ZID (Indianapolis ARTCC) Primary Radar Hole

BCR

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BCR
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The plot below illustrates the primary radar "hole" experienced by ZID on 9/11 and verifies that indeed AAL77 did drop off the ZID (Indianapolis) ATC's radar screens. This contributed to the confusion over what had happened to the plane. The ZID data is from 12:38 to 13:18 (GMT).

zid_qbe_primary.jpg


ZID Primary File 1
ZID Primary File 2
ZID Primary File 3

The red circles are the returns from the QBE antenna which did record primaries for AAL77, but was not the primary (order of preference, not related to type of return) for the sort boxes involved. The last beacon return was at 12:56:57 and QBE started recording primaries for AAL77 at 12:57:09.

The QBE data is in pdf format and can be found here.
 
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While you appear, at times, to have thin skin!
I have to say, YOU DO DAMN FINE WORK! Always nice to see people that REALLY want to find answers, no matter where that may lead them. Bravo!


Have a festive Holiday Season,
DT.
 
911files said:
The plot below illustrates the primary radar "hole" experienced by ZID on 9/11 and verifies that indeed AAL77 did drop off the ZID (Indianapolis) ATC's radar screens. This contributed to the confusion over what had happened to the plane. The ZID data is from 12:38 to 13:18 (GMT).

[qimg]http://aal77.com/jref/zid_qbe_primary.jpg[/qimg]

ZID Primary File 1
ZID Primary File 2
ZID Primary File 3

The red circles are the returns from the QBE antenna which did record primaries for AAL77, but was not the primary (order of preference, not related to type of return) for the sort boxes involved. The last beacon return was at 12:56:57 and QBE started recording primaries for AAL77 at 12:57:09.

The QBE data is in pdf format and can be found here.
Click to expand...

I have to admit I have no idea what I'm looking at, would you care to explain it?
 
Actually, I don't understand it that well myself. Most of my data recovery work has been with individual radar sites such as QBE. The QBE Air Route Surveillance Radar (ARSR-3) antenna is located on top of Apple Orchard Mountain near Bedford, Virginia at an elevation of 4225 feet.

This site feeds into ZDC (Washington ARTCC) and ZID (Indianapolis ARTCC) along with many other sites. Software at ZID then takes input from the many radars which feed it and creates a composite radar output. There is a ranking assigned for these antenna’s and not all of them have the capability to only capture signals (beacon returns) which have transponder tags. In the ZID system, there are areas where the software only used the beacon-only sites for the composite and did not display the primary-only (no transponder) returns. This was something investigated by the 911 Commission in great detail.

The plot is of the ZID composite primary data (blue dots) and the QBE primary data (red circles). What it shows is that after the transponder was turned off at ~12:57 (GMT), the QBE site was recording its primary, so it was on radar. However, the software used by ZID gave preference to other radar sites in this area (radar sort box) which did not record primary returns, so the FAA controllers at ZID did NOT see the QBE primary information on their screens.

This resulted in the now famous flight paths published in the media and other places which show AAL77 with a big gap in its flight path, leading some to assert that the plane went off radar and was replaced with a drone or cruise missile. Those initial flight paths were misleading, because at no time did AAL77 drop out of radar coverage as can be seen in the plot above.

Perhaps CheapShot can fill in some of the blanks on this, but hopefully I've been able to make it a little clearer.

Update: Just to note, the plot is for all ZID primary data for the entire time segment 12:48 - 13:18 (GMT). At ~81W longitude, the ZID track for AAL77 (what is seen on the early public plots) is seen merged with the QBE track. The returns include ground clutter returns and areas with good primary coverage appear as solid blue areas.
 
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By the way, I can use some help on deciphering a few values in the primary files. Here is an example data set.

001,124800 + 370923,0802038 471.8750 121.1875

Here is what I have deciphered thus far.

001,124800 (time GMT) + 370923 (latitude),0802038 (longitude) 471.8750 121.1875

The values in bold I don't have a clue, so any thoughts?
 
They are unique to each return, but as good of a guess as any I can come up with.
 
911files said:
By the way, I can use some help on deciphering a few values in the primary files. Here is an example data set.

001,124800 + 370923,0802038 471.8750 121.1875

Here is what I have deciphered thus far.

001,124800 (time GMT) + 370923 (latitude),0802038 (longitude) 471.8750 121.1875

The values in bold I don't have a clue, so any thoughts?
Click to expand...


Can you give us 2 or 3 in sequence to see if there is any pattern in the rate/direction of change in those values?

ETA: As a wild guess, is the first bolded value a speed in kn?
 
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The FAA should have the specs on the data output fields somewhere.
 
bje said:
The FAA should have the specs on the data output fields somewhere.
Click to expand...

The requirement for radar recording is an ICAO requirement. Based on what I'm finding it must be airspeed (probably ground speed) and track. I'm still not convinced that's what the numbers are because it doesn't quite jive to carry it to that many decimal places. However, those numbers do make sense as ground speed and track for AA77 on the way back to DC....

I should have it nailed shortly......
 
Hokulele said:
Can you give us 2 or 3 in sequence to see if there is any pattern in the rate/direction of change in those values?

ETA: As a wild guess, is the first bolded value a speed in kn?
Click to expand...

#pmy1
001,124800 + 370923,0802038 471.8750 121.1875
001,124800 + 372150,0800513 483.8125 134.0000
001,124800 + 372438,0795011 495.6875 137.3125
001,124800 + 395004,0844528 262.3125 279.3750
001,124800 + 395133,0833532 316.1250 280.5000
001,124800 + 395218,0833551 315.8750 281.2500
001,124800 + 401030,0844005 266.6250 299.7500
001,124800 + 411345,0811503 422.3125 364.0625
001,124800 . 364230,0812847 418.0625 92.7500
001,124800 . 370902,0801704 474.8125 120.9375
001,124800 . 371535,0801002 480.1250 127.6250
001,124800 . 371559,0801011 480.0625 128.0625
001,124800 . 372028,0795244 493.7500 133.0625
001,124800 . 372318,0794812 497.2500 136.0000
001,124800 . 372333,0801221 478.0625 135.5625
001,124800 . 372837,0794949 495.7500 141.2500
001,124800 . 394619,0843245 272.0625 275.5625
001,124800 . 394735,0844219 264.6250 276.8750
001,124800 . 394805,0844319 263.9375 277.3750
001,124800 . 395032,0843613 269.4375 279.8125
001,124800 . 395137,0842404 278.8125

We have pretty much ruled out azimuth/range (a composite, not site specific). One might be speed, but both exceed 400 at times, so that kinda rules out heading. I just thought someone out there might have some special insight.

I opened the beacon data for ZDC and pulled some early AAL77 data. It seems to be the same format, except there is a beacon code included.

#bcn2
1 122111 6553 \ 385607 773126 244.4375 526.25
1 122123 6553 \ 385553 773203 243.875 526.0625
1 122135 6553 \ 385545 773251 243.25 525.9375
1 122147 6553 \ 385535 773349 242.5 525.75
1 122158 6553 \ 385520 773447 241.8125 525.5625
1 122210 6553 \ 385511 773554 240.9375 525.375
1 122222 6553 \ 385502 773700 240 525.25
1 122234 6553 \ 385447 773757 239.25 525.0625
1 122246 6553 \ 385437 773905 238.4375 524.875
1 122257 6553 \ 385422 774012 237.5625 524.6875
1 122309 6553 \ 385413 774108 236.75 524.5
1 122331 6553 \ 385349 774313 235.1875 524.1875
1 122341 6553 \ 385348 774421 234.3125 524.1875
1 122353 6553 \ 385339 774517 233.5 524.0625
1 122404 6553 \ 385337 774635 232.5625 524
1 122416 6553 \ 385329 774741 231.625 523.9375
1 122428 6553 \ 385320 774858 230.6875 523.8125
1 122440 6553 \ 385319 775014 229.625 523.8125
1 122452 6553 \ 385310 775130 228.625 523.6875
1 122504 6553 \ 385301 775247 227.625 523.5625
1 122516 6553 \ 385252 775413 226.5 523.4375
1 122527 6553 \ 385243 775539 225.375 523.3125
1 122539 6553 \ 385233 775715 224.125 523.1875
1 122551 6553 \ 385231 775851 222.875 523.1875
1 122603 6553 \ 385221 780037 221.5625 523
1 122615 6553 \ 385212 780202 220.375 522.9375
1 122627 6553 \ 385156 780338 219.125 522.6875
1 122639 6553 \ 385145 780524 217.8125 522.5
1 122651 6553 \ 385137 780649 216.625 522.4375
1 122703 6553 \ 385134 780825 215.375 522.375
1 122715 6553 \ 385124 781010 214 522.25
1 122726 6553 \ 385115 781156 212.6875 522.1875
1 122738 6553 \ 385112 781342 211.3125 522.125
1 122750 6553 \ 385111 781507 210.125 522.1875
1 122802 6553 \ 385108 781652 208.75 522.1875
1 122814 6553 \ 385113 781829 207.5 522.25
1 122826 6553 \ 385110 782014 206.125 522.25
1 122838 6553 \ 385109 782200 204.75 522.3125
1 122850 6553 \ 385107 782336 203.5 522.3125
1 122902 6553 \ 385111 782532 202.0625 522.375
1 122914 6553 \ 385109 782707 200.75 522.4375
1 122926 6553 \ 385107 782852 199.375 522.4375
1 122937 6553 \ 385112 783038 198 522.5625
1 122949 6553 \ 385108 783223 196.625 522.5
1 123001 6553 \ 385106 783409 195.25 522.5
1 123013 6553 \ 385103 783604 193.75 522.5
1 123025 6553 \ 385101 783749 192.375 522.5625
1 123037 6553 \ 385105 783935 191 522.625
1 123049 6553 \ 385109 784131 189.5 522.75
1 123101 6553 \ 385107 784316 188.125 522.75
1 123113 6553 \ 385104 784511 186.625 522.75
1 123125 6553 \ 385054 784656 185.25 522.6875
1 123137 6553 \ 385051 784851 183.75 522.6875
1 123148 6553 \ 385055 785046 182.25 522.75
1 123200 6553 \ 385107 785242 180.75 523
1 123209 6553 \ 385050 785350 179.9375 522.75
1 123221 6553 \ 385047 785535 178.5625 522.75
1 123233 6553 \ 385045 785730 177.0625 522.8125
1 123245 6553 \ 385040 785925 175.5625 522.75
1 123257 6553 \ 385045 790119 174 522.875
1 123308 6553 \ 385041 790324 172.375 522.875
1 123320 6553 \ 385038 790529 170.8125 522.9375
1 123332 6553 \ 385042 790714 169.375 523
1 123344 6553 \ 385038 790919 167.75 523
1 123356 6553 \ 385034 791125 166.1875 523
1 123507 6553 \ 385057 792325 156.8125 523.75
1 123519 6553 \ 385117 792521 155.25 524.1875
1 123531 6553 \ 385151 792728 153.6875 524.8125
1 123543 6553 \ 385224 792915 152.3125 525.375
1 123555 6553 \ 385251 793101 150.875 525.9375
1 123607 6553 \ 385331 793259 149.375 526.625
1 123619 6553 \ 385405 793446 148 527.25
1 123631 6553 \ 385439 793654 146.4375 527.875
1 123643 6553 \ 385513 793831 145.125 528.5
1 123655 6553 \ 385540 794029 143.6875 529.0625
1 123707 6553 \ 385620 794226 142.1875 529.75
1 123718 6553 \ 385653 794433 140.5625 530.375
1 123730 6553 \ 385727 794611 139.3125 531
1 123742 6553 \ 385754 794808 137.8125 531.5625
1 123754 6553 \ 385828 794945 136.5 532.1875
1 123806 6553 \ 385908 795153 134.875 532.875
1 123818 6553 \ 385935 795350 133.4375 533.4375
1 123830 6553 \ 385953 795537 132.0625 533.8125
1 123841 6553 \ 390003 795743 130.4375 534
1 123853 6553 \ 390007 795928 129 534.1875
1 123905 6553 \ 390002 800124 127.5625 534.125
 
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I'm tired of googling for this tonight. I'm getting close, but no cigar.

There appear to be different requirements for enroute, terminal, tower, etc. None of those requirements include lat/long position, so that has been extracted to satisfy the FOIA. So, I think you have a special format just to satisfy the FOIA as your format does not seem to follow what I'm finding in the ICAO and FAA requirements.

The end numbers in your last post ARE NOT airspeed and heading. The only other thing I can find is that they might be Volume and Record numbers, but that doesn't make sense either because they should be sequential for sequential returns.

I'm going to end my search for tonight and just say that I don't know what those numbers are. Perhaps Cheap Shot has seen similar products and might have an answer.....
 
I know how you feel about the Googling. I found nothing either. Just an FYI, the file dates are 9/11/2001 and 9/13/2001 for these files. They are obviously a data pull done the day of, or shortly afterwards for FAA purposes. They sent me limited stuff for the FOIA and it took sending them a copy of the Court order for service before they sent these files.
 
John, those number appear to be some kind of X, Y coordinate system used to arrive at the lat/long positions.

Take a look at this series of files on your site and I think you'll be better able to see what they are doing. The various symbols are also explained in these files. Basically those numbers at the end are extraneous information......

1 ZID 49 NTAP1.TXT (txt file, 15 kb)
1 ZID 49 NTAP2.TXT (txt file, 16 kb)
 
OK, after staring at those numbers for waaay too long, my second guess is that the second two numbers are a conversion from Lat/Long to some type of display coordinates (tower monitors?). As the Latitude changes, the second value, which I will call "Y", changes roughly the same amount in the same direction (higher or lower). As the Longitude changes, the first value, which I will call "X", changes roughly the same amount in the opposite direction. I am too lazy to do a full coordinate conversion at the moment, but you may want to do a simple Cartesian conversion (here we go again! ;)) and see if it makes sense.

If the scaling grids overlaid on these monitors are divided into halves, quarters, and eighths, this would make sense.


ETA: Reheat posted as I was checking values in Excel. Harumph.
 
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Hokulele said:
OK, after staring at those numbers for waaay too long, my second guess is that the second two numbers are a conversion from Lat/Long to some type of display coordinates (tower monitors?).
Click to expand...

Yep, you've got it..... except (it's the other way around) they are using the X, Y grid system to arrive at lat/long and it might be an overlay on the Radar scope or perhaps a software program to do it.....
 
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Uhm, for #pmy1 the latitude seems be be swinging around pretty wildly. Five degree swings is a lot of miles for consecutive measurements. #bcn2 seems a lot cleaner.
 
Giggywig said:
Uhm, for #pmy1 the latitude seems be be swinging around pretty wildly. Five degree swings is a lot of miles for consecutive measurements. #bcn2 seems a lot cleaner.
Click to expand...


Those are all returns for different objects at the same time stamp, rather than tracking an individual object through time (as in the second sample).


ETA: Thanks for the clarification, Reheat. I am just too used to converting from GPS Lat/Long to something else, it seems unnatural to convert to Lat/Long. :o
 
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