INS Position Update and Offsets

[Joni]

Yeap, I did an update with a TACAN station on thursday I think, and it works, not so good but it works.

 

But I wasnt referring to landing obviously, but for bombing and navigating in enemy territory where there's no nav aids.

 

I was wondering if you have IMC then perhaps they didnt fly that day if you are in deep enemy ground.

 

By the way, the TACAN offset feature is a BLAST!! I've never seen something so simplified. If there real Mirage also has that, then it is a tremendous aircraft. Also the radar has some awesome features. I'll never jump into any FC3 cockpit again!

[myHelljumper]

Yeap, I did an update with a TACAN station on thursday I think, and it works, not so good but it works.

 

But I wasnt referring to landing obviously, but for bombing and navigating in enemy territory where there's no nav aids.

 

I was wondering if you have IMC then perhaps they didnt fly that day if you are in deep enemy ground.

 

Mirage 2000C don't do deep strikes because it is the 2000N and 2000D mission.

 

As I said before 1 nm/h is not a lot for navigation and I don't think that they do A/G when there is a bad weather.

 

And remember that the 2000C is supposed to have a A/G radar that can help for bad weather navigation.

 

By the way, the TACAN offset feature is a BLAST!! I've never seen something so simplified. If there real Mirage also has that, then it is a tremendous aircraft.

 

They have it, it's described in the only real M2000C documentation that is available.

[Joni]

Oki doki. I dont think I fully understand the whole INS nature yet.

[myHelljumper]

Oki doki. I dont think I fully understand the whole INS nature yet.

 

Remember that it is not your only way to navigate and that you HAVE to use other systems to navigate.

 

Also, the 2000C is really not a striker aircraft, it can do strike missions but they have to be simple.

 

IRL their main A/G mission is to carry GBU-12 for the 2000D or 2000N to lase.

[baltic_dragon]

Oki doki. I dont think I fully understand the whole INS nature yet.

 

Yeah, the INS is not as advanced but has a lot of nice options making your life simple. And it is a good fun to use them. Enjoy discovering rest of the stuff!

 

Yeap, I did an update with a TACAN station on thursday I think, and it works, not so good but it works.

 

But I wasnt referring to landing obviously, but for bombing and navigating in enemy territory where there's no nav aids.

 

I was wondering if you have IMC then perhaps they didnt fly that day if you are in deep enemy ground.

 

By the way, the TACAN offset feature is a BLAST!! I've never seen something so simplified. If there real Mirage also has that, then it is a tremendous aircraft. Also the radar has some awesome features. I'll never jump into any FC3 cockpit again!

 

I remember reading a book about A-10A operation - back then they didn't have the EGI but a rather inaccurate INS system (I guess with greater drift that the M-2000C one has). Basically what they did they just used maps in different scale to help them navigate - this was the main instrument. And that is a pure strike aircraft we are talking about - so guess for M-2000C it wouldn't be that different. And I'd guess no deep strike missions in IMC conditions...

Edited July 29, 2017 by baltic_dragon

[myHelljumper]

I remember reading a book about A-10A operation - back then they didn't have the EGI but a rather inaccurate INS system (I guess with greater drift that the M-2000C one has). Basically what they did they just used maps in different scale to help them navigate - this was the main instrument. And that is a pure strike aircraft we are talking about - so guess for M-2000C it wouldn't be that different. And I'd guess no deep strike missions in IMC conditions...

 

True pilots only use a map, a compass and a watch :D.

[Esac_mirmidon]

And the fingers to count XDDDD

[Joni]

Yeap, I've been flying that way for more than a decade. Here in Argentina we dont have much technology to help. We fly planes without DME so you can imagine.

 

What I enjoy of a sim is the technology, because that's what I dont fly in real life. For using maps and mind calculations I already have my RL flying :)

[jojo]

OK, here are my 2 cents.

 

The Mirage 2000C is an all weather look up/ look down single seat fighter interceptor.

To ease the pilot work load there is a great auto pilot, and an INS for navigation purpose.

1 Nm/h drift rate is probably the best you can hope from a single mechanical INS of that time.

 

Mirage 2000N was provided with a dual INS system and Kalman filters calculation to compare the drift between the two INS systems and minimize the drift error. Mirage 2000N also has moving map and can update INS from multiple ways including radar map.

But Mirage 2000N is an all weather nuclear strike aircraft with full auto terrain following radar.

 

Back to the Mirage 2000C. It's a fighter/ interceptor designed to protect homeland = France, or at least fight in Europe during Cold War.

There are (were) VOR, DME and TACAN everywhere and no GPS at that time.

So if you don't have radio-nav devices, INS is good enough to fill the gap.

 

If you fly 1 or 2H air defense mission, 2Nm error is good enough to get back within air base VOR/ TACAN range.

So my guess is that for air defense, they don't care that much about INS update.

 

For AG you have to plan an initial waypoint to update your NAV INS system.

 

There are 2 ways to update the INS system:

- vertical overfly

- HUD designation with radar ranging.

 

If there is a low overcast the radar still allows to dive through thanks to "DEC" function (DECOUPE = Terrain Avoidance, not simulated yet because of lack AG radar support in ED code).

 

For AG you have different type of weapons with associated aiming methods:

1- low drag bomb:

a) direct attack = HUD designation. You're supposed to visually designate the target. Using INS to find the target is an help but not mandatory.

b) PI (Point Initial) = the target coordinates are entered as offset from the Point Initial. During the attack run you designate the Point Initial and this act as INS update. AFAIK this mode doesn't fully works as expected in DCS yet.

2- high drag bomb:

a) CCPI attack (CCIP in English).

b) PI = you can either visually bomb the target or aim for + in the HUD.

3- AG gun & rocket: CCPI again.

 

So only 1-b) (and maybe 2-b) in poor weather) really depends on INS accuracy, and this is the only "blind bombing" mode.

The purpose isn't accuracy but to provide stand off range from heavily defended area or to bomb the target despite low clouds preventing visually acquisition from the target.

With low drag bombs, the accuracy will be lower than with direct attack because of INS relative inaccuracy and longer flight time for the bombs (loft profile).

 

About INS: this comes from Mirage 2000N WSO explanation on another forum. Sorry if it isn't clear.

The gyro-meter has 3 accelerometer on 3 axis 90° apart.

During the the calibration process, the INS system feel the earth rotation and try to assess the true North position as accurately as possible. It is fed with the alignment position which is used as starting point.

So the greater is the North accuracy, the greater is the navigation precision.

The full process takes 8mn, but you can go with shorter alignment time and lower INS accuracy.

To increase accuracy, the Mirage 2000N WSO can perform triple alignment (1 for each accelerometer), but this is almost 30mn alignment procedure.

Edited July 29, 2017 by jojo

[jamie_c]

The thing I do the most for an INS realignment in IMC is to have a waypoint offset from a TACAN location, this way you don't have to overfly the TACAN and you can setup a 2nd point nearby. Of course this can be less accurate than the overfly method, putting you a whole 6 figure grid (or more) off target for precision.

 

Reading the manual the M2000C also has basic ground radar capabilities that aren't implemented because of DCS limitations as mentioned by jojo, it's entirely possible this is another option to real pilots where the terrain has distinct features or there are man made structures giving solid returns. This is similar to how things are in the Viggen, or something that would have been possible in the F-111C if you look at the public images from its radar.

 

Weather is still a huge factor in military operations to this day, moon phases, tides, wind, turbulence, and even planetary alignment, this is why from the 70s to present day we've seen radar and TGP development as well as GPS/GLONASS and ground based augmentation systems. The winner is the guy who can put bombs through windows in a hurricane.

[jojo]

The thing I do the most for an INS realignment in IMC is to have a waypoint offset from a TACAN location, this way you don't have to overfly the TACAN and you can setup a 2nd point nearby. Of course this can be less accurate than the overfly method, putting you a whole 6 figure grid (or more) off target for precision.

 

Reading the manual the M2000C also has basic ground radar capabilities that aren't implemented because of DCS limitations as mentioned by jojo, it's entirely possible this is another option to real pilots where the terrain has distinct features or there are man made structures giving solid returns. This is similar to how things are in the Viggen, or something that would have been possible in the F-111C if you look at the public images from its radar.

 

Weather is still a huge factor in military operations to this day, moon phases, tides, wind, turbulence, and even planetary alignment, this is why from the 70s to present day we've seen radar and TGP development as well as GPS/GLONASS and ground based augmentation systems. The winner is the guy who can put bombs through windows in a hurricane.

 

INS alignment is the process during which the system find the north direction. You need a still plane to do that.

What you do in flight is INS update, you only update the current position to cancel the drift.

 

The Mirage 2000C isn't an all weather strike fighter like AJ-37 or F-111.

So people must accept some limitation in AG missions, this is secondary role for this specific variant.

Mirage 2000N/ D with Antilope V radar, or even export Mirage 2000E with RDM+ (with modes like SEA or DBS) are better equipped for AG.

[Joni]

O

b) PI (Point Initial) = the target coordinates are entered as offset from the Point Initial. During the attack run you designate the Point Initial and this act as INS update. AFAIK this mode doesn't fully works as expected in DCS yet.

 

I think you are right, posted in the bug section.

 

 

https://forums.eagle.ru/showthread.php?t=191454