Questions on radar floor, range, slope, and holes

[Karl Kornel 964857]

Hello!

 

I wanted to be clear on the radar station attributes that we can provide now in EuroScope 3.1a.

 

For the radar range, for example, is that the range at the floor of the station, or at the ceiling? In other words, does the range go up with the slope, or down?

 

Also, I was wondering, for the holes in the radar, do those holes apply to specific radar sites, or do the holes apply to all radar sites?

[Todor Atanasov 878664]

It goes up. If you set the slope to 60, and the floor to 200ft, at range 150nm you will have 11000ft altitude, below which, no aircraft will be seen.

 

The holes are for all radar sites, there is no way one hole to be defined for one radar site.

[Karl Kornel 964857]

Hooray, a diagram! Thanks very much!

[Todor Atanasov 878664]

My pleasure, too 5 min do draw.

[Eivind Fosse 818131]

Regarding the radar holes:

 

I'm not an expert on radars, so correct me if I'm wrong, but is it realistic that some areas suddenly do not have radar coverage? I can see that this happens if for example a mountain is between a radar antenna and the aircraft, but then all the area behind the mountain will be in the radar shadow, and you will not receive any targets behind that mountain unless you have another radar that sees where the first radar do not see.

 

As I understand how the radar holes work: I have a radar at a given position. About 50 miles to the north I have created a radar hole that goes from GND to FL660. Any targets inside this hole will not be seen by the radar mentioned. However; a target even further north of the radar, behind the hole, at FL100 will be seen. And that is true even if the two targets will be on the same straight line from the radar..? Is my understanding of the radar holes correct? What are the purpose of these radar holes and what are they supposed to simulate?

 

Would it not be more realistic adding a “simulated mountain” feature, that will block radar signals behind the mountain?

 

Thank you

[Todor Atanasov 878664]

The "radar hole" is exactly that....a hole, where NO radar can see the track. This is not what you described What you described would be "radar obstacle", which is not simulated yet. [Mod - Happy Thoughts]ume that EuroScope is a multi radar system....not single radar

[Michael Pike]

There don't seem to be any parameters to define the hole (apart from its location). Does a hole have a standard shape and size? Is it cylindrical or conical with a certain diameter?

[Ross Carlson]

I've thought about creating radar holes for VRC as well, and one of the ideas that someone suggested to me was to have a degree of "randomness" as to when the hole actually swallows a target. This would be to simulate varying terrain around the edges of the radar hole. In other words, as a target enters the hole, his blip will appear and disappear somewhat randomly. This randomness would vary with altitude and distance from the radar head. The further the target is from the radar head, the more likely the blip is to be swallowed by the radar hole. And the lower the target's altitude, the more likely it is to disappear. Each hole could have a hard floor below which there is no chance for the target to appear. The randomness would be calculated for each radar sweep. (Each time a position packet is received from the server.)

 

I figured I'd offer the suggestion for Gergely now that ES has this (very cool) feature.

Edited January 5, 2010 at 05:42 PM by Guest

[Todor Atanasov 878664]

Michael => http://euroscope.hu/mediawiki/index.php?title=ESE_Files_Description

 

COORD:<latitude>:<longitude>
COORD:<latitude>:<longitude>

The COORD definition is identical to the one for SECTORLINEs. 

They are the shape you defined them.

 

Ross this is a nice idea, Gergely can implement it for sure.

[Michael Pike]

I've re-read the section now and apologise - I missed that last line! All is clear now thanks. Can I ask another related question?

 

I'm going to try to set up a primary only radar facility such as at EGBJ real life. I'm going to try setting the range for S and A+C mode to zero. I would then expect to see only primary radar information (since all secondary info will always be out of range). I'll report back.

[Michael Pike]

I put this line on the end of the ese file (line 6308) and reloaded...

 

RADAR:EGBJ PSR:N051.53.35.372:W002.10.3.132:30:100:60:0:0:0:0:0:0

 

It didn't like that:- "Error: Invalid keyword on line 6308". Is there something else wrong?

[Todor Atanasov 878664]

You need [RADAR] before that, I think it is missing in the Wiki, I added it.

[Gergely Csernak]

Ross, Todor,

 

Yes the randomly available positions can be added. And I do not think that it is too complicated. Meanwhile you can play with defining different altitudes for S, A+C and primary readouts. I know it is not random, but at least it shows the less and less available data.

[Michael Pike]

I'm going to try to set up a primary only radar facility such as at EGBJ real life. I'm going to try setting the range for S and A+C mode to zero. I would then expect to see only primary radar information (since all secondary info will always be out of range). I'll report back.

Everything seems fine! I used a .ese file with the [RADAR] section shown above and no other radar defined; I selected "Simulate radar range and outages"; I used C mode correlation; I used Professional radar mode in Display Settings; I used the default Matthias tag family.

 

Using the simulator to test it, I found that all radar echoes within the range showed the primary mode symbol and TSSR tag (regardless of code being squawked by the aircraft) and changed to "coasting" when out of range - all correct so far! I also found that I needed to deselect "show FP tracks" for both IFR and VFR flight plans. I found I could manually correlate a flight plan with a radar echo (no problem there) but as soon as the echo moved position the correlation dropped (as expected).

 

I also found that if I hover over an aircraft in the sector inbound list, the flight plan tag was displayed showing the calculated current altitude and position along the flight path. In real life there would not be any tags at all except the possibility of manually created ones, so I will use a tag family where all the tags contain only the scratch pad.

 

VRC came very close to simulating this with its PSR radar mode and realistic tags but I think you have finally cracked it! Thank you so much.

[Nikita Kapko 1015297]

Copy that to Wiki!

[Todor Atanasov 878664]

I can make it even better Will do.

[Michael Pike]

RADAR:EGBJ PSR:N051.53.35.372:W002.10.3.132:30:100:60:0:0:0:0:0:0

Just a further note on this primary radar simulation. I discovered that the secondary radar range is not zero in this example but "less than 1". When aircraft come within less than 1 nm of the radar position the secondary comes in. As soon as it reaches a mile away again the secondary drops out again.

 

On the subject of radar holes, would it be possible in a future version to configure a blind spot overhead the radar facility in the shape of an inverted cone with the slope of the side defined. As you know, when aircraft are very close to a radar they can disappear above the radar "beam".

[Gergely Csernak]

It is strange. There is an explicit distance < range check in the code. I will test it.

[Jean-Frederik Dion 819740]

FAQ

What is a normal slope to get realistic coverage.

What does this value depend on.

Is it the same for PSR, SSR and modeS?

[Eivind Fosse 818131]

FAQ

What is a normal slope to get realistic coverage.

What does this value depend on.

 

I asked a friend of mine, who is an Air Traffic Controller in Norway, this question and even though he did not know the answer, he told me that a few of those radars he used was actually able to look below their altitude..!

 

So I would also like an answer to what is a realistic slope...

 

Eivind

[Todor Atanasov 878664]

The cone is usual around the 70 degree and more. Every radar is different but you can find some data for some models, if you know what radars are used by your ATSA. http://www.radartutorial.eu/19.kartei/karte201.en.html

[Juha Holopainen]

FAQ

What is a normal slope to get realistic coverage.

What does this value depend on.

Is it the same for PSR, SSR and modeS?

Difficult question, as in reality the theoretical lower limit of radar coverage is not a fixed slope but a curve. A formula for it is approximately:

 

R = 1.23 * ( sqrt(h_ant) + sqrt(h_tgt) )

 

R = distance on the ground between radar antenna and target in nautical miles

h_ant = height of the radar antenna in feet

h_tgt = height of the target in feet

 

For all practical purposes the formula should be valid for all the radar types as their frequencies are not very far from each other. The question is then, how much useful information can each type receive from the edge of the radar beam? I guess this would depend on the radar system in question.

 

From the formula, a radar antenna at 0ft can see a target at 100ft if it's within a distance of 12.3nm. An antenna at 10000ft can see the same target within a distance of 135.3nm. A target at 200ft would be seen at 17.4nm and 140.4nm respectively.

 

When you specify a fixed slope for the radar, there is one point where the slope intersects the real curve (unless the slope is very extreme). At distances closer to this point, the real radar would see aircraft that your radar will not (they'll be below the fixed slope), and at greater distances your radar will see aircraft that would be below the real radar's view. Deciding the slope is then a question of at which distances the radar is wanted to show realistic information.

 

A single radar antenna can even be represented with multiple radar definitions to create a realistic slope. A low slope radar with a low range to simulate the low part of the real curve and another at the same location, but with a higher slope and a higher range to show the rest. But this creates more work when defining the radars and possible performance issues if a lot of radars are defined.

[Jean-Frederik Dion 819740]

A single radar antenna can even be represented with multiple radar definitions to create a realistic slope. A low slope radar with a low range to simulate the low part of the real curve and another at the same location, but with a higher slope and a higher range to show the rest. But this creates more work when defining the radars and possible performance issues if a lot of radars are defined.

That's a very good idea Juha, thanks for that. And for the very helpful info too.

 

Based on that, could we think of a way to make all this hard coded and [Mod - Happy Thoughts]ume we then get a realistic coverage for each antenna?

[Juha Holopainen]

No problem. Using the curve instead of the slopes would be easy in the code, but a new ese file radar definition syntax would be needed either to replace the current one or to be used as an alternate way if the old one is wanted as well.

[Juan Amado]

Hello all.

According to the question of Eiving to simulate some radar holes made by obstacles as mountains, what'd be the procedure to create this in the new radar section. We could create the radar, give the cone of silence to each one and it worked perfectly good with the new radar2 object which implements the formula of the earth curvature. The result is a perfect simulation. However we have signal on areas where due to mountains we shouldn't see any traffic.

I've seen the docs but not sure what this does.

Quote

HOLE:<P top>:<S top>:<C top>

• P top – The top of the radar hole for primary radar positions.
• S top – The top for the S-mode transponders.
• C top – The top for the C-mode transponders.

COORD:<latitude>:<longitude>
COORD:<latitude>:<longitude>

I attach a picture about what we'd like to create.

Cheers all.