Military Depot - Giant Circle Next To Runway

On another ATS discussion someone was talking about an underground tunnel they heard existed at a military site in Herlong California. Since I wasn't aware of the base I thought I'd take a look on Google maps. You could see right away that there was a base there and the base appears to serve as an ammo depot. After looking at the site for a while I noticed a very large circular area that appeared to be leveled out next to the base's runway. You can see that there's a road leading from the runway to the center of the circle and back. Here's what I'm referring to...

External Link

Has anyone seen anything like this near any other military runways? I don't recall ever seeing anything like that nor can I come to any concrete conclusions about its purpose. It certainly doesnt appear to be natural, and why a road would exist that leads to just the middle seems strange.

Having been based at quite a few different airbases around the world I think what you are looking at is a compass swing pad which is what is used by Avionic technicians to test the compasses and assiciated systems on A/C.

Sv...Out!

Originally posted by Silentvulcan
Having been based at quite a few different airbases around the world I think what you are looking at is a compass swing pad which is what is used by Avionic technicians to test the compasses and assiciated systems on A/C.

Can you provide the location of any other bases that have what you're speaking of?

Nearly every military or civillian airbase will have a compass swing pad or designated area, whatever country they are in!

Having spent 26 years in the RAF I have seen these pads at every base I have ever been on or detached too!

Nothing sinister...just somewhere where A/C systems are calibrated.

SV...Out!

Looks like minature cricket field!

the correct term is a "compass rose"....and this pic isnt one of those. that's not a taxiway leading up to the area in question, it's a small vehicle type road, and a compass rose would have a line for evey ten degrees of the compass....IOW you would see 60 lines inside the circle. my question is where exactly is this? because i dont see anything that even resembles an airport anywhere near this runway. i'm thinking that the c5 sitting at the hold short line is there for effect, and that this is a mock up for practicing airfield attacks.

Originally posted by snafu7700
my question is where exactly is this? because i dont see anything that even resembles an airport anywhere near this runway.

The answer to your question is in the very first post. The runway in question is located in Herlong California on a military ammo depot site.

[edit on 4-11-2006 by amehrich]

If I'm not mistaken I believe it is a clear zone for munitions and solid rocket fuel which this base was used to dispose of. (Sierra Army Depot / Amedee Airfield
Herlong, CA)

Originally posted by Always Trust_no1
If I'm not mistaken I believe it is a clear zone for munitions and solid rocket fuel which this base was used to dispose of.

Thanks for the post. Can you please elaborate on what a "clear zone" is used for? I'm not familiar with that term.

Originally posted by Daedalus3
Looks like minature cricket field!

Oh yes, but since when have the yankees been able to play that wonderful sport (not a fan myself, don't even know the rules, just seemed like a nice thing to say)

It's a Compass Swing Pad (no this isn't a compass rose)

Here's the specs on them (from Britain)...notice the size of the area:
www.casa.gov.au...

They're mentioned on commercial airport sites -- also called "compass calibration pads"
members.tripod.com...

(there's a lot of other sites with examples of this and rules for it, etc, etc.) So it's a perfectly ordinary thing at a lot of airports. They may be drawn on pavements with a paved area for the plane to taxi up to or they may be off to one side.

Byrd, interesting find...

Having read through some of that content my conclusion is that it's not a compass swinging site. Here's a quote from the pdf link you posted...

"A Compass Swinging Site is a prepared area, with minimum magnetic abnormalities,
on which an aircraft may be oriented (or swung) to various headings, for the purpose of
checking the aircraft on-board compass system(s), including the standby compass."

How can an aircraft be oriented in that circle when only a narrow paved road leads to it? Zoom in as close you can to the access road and you'll see that both sides of the road appear unmaintained unlike the circle itself. Do you think they would drive million dollar planes through unmaintained terrain to orient a compass? I would think not.

Originally posted by Byrd


They're mentioned on commercial airport sites -- also called "compass calibration pads"

that may be what theyre called in australia, but in the states they are "compass roses."

heading calibration
A final installation step is to perform a heading calibration. Heading calibration compensates for any magnetic field created by the aircraft. It consists of putting the unit in calibration mode, and rotating the vehicle in a circle. Most airports have a compass rose, which is the best place to perform the calibration. Unlike some other heading systems, you do not need to position or point the plane in any specific direction. Just turn at least one complete circle while in the calibration mode.

they are circles with lines every 10 degrees. the aircraft lines up with that line to calibrate his compass or other navigation equipment. they are all pretty much uniform in design, and the pic in the first post could not possibly be one.

edit: finally found what i was looking for. this is the definition from the airman's information manual (aim) glossary:

"compass rose: a circle, graduated in degrees, printed on some charts or marked on the ground at an aiport. it is used as a reference to either true or magnetic direction."

source

[edit on 4-11-2006 by snafu7700]

Originally posted by amehrich

The answer to your question is in the very first post. The runway in question is located in Herlong California on a military ammo depot site.

sorry, i missed that part, but now i understand.....this is a hazardous cargo loading area, which is why it seems to be out in the middle of nowhere.