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Author Topic: Tacview; raw data  (Read 261 times)

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Offline Fovos_Von_Trobos

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Tacview; raw data
« on: October 30, 2018, 05:07:46 PM »


Hi,

   An .acmi file is created every time you record a session with Tacview. If this file is opened with notepad, the raw data of the recorded objects can be accessed.
(more info about .acmi file here -->  https://www.tacview.net/documentation/acmi/en/  )
  I was looking for a way to make Tacview extract the speed as raw data, but after six hours of searching, i realized that Tacview exports as raw data of an object only the following ;
longitude, latitude , altitude, pitch, roll, yaw, AGL (Above Ground Level).So, i decided to use the available raw data in order to manually calculate the speed. However, the raw data
of longitude and latitude do not represent the actual coordinates of the object in space .

I would like to let me know whether the raw data of longitude and latitude, in relation to time and altitude, would result to a safe calculation of speed.And if not, it would be great if you could inform me about the formula you use to transform those data to the actual values of longitude and latitude.
 
Thanks in advance,
                             
Christos.




Offline Asid

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Re: Tacview; raw data
« Reply #1 on: October 30, 2018, 05:14:12 PM »
Hi Fovos

 :Welcome to the forum

You have come to the right place.

I am sure that Vyrtuoz, the developer, will be along to answer.

Regards

I stand against Racism, Bigotry and Bullying

Offline Vyrtuoz

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Re: Tacview; raw data
« Reply #2 on: October 31, 2018, 06:19:57 PM »
Hi Christos,

It really depends on your data source:
  • With simulators like BMS & DCS (flat world), the native coordinates are used to calculate the aircraft true air speed.
  • With simulators like FSX/X-Plane (spherical world), then the longitude, latitude, and altitude are converted into Cartesian coordinates (simplified WGS84, which is accurate enough) so the TAS can be calculated.

If you are running Tacview Advanced, you can export aircraft speed from within the charts.

If you want or need to calculate manually the speed based on spherical coordinates, you can use the following formula to get Cartesian coordinates:

Code: [Select]
void LongitudeLatitudeToCartesian(f64 & x, f64 & y, f64 & z, f64 longitude, f64 latitude, f32 altitude)
{
#define F64_WGS84_EARTH_RADIUS 6378137.0 // WGS 84 semi-major axis (https://en.wikipedia.org/wiki/Geodetic_datum)

f64 SinLongitude;
f64 CosLongitude;
f64 SinLatitude;
f64 CosLatitude;

CMath::SinCos(longitude, SinLongitude, CosLongitude);
CMath::SinCos(latitude, SinLatitude, CosLatitude);

const f64 absoluteAltitude = F64_WGS84_EARTH_RADIUS + altitude;
const f64 altitudeCosLatitude = absoluteAltitude * CosLatitude;

x = altitudeCosLatitude * CosLongitude;
y = absoluteAltitude * SinLatitude;
z = -altitudeCosLatitude * SinLongitude;
}

// longitude & latitude are in RADIAN
// altitude is ASL in meter
// x,y,z will contain Cartesian coordinates which can be used to calculate the TAS for example
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Offline Fovos_Von_Trobos

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Re: Tacview; raw data
« Reply #3 on: October 31, 2018, 11:35:33 PM »


I understand. Your explanation was perfect. IL2 is the simulator where the data are being mined. So, I assume, considering the raw data coordinates do not match the real ones,  that
they refer to the spherical coordinate system.

I have the demo version of Tacview and I 'm considering buying the standard version. I am studying parallel programming and I want to process a considerable amount of data efficiently.
Moreover, i wanted to
make this process more interesting and that's why I tried to mine data from a simulation i love. I was planning to calculate the potential energy per frame for each plane. However, I had to do it for
many many fights and different planes (i need a few Gigabytets of *.acmi files) and i can't find a useful conclusion . It would be a correct project but with no meaning at all.  If you have any ideas
about what i could do with the raw data of many different planes and dogfights, it would be great.


Vyrtuoz, thank you for your time, and congratulations for the creation of this amazing tool !


Offline Vyrtuoz

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Re: Tacview; raw data
« Reply #4 on: November 05, 2018, 07:32:43 PM »
Now I understand better!

A word of advice about using IL-2 (in its current state) for your project: The data provided by IL-2 is currently limited and/or not very accurate. I have sent some suggestion to the dev team, but I don’t know when the corresponding improvements will be implemented on their side...

The problem with the actual IL-2 telemetry exporter is that their spherical coordinates are not very accurate compared to real-life / FSX / X-Plane ones. Also, IL-2 does not currently export its native (flat) coordinates. With DCS World and Falcon 4, I can get the flat coordinates, and they give very accurate calculations.

My advice is to consider DCS World (at least the demo version) for your project. You will get the best accuracy currently available for military flight simulator and Tacview. There is a free P-51 available in the demo of DCS World, and additional WWII aircraft can be bought on the side (like the Spitfire and other German aircraft).

Please note that I do not compare the realism or fun of DCS World vs IL-2. I am just talking about the quality of the telemetry currently being recorded.

Another field which can be interesting for your project: the study of SAM or AA missiles from DCS World or Falcon 4. Like the way they are depleting their energy, they agility and so on. Could be an interesting subject too.

I do not know either which data would be the best to crush in parallel. But if you have any other questions, feel free to ask me, I will be glad to help you.

I almost forgot to mention that Tacview now has a public Lua API. While this will not help you with parallel processing, you may consider using it to write a plugin which extract data/convert the recorded data in a format easier to read by your main project.
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