Flight Map Clarity--Map Zoom Level vs Mesh Resolution Level Explained for FS2004

Have you ever opened up the flight map in FS2004, and as you've zoomed in and out, wondered why sometimes the topography (terrain) depicted in a specific area appears clearer at some zoom levels than others? Or why at one zoom level it appears clearer in some areas than others? Well the answer is that there is a direct correlation between focus/clarity in the flight map, and the resolution of the terrain mesh installed in the simulator for that geographic area. In other words, one can use the flight map in FS2004 (World/Map in the simulator pull down menu), to tell which level/resolution of terrain mesh is present in the area within view of the map.

My Primary Motivation:

So why was I motivated to pursue this, you might ask? Well, when I first got FS2004 and loaded the discs into my computer, I (like probably a lot of people) relied upon the flight map to figure out where I was going, as well as to quickly spot-move my plane to various locations. As I zoomed in to get a closer look at where I was, I couldn't help but notice that the terrain image on the flight map got very blurry, to the point where it was almost of no value at all. I attributed this to a limitation on the flight map itself, but so long as the airport labels were legible, I gave it very little thought after that.

Then last year I began including add-on terrain mesh with a higher resolution than the stock terrain mesh that came with the install discs. Originally my greatest concern was how this had improved terrain once flying in the simulator itself, but I also discovered an unintended consequence when I opened the flight map to have a look at the areas where I added the new mesh. I thought to myself, "Hmm... that's odd. I don't remember the terrain in the map image being so clear at this map zoom-level before." And that's when it hit me like a ton of bricks: The new terrain mesh was actually affecting how the flight map topography focused at different zoom-levels.

My next thought was that there had to be a way to quantify this discovery so that it didn't seem so random and haphazard when I attempted to explain it to others. So after installing various levels of mesh in different areas, and testing various zoom-levels on the flight map to compare with them, I started to find consistencies that made sense. That's when I compiled the data for my spread sheet chart, the whole concept came together, and I became really excited about sharing it with others. I have found this helpful in determining which add-on mesh products I might want to include in given areas that are missing them, and I hope others will find this information beneficial as well.

Before I continue, I ought to mention three things:

1. 'tmfviewer.exe' (located within the TERRAIN_SDK\Terrain_Tools folder) is a good program for opening up terrain mesh scenery, and having a good look at the geographic area that each .bgl file includes. Unfortunately though, it provides no information on the "Resolution" (expressed in meters) or "Level of Detail" (LOD) of the file in question. This is the main reason why my method and this article is of relevance.

2. A helpful reference guide that lists all the default scenery in FS2004 by file name, resolution, and location; I have included below in the appendix of this piece. This was originally provided courtesy of Mr. Steve Greenwood, and thank you to forum member "StringBean" for providing access to the list, in his reply to a forum post of mine on September 3, 2011.

3. Except for special circumstances, one can assume that the majority of the world's highest base default mesh is done at LOD 5 (1223m). The prime exceptions to this are the United States at LOD 6 (612m) and Australia at LOD 7 (306m). The others can be found in the chart I mentioned above in #2.

Flight Map Controls:

Upon opening the flight map, the map will always start at what I call the "default-zoom" or "neutral-position". From there, you can either zoom-in with the "+" key or zoom-out with the "-" key. There are 6 mouse clicks from neutral in both the zoom-in (+) and zoom-out (-) directions. Upon reaching the 6th click in either direction, the chosen zoom button will gray out, meaning you can't go any further. It has been my experience that once you've hit the 6th click, it is best not to count back the other way to try to get yourself back to neutral. The count messes up and it will be off 1 or 2 clicks from what it was on the way out. Rather, in this case it's better to either exit the map and come back in, or hit the "plane centering" button to the right of the zoom buttons, which will automatically center your plane in the "default-zoom" position:

As you zoom in and out various levels on the map in a given location, you will notice that the topography depicted in the flight map varies in focal quality, appearing sharp in some cases, while blurry in others, even within the same zoom level. Whichever zoom level brings the map topography in focus, will tell you which level of mesh terrain is installed in that area.

Now certainly more than one level of mesh may be installed in a certain area, be it default from the original FS discs, or an add-on that you may have installed yourself. It is entirely possible to install all the levels of mesh in a given area so that nearly every mouse click you zoom in or out, the map topography will almost always be focused. I say "almost" because there are some exceptions that I have noted. This would be the best case scenario...if one wants to take the time to download and install all that mesh (assuming all of it is even available for every square mile of the globe).

It is also important to note that even if one runs only default terrain straight off the discs, that terrain resolution can vary greatly, especially in areas of special interest where Microsoft presumably wanted to highlight the detail. It may not be so important to note which terrain mesh level is present, as it is to determine which terrain mesh level is missing!

Flight Map Clarity Chart

If you view the following spreadsheet chart I have created, you will see the relationship between mouse-click zoom level on the flight map and the level of terrain mesh (both indicated in meters of resolution and LOD ("Level of Detail"):

Down the vertical left-hand column is the flight-map zoom level:

• Green represents the # of mouse-clicks on the + button to zoom-in.
• Red represents the # of mouse-clicks on the - button to zoom-out.
• Beige represents the neutral/default zoom level when you first open the flight map.

Across the horizontal top row is the corresponding mesh level, indicated in both resolution meters, and equivalent LOD values.

• LOD 3 to 6 is indicated in red, as clarity at those levels is associated with zooming-out on the flight map.
• LOD 9 to 12 is indicated in green, as clarity at those levels is associated with zooming-in on the flight map.
• LOD 7 & 8 are indicated in beige as those are the only two mesh levels that will appear as "focused" on the flight map when first opened in the default-zoom; assuming those levels are indeed present in the area where that map is opened. (San Francisco, CA (LOD and Death Valley, CA (LOD 7) readily come to mind as such examples, for purposes of default mesh. I'll discuss those later).

The rectangles in the center are the results of what happens when one condition from each axis of the chart is met:

• Yellow represents where the map topography will display sharp and in focus, and one can almost certainly conclude that the given mesh level is present in that exact region of the map on the simulator.
• Gray (or beige, in the default rows/columns) represents where the map topography will display blurry and poorly defined. From this one can conclude with "relative" certainty that at least one mesh layer is missing, and maybe more, depending on just how blurry the image appears to be. It's been my experience that the worse the blurriness, the more likely that consecutive layers are probably missing.
• Blue represents the areas where the results are inconclusive, and no distinction between clear and blurry can be determined. Beyond the 2nd mouse click on the zoom-out button, all the map topography disappears and appears flat and simply color-coded by elevation. At this point it's virtually impossible (from the flight map alone) to tell what level of terrain mesh is installed beyond anything less detailed then LOD 5 @1223m. From other reference materials I've read, I can say that there is very little chance that any LOD 4 is installed as default mesh in FS2004, but that the whole world is done up in both LOD 3 & 5, as the very low resolution base terrain mesh. LOD 0, 1 & 2 (though they exist in theory), I don't believe are a part of FS2004.

I should point out that this is simply a rough guide for determining mesh level via the flight map, and is not precise. The fact that a given row shares like-columns and visa-versa, does add some confusion.

• Viewed horizontally, all but two zoom-levels on the flight map share two LOD levels side-by-side with one another (meaning there are two yellow rectangles right next to each other). Zoom-levels +4 and +5 are the exceptions, where they have the unique distinction of being paired up with only one LOD level each (+4 = LOD 11 and +5 = LOD 12). This is especially important because when trying to determine if mesh at this level exists on the map, there is no doubt or ambiguity whatsoever. It would be nice if all the zoom-levels and LOD's shared a 1:1 ratio each... but unfortunately such is not the case.
• Viewed vertically, all but two LOD's share two zoom-levels stacked one-on-top-of-the-other (meaning two yellow rectangles stacked). LOD 5 and LOD 12 are the exceptions, where they have the unique distinction of being paired up with only one zoom-level each (LOD 5 = zoom level -2 and LOD 12 = zoom level +5). Again, LOD 12 mesh will only come into focus at zoom-level +5, and LOD 5 mesh will only be clear at zoom-level -2.

Note that in FS2004, resolution higher than LOD 12 is not possible. Therefore, flight map zoom-level +6 will NEVER BE IN FOCUS... no matter what kind of terrain mesh you try to add. (This may not be the case with FSX).

In situations where neighboring levels of mesh are installed in a given location, it may be difficult to ascertain in a given flight map zoom-level, which level mesh is actually causing the flight map to focus sharply.

There are many unique instances from all over the world where I could probably draw my examples from. Unfortunately, I need to pick just a few, or we'll be here all day. Since I've spent most of my life growing up in California, it makes sense that I cite examples from areas I'm most familiar with. Therefore, to those of you in other regions of the world, I'll apologize in advance for my predominantly "Ameri-Centric" perspective.

For my examples I will be drawing from both San Francisco (the 'demsfr18.bgl' LOD 8 (153m) mesh file), and Death Valley (the 'demdva17.bgl' LOD 7 (306m) mesh file), for the default FS2004 as part of the "Enhanced Mainland USA" group in the Scenery\World\scenery folder:

1. The neutral map-zoom level (0), is the focus level for both LOD 7 and LOD 8 scenery, as is the case with both San Francisco (LOD 8), and Death Valley (LOD 7) below. Note that against the back drop of LOD 6 terrain mesh (which doesn't focus until zoom level -1), that a contrast exists between focused and blurry areas inside and outside the red boxes. At this point, if we didn't know the levels of each scenery, we wouldn't know which was the LOD 7 or the LOD 8 inside the red boxes. However, we can certainly surmise that none of the areas outside the red boxes are LOD 7 or 8:

2. If I zoom-out to -1 , both maps have cleared up and become focused. Uh oh... that's a problem, because now I don't know which LOD is responsible for the clarity. Is it the 6, 7, or 8? We know that LOD 6 is assigned as the base scenery for the entire USA, so zooming-out to -1 is going to sharpen the image regardless of what special higher resolution mesh is in place for either San Francisco or Death Valley. In the case of both SF and DV, zooming-out is inconclusive and is of no help whatsoever. They only way I could tell LOD 7 from LOD 8 by zooming-out in the negative direction, is if I were to go into the Scenery\World\scenery folder and disable the LOD 6 .bgl file that controls the San Francisco and Death Valley areas. At that point, with the LOD 6 disabled, focus at -1 would indicate LOD 7, and blurry at -1 would indicate LOD 8. (Having already tried it I can tell you that in that situation, San Francisco will fall blurry while Death Valley remains focused; but we wouldn't be privy to that information under default circumstances).

3. However, if I zoom-in to +1, and know that there is no default LOD 9 (76m) mesh anywhere near these areas, and the map image immediately turns blurry on the right (which it has), then I know that Death Valley must be LOD 7, because at zoom-level +1, only LOD 8 or LOD 9 would have shown as focused. Therefore, no LOD 8 exists here, so by process of elimination, it must be LOD 7 in Death Valley.

A very important side-note to point out here: In the Death Valley map, not only is there a distinction between "focused" and "blurry"... but also between "blurry" and "more blurry"! Although inside the Death Valley "box" is in better focus than outside the box, neither are as focused as they were a few zoom-levels back. Zoom level +1 is the proper zoom for LOD 8 & 9. LOD 7 is a little more focused than LOD 6 because it's only once-removed from its zoom-level of focus (0). However, LOD 6 is twice-removed from its zoom-level of focus (-1), so it will actually appear blurrier. The degree of blurriness between two separate "panels" of mesh is a good indication of the gap between LOD values. As this gap grows, incidents of "texture tearing" (i.e. the "blue slivers") are more likely to occur. If one is to consider filling in areas with after-market terrain mesh products, I would think areas with the greatest gap between the lower default and higher add-on are the areas where one might want to start first. In other words, if you're working with Europe (much of which is default LOD 5), and you have this fantastic 19m (LOD 11) mesh you want to install, you may not be doing yourself any favors if you completely disregard the LOD 6 through 10 that's missing. How blurry the flight map gets as you zoom in and out will help you to determine the size of this gap.

Back to the map discussion... San Francisco (left picture) on the other hand offers a bit more ambiguity than the Death Valley example. It is still in focus at +1. Chances are that it's LOD 8 because it was in focus at zoom 0, and still remains in focus at +1. However, we can't be absolutely sure unless we see it blur at zoom +2:

4. Now we zoom-in to level +2 on the map. As expected, San Francisco has fallen blurry as there is nothing higher than its LOD 8 and the LOD 6 surrounding it. Note that Death Valley has gotten even blurrier than the last image, and the LOD 6 outside the box, even more so than the LOD 7 area inside the box. As there are no higher resolution default mesh products at this point, further zoom-in beyond +2 will only make it worse.

5. Now... let's add a new variable: I installed add-on 38m (LOD 10) mesh for the Western United States. Same zoom-level, planes in same location, etc. Only now the terrain image is crystal clear. Why? Because the LOD 10 mesh at zoom-level +2 coincide with one another according to the chart above, and we can see the difference clearly in this example. In the fourth photo above, the distinction inside and outside the red boxes mattered, because the separation of the LOD's made a difference (albeit a blurry difference). However, in this case the red boxes are actually a moot point. I just left them there for sake of reference. In all actuality, the 38m (LOD 10) mesh here includes all of California. LOD 10 trumps the base LOD 6 by 4 levels, the Death Valley LOD 7 by 3, and the San Francisco LOD 8 by 2, so the entire map area in and outside the boxes is clear, regardless. The San Francisco and Death Valley exclusions no longer have any bearing on map clarity for these regions.

6. I didn't feel it necessary to take map pictures here, but to take it out in theory a little further; I also have 19m (LOD 11) mesh installed individually for the State of California. Therefore, in my situation, zoom levels +3 & +4 will also remain in focus because of the LOD 11 mesh.

I have no LOD 12 for California, so the map will finally fall blurry when I zoom-in to +5 and +6. However, if I venture over to Hawaii, where I do have LOD 12 (10m) mesh installed, I will maintain focus on the flight map, even down to zoom-level +5. Zoom-level +6 (as I mentioned above) will always be blurry in FS2004. This is because the zoom-level of the flight map exceeds FS2004's ability to use mesh at that high of a resolution. I believe this limitation is not a factor in FSX.

In Summary...

A. All of the USA is done up in LOD 6 (612m) as its base minimum resolution. Therefore, except for the areas of special exception, most of the U.S. topography on the flight map will not appear focused at the default zoom level. Zooming-out one mouse click to -1 will be required to see an LOD 6 portion of the map topography clearly.

B. Much of the rest of the world is done up in LOD 5 (1223m) as its base minimum resolution. This will require zooming-out two clicks with the mouse to -2, before this terrain mesh level displays as clear on the flight map.

C. Anything out beyond zoom-level -3, one cannot tell exactly what they are looking at. The topography disappears (replaced simply by 2-D color coding of the elevation ranges), and while we know there is LOD 5 installed, I don't believe there is any LOD 4 terrain installed stock from the FS2004 discs.

D. Finally, we can readily assume that LOD 3 is present 'dem4km.blg' (in the Scenery\base\scenery folder), as the simulator won't even run if this file is removed. There is no way to confirm its presence on the flight map as it falls into the blue region on my spreadsheet chart. However, if one were to extrapolate from the diagonal angle of my yellow rectangles, one could imagine it would probably fall into focus around zoom-level -5 or -6.

In conclusion, I realize that this is not an ideal, scientific approach to answering the question of which terrain resolution levels reside in which areas, but if you want a down-and-dirty method to take an educated guess as to what you have, then using the flight map with the zoom buttons, along with my spreadsheet chart above, should be sufficient.

Appendix:

An overview of the terrain mesh files provided in FS2004 by Steve Greenwood

(Please note that some of the titles, color-codes, and descriptions of each section are mine, and not the original text of Mr. Steve Greenwood):

* indicates new in FS2004

A. Foundation Scenery:

FS9\Scenery\BASE\scenery - Very low resolution mesh for the world (LOD 3)

dem4km.bgl (The flight simulator will not start up without this file installed!)

B. Basic Scenery (a little better, but not much):

FS9\Scenery\world\scenery - Low resolution mesh for the world (LOD 5)

(Please note: Longitude/Latitude coordinates in the file names below are labeled from the NW corner of each section; divided in 60-deg long and 45-deg lat segments)

dw180n90.bgl, dw120n90.bgl, dw060n90.bgl, dw000n90.bgl, de060n90.bgl, de120n90.bgl
dw180n45.bgl, dw120n45.bgl, dw060n45.bgl, dw000n45.bgl, de060n45.bgl, de120n45.bgl
dw180n00.bgl, dw120n00.bgl, dw060n00.bgl, dw000n00.bgl, de060n00.bgl, de120n00.bgl
dw180s45.bgl, dw120s45.bgl, dw060s45.bgl, dw000s45.bgl, de060s45.bgl, de120s45.bgl

C. Premium Scenery (considerably better than A & B):

FS9\Scenery\world\scenery - Medium to high resolution mesh for selected areas of the world (LOD6 through LOD10). Includes extensive coverage of the following (Coordinates as reported by BGLAnalyze):

1a. Base USA Mainland (LOD 6)
1b. Enhanced Mainland USA (LOD 7-10)
1c. Enhanced Remaining USA (LOD 8 & LOD 9)
2. Caribbean Sea (LOD
3. Australia (LOD7)
4. Western Pacific Islands (LOD 9)
5. Other (Brazil, Greece, Africa, Himalayas, China, Japan) (LOD 8-10)

(Please note: In each section below, Latitude/Longitude coordinates in the file names are labeled as ranges, starting from the SW corner of each section, listed S to N, and then W to E)

1a. Base Mainland USA - includes terrain along borders of Canada, Mexico (LOD 6):

demusab6.bgl N45:00:00.00 N49:13:07.50 W125:37:30.00 W120:00:00.00 North West Coast
demusac6.bgl N45:00:00.00 N49:13:07.50 W120:00:00.00 W090:00:00.00 North Central
demusad6.bgl N45:00:00.00 N49:13:07.50 W090:00:00.00 W065:37:30.00 North East Coast

demusaa6.bgl N33:45:00.00 N45:00:00.00 W125:37:30.00 W120:00:00.00 Mid West Coast
demusae6.bgl N33:45:00.00 N45:00:00.00 W120:00:00.00 W105:00:00.00 Mid South West
demusag6.bgl N33:45:00.00 N45:00:00.00 W105:00:00.00 W090:00:00.00 Mid Central
demusai6.bgl N33:45:00.00 N45:00:00.00 W090:00:00.00 W075:00:00.00 Mid East Coast
demusak6.bgl N37:58:07.49 N45:00:00.00 W075:00:00.00 W065:37:30.00 Mid North East Coast

demusaf6.bgl N29:31:52.49 N33:45:00.00 W120:00:00.00 W105:00:00.00 South West Coast
demusah6.bgl N23:54:22.47 N33:45:00.00 W105:00:00.00 W090:00:00.00 South Central
demusaj6.bgl N23:54:22.47 N33:45:00.00 W090:00:00.00 W073:07:30.00 South East Coast

1b. Enhanced Mainland USA (LOD 7 to LOD 10):

dembak18.bgl N48:30:56.24 N49:13:07.50 W122:20:37.50 W121:24:22.50 Mt Baker-North Cascades, Washington
demrai19.bgl N46:24:22.49 N47:06:33.75 W122:20:37.50 W121:24:22.50 Mt Rainier, Washington
demhel18.bgl N46:03:16.87 N46:24:22.49 W122:20:37.50 W121:52:30.00 Mt St Helens, Washington
demadm18.bgl N46:03:16.87 N46:24:22.49 W121:52:30.00 W120:56:15.00 Mt Adams, Washington

demhod18.bgl N45:00:00.00 N45:42:11.23 W121:52:30.00 W121:24:22.50 Mt Hood, Oregon
demcrl18.bgl N42:32:20.60 N43:14:31.86 W122:20:37.50 W121:52:30.00 Crater Lake, Oregon

demsha18.bgl N41:07:58.12 N41:50:09.34 W122:20:37.50 W121:52:30.00 Mt Shasta, California
demsfr18.bgl N37:37:01.84 N37:58:07.49 W122:48:45.00 W122:20:37.50 San Francisco, California
demyos19.bgl N37:26:29.05 N38:19:13.11 W120:00:00.00 W119:03:45.00 Yosemite, California
demcat19.bgl N33:13:21.55 N33:34:27.17 W118:49:41.25 W118:07:30.00 Santa Catalina, California

demgrc17.bgl N43:35:37.48 N44:17:48.74 W104:03:45.00 W103:07:30.00 Rapid City, South Dakota
demrus10.bgl N43:40:53.87 N44:01:59.52 W103:42:39.38 W103:14:31.88 Mt Rushmore, South Dakota

demhov10.bgl N35:56:50.14 N36:07:23.00 W114:50:37.50 W114:36:33.75 Hoover Dam, Arizona Nevada
demgrc19.bgl N35:30:28.09 N36:33:45.00 W113:54:22.50 W112:58:07.50 Grand Canyon West, Arizona
demgrc29.bgl N35:51:33.74 N36:33:45.00 W112:58:07.50 W111:33:45.00 Grand Canyon East, Arizona

demgla18.bgl N48:09:50.62 N49:13:07.50 W114:50:37.50 W112:58:07.50 Waterton-Glacier National Park, Montana Canada

demnia10.bgl N42:58:42.65 N43:19:48.26 W079:27:11.25 W078:59:03.75 Niagara Falls, New York Canada
*demdva17.bgl N35:09:22.48 N37:15:56.23 W118:07:30.00 W115:18:45.00 Death Valley, California

1c. Enhanced Remaining USA (LOD 8 and LOD 9):

demhaw19.bgl N18:48:30.92 N22:19:27.16 W160:18:45.00 W154:41:15.00 Hawaiian Islands, Hawaii

demden18.bgl N61:52:30.00 N63:59:03.75 W153:16:52.50 W149:31:52.50 Mt McKinley, Denali Nat'l Park, Alaska
demwra18.bgl N60:28:07.47 N62:55:46.87 W145:46:52.50 W140:37:30.00 Wrangel Mts, Alaska

2. Caribbean Sea (LOD 8):

*demcar18.bgl N17:34:41.22 N26:43:07.48 W084:50:37.50 W072:11:15.00 Caribbean Sea - NW (S. FLA, Cuba, Haiti, ...)
*demcar28.bgl N11:57:11.24 N22:08:54.37 W072:11:15.00 W059:03:45.00 Caribbean Sea - SE (Dominican Rep., Puerto Rico, ...)

3. Australia (LOD 7):

*demaus47.bgl S20:23:26.23 S10:32:48.75 E126:33:45.00 E140:37:30.00 Australia
*demaus77.bgl S21:47:48.72 S09:08:26.23 E140:37:30.00 E153:45:00.00 Australia
*demaus37.bgl S21:47:48.72 S13:21:33.73 E113:26:15.00 E126:33:45.00 Australia
*demaus27.bgl S26:43:07.48 S21:47:48.72 E112:30:00.00 E126:33:45.00 Australia
*demaus57.bgl S26:43:07.48 S20:23:26.23 E126:33:45.00 E140:37:30.00 Australia
*demaus87.bgl S26:43:07.48 S21:47:48.72 E140:37:30.00 E153:45:00.00 Australia
*demaus97.bgl S33:45:00.00 S26:43:07.48 E140:37:30.00 E153:45:00.00 Australia
*demaus17.bgl S35:51:33.74 S26:43:07.48 E113:26:15.00 E126:33:45.00 Australia
*demaus67.bgl S38:40:18.72 S26:43:07.48 E126:33:45.00 E140:37:30.00 Australia
*demaus10.bgl S44:17:48.74 S33:45:00.00 E140:37:30.00 E151:52:30.00 Australia (Please note: This file is a special exception from the standard nomenclature. Though the file is numbered "10", the LOD is still 7. 1 through 9 in the tens- place was used up, forcing the use of this number. This is not LOD 10 scenery.)

4. Western Pacific Islands (LOD 9):

demoki19.bgl N25:50:23.43 N27:14:45.92 E127:30:00.00 E128:40:18.75 Okinawa Prefecture, Japan
demiwa19.bgl N24:36:33.73 N24:57:39.35 E141:05:37.50 E141:33:45.00 Iwo Jima Island, Volcano Islands, Japan

demsai19.bgl N14:45:56.25 N15:17:34.68 E145:18:45.00 E146:00:56.25 Saipan Island, Marianas
demrot19.bgl N14:03:45.00 N14:14:17.81 E145:04:41.25 E145:18:45.00 Rota Island, Marianas
demgua19.bgl N13:11:00.93 N13:42:39.37 E144:36:33.75 E145:04:41.25 Guam Island, Marianas
dempal19.bgl N06:51:19.69 N07:54:36.56 E134:03:45.00 E134:45:56.25 Palau Islands, Republic of Palau

demtrk19.bgl N07:01:52.48 N07:33:30.91 E151:24:22.50 E152:06:33.75 Truk Island, Micronesia
dempon19.bgl N06:40:46.86 N07:01:52.48 E157:58:07.50 E158:26:15.00 Pohnpei Island, Micronesia

dempng29.bgl S06:19:41.25 S01:13:49.67 E147:53:26.25 E153:45:00.00 Papua-New Guinea
dempng19.bgl S06:19:41.25 S01:45:28.10 E145:18:45.00 E147:53:26.25 Papua-New Guinea
dempng59.bgl S07:44:03.74 S06:19:41.25 E145:18:45.00 E147:53:26.25 Papua-New Guinea
dempng39.bgl S10:11:43.10 S07:44:03.74 E145:18:45.00 E147:53:26.25 Papua-New Guinea
dempng49.bgl S11:46:38.41 S07:54:36.56 E147:53:26.25 E153:45:00.00 Papua-New Guinea
dempng69.bgl S11:46:38.41 S11:15:00.00 E153:45:00.00 E154:27:11.25 Papua-New Guinea
demsol19.bgl S10:53:54.36 S04:55:18.73 E154:27:11.25 E162:39:22.50 Solomon Islands, United Kingdom
demvan19.bgl S15:49:13.12 S14:35:23.42 E166:24:22.50 E167:20:37.50 Luganville Island, Vanuatu

5. Other (Brazil, Greece, Africa, Himalayas, China, Japan) (LOD 8 to LOD 10):

demrio10.bgl S23:06:54.82 S22:35:16.38 W043:28:35.63 W042:53:26.25 Rio de Janeiro, Brazil
demath10.bgl N37:47:34.67 N38:08:40.28 E023:26:15.00 E024:01:24.37 Athens, Greece
*demkil19.bgl S03:20:23.42 S02:48:45.00 E037:01:52.50 E037:30:00.00 Mt Kilimanjaro, Tanzania Africa

demhimb8.bgl N26:22:01.87 N28:07:30.00 E082:58:07.50 E090:00:00.00 Himalaya Mtn Range, Northern
demhimc8.bgl N26:22:01.87 N29:31:52.49 E090:00:00.00 E091:24:22.50 Himalaya Mtn Range, Southern (Mt Everest)
demhima8.bgl N28:07:30.00 N29:31:52.49 E082:58:07.50 E090:00:00.00 Himalaya Mtn Range, Eastern

demhong9.bgl N21:58:21.55 N22:40:32.81 E113:54:22.50 E114:36:33.75 Hong Kong, China
demfuj19.bgl N35:09:22.48 N35:30:28.09 E138:30:56.25 E138:59:03.75 Mt Fuji, Japan

Notes:

1) LOD: Level of Detail - specified by the mesh developer. This value determines the spacing of the elevation data points on the surface of the FS2004 world. A higher LOD means the data points are closer together. This resolution is often close to the resolution of the source data and can therefore usually be used as a crude measure of relative accuracy. The radius of the foreground area rendered using the highest priority mesh decreases with increasing LOD. Both file size and processing requirements increases with LOD.

Example: LOD10 has a data spacing of 38.2m, LOD7 has a data spacing of 305.8m; LOD12 mesh has a radius of only 6-7nm under the aircraft, LOD7 mesh has a radius of over 30nm.

2) The filenames give us the LOD values for the higher resolution mesh files. Microsoft uses 8.3 filenames:

"dem" area (3 chars) filler (0 or 1 char) LOD (1 or 2 chars) ".bgl"

filler is not used for LOD 10 files, otherwise it is one character usually the number 1 or a sequence of numbers for block of related bgls (19, 29, ...) there are two exceptions, where a sequence of letters is used (a, b, c, ...) the usa (because there are 11 bgls and use of numbers would exceed the 8 char maximum?) the himalayas (I don't know why!)

Example: demnia10.bgl is LOD10, demfuj19.bgl is LOD9, demusad6.bgl is LOD6

3) Source data resolution - from real world sampling. This value defines the maximum possible accuracy of the terrain in the simulator. We do not know what source data was used for FS2004, so the examples are for common data sources used for add-on mesh.

Example: 30 arcsec/1000 m, 3 arcsec/100m, 1 arcsec/30m and 1/3 arcsec/10m

4) When multiple mesh files cover the same area, the one with the highest LOD is usually displayed in the foreground. Where the LOD for two overlapping mesh files is the same, the mesh with the highest source data resolution is given priority. (CAUTION: LOD12 or higher mesh will not be used unless your TERRAIN_MAX_VERTEX_LEVEL is set to 20 in fs9.cfg - maximum useful value is 21, but 20 seems to be optimal for FS2004)

Since the radius of the mesh displayed is determined by LOD, you may see the highest priority mesh (smaller radius) in the foreground, LOD3 mesh (largest radius) at the horizon, and mesh with intermediate LOD/priority values between them.

5) Mesh bgl files can be viewed using tmfviewer.exe, included in the FS2002 Custom Terrain Textures SDK. See the areas covered, or not, by your favorite mesh!

John O'Flaherty
b3burner@yahoo.com