials with experienced deminers to evaluate not just the detection capabilities but also the impact on the existing demining toolkits and the training of new deminers.

The sonification methods need to be improved, paying particular attention to the fact that a deminer may be listening to these sounds for an hour or more at a time. They must not be monotonous nor fatiguing yet they must maintain a level of discretion as a deminer must always be aware of other sounds in the field.

There has been considerable research in other sensing technologies appropriate for use in mine detection, such as Nuclear Quadrupole Resonance which can be used to determine the type of materials buried in the ground. Investigation into how this could be incorporated and to the improvements in detection possible could prove advantageous.

Further work on interpreting data from the metal detector should also be undertaken. Phase information of pulse induction metal detectors can be used to indicate the shape and size of the metallic object.

By improving the methods of sonification and including new and appropriate sensors, it is hoped that a sensor can be made which can produce a detailed and accurate aural representation of the shape, depth, material and metallic content of buried objects.

If you’d like a copy of the full dissertation research, then please get in touch by leaving a comment below.

Posted in Landmine clearance | Tagged , , | Leave a comment

Fat Controller v0.0.5 released!

After a hiatus of almost two years, here’s the latest instalment of the Fat Controller. No fancy new features I’m afraid, just the odd bug fix and a tidy-up of some of the internals. All being well, this should make it to the v1.0.0 release.


Project web:

What’s next?
After the 1.0.0 release, I am thinking of creating a monitoring application with a GUI, so you can remotely communicate with and monitor a running instance. Another idea would be to allow one instance of the Fat Controller to handle multiple configurations, avoiding the need for multiple instances of the Fat Controller running simultaneously.

I’m pretty short of spare time, so it depends on interest in the program. As always, any new ideas, comments and suggestions for future versions are all welcome!

Posted in The Fat Controller | 4 Comments

Page onload Ajax request in Wicket

A new requirement arrived this week to display a load of statistics on the main page of the application. Simple enough, except that the collection of these statistics from the database took an unacceptably long time to load. As this was the main page, every user had to wait for the statistics to load after logging in before they could navigate to the page they wanted. Unfortunately simple caching wasn’t an option as the data must be up-to-date and more elaborate caching techniques were off the cards due to time restrictions on the implementation effort.

The solution I came up with was to render the page without the statistics but instead showing a message saying “Statistics loading, please wait…”. Once the page loaded, an Ajax request was fired which generated the statistics and replaced the message. Now the page loaded immediately and users did not have to wait for the statistics to load before navigating to another page.

However, implementing this in Wicket was not so straightforward, so I thought I’d write up my solution.

The first step was to create an implementation of AjaxEventBehavior which created a new instance of the statistics panel to replace the “Loading…” message component. So far all pretty basic.

AjaxEventBehavior loader = new AjaxEventBehavior("onload") {

Getting this Ajax event to fire on page load was a bit trickier. The normal way is to attach a Javascript event to the tag, or specify its onload attribute. Luckily, there is a way to do this in Wicket. All the pages in the application extend from a base class which itself extends Page. This base class provides standard layout so that all the pages in the application look similar, share the same HTML headers and so on. The associated HTML of this base class defined the tag, so in order to be able to access it in Wicket I added a wicket id, something like this:

Great, so I can access the body tag – but now I’ve broken the hierarchy, all the components now need to be added to the body tag, not the page. Rather than rework the entire page class, it is possible to set the body element to be transparent in the hierarchy:

        body = new WebMarkupContainer("body"){
            public boolean isTransparentResolver()
                return true;


Now all I had to do was create a protected getter method to allow access to the body element and now I could add the Ajax behaviour from the main page.

Posted in Java | Tagged , , | 1 Comment

Service initialisation with automatic dependency based ordering


The Application Controller of our application initialises all of its services when it itself is initialised. Unsurprisingly, some services must be started before others; for example the Logging service must be started before the Configuration service, which must be started before the Persistence service, which must be started before the Authentication service and so on. It sounds hard but it’s easier than playing an online game or getting booster from P4R Gaming.

Currently, all this initialisation is done in one long initialiseServices() method, initialising each service in the correct order. If we create a new service then we just slot it into this method in the right place. Providing this order is not changed then everything is fine.

The problem

So what’s the problem? Well, apart from being a bit ugly, there is a practical problem that has arisen. Our client would like to be able to deploy parts of the application separately, which means we need to split it up into a core which rarely changes and separate modules which can be deployed independently. If one of these modules requires a new service, or one of its services becomes dependent on another, then the Application Controller will also need to be deployed. Not only will the client need to deploy the new module but also a whole new core. Also, the client must wait until both the module and the core builds become stable.

The solution

What would be ideal is if each module could tell the Application Controller which services it needs when the application starts. The Application Controller would then determine the order in which to initialise the services based on their dependencies. Cyclic dependencies would be detected upon startup.

A prototype

In order to demonstrate this, I’ve made a little mock-up. This is probably best understood by looking at the code, but I’ll try and explain it as best I can in words.

The idea is that all Services must extend an abstract base class; Service. The abstract Service class provides public method addDependency(Service service) which is used to specify the other services on which it is dependent. The sorting algorithm is not interested in services on which each service is dependent, but rather the services which depend on each service. This is because the graph of service dependencies is traversed depth-first, from the services without any other services on which they depend. Therefore, the addDependency(Service service) method actually calls a package-private addDependent(Service service) method on the passed service object.

Services are then added to a Service Manager. The services are initialised by calling initialiseServices() on the Service Manager which creates an instance of ServiceReactor which does the sorting, returning an ordered list of services which are to be initialised sequentially.

The ServiceReactor uses topological sorting to arrange the services based on the graph of dependencies.

The example I’ve provided sets up the simple graph as described here:

Note that I didn’t want to make a separate Service classes for each node, so I made an IdentifiableService which gets a unique integer passed to its constructor which is used to identify it as a separate Service. Of course in reality each Service would be defined by its own, separate implementation of the base Service class.

Feel free to download it and have a play with it. For example, try creating a circular dependency and you should get a DirectedCycleException. I know, it really is that much fun!

Download example:

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The Fat Controller v0.0.4 released!

I’m sorry it wasn’t in time for Christmas, I hope everyone managed to have at least a little bit of fun on Christmas day without it – but finally it’s here – version 0.0.4! This version involved the rewriting of the entire logging system for sub-processes, so plenty of testing was needed which wasn’t always compatible with Christmas festivities, (oddly enough).


Project web:

Continuous logging

The main aim for this release was to fully support the “daemonise anything” point of the Fat Controller raison d’etre. Prior to this release, output from sub-processes was collected and then written to the log file only once the process had ended. This was bad for two reasons:

  • it only logs output on STDOUT, anything on STDERR is ignored
  • no good for long-running daemon processes as nothing is logged until it ends

The Fat Controller now continually monitors STDOUT and STDERR of all sub-processes and immediately writes anything to the log file.

The whole logging system can be re-initialised by sending SIGHUP to The Fat Controller. So if, for example, your log files get deleted due to log rotation, simply send SIGHUP and The Fat Controller will re-open file descriptors to the log files. This can be easily added to your log rotation mechanism.

So, what else is new in v0.0.4? Here’s a brief summary taken from the changelog:

ADDED –run-once
Also to support daemon processes, using the –run-once argument it is possible to tell The Fat Controller to, (cunningly) run a process only once and then end.

ADDED –test-fire
If this argument is specified then The Fat Controller initialises but does not actually run, i.e. it does not daemonise (if it is specified to be in daemonise mode) nor does it run any processes. It is useful combined with the –debug option when testing to check arguments have been correctly read and interpreted.

CHANGED Debug mode
Debug mode is turned on by using the –debug argument when running The Fat Controller. Previously this was added by the init script /etc/init.d/fatcontrollerd if the file fatcontroller.debug was found in the current directory. In addition to turning on debug mode, it also looked for the configuration file in the current directory, and not in /etc/

This has now been substantially simplified. All you need to do to enable debug mode is instead of running the Fat Controller with:

sudo /etc/init.d/fatcontrollerd start


sudo /etc/init.d/fatcontrollerd debug

My plan is that if no major bugs are found in this release then I will re-release it as v1.0.0 as it will finally be everything that I imagined when I first started this project over a year ago.

I’ve still got plenty more ideas for development and I’m eager to hear any other ideas people may have. Please let me know if you have a great idea or suggestion!

Posted in The Fat Controller | Tagged | 11 Comments

The Fat Controller v0.0.4 almost ready – testers wanted!

I’ve just about finished the next version of The Fat Controller, v0.0.4. I’ve completely refactored the way it writes output from sub-processes so it needs some careful testing. It would be great if other people could give it a try and do some testing as well, if you’re interested then just leave a comment and I’ll send you the source. Perhaps version 0.0.4 could be ready in time for Christmas – and what better Christmas present than a new version of The Fat Controller?!

Here are the main new features:

Continuous logging
One of the shortcomings of previous versions was that output from sub-processes was only written to the log file once the process had ended. This is of little important for scripts which run quickly, but this is obviously no good for longer scripts or even when used to daemonise a program.

Now, output is written immediately to the log file which means that The Fat Controller can easily be used to daemonise other programs.   One of the issues I sometimes have with Java applications is that there’s not a simple way to run them as a daemon.   With The Fat Controller this is now possible, as well as provide handling should the Java application terminate for whatever reason.

Logging STDERR
In previous versions, only STDOUT from sub-processes was logged.   In v0.0.4 STDERR is also logged and you can specify either a separate log file for STDOUT and STDERR or simply log both into one file.

If you want to impress and amaze your friends and get your hands on the latest version before everyone else then just leave a comment below and I’ll send you the source and you can get testing!

Posted in The Fat Controller | 16 Comments

The Fat Controller v0.0.3 released!

Finally, after almost five months, version 0.0.3 is ready!

There are plenty of changes, mostly bug fixes which relate to startup options (not the actual running of The Fat Controller) and a new thread model – fixed interval – which runs processes like cron at fixed, regular intervals between each new process creation.

Here are some highlights from the changelog:

ADDED Fixed interval thread model
The ‘independent thread model’ and ‘dependent thread mode’ start another instance of the target program a specified number of seconds after the previous instance ends. The ‘fixed interval thread model’ starts another instance a specified number of seconds after the previous instance starts, hence the interval beteen new instances is fixed. The interval is specified using the -s,--sleep argument, just as for the other thread models. Note that the interval is respected even if a process returns status 64. Only if a process returns a status of -1 will the interval specified by -e,--sleep-on-error be used.

ADDED Long running instance termination
Using the --proc-run-time-max argument, it is now possible to specify that an instance be terminated if it runs longer than the specified number of seconds. Default behaviour is never to terminate processes unless the main Fat Controller process is requested to shutdown. (Processes terminated by sending SIGTERM). It is advised to specify this argument.

Plans for v0.0.4
I’ve already drawn up a rough list of features and improvements for v0.0.4, the most important being changing the logging of sub-processes. Rather than collecting from STDOUT and writing everything to the log file once a sub-process ends, The Fat Controller will continually write whatever arrives from STDOUT and STDERR to log files. This will make things much better for long running sub-processes.

If you have any ideas or suggestions then please comment or file a report on the Sourceforge Fat Controller tracker page:

Posted in The Fat Controller | 8 Comments

Fat Controller 0.0.3 almost ready

It’s been ages in development (sorry about that) but the next version of The Fat Controller is almost ready! Apart from really quite a lot of bug fixes the main new feature is called “fixed interval mode” which works more like CRON in that scripts are executed at precise time intervals, unlike measuring the interval from when a script ends. This brings in a whole host of new problems, such as multiple instances, maximum instances, what to do when we’ve reached the maximum number of instances and so on, and yes, there are plenty of new configuration options to address all of this!

After finding quite a few embarrassing bugs in v0.0.2, I’ve decided to spend some time on Quality Assurance, which is what I’m currently doing before releasing v0.0.3. If anyone wants to help out with this then please let me know – any and all help is appreciated!

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Javascript: Exception thrown and not caught

I recently started getting this Javascript error message on every page in my application:

Exception thrown and not caught

Interestingly, I only got this message in Internet Explorer (IE7) and only on the first page view after clearing my temporary internet files (cache). If I refreshed the page, the error was gone and only reappeared when I cleared my browser cache – again disappearing after a page refresh.

My suspicion was that some Javascript in the HTML was trying to call a function or a method on an object that was declared in an external Javascript file, crucially before that external file had loaded from the server. This would explain the fact that the error disappeared after a page refresh, as the external file would already be available from the browser cache.

The solution was simple – I wrapped the Javascript that was in the HTML file using jQuery’s $(document).ready() function and the problem was solved.

Interesting note for Wicket users:

My application is built in Wicket and I embed the Javascript into the HTML response using AbstractBehavior.renderHead(IHeaderResponse response). Initially I used response.renderOnDomReadyJavascript(String javascript) which executed the Javascript once the DOM was ready but before the external Javascript dependencies were loaded. My first attempt to fix this was to used response.renderOnLoadJavascript(String javascript) which, as the JavaDoc states, executes the Javascript after the the entire page is loaded. This worked fine, except when the behavior was applied to components rendered in an Ajax response, as of course there was no page load event when the ajax request completed.

My solution was to move back to using response.renderOnDomReadyJavascript(String javascript) and, as stated above, wrap my Javascript in jQuery’s $(document).ready() function.

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Attach IntelliJ debugger at application startup

Normally when I want to debug a Java appliaction, I run the application and then connect the IntelliJ remote debugger to the JVM. Today I needed to debug the boot sequence of the application which meant I needed the debugger attached right from the start so as to catch the breakpoints at the beginning of the boot sequence, connecting manually would be too late.

In IntelliJ I changed the debugger mode from “attach” to “listen”. It then told me to use these command line arguments for the JVM:

-Xdebug -Xrunjdwp:transport=dt_socket,server=n,address=nick-laptop:5005,onthrow=,suspend=y,onuncaught=

What it doesn’t say is what values to use for the “onthrow” and “onuncaught” options. After a bit of fiddling I got it to work by setting “onuncaught=n” and removing entirely the “onthrow” clause:

-Xdebug -Xrunjdwp:transport=dt_socket,server=n,address=nick-laptop:5005,suspend=y,onuncaught=n

Linux users…

If you’re not using Linux then you can skip this bit, if you are, then this might be useful. I found it annoying to set IntelliJ to listen for incoming debug connections before starting the application, most of the time it’s fine tohave the JVM in listen mode and initiate connections as-and-when from IntelliJ. As a solution I added a couple of aliases to my ~/.bashrc file so that I could swap the behaviour easily:

# For IntelliJ in attach mode
export MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005"
alias ijattach='export MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005"'

# For IntelliJ in listen mode
alias ijlisten='export MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=n,address=nick-laptop:5005,suspend=y,onuncaught=n"'
Posted in Java | Tagged , , , | 2 Comments