reported earlier Scud accuracy and "sigma" values in missiles_data.lua

[meltingSnowdrift]

This is not really a bug, but this feels like the most suitable place to ask because this is still about DCS behaving in a way that I found unexpected.

 

I was trying to make the Scud more accurate by editing some game files. In missiles_data.lua, each type of missile is given a "sigma" value consisting of a set of 3 numbers which appear to always be identical. Using Google Translate to translate the explanation of the variables at the beginning of that file, the relevant line was translated as:

Quote

sigma = {x, y, z}, maximum aiming error in meters, in target coordinates. x - longitudinal axis of the target, y - vertical axis of the target, z - transverse axis of the target

 

I then changed the sigma of the Scud to {4, 4, 4} to match that of the ATGMs in the same file and then launched the game. I made a scenario containing only a Scud which fires at a point approximately half way between its minimum and maximum ranges. The missile hit a point quite far from the target specified in the mission editor.

 

Why did decreasing the sigma values like this not greatly improve the accuracy of the Scud? Is its accuracy controlled in a way that does not involve these sigma values at all? Is its accuracy instead limited by something that does not involve artificial accuracy values at all? For example, is the guidance method inherently inaccurate?

[meltingSnowdrift]

Since making the original post, I have attained a better accuracy by making "t_marsh" very large to allow the missile to continue guidance after the rocket motor has burned out. I also set the sigma values to 0 in case that helps.

 

However, this accuracy is still considerably worse than that of GPS-guided bombs. The scud now always falls short of the target by about the same distance. Could the remaining inaccuracy be inherent to the ballistic missile guidance method in DCS? If so, why is it not also present in GPS-guided bombs, which have similar trajectories near the target?

 

Although this obviously does not matter much for the Scud as it currently exists in the stock game, this may indicate that the ballistic missile guidance method would need to be improved if more accurate types of SRBM are added in the future.

[VFA41_Lion]

ballistic missile guidance is still WIP

[BIGNEWY]

Hi,

 

we do have some scud reports open already and I am sure it will be tweaked some more in future patches.

 

thank you

[Aarnoman]

SCUD issue is unrelated to the sigma value, it's due to the missile trajectory calculation assuming completely flat ground at launch location, therefore any angular offset of the unit will introduce a significant error to the trajectory. The linked report explains this further.