Calculate Angle / Distances Between locations

How do I manually calculate the angle and distances between airbases from the DCS world map?

I'm really interested in plotting my own waypoints and flight path before I set foot in a DCS mission. I've been a huge fan of the Mi-8 since the Belsimtek module converted me, so I don't have any advanced navigation equipment on board.

Ideally, I'd like accurate data, not estimates.

I have a few questions that need to be answered to figure this out:

1. How are bearings calculated on the DCS map? Magnetic? True? Other?
   
2. If magnetic, what data is used for magnetic declination?
   
3. How are distances calculated? Via Great Circle or Rhumb lines?
   

I've looked into this a bit myself, but I really am just learning all this right now.

Lets use Kobuleti to Guudauta as an example:

We can use haversine with great-circle navigation or Rhumb lines to calculate distances and angles. Both have their merits.

It should be noted that they both use a spherical model of the earth, not an elliptical one. This would explain a slight inconsistency between results, but nothing like the inaccuracies we experience.

We can compare this to the results we get in-game using the mission editor or F10 map (I used mission editor as it reported more accurate figures) and the data from the Ka-50 navigation suite:

Haversine great-circle:

Rhumb:

In-game

Ka-50:

The in-game results are quite different from the real-world formulas.

The Ka-50 system seems to match up correctly to the f10 or mission editor view. So I use that for further tests.

It seems we're basically looking at a 6 degree inaccuracy here, and a slight difference in distance. 6 degrees is significant. Very significant. Now, if it was constantly a 6 degree difference, it wouldn't be a problem. We could compensate. But, it's not.

Let's have a look at some other extreme examples:

From:

47 40 17N 45 16 4E 1000km 90° from this point

Results:

From:

48 7 46N 27 7 2E 1000km 270° from this point

Results:

I'm sure there are plenty of other examples that could show how far out this gets. But I think these are enough to show what I'm getting at.

So, I'm guessing it would be possible to work out a formula to discover how much the angles and distances are out at each point, but I think that'd take a long time. Has anyone already done this? Is there any public information available?

Thanks for reading.

Tbh, I have absolutely no clue how these calculations are done that you mention here. But that 6 degrees off make me wonder if that can be related to an (accumulated) error caused by the magnetic deviation.

Afaik DCS uses not a fixed deviation for the whole map, but uses data that is derieved from the "World Magnetic Model" to get the local deviation for each place on the map:

See here for details: http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml

Please be aware that the F10 map bearing using the tool at the top of the screen gives the degrees relative to the game map and not the the (real-world) grid. There is about 6 degrees difference between the two.

Tbh, I have absolutely no clue how these calculations are done that you mention here. But that 6 degrees off make me wonder if that can be related to an (accumulated) error caused by the magnetic deviation.

Thanks for the post Flagrum. Magnetic deviation is indeed one factor to think about.

The first 6 degrees off could well be explained by magnetic deviation. However, the -4.4 and 9.2 degrees off definitely can't. Looking at that map, we are at between a +4 to +8 degree range (if I'm reading it right).

There is about 6 degrees difference between the two.

This is the interesting point. The 6 degrees is probably the magnetic deviation. This would make sense. A -4.4 degree error cannot be explained by that.

There is of course, a chance that I'm messing all this up. If so, I'd be happy to be corrected for !SCIENCE!

EDIT: I should also note that some of these destination points are off-map.

Yes should be 6 degrees

http://www.annalsofgeophysics.eu/index.php/annals/article/viewFile/5575/6184

I have found using the F10 Map ruler/ bearing is more than accurate enough to allow navigation with the doppler navigation system in the Mi-8. (you have to subtract the 6 degrees though when you enter the bearing into the doppler system). For example, I had no problems flying say five legs in bad weather with leg distance say between 30 - 100 km aiming for a geographic feature such as an airbase or beacon building or something off that nature. I was quite surprised actually. Give it a go.

Are you sure the extreme examples aren't the other way around? The deviation should increase when going east and decrease when going west.

Are you sure the extreme examples aren't the other way around? The deviation should increase when going east and decrease when going west.

Possibly so. I'm still researching.

Another interesting point, if you open up the map and turn off everything except the geographical grid, you will notice that the lines do NOT match up with the reference points given.

If you zoom in and place your mouse cursor over the grid cross, it will not match where the lat and lon lines should match.

Go to 46 0'8N 37 59'45E and you will see that is where the lines cross. Not 40 0'00N 38 0'00E. The lines cross 1339 feet at 305 degrees away.

Perhaps this is a clue?

A geographic system uses three different North Marks

Magnetic north

Almost not calculable, because it depends of the location of the magnetic North pole and the local tectonic environment like iron ore deposits and more. Therefore, every aviation map has reference lines for magnetic North determinations.

True North

This North direction is always along the meridians and can be taken for navigational planning.

Grid North

This is the most misunderstood direction. It is the result of the attempt to project the globe into a flat, two dimensional representation. Because there are a huge number of different methods used, the resulting representations are different.For position calculations in the simulation, a rectangular cartesian X/Y/Z system is necessary which is projected onto a map representation.Depending on the projection method used, the relation between the Y axis of the cartesian system to the meridians has a specific variation , called Grid Variation. In the DCS mission editor, Grid North is used for whatever reason. If you open the mission editor, you will see, that an exact vertical line (use the distance measuring ruler) has always the heading 360°. Regardless, what location you use. The vertical line is always parallel to the Y axis of the cartesian system (Grid North). You will even see, that the meridians are running into a different direction bound to the location you use. During a running scenario, two different north directions are used. The A10C follows magnetic North, indicated on the HSI while the F15C, as FC3 aircraft, shows grid North on the HSI. More confusion: magnetic north is calculated from Grid North + local magnetic variation, which is completely wrong. This is really confusing if someone wants to create an addon based on any navigational standard.

Example:

• 
  
• Measured RWY heading Sochi 62° G
  
• Grid variation Sochi measured from ME ~ 5° East
  
• True RWY heading measured from ME 62° G + 5° GV = 67° true
  
• Magnetic RWY heading from Cockpit HSI A10C 56°
  
• Magnetic Variation Sochi calculated from ME (56° - 67°) 11° East (instead of 6° East)
  
• Official reported Variation from http://worldaerodata.com/wad.cgi?id=RS08294&sch=Sochin is 6° East
  

Conclusion

Distances and directions cannot be taken from a map with mathematical precision. It is always distort by the projection method used. Only the use of geographical coordinates, based on WGS84 and a formula promises the right result (which is finally not compatible with DCS). DCS uses Grid North internally, which simplifies calculations, but delivers the most imprecise Results compared to the real world. Furthermore, two different North directions are used for different aircraft in the cockpit representation.

The image below shows the rough relationship between the different North directions:

• 
  
• Blue is the cartesinan system representing Grid North
  
• Black are the meridians (pointing to true North) and the parallels of latitude
  
• Brown is a magnetic North reference line
  

Great info, towsim. Where did you get this all from? Was this discussed in a previous thread?

Thanks a lot for the reply. It gives me a lot to look at tomorrow.

As far as I know, it was not discussed in this way. The official VAD charts, created by Schleudi, a fellow sim pilot of mine, try to take care of the problem. But the main issue is, that the locations and orientations of the important map objects do not reflect the real world. Together with the north mark mix up, it is almost impossible to do a precise preflight planning. I was an air reconnaissance specialist and air traffic controller in another millennium. Together with the problems to align my GCI Radar project with the simulation environment, these issues came up.

Thank you so much towsim. I'm going to keep looking at it and see if I can come up with appropriate modifiers for different areas of the grid. I doubt I'll be as accurate as I'd like, but I'm sure I can make some improvements to the results I'm getting.

Thanks again.

I'm reviving this thread because soon new maps will be released and also a new version of DC World.

Right now I'm not sure if Eagle have been updated the charts, but if not, does anyone have insight if Eagle is aware and will make updates of the charts with the new versions and maps?

Caucasus map is projected on a plane as the old DCS engine doesn't support curved earth surface. The projection distorts distances and bearings farther you go from map origin which is at the center of Crimean peninsula. Of course projecting world to a flat plane doesn't happen by mistake or by dumb luck so ED has to be very aware of the problems associated with it. There's nothing that can be done other than rebuilding the map for the new engine with curved earth surface.

I'm running into issues with this in Mission's i'm building. I'm noticing 15 degrees off for my Mig-15 on F10 HDG and Mag Compass. I was hoping it was Magnetic Variance that I wasn't accounting for, but from the looks of the previous posts, there's more to it. Anyone find out the definitive number yet? As large as the map is, Magnetic Variance shouldn't change more than 1 or 2 degrees from one side to the other (land portion of the map that is)

Headings measured on the F10 map view are always grid headings. Means, it references grid north which is bound to the projection method used in DCS. It cannot be used for navigational purposes. The black grid represents the geo grid and points upwards to true north. You need to find out what reference is used for a specific aircraft. A10C uses mag north while the MIG21 uses grid north. I did not check out the Mig15 but it seems, that it uses mag north as compass indication while the F10 map heading uses grid north.

... the MIG21 uses grid north.

That's strange, isn't the only heading reference in the mig21 magnetic?

You can test it out easily. Place a MIG21 aligned on the runway 24 of Sochi. The heading you read on the compass gauge is about 242°. If you consult the approach charts of Sochi, you will find the mag runway heading as 236°. Now change to the F10 map view and measure the runway heading with the ruler. The result is the same as seen on the compass gauge. Since the ruler is grid heading orientated, the MIG21 is assumed to use grid north.

You can test it out easily. Place a MIG21 aligned on the runway 24 of Sochi. The heading you read on the compass gauge is about 242°. If you consult the approach charts of Sochi, you will find the mag runway heading as 236°. Now change to the F10 map view and measure the runway heading with the ruler. The result is the same as seen on the compass gauge. Since the ruler is grid heading orientated, the MIG21 is assumed to use grid north.

I wasn't suggesting you were wrong, I was saying it seemed to be modelled wrong.