LASTE CCIP/CCRP Wind Correction

[MoppleTheWhale42]

I was testing the LASTE wind correction, and therefore I have set up wind in the mission editor as follows:

   33 ft, 22 kn   0°
 1600 ft, 52 kn
 6600 ft, 34 kn  52°
26000 ft, 18 kn 325°

Temperature on ground level 20° C.

I flew 10000 ft AGL and dropped an MK-82 in CCRP mode. To my very surprise, the bomb hit with an accuracy of 2-3 meters. I repeated this several times, approaching the target from different directions. I always got very accurate hits.

Then I added wind correction in LASTE. I entered
Height 00; 180°; 22 kn;  20 °C
Height 02; 180°; 54 kn;  17 °C
Height 07; 232°; 34 kn;   7 °C
Height 26; 145°; 18 kn; -32 °C

Again I dropped an MK-82 from 10000 ft AGL. Now, the bomb missed the target by > 10 meters.

Thus, I am either doing something wrong, or LASTE is doing some auto wind correction.

What's your experience?

[Yurgon]

5 hours ago, MoppleTheWhale42 said:

Thus, I am either doing something wrong

I believe the wind is set with true headings. Depending on the map, you might be missing up to 13 degrees of magnetic variation.

A quick track might reveal that.

5 hours ago, MoppleTheWhale42 said:

or LASTE is doing some auto wind correction

It does. It constantly measures the wind and builds its own wind data information. As far as I know, entering this data manually is rarely done in real life and is reserved for situations where the wind in the target area is notably different from the aircraft's ingress direction (and is known to someone who can relay it to the pilots).

Following this topic here over the years, it seems there are basically 2 factions: those who swear that entering wind data manually is absolutely required and necessary and improves their accuracy by a large margin, and those who just stick with whatever the jet measures.

[jaylw314]

1 hour ago, Yurgon said:

I believe the wind is set with true headings. Depending on the map, you might be missing up to 13 degrees of magnetic variation.

A quick track might reveal that.

It does. It constantly measures the wind and builds its own wind data information. As far as I know, entering this data manually is rarely done in real life and is reserved for situations where the wind in the target area is notably different from the aircraft's ingress direction (and is known to someone who can relay it to the pilots).

Following this topic here over the years, it seems there are basically 2 factions: those who swear that entering wind data manually is absolutely required and necessary and improves their accuracy by a large margin, and those who just stick with whatever the jet measures.

I wonder how much the DCS A-10C does the automatic LASTE wind correction calculations?  Is there a difference, say in starting a mission in the air and dropping bombs vs taking off and then dropping bombs?  Presumably in the 2nd situation, the LASTE would have the data to correct for wind and temps at different altitudes as you climb, whereas in a air start, it wouldn't.  These are the sort of things I should probably test but am too lazy to get around to it, since we can just lob GBU-54's at targets anyways

 

[WobblyFlops]

Winds in DCS are confusing as hell. The briefing and the mission editor shows you the direction the wind is blowing to as opposed to what everyone uses; where it's blowing from. I can see that you know this, which is good. Someone mentioned true north, which is incorrect. In DCS, the mission editor shows grid north as opposed to true north. What you're likely missing is described here and that's the wind compensation between layers: https://forums.eagle.ru/topic/103956-cdu-wind-correction-done-right/ The last page describes a step by step process that will allow you to do it right, although as mentioned earlier, this is very rarely if ever done in the real aircraft.

 

 

[Yurgon]

19 hours ago, jaylw314 said:

I wonder how much the DCS A-10C does the automatic LASTE wind correction calculations?

As far as I'm aware, it has a magic knowledge of the current wind at all altitudes, regardless of air start of runway start. Seeing as real aircraft don't magically appear mid air, unless they're visitors from Mars or Alpha Centauri or whatever, it wouldn't make much sense for DCS to populate the IFFCC/CADC with an empty set of data for air-starts, me thinks. But truth be told, I haven't tested it either, so if you do, let us know what you find out.

11 hours ago, WobblyFlops said:

Someone mentioned true north, which is incorrect. In DCS, the mission editor shows grid north as opposed to true north.

Good to know, thanks!

Do you know how much of a deviation that makes for us in the current maps? I assume when we talk about wind directions in DCS, it doesn't actually have any impact, or does it? If I understand the difference correctly, this would only manifest itself when comparing a real life, true-north oriented map with a DCS map, right?

[Frederf]

My understanding is that LASTE measures atmosphere on the way up (and an air start may assume that you climbed to get there) and it also will interpolate downward. E.g. if it's X knots at Y altitude then linear decrease to 0 knots at some negative altitude (like -4000' or so). If one was truly determined one could take off without any computers switched on and then only turn them on at altitude. Then with some drastic wind shift below it may be able to be tested if LASTE magically knows this. I somehow doubt that it's quite that detailed. I have input false LASTE atmo info and gotten the corresponding error in aiming but the rest deserves test.

The concept of "north" is a bit wiggly in DCS. Ruler direction is used as true heading for all purposes even though it doesn't not run parallel to the lines of longitude. Almost certain that LASTE pilot info would be in magnetic.

[WobblyFlops]

10 hours ago, Yurgon said:

Do you know how much of a deviation that makes for us in the current maps? I assume when we talk about wind directions in DCS, it doesn't actually have any impact, or does it? If I understand the difference correctly, this would only manifest itself when comparing a real life, true-north oriented map with a DCS map, right?

That is true, I only corrected it because when it comes to navigation, there will be some level of inaccuracy when compared to real maps. I've never done any tests so unfortunately I can't give you an exact number or anything more tangible other than this thread: https://forums.eagle.ru/topic/105862-calculate-angle-distances-between-locations

 

[Yurgon]

2 hours ago, WobblyFlops said:

That is true, I only corrected it because when it comes to navigation, there will be some level of inaccuracy when compared to real maps.

Good point!  

[MoppleTheWhale42]

Thank you guys for this very interesting discussion. As a bottom line, I would say that it is not worth to program the wind into LASTE, but to rely on the A-10 to measure the wind.

 

Regarding the difference between geographic north and true north, this depends on your location and, as the magnetic north pole is wandering, it also depends on the date. For the Caucasus, the difference is about 6 degrees. On the graphic, you can see the difference back in 2015 for the whole world.

 

[jaylw314]

On 2/22/2022 at 5:57 AM, WobblyFlops said:

Winds in DCS are confusing as hell. The briefing and the mission editor shows you the direction the wind is blowing to as opposed to what everyone uses; where it's blowing from. I can see that you know this, which is good. Someone mentioned true north, which is incorrect. In DCS, the mission editor shows grid north as opposed to true north. What you're likely missing is described here and that's the wind compensation between layers: https://forums.eagle.ru/topic/103956-cdu-wind-correction-done-right/ The last page describes a step by step process that will allow you to do it right, although as mentioned earlier, this is very rarely if ever done in the real aircraft.

 

 

Wait, I thought grid zones were aligned with true north, so they should be the same? 

[Frederf]

He's using "grid north" to mean XYZ coordinate or ruler north. Grid north is a generic term to describe the reference direction of any grid system. MGRS or UTM grid north is a specific example. And I haven't checked but UTM grid north, XYZ grid north, and latitude-longitude grid north should be three separate directions. In real life UTM grid north is not exactly aligned with true north.

[jaylw314]

2 hours ago, Frederf said:

He's using "grid north" to mean XYZ coordinate or ruler north. Grid north is a generic term to describe the reference direction of any grid system. MGRS or UTM grid north is a specific example. And I haven't checked but UTM grid north, XYZ grid north, and latitude-longitude grid north should be three separate directions. In real life UTM grid north is not exactly aligned with true north.

Oooh, I hadn't thought about the ruler/XYZ north, I was just turning my eyeballs to follow the grid squares

I still don't get how UTM north would be different from lat/long north, though; I mean, the grid zones are DEFINED by the 6 deg lines of longitude, right?

[Frederf]

This is a good question which took me a while to answer. The lateral extent of each UTM zone is defined by lines of longitude but the grid orientation and metric interval associated with each zone is not. Grid north is the direction on the map which increases northing without changing easting. UTM grids are constant in size and spacings of longitudes are not. Thus lines of constant easting and lines of constant longitude can't be parallel.

Longitudes are fractional as in 10°30' is half way between 10° and 11° regardless of how much distance separates them. UTM grids are not, an easting is 100,000m lateral regardless of how far spaced longitudes are.

[jaylw314]

On 2/24/2022 at 11:31 AM, Frederf said:

This is a good question which took me a while to answer. The lateral extent of each UTM zone is defined by lines of longitude but the grid orientation and metric interval associated with each zone is not. Grid north is the direction on the map which increases northing without changing easting. UTM grids are constant in size and spacings of longitudes are not. Thus lines of constant easting and lines of constant longitude can't be parallel.

Longitudes are fractional as in 10°30' is half way between 10° and 11° regardless of how much distance separates them. UTM grids are not, an easting is 100,000m lateral regardless of how far spaced longitudes are.

Oookay, I think I get it now.  At the east/west edges of each grid zone, the northing lines don't quite line up with true north, they actually overlap a bit, since there's no way to paste 100,000m flat squares on a round surface.

I was just thinking about the whole grid zone itself is aligned with true north, but that's only true in the middle, then