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www.terraserver.microsoft.com s ’ t a h t e t i s b e w A ! d l r o W s i h T f O t u O r s Teste s o R y B Recently we came across a web site that could be described as the world’s greatest site – in the true sense of the word great, that is. www.terraserver.microsoft.com is, without doubt, the world’s largest site and its contents could truly be described as “out of this world”. With more than 1.2TB of data, TerraServer contains more data than all the HTML pages on the web combined. Hang on a minute, what’s a TB? You’ve heard of megabytes (most web sites are less than 1MB). Next up the scale is the gigabyte (GB), or 1,000MB. A terabyte, TB, is 1,000,000MB or 1,000,000,000,000 bytes. That's equivalent to about a billion pages of text or four million books. Whew! What occupies this mind-boggling storage space? Thousands upon thousands of black and white photographs of the Earth, taken from one of two satellites over the past decade or so. One of those satellites is courtesy of the United States Geological Survey and the other is from the Russian Space Agency, Sovinformsputnik. The US satellite has concentrated mainly on the United States, while the Russians are responsible for most of the rest of the world. While most populated areas of the US are covered, the rest of the world is someMAY 1999  3 MAY 1999  3 You can point and click to anywhere on the world map shaded in green (we've enlarged the map of Australia to show the areas that aren't covered). The area under the map allows you to select a number of famous places. what less represented – and patchy. In Australia, Melbourne, Brisbane and Perth are all covered but for some reason, the centre of the Universe (Sydney, to those living in it) is not. Melbourne, Brisbane and Perth readers are probably saying “rightly so!” Enough frivolity: let’s get back to TerraServer. By a happy coincidence (?), tera not only means 1012, add another “r” and you have the Latin word for earth. The surface area of the Earth is about 500 square terametres (there’s that word again!), of which about 100 are dry land. Of that, only about four square terametres are populated, the rest being mountain, desert, ice capped, farmland and so on. The Soviets have so far managed to photograph about two square tera-metres, or about half of the populated area. While some of the information is getting a little dated (Melbourne, for example, was photographed in 1991), it is still a valuable source of information for a huge variety of people. The Soviet images, by the way, are called SPIN-2, a reference to that two square terabytes. Or you search for a city/area and see if it is covered. The two columns on the right show the images from the US (left) and Russian (right) satellites. Point and click on either to load the respective image. virtually seamless precision. Those 16 photos will give you a base resolution of 16m to the centimetre. Click on an area of the photograph and the next resolution will load, this time at 8 to the centimetre. The highest resolution depends on the source of the photos: the US satellite pics are at the incredible resolution of 1m per pixel. That’s enough to pick out individual cars on a roadway but not, as you might have seen in spy movies, read their number plates or view the driver. Incidentally, such resolution, in real time, is believed to be possible from many of the spy satellites now in use. Number plates with their 100mm high letters are said to be a doddle. Fairly believable reports state that today’s spy satellites are good enough to pick up the dateline on the front of a newspaper (usually about 12-14pt type) while less believable rumours state that the latest generation of spy satellites can actually read the news- How does it work? When you access the TerraServer web site, you are presented with a map of the world with photographed areas coloured green. Click on any of these areas and the photographs for that area begin to download. When we say photographs, we mean just that: up to 16 photographs are assembled on screen with 4  Silicon Chip Melbourne's CBD as loaded from TerraServer. This is the lowest resolution image but even this is more than adequate to easily spot major landmarks – Docklands, the Yarra and the MCG, for example. We've also chosen the lowest size – this could be increased to full screen with the buttons on the left side of the screen. This montage covers roughly Ascot Vale in the top left to Richmond bottom right. paper itself (usually 7 or 8pt type!) But we digress – again. The resolution from the Russian-sourced photos is not quite as good; they are at 1.56 metres per pixel. More importantly, though, if you want to view hi-res images from the Russian source, you have to pay for them. But we imagine that most people using the site will be more than happy viewing the on-screen images (free). Hey, look, there’s our house. . . Terabytes of storage To hold, access and download Terabytes of information you might expect a system that’s a bit more than an old AT with a big hard disc. And you’d be right! The TerraServer system runs on a Digital Alpha 8400 system with eight (yes, 8) 440MHz Digital Alpha processors and a massive ten gigabytes (10GB) of memory (yes, memory!). The machine is connected to seven dual-ported Ultra-SCSI host-bus adaptors, each of which interfaces with a disc drive cabinet containing 46 nine gigabyte drives. Quickly doing a bit of mental arithmetic, 7 x 46 is 322 drives, plus the couple in the Digital Alpha 8400 – means a system with 324 drives totalling 2.9TB of storage. Using a RAID (redundant array of independent discs) setup, the drives are configured to act as four logical drives of 595GB each. SQL Server Enterprise Edition stripes the database across the four logical volume. After taking the data-management overhead into account, the array has about 2.4TB of storage capacity. And if something goes wrong, there’s a tape back-up which can handle 5TB of data. The system runs on Microsoft NT Server V4.0 with SQL Server, already mentioned. Here is the Brisbane CBD and inner west, photographed from space courtesy of the Russian satellite. This covers an area from about The Gap top left through to Kangaroo Pt in the bottom right. The white lines in the centre of this pic are where the joins between frames (automatically done on download) were not quite seamless. Enlarging up one step we find the CBD coming more clearly into view, along with the bridges over the Brisbane River. Note the shadow cast by the Story Bridge (right side) – obviously an early morning photograph. The advert (top right) helps pay for the site so it’s free for you to browse. We’ve enlarged again but this time also selected the larger view. We're looking here at Brisbane City, with the Roma Street station and goods yard along with the Brisbane River bottom left. At this scale you can start to pick out vehicles on the bridge and rail wagons. Who pays for it all? Love ’em or loathe ’em, you have to take your hat off to the people at Microsoft for getting behind this project. While the site is also supported by on-screen adverts (not too intrusive, as you’ll see from the screen grabs), it would appear that Mr Gates and his team are the money behind it. Of course, this is also an excellent advertisement for Microsoft and its operating system: if it can handle the world’s largest website 24 hours a day, Enlarged yet again to the highest resolution, this time back on the eastern City with the Story Bridge/Kangaroo Point on the right. Note the grey patches middle and lower left – these are glitches in the system which can sometimes be removed by refreshing the screen. MAY 1999  5 By way of contrast, here is an image of the San Francisco Fisherman's Wharf area, taken from the USGS satellite. There’s not a huge amount to choose from in this screen image but remember you can download a hi-res image of any of the USGS files free of charge. The Russian SPIN-2 images are also available but you have to pay for them! such as this, we want to use a system typical of that which most readers would have (we were using a midrange 486 with a pretty good graphics card and a fast [56K] modem). One of these days we’ll give it a fly on a fast Pentium II machine with heaps more “grunt” just to see how it goes. Obtaining images seven days a week, think how easy your system will work. . . Naturally, accessing Microsoft’s MSN is only a click away from the site, too. Others supporting the venture are Compaq, Storageworks and Storagetek. Once loaded, you can also move in any direction from that photo to the next (we have difficulty not calling them maps, but they are real photos) by clicking on any of the eight green arrow buttons around the edge of the pic. Accessing images But wait, there’s more! We’ve described how easy it is to “point and click” to obtain any area on Earth. But there’s more than one way to skin a dead cat, so to speak. You can also type a place name into the system’s search engine and it will find ALL places on Earth with that name. (Bet you didn’t know that there are 16 Sydneys, did you?). If the location is on the database, alongside it will be one or two clickable filenames. One column lists the USGS images, the second the Russian images. If the name is present, clicking has the same effect as clicking a location on the world map. When it loads, the name of the location is shown above the photo image. In fact, the name may be much more localised than you asked for: we loaded Brisbane by clicking on it, zoomed in and found that the name had changed to Petrie Terrace. Sure enough, our image showed the Brisbane suburb of Petrie Terrace! You don’t have to search for just a location, either: a pull-down menu lets you specify a qualifier such as river, bay, airport and so on. There are also images of famous places to view (mainly US, of course), many in superb resolution. But where is the Sydney Opera House or the Coathanger? As you might expect, the site is continually evolving and will – hopefully – contain many more areas in the not-to-distant future. A couple of negative comments, though: downloading huge files (which is what you are doing) takes a significant amount of time. And the system is by no means perfect – we found several times that one frame out of 16 simply refused to load; or one, perhaps two frames were corrupted, with “holes” in them or areas not appearing. Sometimes, the seams between adjacent frames did not quite work and a thin white line appeared. And sometimes, frames simply refuse to load. In many cases, hitting the “refresh” tab cleared these problems, but not always. It is more than possible that some of the limitations in the system were at our end. But whenever we do reports 6  Silicon Chip The vast majority of web surfers would simply visit the site to view places of interest. But if you want to obtain hi-res images, you can. If they are from the USGS satellite you can download them free of charge. The Russian images, though, will cost you (they’re actually provided by an American supplier – good ol’ capitalism strikes again!). Details are provided on the web site. If you get the impression that we’re pretty impressed with www.terraserver.microsoft.com, you’re spot on. Not just because of its awesome size and power; not just because it’s a site which will interest everybody; not just because it’s a technological breakthrough; not just because of its ease-of-use and, to use a hackneyed term these days, “user friendliness”. We’re also mightily impressed that, even if the technology to do all this was available a decade or so ago (it wasn’t!), can you imagine the Russians allowing Americans access to what would be (then) a top-secret photo library and then make it available to the world? Let’s just hope the spirit of cooperation which has seen this site evolve can find its way into other areas of technology. SC Acknowledgement: Much of the technical information in this article first appeared in the US magazine, Popular Electronics, March 1999. Screen grabs courtesy of www.terraserver.microsoft.com