In Depth: How your sat-nav works out the best route
Sat-navs are a fascinating offshoot of both the US military's desire to equip its units with the facility to find out their position and the ability to display maps on a computer screen.
But though the devices are extremely popular, the algorithms that they use in order to provide the shortest distance route to your destination are less well known.
There are two major algorithms that come into play with sat-navs. The first is perhaps the simplest: the ability of the unit to use the GPS (global positioning system) satellites to work out where in the world the unit is situated.
The second is rather more complicated: the ability of the sat-nav to determine the shortest distance from point A – where you are – to point B – where you'd like to be. There are other algorithms in play, mostly dealing with the visual display of the route to take, but these two algorithms are the most important.
The GPS satellite network started out as a US Air Force system to help determine the position of any receiver to an accuracy of 15 metres. Following the downing of the civilian KAL 007 airliner after it drifted into Soviet restricted airspace, Ronald Reagan promised to make the system available for civilian use once it became operational.
This happened in late 1993, and the unencrypted civilian signal was deliberately downgraded so that GPS units would only be accurate to about 100m. This limitation (known as Selective Availability) was removed in 2000.
The positioning algorithm is fairly simple. Currently there are 30 satellites spread out in medium Earth orbit, each transmitting the same information. The messages consist of three main pieces of data: the exact time the message was transmitted, precise orbital data for the satellite (known as the ephemeris) and the overall system health.
The GPS unit listens for these messages and interprets them. From the time of the message, the GPS unit can work out how long the message took to reach the unit, and, from that and the known speed of light, how far away the satellite is. From the ephemeris data, the unit can work out the direction to the satellite.
Calculating the position
Using just the messages from one satellite, the GPS unit is going to be somewhere on the surface of a virtual sphere centred on that satellite. That's fairly interesting to know, but not very helpful.
So the GPS unit listens for messages from other satellites. Using the messages from two satellites, the GPS unit can work out its position to be somewhere on the circle that forms the intersection of the two spheres centred on each satellite.
If you think about it geometrically, either the spheres don't intersect at all, or they intersect at just one point (the spheres just manage to 'touch'), or, in the more general case, they intersect as a circle. Think of soap bubbles joined together. Interesting to know, but again pretty useless.
Using three satellites, the GPS can calculate its position to be at one of two points on that circle from the previous case. Again, thinking geometrically, the intersection between a sphere and a circle is going to be either non-existent, a single point or two points.
So GPS units use the messages from at least four different satellites to resolve their location to a single point. GPS satellites are positioned in orbit so that from any point of Earth about 10 satellites will always be 'visible' in the sky, an ample number from which to calculate the position of a GPS receiver. The position of the receiver, using just the GPS satellites, is calculated to within about 15m.
The reason for the comparatively large error is due to many factors, including the atmosphere (light travels slightly slower in air than in the vacuum of space), any errors in the clocks involved, bouncing of the GPS signals off buildings and so on. Yet, as we all know, a GPS unit seems to be way more accurate than that.
The reason is that terrestrial sat-navs do not rely exclusively on GPS satellite signals: they also make use of other signals such as those from mobile phone towers and the like to refine their location to within a few metres.
If the GPS receiver is in a car and forms part of a sat-nav system, the unit will also make use of further information from the car itself, such as speed, distance travelled, acceleration and so on. This helps in urban environments where the GPS signal can be blocked by bridges, or by being in a tunnel, or messed up by being reflected off buildings and the like.
Of course, a further refinement is that, usually, the car is on a road, and so the sat-nav can 'fix' the location of the car to a road on its internal map.
It's now time for the second algorithm: determining the optimal route from the current position (defined as a point with some latitude and longitude values) to a destination (defi ned in the same way).
An immediate prerequisite is the map. The map in a sat-nav is a peculiar beast. It's first and foremost a vector map – it consists of a set of data that is primarily in vector format. Since it comprises a set of vectors, the display part of the sat-nav unit must draw the vectors (that is, the roads, mostly) on the screen at runtime, and take account of the orientation and position of the car at that moment.
Compare this with the mosaic maps (or tiled maps) used by mapping websites like Google Maps. Here the map is served up as a pre-calculated set of square images (tiles) which are then painted onto the screen by the browser. The tiles sent to the browser are those needed for the current resolution of the map and for the area covered by the browser's window. The tiles are always oriented in the same manner, with north to the top.
Think of the vectors in the vector map in a sat-nav as straight road segments. They consist of two positions (beginning and end) defined by latitude and longitude, and will have further information tagged with them, such as the name of the street or road and whether the road is a major thoroughfare such as a motorway or A road or a smaller one like a backstreet or one-track lane. A road then consists of several segments placed end to end.
Now the fun starts. We have two points of interest: the current location and the destination. We have a map that's defined as a large set of vectors. We have to use the latter to calculate the most optimal route to go from the current location to the destination.
The usual algorithm used is Dijkstra's algorithm for finding the least-cost path between two nodes in a weighted graph or network. To recap, a graph is a data structure that consists of a set of vertexes (sometimes known as nodes) with links (usually known as edges) between them. A weighted graph has a cost associated with each edge.
If you think about it, a vector map is such a graph. The vectors are edges, and the ends of each vector can be thought of as the nodes. Since a road will consist of a set of vectors joined end to end, you can visualise that most nodes in the map just have two edges. Without any real loss of generality, we'll assume that the starting and ending locations are defined by latitude/longitude pairs and happen to be the ends of vectors (that is, we don't want to get into the geometric algorithm that determines inside which vector a particular point can be found).
Above shows a simplified example of a vector map of the Pinewoods estate where I live (the lower left node, coloured grey, continues out of the estate). I've marked the lengths of each vector, delimited by the red nodes, to the nearest 5m. The cost of each vector is a function of the way it has been tagged and also of its length. We can imagine that motorways and A roads have a low 'cost' value whereas streets and C roads have a high 'cost'.
The length of a vector also has a cost, one that is proportional to the length of the vector. Dijkstra's algorithm is intended to calculate what's known as the shortest path tree from a given node, or in other words, to reorganise the nodes in the network into a tree such that, if you follow the links from the initial node (the root of the tree) to any other, you will traverse the path with the smallest cost.
We're not particularly interested in the full tree though, since the number of vertexes and edges in any sat-nav city map is going to be huge, and, in planning the route, the sat-nav will be (or rather, should be) ignoring the vast majority. Dijkstra's algorithm also fails in the sense that all nodes are equally 'important', whereas we know that the nodes in the direction we want to travel are going to be more important than others.
What we need is a directed version of Dijkstra's algorithm, one that takes into account the fact that the sat-nav map database is, well, a map. Certain vectors in the map just won't be considered; they're in the opposite direction, for example.
Somehow we need to encode nodes that are closer to the target as being more significant than nodes that are further away.
The A* algorithm
The algorithm used is called the A* algorithm (pronounced 'A star'). It is a graph algorithm that finds the path with the smallest cost from a starting node to the target node. It was devised by Hart, Nilsson and Raphael in 1968.
A* uses two values when considering a node to be added to the smallest cost path: the actual smallest cost of reaching the node from the start node – usually called g – and a heuristic estimate of the distance from the node to the target node, usually called h.
The simplest heuristic we can use is a simple 'as the crow flies' distance to the target, taking no account of any roads, corners or whatnot. A further value called f is calculated as g + h. (Let's note in passing that Dijkstra's algorithm is equivalent to the A* algorithm with the heuristic h set to 0 for every node.)
This is how it works. (Follow along with Figure 2 as we find the path from A to Z on my vector map.) We set up the path to be empty. For the source node, g is 0, and h is the direct 'crow' distance to the target node. Add it to a priority queue, which is a data structure that releases nodes with the highest priority first.
Our priority here is going to the inverse of the f value – so lower values of f mean higher priority. Go into a loop until the priority queue is empty or we've found the target node (the more preferable outcome). Each time round the loop, remove from the priority queue the node with the smallest f value. Add it to the current path.
Now search through all the nodes that can be reached from this node (that is, find all the vectors that have the current node as an end point). Ignore all nodes that are in the current path. For each of these reachable nodes, calculate their possible g value (it will be the current node's g value plus the edge cost to the other node).
If the node has been 'seen' before (that is, it's somewhere in the priority queue), this possible g value may be smaller than the previous one, in which case we can replace it. Calculate the h value and therefore the f value, and, if the node is not in the priority queue, add it.
Of course, if the node from the priority queue is the target, we add it to the current path and stop as we've solved the problem. If we run out of nodes in the priority queue, it means that the target node is not reachable from the start node. We've failed to find a path.
Of course, in the real world, we wouldn't expect this to happen (unless we were trying to get from London to the Isle of Man with a sat-nav that doesn't 'know' about ferries). After we have the shortest route (or, rather, the route with the smallest cost), the software in the sat-nav unit then has to display it on the screen, either as a 2D map or, more commonly nowadays, as a 3D projection of the map, and then update it as you travel along.
But that, as they say, is an article for another day.
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In Depth: The beginner's guide to the iPad
According to Steve Jobs, a device that sits between the laptop and the smart phone must be better than either at several key tasks. So how does it perform in these all important fields?
Web browsing
iPad's Safari is very similar to the iPhone's, though it obviously benefits from a bigger screen. It doesn't support Flash. Like all the apps on iPad, Safari makes use of 'popovers' – menus that look half way between OS X menus and drop-down lists. An example of popover is in the image from Mail on the right.
iPhone users will find iPad's Mail app very familiar, but there are a few enhancements. When viewing in portrait mode, your inbox is displayed in a popover window, floating over the email you currently have open. Rotate the device to a landscape orientation and it's added as a permanently visible sidebar.
Pressing Compose gives you a virtual keyboard that's almost life-sized in landscape mode. The iPhone's much lauded auto-correct feature is retained in the iPad Mail app too.
Maps
The iPad's Maps application is very similar to the iPhone's. By default the classic street plan is displayed, but you can easily switch to a satellite view, a hybrid of the two or the new terrain view showing hills and valleys, which is found on the Google Maps website but not the iPhone's Maps.
Integration with Google Streetview is again implemented, and it's far more usable on the iPad's larger screen.
Photos
Like the iPhone app, Photos lets you flick through your snaps by swiping your finger over the screen. Open pictures can once again be manipulated using Gestures. The iPad application displays albums as stacks of photos.
Tap or pinch to open the stack and look for specific photos. Syncing with your Mac retains Faces, Places and Events information from iPhoto, and you can also view a slideshow set to music.
Movies
Video viewing is a key feature with the iPad. The original YouTube application has been revamped, making it easier to navigate. But there's also a dedicated video viewing application; you don't have to watch your films and home movies through the iPod feature.
Video files are divided into movies, TV shows and music. Select a movie and you're invited to pick a chapter, or watch from the beginning. Selecting a television show brings up a list of available episodes, and tapping the screen toggles between full screen and widescreen modes. With no buttons or controls to get in the way of the video, you can really immerse yourself in the on-screen action.
Music
iPad includes iPod functionality, as well as full access to the iTunes Store. Making good use of the larger screen, navigating through your music feels more akin to the Mac's iTunes than the iPhone's iPod app. Albums are displayed in a grid, and clicking on an individual album gives you a floating window listing its songs.
Calendar
Calendar is far more accessible on the iPad. Taking its lead from OS X's iCal, the extra screen space allows individual event titles to be displayed in the Month view, instead of entries being indicated by a dot under the date. Weekly, daily and list views are also available, and the application can be navigated in portrait or landscape orientation.
Contacts
The iPad Contacts app is designed to look just like a paper address book.
Your contacts list is shown on the left-hand page, with the currently selected entry displayed on the right.
Games
The iPad offers exciting opportunities for games developers. Existing iPhone games will of course run on an iPad, but the larger form factor allows for a greater degree of interaction with the touch screen, meaning games will be specifically written for the iPad.
For example, Gameloft's first-person shooter N.O.V.A. – demoed at the iPad launch event – benefits from an overhauled interface. To select a weapon you drag its icon onto the fire button, a feature that would be space-prohibitive on the tiny iPhone. An expandable on-screen map has been added too, taking even more advantage of the larger screen.
Long-time iPhone supporter Electronic Arts demoed an iPad version of its popular racing game Need for Speed Shift. You can now switch to an in-car view by tapping on the vehicle. Mirrors have also been added; touch them to switch to a rear view.
These developments have been achieved in just a couple of weeks, building on already-existing iPhone games. Just imagine what will be possible over time…
Ebooks
One of the iPad's key selling points is its new iBooks application that includes an iTunes-like online store where you can purchase and download ebooks. Books purchased through iBooks are displayed on an attractive virtual bookshelf. Just tap a cover to open it. Hold the iPad in Portrait mode to display a single page, or turn it sideways to show two facing pages.
Graphically it looks just like a physical book, with the edges of the cover visible around the pages' perimeter and a shadow in the centre as they bend into the spine. To turn a page, just tap the side of the screen. Like most ebook readers, you can adjust the text size, but with iPad, you can also change the font.
Five of the world's largest publishers are already on board; HarperCollins, Penguin, Simon & Schuster, Macmillan and Hachette Book Group. More are sure to follow in the near future.
iPhone apps
According to Apple, "virtually every one" of the 140,000 applications is already available in the App Store function on the iPad. At the time of writing it hasn't elaborated on which ones won't work, though anything requiring telephony or a camera are obviously not iPad-friendly at this time.
An iPhone/iPod touch application can be run with "pixel-for-pixel accuracy" in a window the size of the iPhone's screen. Alternatively, they can be scaled to fill the iPad's viewing area using a technique called pixel doubling.
A new version of the iPhone Software Development Kit (SDK) has been released for programmers to tailor their applications specifically for the iPad, taking full advantage of the large touchscreen display.
But perhaps most interesting is that Apple's iWork applications have been reimagined for the iPad. Mobile versions of Keynote, Pages and Numbers are compatible with OS X's iWork '09 and Microsoft Office, and are sold individually for just $10 each, which is around £5.90. This is welcome and aggressive pricing from Apple.
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Review: Acer Aspire 8942G-526G64Bi
The Acer Aspire 8942G-526G64Bi is a very large and comfortable laptop that offers exceptional performance and a great Blu-ray experience. It's also one of the most fully featured machines we've seen, making it a great desktop replacement multimedia system for all the family.
The laptop's comprehensive power comes courtesy of an Intel Core i5 processor. This is combined with 6144MB of DDR3 memory. As a result, it is able to run resource-intensive programs without issue, even concurrently.
A dedicated graphics card from ATi's latest line provides great 3D performance, and you'll easily be able to edit photos and HD movies while enjoying the latest games.
The 640GB hard drive is capacious, and provides plenty of room for storing your content.
Photos, films and games look fantastic on the laptop's massive 18.4-inch screen which dominates the chassis. It is a gorgeous panel with vivid colour reproduction and detail that is a pleasure to use for everyday tasks such as editing a spreadsheet. It's also perfect for watching Blu-ray discs thanks to the laptop's screen size and 1920 x 1080-pixel Full HD resolution.
We felt utterly immersed in the content, with images proving extremely sharp and vibrant. Due to the size of the screen, the laptop's 4.3kg chassis is also huge, however, and you won't want to be carrying it around for long periods of time, if at all, making it more suited to home use.
Premium feel
It's a very well built laptop, with a shiny lid and textured palm rest that provide a premium feel. A set of dedicated stereo speakers are also in place, positioned below the screen, and produce surprisingly good sound quality – only enhancing the multimedia credentials of this machine.
Networking is top-notch, with 802.11n Wi-Fi and Gigabit Ethernet providing you with the fastest connections.
The laptop also has a huge range of connectivity options. VGA, HDMI and DisplayPort let you connect to external monitors, and the five USB, one eSATA and one Firewire ports let you connect peripherals and external hard drives. This gives real flexibility and provides a good deal of future-proofing.
We were extremely impressed by the Acer Aspire 8942G-526G64Bi. While it is expensive, it offers everything and more that you could possibly want from a Blu-ray laptop, despite its limited portability.
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Guide: How to automate Windows applications
The first part of this tutorial explained how AutoIt can help you to automate tasks by simulating keypresses. But while this is a powerful technique that enables you to control just about any application, it does have its problems.
The scripting code quickly becomes cryptic; there's no way to tell what a keypress sequence does without looking at the app. It's not always reliable, either – a simple interface change can break your keypress sequence and force you to start again.
However, there's a smarter automation alternative out there called the Component Object Model (COM). Some apps use it to make their functionality available to other scripts and programs, including Windows, Microsoft Office, Skype and many others. Using it you can send emails in Outlook, automate Skype calls, create spreadsheets and more.
Getting started
The first step in using COM is to create a variable that refers to the application object we need (or create an instance of the object, in programmer-speak). In AutoIt, that looks something like this:
$oShell = ObjCreate("Shell. Application")
The 'sign tells us that this is a variable called '$oShell'. We use a lower-case 'o' as the first letter of the variable name to reminds us that this is an object. We then ask the ObjCreate function to create a 'Shell.Application' object. This is a copy of Explorer that gives us instant access to lots of useful Windows features.
The easiest way to make use of an object is to apply one of its methods. These are commands that the object makes available. Our Shell.Application object, for instance, has a method called 'MinimizeAll' that will minimise all open application windows so we can see the desktop. We can use it by applying that method name to the variable we've just created, like this:
$oShell. MinimizeAll.
Similarly, we can use $oShell.UndoMinimizeAll to undo the minimise command, restoring application windows to their previous positions. We can also rearrange windows by appending TileHorizontally, TileVertically or alternatively CascadeWindows.
Our Shell.Application object provides plenty of handy shortcuts, too. If we want to launch the Search window, for instance, then we can use this:
$oShell.FindFiles.
Then there's the 'FileRun' method, which launches the Run box; 'SetTime', which opens the Date and Time dialog; and 'ControlPanelItem', which displays an applet that you specify. For example, typing ControlPanel Item("Inetcpl.cpl") will launch the Internet Options dialog.
Need some more? Check out the official Microsoft Shell.Application documentation for the full list of methods here.
Controlling services
We've started gently with some of the simpler Shell.Application options, but the object provides plenty of more interesting features for us to explore.
The 'AddToRecent' method, for instance, will add the document you specify to the Windows Recent Files list. Use it like this (ensuring that 'c:\file.ext' is replaced with the path of a real file on your PC):
$oShell = ObjCreate(FShell.Application") $oShell.AddToRecent("c:\file.ext")
By adding more file names, you could customise a script like this to ensure that the Recent Files list always includes a particular set of commonly used documents.
Alternatively, you could protect your privacy by creating a script that replaces the Recent Files list with your choice of files, so nobody can use it to keep an eye on what you've been doing. The ability to stop and start Windows services introduces more interesting possibilities.
You could create a script to close down non-essential services to save resources before you run a demanding game, for instance, and another that will start them again afterwards. Here are a couple of short examples of this:
StopServices.au3
$oShell = ObjCreate("Shell. Application")
$oShell.ServiceStop("wuaserv", false)
$oShell.ServiceStop("wsearch", false)
StartServices.au3
$oShell = ObjCreate("Shell. Application")
$oShell.ServiceStart("wuaserv", false)
$oShell.ServiceStart("wsearch", false)
Here the 'StopServices.au3' script begins by creating a Shell.Application object, then uses the 'ServiceStop' method to stop the 'wuaserv' (Windows Update) and 'wsearch' (Windows Search) services. The second ServiceStop value tells Windows whether you want this change to be permanent. Set it to 'true' and Windows will disable the service, so it won't start when you next reboot.
However, as the Search and Windows Update services are important, we only want to turn them off temporarily, so we should set the second value to false. Run this script first to free up RAM and system resources, then launch your hungry app. When you're done, run the StartServices script and it'll reverse the process, using the ServiceStart method to relaunch services that were closed.
If you forget to run StartServices, don't worry – any services you've paused will be started again the next time you reboot. To make this really useful we could expand it to include other non-essential services. Candidates for this include Spooler (the print spooler), BITS (Background Intelligent Transfer Service), EMDMgmt (ReadyBoost) and third-party services such as Apple Mobile Device (only necessary when you're connecting an iPod or iPhone to your PC).
To explore this further, run services.msc to view the services that are active on your PC. Find a service that you think is nonessential and could be turned off safely for a while. Double-click it and note the service name. Disabling a critical service could disable your PC, so check at www.blackviper.com to confirm that a service is safe to turn off temporarily.
If it is, add $oShell.ServiceStop("W32Time", false) to StopServices.au3 and $oShell. ServiceStart("W32Time", false) to StartServices.au3.
Automating Word
If you've got a copy of Word installed, you can automate the creation of a Word document with a script along these lines:
$oWord = ObjCreate("Word. Application")
$oWord.Documents.Add
$oWord.Selection.TypeText("Some words go here")
$oWord.ActiveDocument. SaveAs("c:\autoitcreatedme.doc")
$oWord.Quit
Here we've created a 'Word. Application' object (essentially loading an instance of Word) and added to its collection of documents (you could have several open at once, but this just creates the first).
The 'Selection' property corresponds to the current insert point, where the cursor would be if you'd opened the document manually, and the 'TypeText' method enters some text there. Finally we save our work to a specified path and use the 'Quit' method to close the object.
The last step isn't strictly necessary when it's the end of the script, but if we were carrying on then it would be a good idea. A Word.Application object takes up a sizeable amount of RAM, and it's worth freeing that up as soon as you can.
You can extend scripts like this in many different ways. Open a document instead of creating one by replacing '$oWord.Documents.Add' with $oWord.Documents.Open("c:\filename.doc"*.
Style the text in your document by setting the font name – add $oWord.Selection.Font.Name = "Arial" – and size – use $oWord. Selection.Font.Size = "24". Add the line $oWord.PrintOut() before the final 'Quit' and it'll send your work to the printer too.
Using Outlook Microsoft
Outlook provides a powerful COM object that presents all kinds of automation possibilities. Perhaps the most useful of these is the ability to send an email from a script. Here's an example:
$oOutlook = ObjCreate("Outlook. Application")
$oMsg = $oOutlook.CreateItem(0)
$oMsg.To = "persons.name@ domain.com"
$oMsg.Subject = "COM test"
$oMsg.Body = "important content goes here"
$oMsg.Send
Our script starts by creating an 'Outlook.Application' object. This will usually load Outlook if it's not running already, but it may not always work. Launch Outlook before running the script if you get errors. The script then uses '$oOutlook' to create a further object and '$oMsg' to create a new message before setting its recipient, subject and body.
We could have set a CC address using $oMsg.CC = "you@youraddress.com" or the sender's address with $oMsg.SenderEmailAddress = me@myisp.com, but simpler is better right now.
We finish with the 'Send' method, which sets our message on its way. At least, that's the plan. In practice, you'll probably find that Outlook pops up a message complaining that a program is trying to access it to send emails. This is a security feature that's designed to stop malware using your PC to send spam, but unfortunately it'll block your legitimate script too.
If you'd like to be able to send emails from a script then the best solution is to install Advanced Security for Outlook. This clever tool detects programs trying to access Outlook and gives you the option to block them if they're unexpected or run them without warnings if you're sure they're legitimate. It works on every version of Windows from 95 to 7, and every version of Outlook from 2000 to 2010. Best of all, it's free.
Going further
If you're interested in using COM to automate functions and would like to create more advanced scripts, you'll need to learn more about COM and the individual objects that different applications make available. The simplest way to go about this is to open the AutoIt Help file. Click the Contents tab and select 'Obj/COM Reference' to find a quick COM primer with some handy examples, including one on automating Excel functions.
If you expand the Word Management folder, you'll find information on some functions bundled with AutoIt that let you automate Word. Look at the example for '_Word DocAddPicture', for instance, to see how you can create a Word document from an AutoIt script and then add some pictures to it.
The AutoIt forum is another essential source of help. If you have a question, it's probably been asked before, so the Search tool should reveal a variety of useful answers. If you're lucky, someone may have already uploaded a script that does what you want in the Example Scripts section of the forum. Be sure to search the forum before you start writing something – you could save yourself a lot of time.
If you're feeling really ambitious then you could browse Microsoft's own documentation. Its pages on the Shell.Application object don't use AutoIt examples, but you'll get more details on the various methods the object makes available and how they should be used.
Alternatively, if you don't have much use for COM then you could simply wait until the next issue of PC Plus for the third and final part of this tutorial series. We'll be combining everything we've learned so far, giving our scripts an interface so that they can communicate with the user, adding some low-level tricks and showing how the leading AutoIt scripts can compete with the best that any other programming language has to offer.
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Competition: WIN! A Creative Vado HD pocket video cam
TechRadar has teamed up with Creative to offer lucky TechRadar readers the chance to win one of five third generation Vado HD pocket camcorders worth £129.99 each.
The new 3rd generation Vado HD is designed to offer one-touch HD video recording for people who don't want to mess around with fiddly full-size camcorders. You simply turn it on and press the red record button to start and stop recording.
The wide angle lens helps you get as much into shot as possible, and you can record up to two hours of high definition footage (1280 x 720) on the 4GB internal storage drive.
Once you've shot your footage, you have the option of selecting the 'one-click uploading' option. It helps you upload your videos to a number of popular social media sites, including Facebook and YouTube, and your videos will be ready to view or share in a matter of minutes.
The Vado HD's other features include stills capturing, two hours of battery life per charge, HDMI-out port to plug into your high def tv as well as ports for external microphones, headphones and an AV output.
The camcorder also has a flexible, pull-out USB cable which allows you to recharge the battery and offload your videos onto your PC or Mac. It's all about making HD video recording easy and convenient.
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Please note that this competition is only open to UK residents over 18 years of age and the winner's prize will not be sent out until the Nexus One becomes available in the UK.
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