• VFR Terrain Volume 1: England And Wales

    VFR Terrain Volume 1: England and Wales for FS2002 and FS2004

    Developed by Visual Flight in association with Horizon Simulation and published under license by Horizon Simulation Ltd.

    By Andrew Herd (1 October 2004)

    Looking south-east from the windows of Cleveland Flying Club at Teesside Airport (EGNV), a low line of hills should be visible. Even allowing for the tendency the club has developed to move itelf around in recent years, those hills have always been there. Some days you can't see them, which means that vis is less than 10 nautical miles; other days cloud hangs about their summits, though the hills are by no means high, rising to 1490 feet above sea level at the most. Collectively, they are known as the North Yorkshire Moors and though they may not amount to much, they present a substantial obstacle to GA navigation.

    Those hills are one of the reasons why I have an instrument rating. It means that on days when the hills are shrouded in cloud and the Vale of York is full of young maniacs in jets, I can climb over the moors in IMC and fly in the golden sunlight on top, before letting down over the flat land to the south. This puts me well clear of the 2500 foot high aerial that reaches into the murk trying to trap unwary pilots, and into clean air fit for a Lycoming to breathe.

    As you can see in the screenshot above, the North York Moors do not exist to any significant extent in Flight Simulator, nor had I, until 14th May 2004, seen a mesh addon which did anything to put them back.

    American readers are lucky enough to have relatively detailed terrain mesh in the default installation of Flight Simulator, but European simmers have had to cope with the variable quality of the default scenery, or try to improve it by purchasing addon packages to create more realistic elevations. Nowhere has this situation posed more of a problem than with England and Wales, where 95% of the attraction of the countryside lies in subtlety, rather than drama. Taken as a whole, mesh packages have been the least satisfying class of addons available for Flight Simulator, largely because their authors either haven't realised that there is more to a usable mesh than a simple elevation model, or they haven't cared. Various meshes have been released over the years and I have tried them all, but every single one has been wanting in one respect or another.

    But that might be about to change...

    Horizon Simulation bills VFR Terrain: England & Wales as the most detailed and accurate countrywide terrain mesh upgrade ever released for Microsoft Flight Simulator and having used the product for a while, I am inclined to believe they are not jesting. One of the keys to the success of their approach is that they have used elevation data sourced from NEXTMap Britain. Unlike the publically available sources of satellite data traditionally used to generate FS mesh, NEXTMap is based on much more reliable 'interferometric synthetic aperture radar imagery' with a resolution of 5 meters - as it happens, far better than anything Flight Simulator is capable of displaying. The radar image the NEXTMap people built up was obtained by flying a Lear in parallel strips up and down the land doing 300 knots at 20,000 feet - which must have been a great way of building hours for the guys that flew the detail, though I wonder how they managed to stay awake. Two versions of the radar data are available: a Digital Surface Model (DSM), which represents the highest surface at any point, regardless of whether it be the ground, a tall tree, or the top of an office block; and a Digital Terrain Model (DTM), which presents a mesh based on ground elevation, as if the Earth had been cleared of buildings and vegetation. Quite clearly, when you are dealing with rolling hills, rather than lofty mountains, a DTM is the thing to go for and sure enough, it is the base for VFR Terrain.

    Though the scenery of England and Wales might be subtle, that isn't to say that the UK doesn't have its moments and there are plenty of places where the foolish or the unlucky can encounter cumulus granitus, but in general, you don't get to fly Jet Provosts down valleys like the one on the right unless you go looking for them. In Flight Simulator, you don't get to go flying down valleys like the one on the right at all, or you didn't until now, because they didn't exist in England and Wales. Even Scotland's Great Glen, which runs from Inverness to Fort William, is a disappointing thing in FS2004, though we will have to wait for VFR Terrain Volume 2 to see that.

    The package was developed by John Farrie at Visual Flight using data supplied by Getmapping, a pairing familiar to users of the VFR Photographic Scenery. As the title of the terrain addon suggests, the new product complements VFR Photographic Scenery to the extent that additional enhancements are included to make them fit like a hand into a glove. Horizon have done a great job on the publishing side, the mesh installing off a single CD and running on any system that can run FS2002 or FS2004, as long as it has 400 Mb of free hard disk space.

    Though the mesh is based on 1.25 m base data, it has been downsampled to the maximum level of detail that Microsoft Flight Simulator can support, which is 19m in FS2002 and around 38m in FS2004. The screenshots were taken using FS2004 and as you can see, 38 meter data is fine, especially when it is accurate - something that satellite derived Digital Elevation Models (DEMs) seem to have a problem with as far as Europe is concerned. Part of the trouble with satellite DEMs is that they are cursed with missing data, which is the source of those infinitely high towers or bottomless pits that many simmers will have encountered.

    Apart from the sheer quality of the VFR Terrain mesh, the package steals a lead over its rivals in that special attention has been paid to the representation of coastlines - the developers having included nearly a gigabyte of replacement photographic textures for VFR Photographic Scenery users. Even if you don't use that package, the coastlines have been carefully edited and a custom land/water mask generated which ranks among the best I have ever seen. Addon meshes sold without masks do not do coastlines well and usually create all kinds of unacceptable weirdness where the land meets the ocean. This is a particular problem somewhere like the UK, where it is difficult to get more seventy miles from the salt and you end up seeing a lot of coast - triangular pits and rectangular bulges along shorelines are in your face all the time with conventional mesh addons.

    FS2004 users will also be familiar with the way that lakes are inclined to scale mountains and seas to roll uphill - and that is just with the default scenery. Use addon mesh and just about anything can happen and usually does, because in the absence of a properly designed land/water mask, seas and lakes aren't inherently smart enough to realise that they ought to be flat. One reason why I am not a fan of addon meshes and have reviewed very few is that watching water defy gravity sets my teeth on edge, but between a new vector coastline that ensures that FS2004's animated waves break on the beach and not in the high street, and the land/water mask, the shores of the UK have never looked so good in Flight Simulator with VFR Terrain added.

    Just to give an idea of the huge amount of work involved in making this product, a new coastal landclass has also been provided to ensure that coastal textures actually match up, and when you put it all together, it ends up looking like the screenshot below, where the white cliffs of Dover are, by some lucky chance, almost white. Well, they are if you look slitty eyed at them. Okay, okay, gray. The mask means that the coastline always looks believable and in some places it is better than good. When I took a day trip to Blackpool I was amazed to discover that the coastal edit there included the piers, which are a useful identification feature for visual navigation. All that was missing was sunbathers, girls in kiss me quick hats and the amazingly boring man we met last time we landed there.

    Another thing that always annoys me about addon meshes (I can supply the entire list on request) is what they do to lakes. Apart from adopting crazy angles, new lakes added with these packages rarely contain landable water, which means that you crash and burn if you set down on them. While VFR Terrain doesn't add in every missing lake in England and Wales, all the larger ones are all there and both they and the estuaries have been designated 'interactive', which means you get moving, reflective surfaces, and can land planes on them, assuming you remember to bring your floats. A few of the larger estuaries have been redesigned to look more like the real thing and though this rarely affects more than the first few miles, it certainly makes map reading a whole lot easier.

    One snag with the methods used is that there are some places which have elevations at or below sea-level where the VFR Terrain have assumed water must be present and have created new lakes. I went looking for examples, but they are hard to find and it doesn't seem to be too much of a problem. Another is that FS2004's bridges haven't woken up to the redesign and in a few places they fall woefully short. Against this, the rivers line up in the valleys with almost uncanny accuracy and I have seen a couple of places where a road goes slap through the middle of a cutting, which says something about the quality of some of the base data in FS, not to mention how accurate the mesh is. A third issue is that all complex meshes seem to cause occasional slight hesitation in screen panning, but this was a relatively minor problem with this package.

    All in all, VFR Terrain would be my idea of perfection, were it not for one small fly in the ointment.Since the arcane laws of flight simulation dictate that all runways shalt be perfectly flat, yea, until the ninth generation; airfields take their elevation from the Jeppesen data and do not conform to the mesh around them. When you combine a minimum terrain resolution of 38 meters in FS2004 with even the most accurate possible mesh, it is inevitably the case that some airfields are going to stand on mesas or (worse) lie in pits and this definitely is a problem with the VFR Terrain, though to a much lesser extent than any other mesh package I have tested. RAF St. Mawgan is the worst example I have found so far, though even it doesn't look too bad - while on the other hand, the effect serves Leeds Bradford rather well, because the real airport actually does stand on top of a tall hill that is completely missing from the default scenery. The approach to 27 there actually does look something like the way VFR Terrain has it and wind shear there has seen more than one student approach that threshold from below.

    However, given that this mesh is likely to become the gold standard for UK simmers (I can't see the point of buying any of the competing packages any more), I would hope that developers like Gary Summons of UK 2000 fame will develop compatibility files, so that his airports make the best possible match. Gary already has a track record of coordinating his airports with the VFR Photographic Scenery, so it would be a logical move for him to support the VFR Terrain mesh as well.

    The blurb says that you can use VFR Terrain to 'fly spectacular sight-seeing sorties, or push the limit with a fighter in the valleys with Microsoft Flight Simulator'. Well, Mr. Farrie of Visual Flight, you are right, it is possible. My thanks are due to Rick Piper, for his superb freeware Jet Provost, which I used to test the developer's assertion. It was a tough job, but I guess someone had to do it.

    The North York Moors are back. Subtle, but looking just the way they should.

    Andrew Herd
    andy@flightsim.com

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