Jump to content

The new radar ground clutter is amazing!


asla36

Recommended Posts

Thank you so much! Now it really feels like ground clutter, and not weather anymore!

 

I get that this is a pointless thread, but I just wanted to express my gratitude for the changes. It feels amazing!

 

Also a question: is this in any way related to the new ED radar tech?

 

Thanks in advance for the reply!

  • Like 1

DCS: MiG-23

[sIGPIC]

[/sIGPIC]

Make it happen, and take my money! :D

Link to comment
Share on other sites

The ground clutter is now displayed when inverted, or there is hill in front, etc.

Before we had it only as sidelobe noise.

 

It used to do this in previous builds, but the effect disappeared when the radar got broken a while back. Pity the clutter is still 'fuzz' rather than actual false returns as seen in the F-5's radar, but this fix is definitely a big improvement on the previous state of affairs.

Link to comment
Share on other sites

@Nerd1000

 

Yes, the clutter should be made out of - & I, however there is also blooming effect (crt brightness side effect) when you have a lot of ground return. This is what we see with those "fuzz" as you mentioned.

True, it would been nice to have it done properly.

 

(ground clutter of RP21: http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm )

  • Like 3
Link to comment
Share on other sites

@Nerd1000

 

Yes, the clutter should be made out of - & I, however there is also blooming effect (crt brightness side effect) when you have a lot of ground return. This is what we see with those "fuzz" as you mentioned.

True, it would been nice to have it done properly.

 

(ground clutter of RP21: http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm )

Thanks for posting this link. I've read the real pilots manual and had seen the schematics but seeing a real pictures is much better. Great find :thumbup:

 

If I get it correctly at low altitudes the radars screen should fill-in with false returns from the ground. Also the closer to the ground the more of the radar screen should be filled with the ground clutter.

The DCS implementation from the visual perspective is quite an opposite - though the result is generally the same (not being able to recognize the target). Rather than clutter being dynamic in size and masking the target return (which is still there) what we have is the target disapering on a clean screen while the clutter is a fixed ~1 cm line at the bottom.

Looking forward to check how the new radard implementation works!

F/A-18, F-16, F-14, M-2000C, A-10C, AV-8B, AJS-37 Viggen, F-5E-3, F-86F, MiG-21bis, MiG-15bis, L-39 Albatros, C-101 Aviojet, P-51D, Spitfire LF Mk. IX, Bf 109 4-K, UH-1H, Mi-8, Ka-50, NTTR, Normandy, Persian Gulf... and not enough time to fully enjoy it all

Link to comment
Share on other sites

@Nerd1000

 

Yes, the clutter should be made out of - & I, however there is also blooming effect (crt brightness side effect) when you have a lot of ground return. This is what we see with those "fuzz" as you mentioned.

True, it would been nice to have it done properly.

 

(ground clutter of RP21: http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm )

 

Very interesting website. Thanks! :thumbup:

Intel i7-12700K @ 8x5GHz+4x3.8GHz + 32 GB DDR5 RAM + Nvidia Geforce RTX 2080 (8 GB VRAM) + M.2 SSD + Windows 10 64Bit

 

DCS Panavia Tornado (IDS) really needs to be a thing!

 

Tornado3 small.jpg

Link to comment
Share on other sites

Just did some testing, seems that the radar is finally horizon stabilized, that the antenna tilt filter is working again and they indeed increased the clutter when you are getting ground returns from a hill or clouds. Even if the radar is horizon stabilized thought, when i point my nose to the ground (shallow dive, -10°) i get more clutter then when i'm level (i tested it for a couple of different altitude and observed the same behavior), now i think the antenna can tilt up and down more then 10°, so that would be wrong.

  • Like 1

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

Just did some testing, seems that the radar is finally horizon stabilized, that the antenna tilt filter is working again and they indeed increased the clutter when you are getting ground returns from a hill or clouds. Even if the radar is horizon stabilized thought, when i point my nose to the ground (shallow dive, -10°) i get more clutter then when i'm level (i tested it for a couple of different altitude and observed the same behavior), now i think the antenna can tilt up and down more then 10°, so that would be wrong.

 

Nice info, thanks !

 

Some screens would be welcome to illustrate ;)

Helljumper - M2000C Guru

 

Helljumper's Youtube

https://www.youtube.com/channel/UCK3rTjezLUxPbWHvJJ3W2fA

Link to comment
Share on other sites

The effect breaks off at ~12k feet, wich makes sense since this is about the altitude where clutter starts to disapear alltogether. Same altitude as another Mig-21 flying in front (to test for antenna stab).

 

attachment.php?attachmentid=169086&stc=1&d=1505239735

 

Level, the contact is in the clutter a little bit to the left.

 

attachment.php?attachmentid=169087&stc=1&d=1505239735

 

10° dive, contact is still there, in the clutter, but i've got returns from the ground, far.

 

attachment.php?attachmentid=169090&stc=1&d=1505240675

 

20°, contact is still here, clutter all over the place.

 

It all depends on how much the antenna can tilt up and down and how big the cone is, the "radar field was limited to 20° vertically" taken from wikipedia page on the RP-21, not sure if it's cone + tilt or just tilt, is it 10° up, 10° down tilt only,..... Many questions :D.

 

EDIT : Two screenshots are gone for good :/


Edited by Rex854Warrior

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

Radar is not older RP-21 (Spin Scan) but is new RP-22 (Jay Bird). The RP-21 had a scan pattern that was fixed relative to the airframe. It had up to 3 lateral bars about which the conical spinning beam traversed.

 

The RP-22 is different having no rotation to its pattern, 10 lines of scanning (5 interleaved with 5), and this pattern was stabilized relative to the horizon within antenna limits.

 

The RP-22 antenna is mechanically limited to approximately 60 degrees in traverse and 60 degrees elevation. In the normal scan mode only a portion of this solid angle is searched, roughly a 60 degree wide, 20 degrees tall wedge. Mostly this scan zone is pointed above the horizon with a small extent vertically below. The lower altitude filters would reduce sensitivity and in the lowest alt filter also shift the scan pattern totally above the horizon. The limits of antenna axis (in scan) are actually 28° from center laterally and the vertical range of 17°40'. The zone which targets may be detected in is slightly larger than this as the beam itself has some width (~3°).

 

The radar may track a 16m^2 target at 15km (MiG-21 being 3m^2 for comparison). Assuming an R^4 range relationship being 3/16th the size would be tracked at (3/16)^1/4 distance (65.8%, 10km). A B-52 having 100m^2 RCS would have a simple math improvement of (100/16)^1/4 power (158%).

 

https://www.flightglobal.com/FlightPDFArchive/1978/1978%20-%200515.PDF (and ...516.PDF)

 

Jay Bird

Late-model MiG-21s carry a more advanced radar than the Spin Scan fitted to earlier aircraft. The Nato reporting name Jay Bird may refer either to the operating frequency, which lies in J-band, or to the Fishbed J (MiG-21MF), which first carried the set. Jay Bird operates at three different PRFs: 1,592-1,792 pulses/sec, 2,042-2,048 and 2,716-2,724. For search operations the antenna performs a raster scan at between 2.9 and 3.6 scans/sec. Lobe switching is used when tracking targets. Unlike Western radars of similar vintage, Jay Bird does not use pulse-compression techniques to improve the resolution. US sources claim that, like all current Soviet Al radars, it cannot reliably distinguish low-altitude targets and ground clutter.

 

 

Average 3.25 scans per second means lateral bars. As each half-scan consists of 5 sweeps at different elevations it would take approximately 1.5s or 3.1s for all 10 bars. As 17.67 degrees is nearly exactly covered by 5 bars of 3 degree width it's likely to detect a target each half-scan within the scan region.

 

The intermediate filter "may be insufficient if target is <3000m and in mountainous terrain" to the extreme low altitude filter which raises the bottom of the scanning by ~3° to above the horizon. From there the primary limitation in radar use is safety when flying beneath a low altitude target.


Edited by Frederf
  • Like 2
Link to comment
Share on other sites

Radar is not older RP-21 (Spin Scan) but is new RP-22 (Jay Bird). The RP-21 had a scan pattern that was fixed relative to the airframe. It had up to 3 lateral bars about which the conical spinning beam traversed.

 

The RP-22 is different having no rotation to its pattern, 10 lines of scanning (5 interleaved with 5), and this pattern was stabilized relative to the horizon within antenna limits.

 

The RP-22 antenna is mechanically limited to approximately 60 degrees in traverse and 60 degrees elevation. In the normal scan mode only a portion of this solid angle is searched, roughly a 60 degree wide, 20 degrees tall wedge. Mostly this scan zone is pointed above the horizon with a small extent vertically below. The lower altitude filters would reduce sensitivity and in the lowest alt filter also shift the scan pattern totally above the horizon. The limits of antenna axis (in scan) are actually 28° from center laterally and the vertical range of 17°40'. The zone which targets may be detected in is slightly larger than this as the beam itself has some width (~3°).

 

The radar may track a 16m^2 target at 15km (MiG-21 being 3m^2 for comparison). Assuming an R^4 range relationship being 3/16th the size would be tracked at (3/16)^1/4 distance (65.8%, 10km). A B-52 having 100m^2 RCS would have a simple math improvement of (100/16)^1/4 power (158%).

 

https://www.flightglobal.com/FlightPDFArchive/1978/1978%20-%200515.PDF (and ...516.PDF)

 

Jay Bird

Late-model MiG-21s carry a more advanced radar than the Spin Scan fitted to earlier aircraft. The Nato reporting name Jay Bird may refer either to the operating frequency, which lies in J-band, or to the Fishbed J (MiG-21MF), which first carried the set. Jay Bird operates at three different PRFs: 1,592-1,792 pulses/sec, 2,042-2,048 and 2,716-2,724. For search operations the antenna performs a raster scan at between 2.9 and 3.6 scans/sec. Lobe switching is used when tracking targets. Unlike Western radars of similar vintage, Jay Bird does not use pulse-compression techniques to improve the resolution. US sources claim that, like all current Soviet Al radars, it cannot reliably distinguish low-altitude targets and ground clutter.

 

 

Average 3.25 scans per second means lateral bars. As each half-scan consists of 5 sweeps at different elevations it would take approximately 1.5s or 3.1s for all 10 bars. As 17.67 degrees is nearly exactly covered by 5 bars of 3 degree width it's likely to detect a target each half-scan within the scan region.

 

The intermediate filter "may be insufficient if target is <3000m and in mountainous terrain" to the extreme low altitude filter which raises the bottom of the scanning by ~3° to above the horizon. From there the primary limitation in radar use is safety when flying beneath a low altitude target.

 

very intresting, that explains the clutter when diving then (if i understood well).

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

Sorry to burst your joy bubble, but ground clutter in the Mig continues to be as unreal as it used to be. It shouldn't be a yellow glowing stain on the scope, but a bunch of false contacts that should dinamically be affected by terrain geometry - as somebody already stated on this thread.

 

BST F-5 did an excellent modelling of ground clutter for the APQ-159, for example.

 

Regards!



Link to comment
Share on other sites

Sorry to burst your joy bubble, but ground clutter in the Mig continues to be as unreal as it used to be. It shouldn't be a yellow glowing stain on the scope, but a bunch of false contacts that should dinamically be affected by terrain geometry - as somebody already stated on this thread.

 

BST F-5 did an excellent modelling of ground clutter for the APQ-159, for example.

 

Regards!

 

It is affected by hills and moutains. i'll report on Mantis hub the clutter not being correctly represented.

 

And BST, while modelling the ground clutter nicely, forgot about clouds and chaffs ^^.


Edited by Rex854Warrior

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

It is affected by hills and moutains. i'll report on Mantis hub the clutter not being correctly represented.

 

And BST, while modelling the ground clutter nicely, forgot about clouds and chaffs ^^.

 

Last time I checked (it was long ago, I admit), clouds representation in the Mig was pretty random, like it just read how broken the sky was and then adjust "stain density" accordingly, but randomly distributed. It didn't work well with dynamic weather. I don't know if in the meantime they've reprogrammed the whole thing to read actual cloud positions, I doubt it though.

 

Regards


Edited by amalahama



Link to comment
Share on other sites

Last time I checked (it was long ago, I admit), clouds representation in the Mig was pretty random, like it just read how broken the sky was and then adjust "stain density" accordingly, but randomly distributed. It didn't work well with dynamic weather. I don't know if in the meantime they've reprogrammed the whole thing to read actual cloud positions, I doubt it though.

 

Regards

 

Clouds are not synced properly in multiplayer, that's why it doesn't really work, but in singleplayer, it's kinda working, most of the clouds appear, but of course it's not perfect,

 

attachment.php?attachmentid=169145&stc=1&d=1505336965

 

without weather filter,

 

attachment.php?attachmentid=169144&stc=1&d=1505336965

 

with weather filter,

 

Way better then it used to be.

 

Goodnight, Rex.

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

so the scan pattern is one of the two attached?

 

"B" I think. Lock on scan similar except compressed in azimuth.

 

Unknown how ground clutter works with RP-22. I have seen scattered dots from RP-21 but it has a different beam pattern (spinning). It should be remembered that RP-21 used multiple altitude indication ticks where more ticks means farther from the center vertically. For a point target like an airplane the RP-21 might show a "comb" of elevation ticks but RP-22 would only show one. Thus much of the visual clutter is from these elevation marks, not the returns themselves. RP-22 might show several individual ticks spaced laterally for a very wide target return but fewer overall. http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm

 

When the beam is directed above the horizon the only clutter contacts are those from the side lobe forming a thin layer at the bottom of the scope (fig. 52). They have the level marks as they are being detected by the middle sweep of the radar's main lobe. In the upper sweep not shown as side lobe is sufficiently redirected (would appear farther up the scope as the side lobe would hit the ground farther away). And since this is the strongest filter setting the lower sweep is deleted entirely.

 

The RP-22 in comparison does not have 2-3 sweeps but 10. The result should be that side lobe ground return would occur in up to 10 bands (ranging anomalies notwithstanding). At lowest sweep side lobe clutter would be strongest and near the bottom of the scope having only single "below" ticks. The next sweep's side lobe clutter band would be at a farther range corresponding to where the side lobe struck the earth and take on the tick marks associated with the main lobe's sweep ("below" or both).

 

Each successively higher main sweep would have a side lobe return at a farther range and at less intensity. The intensity would also be less off azimuth as it is effectively a shallower grazing angle and longer range. At some point the side lobe would not return strongly enough to display on the scope being either too shallow a grazing angle and/or too great a range. It's also expected that lower grazing angles give more spread in range extent as the beam represents a greater diversity of distances.

 

The maximum number of side lobe return layers would be 10 if it is the case the side lobe would make a strong return when the main lobe is in all 10 of its sweep positions. Unless the side lobe angle is very large this is unlikely while main lobe is horizon stabilized as the main lobe is pointed quite high at the highest sweep and the side lobe is probably pointed above the horizon, level, or slightly below.

 

Main lobe is much higher power than side lobe and would produce ground returns at less favorable geometry (shallow graze, long range). Thankfully the beam is rarely pointed at the ground, to an extent about 3 degrees in normal scan volume (-1.5 antenna position and 1.5 beam radius). The lowest filter puts the beam axis at +1.5 so the lower limb of beam would be at ~0 with the horizon.

 

Not all of the surface is equal reflection and there are multi/indirect path effects possible with corresponding shifts in return range/azimuth from true. This is potentially the most complex aspect of clutter.

 

This is a long way to say I don't know what the ground clutter should look like exactly. It stands from geometrical argument that particular angles of beam returns will appear at long range before reducing in range at lower height by virtue of reducing distance. When beam returns are shown depends on their strength with shorter range and steeper incidence causing a greater effect. Main beam generates return before side lobe given the same geometry due to its greater power. If clutter begins at long range or near range depends which displays first, strong main beam shallow to distant or weak side lobe steep to near terrain.

 

Shader-based radar rendering is probably prohibitively expensive of computing resources. The most practical simulation for modeling is probably to mimic the subjective experience and variation with a few conditions such that the DCS user pilot capability is similar to the real pilot's.

 

My understanding of the subjective experience of clutter isn't that the desired target is entirely invisible in a solid glow of return, but usually it's visible among so many other lookalikes to be impractical. The tracking method takes much longer into clutter, may lock onto a clutter, or may fail entirely.

 

What I think is lacking currently is all the clutter "stamps" are too few in variety (one?) and easily distinguishable from an airplane return. If the stamps were much more varied (10-30 stamp shapes) and similar in appearance to real contacts it could be a real chore to separate clutter from desired return.

 

Clutter generation due to terrain (dirt, clouds, water, chaff, etc.) might be able to be somewhat randomized with or without some monte carlo ray casting to terrain. You'd want the clutter to persist enough that it didn't just twinkle rapidly which would be easy to distinguish. Real clutter would be semi-permanent at least on the PRF time scale.

 

The filters should also have a real effect on detection range to be meaningful subjectively. The cloud or middle alt filter reduce sensitivity and thus overall performance. Really even at high altitude a B-52 and MiG-21 should not be detected equally out to 30.00km.

 

At lower altitude clutter presumably fades in say in 6km to 3km alt which the middle filter solves almost perfectly. Below 3km the main lobe hitting the ground (and side lobe from the lowest sweep) produce clutter despite the reduced sensitivity of the filter. At the lowest filter setting clutter should be practically solved except for a small band of side lobe clutter very close in front at the expense of losing the bottom of the normal scan volume (rising terrain notwithstanding). The limitation of engaging at the lowest altitudes should be the safety of not hitting the ground while under flying your intended target, not clutter. Steep pitches which disallow the normal scan volume from staying above the -3 horizon line should produce tons of clutter as the main beam is steeply striking the surface.

 

This has been another aimless yak. Any information that happens to be true is purely accidental. Your mileage may vary. Floss daily.

Link to comment
Share on other sites

Would be nice to hear something from Dolphin about this issue. I mean he's flying the real thing and therefore should know how it should be.

Intel i7-12700K @ 8x5GHz+4x3.8GHz + 32 GB DDR5 RAM + Nvidia Geforce RTX 2080 (8 GB VRAM) + M.2 SSD + Windows 10 64Bit

 

DCS Panavia Tornado (IDS) really needs to be a thing!

 

Tornado3 small.jpg

Link to comment
Share on other sites

Clouds are not synced properly in multiplayer, that's why it doesn't really work, but in singleplayer, it's kinda working, most of the clouds appear, but of course it's not perfect,

 

It looks OK then! A bit blocky, but at least it seems to take into account the actual clouds position!

 

Shader-based radar rendering is probably prohibitively expensive of computing resources. The most practical simulation for modeling is probably to mimic the subjective experience and variation with a few conditions such that the DCS user pilot capability is similar to the real pilot's.

 

My understanding of the subjective experience of clutter isn't that the desired target is entirely invisible in a solid glow of return, but usually it's visible among so many other lookalikes to be impractical. The tracking method takes much longer into clutter, may lock onto a clutter, or may fail entirely.

 

What I think is lacking currently is all the clutter "stamps" are too few in variety (one?) and easily distinguishable from an airplane return. If the stamps were much more varied (10-30 stamp shapes) and similar in appearance to real contacts it could be a real chore to separate clutter from desired return.

 

Clutter generation due to terrain (dirt, clouds, water, chaff, etc.) might be able to be somewhat randomized with or without some monte carlo ray casting to terrain. You'd want the clutter to persist enough that it didn't just twinkle rapidly which would be easy to distinguish. Real clutter would be semi-permanent at least on the PRF time scale.

 

Ey great post! Just to note, shader based radar rendering shouldn't be such a big sucker, and in fact ED will follow that approach for the Hornet. It just renders the scene with different material properties and different camera and light position, and then geometrically transform the image into a polar projection using relatively heavy algorithms, but shouldn't be a big issue for GPUs.

 

And ground clutter as pure ground return is not a big deal either, no need to randomize; in a first shot it can be considered that ground return gain is high enough as to ignore normal angle or terrain type, specially for an air-to-air radar which not too much detail is expected. A more sophisticated raycasting system like the one implementing in the Viggen, which considers terrain type and geometry for the Mig-21 would be an overkill, in my opinion.

 

A different story is to model ground return from sidelobes though...

 

Regards



Link to comment
Share on other sites

BST F-5 did an excellent modelling of ground clutter for the APQ-159, for example.

 

I disagree..

 

-The Clutter points are all the same size, shape and intensity

-No Chaff or cloud clutter

-Theres no CRT glow effect

-The return of any aircraft is the same. (RCS isn't factored in the render)

-I dont think there is a 'visible beam sweep', but it only looks like there is one because of the azmiuth scan sweeping across clutter (if that makes sense) (heres what I'm takling about http://i.imgur.com/XXNjD6e.gifv it only looks like a visible line but only because our brains interpret the line. But in places where theres no clutter you shouldn't see the bar.

 

You can only see one sweeping bar in all the APQ-159 images, but it may just be clutter being highlighted at that moment.

nwaLUAv.jpg

 

This is what I think the APQ-159 should look like, based on the above images.

5pGk0EV.png


Edited by Beamscanner
Link to comment
Share on other sites

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...