What is a mesh?

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..other than a series of points defined by a latitude, a logitude (how do you pronounce that?) and an elevation (altitude.)I dismiss the argument that detailed information for UK altitudes don't exist as they do for the US.If that's the case then how then did I discover that a point just 10 miles east of Manchester city centre was off by 310 feet or about 100 metres.Seems I have to do it myself.Ever since Junior High, I've known about Ordnance Survey maps. They show correct elevations. What is the format of elevation point information? Seems all I have to do is lay a 30m grid over the map and extract the elevation points.The main complaint about the UK is that it doesn't look right, looks too flat. The rolling hills are subtle and should be able to be reproduced.Is the Visual Flight 2.0 UK mesh any good, anyone?What exactly is the "Visual Flight advanced data processing system "?Sounds like something from a male bovine.Why don't they just say how they arrived at their data?I would have bought a bunch of Ordnance survey maps and extrapolated the elevations from there.What elevation is reported at N54 31.02 W2 04.61 using the Visual Flight 2.0 UK mesh!Thanks!I've been spoiled by Orlando Sotomayor work!

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>Seems I have to do it myself. >Ever since Junior High, I've known about Ordnance Survey >maps. They show correct elevations. What is the format of >elevation point information? Seems all I have to do is lay >a 30m grid over the map and extract the elevation points. Quite right - but are you volunteering to do it? For 1 square kilometer you'd have to do over a thousand points. Manually, with several significant digits...Have funFinn

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Yes, of course! if I collect money for it. I'd start right away.I'll charge the same as the Canadians 5 cents per elevation point.No, not for free, I'll wait for the data later this year from the NASA/JPL Space Shuttle mission. Actually I could have the data now.Several friends of mine work there!My point was, don't ask for money if it isn't right!Around here in LA, 100 metres elevation height error I can live with. In England, there has to be a different approach.

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Ihor>I dismiss the argument that detailed information for UK >altitudes don't exist as they do for the US. Of course detailed information for the UK exists, but here, as in many other parts of the world, the substantial costs of obtaining it means that it really becomes more a question of commercial viability rather than availability.>If that's the case then how then did I discover that a point >just 10 miles east of Manchester city centre was off by 310 >feet or about 100 metres. That's a very good question - how did you discover it? - it's clear from the rest of your post you don't have a copy of the Visual Flight mesh. Do you have any more details of where this point is, and how you've arrived at your 100m figure?>Ever since Junior High, I've known about Ordnance Survey >maps. They show correct elevations. What is the format of >elevation point information? Seems all I have to do is lay >a 30m grid over the map and extract the elevation points. I think Finn has already answered this, but it's worth pointing out that the land mass of the UK and Ireland is 310,000 km sq approx, so we really are talking silly numbers here. This is why anyone taking this approach is going to be severerly compromised in either resolution or area covered.>The main complaint about the UK is that it doesn't look >right, looks too flat. The rolling hills are subtle and >should be able to be reproduced.Again, I'm not sure how you're reaching this judgement without having a copy of the scenery. However, it's certainly true that it is more difficult to do justice to the more subtle features of low-lying areas. The results in these areas won't be as dramatic as in the hillier and more mountainous regions. However, having already made big improvements going from version 1.0 to 2.0 of the Visual Flight scenery in just over six weeks (not a bad achievement), I'd expect to see further improvements in these areas as part of the continuing process of improvement.>What exactly is the "Visual Flight advanced data processing >system "?It's a custom data processing system unique to Visual Flight designed to make the absolute best of the data that's available. Sorry, but I can't say more than that because it is proprietary information. >What elevation is reported at N54 31.02 W2 04.61 using the>Visual Flight 2.0 UK mesh!I'm intrigued as to why you've chosen this particular spot - there doesn't appear to be any obvious topographic or geographic feature there. It is on the side of a hill at an elevation of approximately 380m. The elevation reported with the Visual Flight scenery is 318m. This isn't spot on, but there are many factors at work here as well as the simple fact that we don't have the luxury of free 30m data available in this part of the world (even RT seems to have lost his 30m data!).I'd just like to say a little about the nature of the errors that can occur in DEM data. No DEM data is perfect, whatever its resolution. As well as a degree of error in the vertical plane, all DEM data sets have an error in the horizontal plane. Depending on how the data was acquired, this can be a very significant proportion of the horizontal resolution. On the side of a hill the elevation value at a particular data point could represent a point further up or down the slope, or on the top of a nearby crag or down in a nearby dip.Bear in mind also that the scenery designer/producer has very little control over how the DEM data is interpolated by FS2002, so this may introduce an additional error if there isn't a data point at the precise point of interest.I'm currently concentrating on getting accurate terrain clearance elevations, i.e. the tops of hills and mountains which are of the greatest significance to real-world pilots, rather than the elevations on the slopes. I know that there's still a lot of work to do here, but I believe the Visual Flight scenery is ahead of any other mesh scenery for the UK in this respect. If anyone knows any different, then please tell me.>In England, there has to be a different approach. I think we can agree on that.JohnVisual Flighthttp://www.visualflight.co.uk

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What I'm about to say is pure speculation, but here goes...I strongly suspect that a lot of mesh sceneries out there that use interpolation routines more complex than simply taking some sort of simple average. There are quite a few of these but the most obvious one that comes to mind are the 'fractal landscape' routines that are fairly well documented and not too hard to implement ('The Science of Fractal Images' is one book for example). All you'd do is 'seed' it with the low res DEM and the routines will make some sort of vague attempt at replicating ravines, low altitude bumpiness and so on. This would make the resulting mesh realistic 'looking' but obviously not actually correct necessarily. Not a problem if you're unfamiliar with the territory but not much good if you are. There are other routines that do something similar. Also of course some of these meshes might have some tricks in them that improve how they're displayed in the sim (Visual Flight claims this for example).Just like the Landclass files (which I've bought a few of and am very happy with indeed) you'd probably end up with something that looks better and individual enough that if you repeated a flight you could easily start to use familiar patterns and landmarks to navigate by. If you get out your ordinance survey map and try to use that and looking out your virtual window then you're likely to be a little disappointed.Anyway - which meshes do people like? I'm looking for something for Northern Europe (West and East) - which packs are out there? Do people think they're better than the stock ones? I have to say I'm tempted by the Visual Flight ones, but I'd be interested to hear some opinions.Have funFinn

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>something similar. Also of course some of these meshes might >have some tricks in them that improve how they're displayed >in the sim (Visual Flight claims this for example). I don't think Visual Flight does claim this does it? It doesn't sound familiar to me.... The aim is to improve the accuracy and detail, not to introduce any tricks just for effect.JohnVisual Flightwww.visualflight.co.uk

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I'm interested in buying a UK mesh but have some questions .Do I have to buy a land class set as well to make the scenery more accurate ?If so, what will the effect be and does Visual flight provide one ?I've tried some replacement textures that are supposed more like the terrain in UK, however they make the airports stick out like sore thumbs as the boundarys show, similar to FS2000.Sry if this sounds more like a texture query than a mesh one, but I'd like to know how one interacts with the other, if indeed they do.Tony

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I wish there wasn't a 60 minute deadline on correcting posts!Would you believe I didn't even have the Visual Flight scenery enabled when I checked the spot height for Ihor?I've checked the height again with the Visual Flight enabled this time, and it is 358m - a lot closer to the target OS map value of 380m than I first thought :-)Ihor has clarified offline that he was really interested in establishing the elevation of Hartshead Pike, which he assures me is 940 feet. I can't quite make out the height of the peak on my OS map, but that seems about right from the surrounding contours. I've checked the height with the Visual Flight scenery, and it comes out as 977 feet - just a little bit over the top, but not too bad.I'm still not sure where Ihor's original 100m error came from - maybe he was thinking of another mesh?JohnVisual Flightwww.visualflight.co.uk

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TonyThere's a number of factors that FS2002 takes into consideration when deciding what texture to display at any particular point. Apart from things like the season and the weather, there are two other important criteria:What type of land is there at a particular point, i.e. is it barren desert, rich farmland, small village, etc. This is determined from the landclass scenery, and obviously the more accurate and the higher the resolution of the landclass data, the better.You can see the effect of landclass scenery of you have an extended area of flattish scenery - you will probably be able to make out the rectangular borders of the landclass tiles, typically on 1km squares. You're far less likely to see this effect when using the Visual Flight mesh of course :-)The second criteria is the degree of slope at a particular point, i.e. the gradient of the land. For example, if the slope is flat or almost flat, FS2002 might display fields. If there's a bit of a slope, it might populate it with a few trees. If there's a steep slope, it might put a lot of trees. If there's a very steep slope, it might put a rocky terrain.(I say "might" because this is decided in combination with the land class at any particular point. Desert land-class hopefully won't have the trees.)There is another factor - each of the above combinations is mapped to an actual texture. The end result can therefore also be changed if custom/replacement textures are used, or if the texture mapping is changed.So the answer to your question "Do I have to buy a land class set as well..." is No, but if you do buy one, it will play its part, as does the terrain mesh, in improving the overall accuracy of the scenery.Visual Flight only sells mesh scenery at the moment, and I'm not in a position to recommend any particular land class scenery or replacement textures, but it would be nice to find a landclass that didn't insist on putting so many trees on the Shetlands...(If any of the above is wrong, tell me tomorrow - it's way past my bedtime!).JohnVisual Flightwww.visualflight.co.uk

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HiI am very pleased with the VISUAL FLIGHT Scenery. The area I am interested in is from Stratford-on-Avon in the North to just north of Cheltenham in the South. This covers rolling scenery of the North Cotswold Hills and the Vale of Evesham.I was using Grises50 with the SDK to put individual hills in my original scenery but upon obtaining the VISUAL FLIGHT Scenery I have decided to take them all out except one and use the VF Scenery for my webspace. It is by far superior to my efforts as I was getting in one case, at Meon Hill, (the site of the witchcraft murder in the war years), my trees and buildings in the default scenery were above ground level.I am very soon updating my scenery on my webspace to include two versions of the scenery, the FS2002 default and the Visual Flight Version 2.When I can get the necessary aerial photos I intend to use VF scenery overlaid with the photo detail produced by Terrabuilder.ngowww.users.globalnet.co.uk/~ngo

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For UK aerial photos:http://www.multimap.com (originally from http://www.getmapping.com)Have funFinn

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Could be! >:)~Wow check out the new 'smilies'

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Thank you Finn.I have now uploaded my scenery with Visual Flight terrain on www.users.globalnet.co.uk/~ngoThe default FS2002 scenery is also there plus version for FS2000 and FS98.ngo

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STREETMAP.CO.UK I think they have a better resolution though not every area is available:-outta

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Thank you for the information.Will have a look.ngo