OVER 2 YOU, 155 (11/11/03)

DESTROYING DATA CDS

My company has amassed several hundred outdated CD-R data backup discs, containing sensitive information. Aside from smashing them with a hammer, which I imagine would be both messy and dangerous, can anyone suggest a simple, safe and environmentally friendly way of rendering them completely unreadable, prior to disposal or recycling at the local refuse facility?

Gerald Taylor, via email

To render CDs unreadable "zap" them in a microwave oven. Stack them a few at a time in something like a wooden toast rack, place them in a microwave oven with a glass of water to load the oven. "Cook" them on full power for a few seconds, until they are well crazed or until the fireworks stop. 

It's quite exciting and you get some pretty patterns, but I imagine it could be quite boring if you have several hundred to do. I disclaim any responsibility for any consequences of this procedure.

David Green, via email

You may permanently destroy your CD-R data back-up CDs by the
simple process of scoring them with a sharp-pointed nail or some similar tool. Ensure that the scratch is reasonably deep and cuts across the entire disk surface (on the data side!). CDs hold their directories on tracks nearest the centre hole (opposite to floppy disks). This should prevent anybody, with the possible exception of genuine high-end experts, who would have something better to do with their time. Just don't try it on your current data CDs!!
Michael J. Stock, Breaston

You can get a mains-powered CD Data Destroyer, which will tackle 15 discs a minute, from Maplin Electronics.  It costs £39.99, order code A92AL from www.maplin.co.uk.
Brian Cook, Guildford

Buy a pair of tin snips from a tool store or ironmonger, get two waste-paper baskets or containers, and simply cut each disk in half, throwing one half in one bin and the other half in the other bin. Then take them to the disposal location on two separate occasions so that they can't be put back together. Cutting them up should not take more than about an hour and a half.
A.L.Minter, Sandwich

Leave them on the parcel shelf of a Ford Orion (I am fairly sure it works with other makes), data side up, and in a few days ultra violet radiation of the sun will do to them what it did to my collection of audio CD-Rs and make them unreadable.

Dave Keys, via email

Pop them in the oven, on a baking tray. Gas mark 4 or 180 degrees Celsius for around fifteen minutes should do the trick and the interesting shapes that emerge can be used to create eye-catching mobiles or bird scarers.

Jill Stevens, via email

MAPPING PROGRAMS

Could I have recommendations for mapping programs, either downloadable from the Internet or available commercially, which searches for locations in the UK and Europe based on longitude and latitude data?

Niall Hall, via email

I thoroughly recommend the on-line map service from MapQuest. All you have to do is tap in the longitude and latitude details (in conventional or decimal formats) and a couple of second later a detailed map appears on your computer screen. As far as I can see it works for just about any location, though the amount of detail for some of the more remote corners of the world is a bit variable. You can shift the view and zoom in for a closer look, print the map out or send it as an email and it’s all absolutely free. The data entry page for longitude/latitude is: http://www.mapquest.com/maps/latlong.adp

Mel Turner, via email

MS Autoroute has three location finder options: Address, longitude/Latitude and Ordnance Survey grid co-ordinates. Using any of these reference systems and the "Find" button will bring up the required map for the values entered.   

Fraser Jordan, Diss, Norfolk.

I can’t suggest any mapping programs but I do know of an excellent web resource, called Heaven’s Above, for finding out the latitude and longitude for any location. Just click on the country then the name of a town of city and Heaven’s Above displays the exact map references. The site is primarily devoted to astronomy, and it shows the current position of the International Space Station but it’s an excellent resource for earth-bound travellers and can be found at:

http://www.heavens-above.com/countries.asp

W. P. Teacher, south London

SPEEDO CALIBRATION

I live in dread of being ‘flashed’ by speed cameras. I do not knowingly exceed the speed limit but I have only my car’s speedometer to rely upon. Reports that speeding tickets could be issued for breaking the speed limit by only a couple of miles an hours prompts me to ask if anyone can suggest a method of checking the accuracy of my car’s speedometer, possibly using my laptop PC and some sort of distance/speed measuring software?

Arthur Kennedy, via email

Your correspondent wanted assistance in discovering the true road speed of his car. I downloaded GearSpeed.exe from http://www.e31.net/GearSpeed.html. Written by Mike Coenen it is freeware and calculates the speed a car could achieve with certain tyres, gears and final drive ratio.  The program is set up for the BMW 8 series, which has a notoriously inaccurate analogue speedometer) but manual input allows it to be used with any car.

Iain Hughes, via email

Drive past a speed trap with your speedo reading at least 95 miles an hour, and when the police catch up with him they’ll tell him exactly how fast he was going.
Julian Swinden, via email

CAN YOU HELP?

Can anyone suggest a way of taking an aerial photograph of my property, preferably using my own digital camera? Would such a thing be possible, using a tethered balloon or perhaps some sort of radio-controlled aircraft?

Peter Mitchell, via email

I am trying to set up a "rolling count" formula in Excel whereby a column of
movements in daily stock index data is analysed for the frequency of particular events. The normal COUNT function works with a range of data set by the user but I wish the formula to perform a rolling analysis on a column of data, for example, on a moving 4-week basis. Any ideas?
Mark Wright, via email