INS bombing using DL/DG method

Hi guys,

In order to drop bomb with the INS system we can choose the rho/teta method which represent the distance and bearing of the target from the initial point OR we can also use the DL/DG method.

How do I define the values DL and DG to insert in the INS from the long/lat coordinates of the the target and the initial point without using the map?

Ty

I think you are referring to ΔL/ΔG.

IRL the JTAC would give this info to you or you would find it using a map prior to the mission.

I don't think you can easily calculate the ΔL/ΔG from the IP and target coordinates.

IRL the JTAC would give this info to you or you would find it using a map prior to the mission.

From this link here i read :

The target offset can be set as follows:

a. In x/y coordinates by using ΔL/ΔG:

ΔL = Distance difference between the IP Latitude and the BAD Latitude expressed in kilometers to the North or South. (True North is used)

ΔG = Distance difference between the IP Longitude and the BAD Longitude expressed in kilometers to the East or West. (True North is used)

So Im wondering if we could easily calculate these values from a formula online for example. It would be much more precise and convenient than using the map and the ruler tool in the F10 view I think.

JTAC doesn't give such info, because it's too specific to M2000. But it gives precise lat/long coordinates of the target.

 

From this link here i read :

The target offset can be set as follows:

a. In x/y coordinates by using ΔL/ΔG:

ΔL = Distance difference between the IP Latitude and the BAD Latitude expressed in kilometers to the North or South. (True North is used)

ΔG = Distance difference between the IP Longitude and the BAD Longitude expressed in kilometers to the East or West. (True North is used)

 

So Im wondering if we could easily calculate these values from a formula online for example. It would be much more precise and convenient than using the map and the ruler tool in the F10 view I think.

I found this that you can use :

https://www.movable-type.co.uk/scripts/latlong.html

It's not very accurate thought since the value of how much a degree equals in kilometers is estimated (it depends on what latitude and longitude you are at). The F10 map and the ruler will probably be more precise. For an IP to target offset tought it's negligeable.

EDIT : The website uses Degrees minutes seconds format coordinates, unlike the Mirage wich uses degrees minutes decimals.

Tested it from point to point, the F10 map indicates 57.7 miles in between the TACAN station on tonopah test range airfield and the TACAN station on Groom Lake AFB, the website says 58.7 miles (105.8 km).

I found this that you can use :

https://www.movable-type.co.uk/scripts/latlong.html

The tools provided on the link doesn't calculate the deltaL and deltaG between 2 coordinates. It only calculate the distance between 2 points and the bearing which is something you would use more for the rho/theta method bombing.

The website uses Degrees minutes seconds format coordinates, unlike the Mirage wich uses degrees minutes decimals.

Ty for this precision, it always make me confused.

I actually find a way to use the DL/DG INS bombing method. This webpage calculate the DL and DG between 2 points: http://www.whoi.edu/marine/ndsf/cgi-bin/NDSFutility.cgi?form=0&from=LatLon&to=XY

The tools provided on the link doesn't calculate the deltaL and deltaG between 2 coordinates. It only calculate the distance between 2 points and the bearing which is something you would use more for the rho/theta method bombing.

You can get DeltaL and DeltaG with the website i sent, it's less convenient then the one you found because you need to enter Lat only or Long only and add the minus if it's further south or further west. It's also less precise because it rounds numbers to the tenths. Anyways, what you've found works better :D

All this won't work, because in DCS, "True North" doesn't run along meridians. This means that if your IP is at, say, N44°01.00' E044°00.00' and your target is due north, at N44°08.00' E044°00.00', any real-life tool will give you 0 m ΔG. But in DCS, you will have a non-zero ΔG.

The only way I know to do it is use the map, and measure it there (which is tricky because you have to estimate the target position).

All this won't work, because in DCS, "True North" doesn't run along meridians. This means that if your IP is at, say, N44°01.00' E044°00.00' and your target is due north, at N44°08.00' E044°00.00', any real-life tool will give you 0 m ΔG. But in DCS, you will have a non-zero ΔG.

 

 

The only way I know to do it is use the map, and measure it there (which is tricky because you have to estimate the target position).

Ty for your answer.

That's a very interesting point that you mentioned but you are wrong (or not see my edit answer). As mentioned by developers here:

The target offset can be set in x/y coordinates by using ΔL/ΔG:

ΔL = Distance difference between the IP Latitude and the BAD Latitude expressed in kilometers to the North or South. (True North is used)

ΔG = Distance difference between the IP Longitude and the BAD Longitude expressed in kilometers to the East or West. (True North is used)

We enter in the INS coordinates referring to the true North and not the magnetic north. Then you can use the tool provided at the link above to calculate precisely these DL and DG.

It works very well but i have used this INS bombing method with JTAC only so i don't need to be very accurate. I haven't use this method by its own already.

EDIT

I just realized what you meant by

DCS, "True North" doesn't run along meridians.

Then in order to check what you said, I took 2 points on the map separated with a long distance (330km from Meneralnye airport and Tbilisi). And I measured the DL and DG with the ruler along the meridian and parallel (i displayed those lines by pressing LL in F10 map) in order to check if the web-tool returned the same results as my measurement in the game. And, I found an error (between the calculation and the measurements) along the parallel (horizontal line) of ~10km and a shift of 2km along the meridian (vertical line)...

Can you confirm that shift?

For an INS bombing we would take an IP separated from the target at ~15km. With a simple cross product I calculate that we would have an error of 500m along the parallel and an error of 90m along the meridian. Which is not good at all for INS precision, but good enough with a JTAC...

Does it means that meridians and parallel lines are completely bullshits in DCS? Normally meridians should point true north (0° heading) which is not the case here? Same for parallels, they should be oriented to east (90° heading) which is not the case either?

All those imply that DL/DL INS in M2000 is completely useless for INS bombing?

Why DCS decided to draw meridians like this?

Im sure there is a good reason...

That posts only forgets to say that all true headings in DCS (as indicated by instruments) are actually relative to grid north (and magnetic headings are Grid+MagVar). So it's not only a matter of the Mission Editor or the F10 map. This is one of those things I would really like to see fixed in DCS. I hoped it would be in 2.0 but no luck. I understand this is not an easy fix, though.

In fact, in DCS we can call grid north "True North" for nearly all purposes, except the ones that are related to coordinates (as in our case here), since now our new true north doesn't run along the meridians.

Yeap! I replied here as well. https://forums.eagle.ru/showpost.php?p=3290138&postcount=9

Thanks

That posts only forgets to say that all true headings in DCS (as indicated by instruments) are actually relative to grid north (and magnetic headings are Grid+MagVar). So it's not only a matter of the Mission Editor or the F10 map. This is one of those things I would really like to see fixed in DCS. I hoped it would be in 2.0 but no luck. I understand this is not an easy fix, though.

 

In fact, in DCS we can call grid north "True North" for nearly all purposes, except the ones that are related to coordinates (as in our case here), since now our new true north doesn't run along the meridians.

If I sum up, in DCS:

- True north = grid north.

- Ruler heading on f10 map = true north.

- Latitude North Not equal to true north.

- Tools in real life are not able to measure bearings and distances in DCS.

Conclusion: DL/DG in INS is completely useless ??

Not useless if you tune them to treat true north as one equal in the whole map.

One thing I was surprised about today, is that the Mirage shows positive declination in the INS no matter if you are in the left side of the crimea peninsula or to the right of it.

That is so wrong it makes me :cry:

One thing I was surprised about today, is that the Mirage shows positive declination in the INS no matter if you are in the left side of the crimea peninsula or to the right of it.

 

That is so wrong it makes me :cry:

Why do you think it's wrong?

The error between DCS 's Grid north and lines of longitude (Geographic True North) may change direction (due to map projection), but magnetic declination remains positive (between +6 to +8 ) in the Caucasus region.

https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/World_Magnetic_Declination_2015.pdf/page1-1200px-World_Magnetic_Declination_2015.pdf.jpg

Good catch, I guess I got mixed up with the errors in DCS.

By the way, it is called longitude north or meridian north, not latitude.

So I guess the INS gets useless on the left side of crimea, as it will calculate the wrong direction of correction versus what it is comparing, since in DCS declination gets compared to grid north and not true north or meridian north.

Whats worse, nevada has all the same mistakes as the caucasus.

The reason for grid north and true north being identical is because DCS World is a flat Earth, right? Or is there some other bug causing this?

Not useless if you tune them to treat true north as one equal in the whole map.

Yeah Piston but this thread is about how to tune DL/DG in order to use it. Since nobody know exactly how to calculate it from 2 coordinates, it makes this feature useless.

So I guess the INS gets useless on the left side of crimea, as it will calculate the wrong direction of correction versus what it is comparing, since in DCS declination gets compared to grid north and not true north or meridian north.

Idk what you are talking about.

Yeah Piston but this thread is about how to tune DL/DG in order to use it. Since nobody know exactly how to calculate it from 2 coordinates, it makes this feature useless.

 

 

 

Idk what you are talking about.

1. That feature is for ground troops who use maps in kms.

2. What would you like to know? I could elaborate more, but dont know which part was not clear. Sorry man.

Thanks.

Wait, I thought about it.

What is the exact issue about entering the distance in kms north/south and east/west from the latitude and longitude?

Thing is, you cannot calculate ΔL/ΔG from two sets of coordinates (it would require knowledge of the exact grid-to-true north variation everywhere on the map. However, you can absolutely measure it, whether from the F10 map or a paper map, but you have to make sure to use the "DCS true north", or grid north.

I imagine that for short enough distances, you can measure the local G-T variation (with approx. 0.1° or 0.2° precision if you're careful), then use that in a computation.

PS: unfortunately, "DCS true North" doesn't run along MGRS grids either.

I still dont get it.

Lets talk about how it would work IRL and separately in game.

IRL: You (ground troops) take the BUT coordinates from where you want to set the BAD. Then you measure on the map the distance north or south from the latitude and west or east from the longitude, to the BAD point. You input this in the INS and that's it since the INS works in true north and since the true north follows meridians which is the same way to get coordinates.

In Game: Same procedure but using the grid north (true north in dcs)

Yes, absolutely correct. Thing is, earlier in the thread, people wanted to use a tool to calculate the distances from the coordinates of the two points, which obviously won't work in DCS.

By the way, I'm not sure why you necessarily talk about ground troops. PI can be used for Strike planning for example, where squadron planners will do that, not "ground troops".

Agreed, although the INS feature was said to be created for JTACs. Doesnt matter anyway.