Note the last 3 paragraphs. I can't tell you how many times I've seen folkks use the wrong projection or datum, (usually both) or the wrong UTM Zone or even hemisphere! I wonder if the Iranian skipper just plain goofed.

Bot



Standoff Over Britons Held in Iran Escalates

By ALAN COWELL
Published: March 28, 2007

LONDON, March 28 — Britain today escalated its dispute with Iran over the capture of 15 British naval personnel by revealing charts, photographs and previously secret navigational coordinates purportedly proving that the British sailors were 1.7 nautical miles inside Iraqi waters when they were seized six days ago.

“It is now time to ratchet up international and diplomatic pressure” on Iran to demonstrate its “total isolation,” Prime Minister Tony Blair told parliament after the Royal Navy made public details of what it said was the sailors’ position when they were apprehended.

The Royal Navy rejected two sets of coordinates provided by Iran as evidence of Tehran’s claim that the British sailors had strayed into its territorial waters.

The publication of the British data followed a warning by Mr. Blair on Tuesday that the dispute would enter a “different phase” if the sailors were not released.

Iran has not so far permitted British officials to visit the 15 sailors, who include a 26-year-old woman, and has refused to say where they are being held. In parliament on Wednesday the Prime Minister called the seizure of the British personnel “completely unacceptable, wrong and illegal” and renewed calls for their immediate return.

Vice Admiral Charles Style told a news briefing in London that British authorities “unambiguously contest” Iranian assertions that the sailors were in Iranian waters.

He accused Iranian forces of ambushing the group of British naval personnel, which included seven Royal Marines and eight sailors. After the news briefing, Vice Admiral Style did not offer to answer questions.

He said that, in secret diplomatic contacts, Iran had produced two conflicting sets of coordinates to support its case, the first placing the British soldiers in Iraqi waters.

Britain says that the sailors were on a routine anti-smuggling patrol authorized by the United Nations and the Iraqi government.

Sky News broadcast what it said was a statement from the Iranian Embassy here, saying Iran said it has “sufficient evidence” to prove that the British sailors had penetrated 0.5 kilometers — roughly 500 yards — into Iranian waters.

Vice Admiral Style said the British boarding party, in two inflatable boats, had boarded an Indian-flagged naval vessel on March 23 after observing it unloading cars.

He said the boarding took place at these coordinates: 29 degrees 50.36 North, 04 degrees 43.08 west. That placed it 1.7 nautical miles — almost two miles on land — inside Iraqi waters.

In diplomatic contacts, Iran had provided Britain with an initial set of coordinates for the position of the boats that placed the incident in Iraqi waters.

“We pointed this out to them on Sunday in diplomatic contacts,” Vice Admiral Style said. “After we did this they then provided a second set of coordinates that places the incident in Iranian waters” over two nautical miles away from where they were said to be by Britain, he said.

“It is hard to understand a legitimate reason for this change of coordinates,” he said.

I was taught about Datums (sic?) in Air Force GPS school, but that was 3 days long, and light on content. Never heard of projections though.

I **never** see mention of it in any of the civilian GPS's that I see - maybe its in the instrcutions (I dont currently own a GPS myself...save my blackberry =)

Maybe a poll is in order, for this board and the world militaries in general

Q: Do you know what Datum your GPS is working under ? Yes/No


Did we accidently cruise missle a chinese building somehwere because it was 1 datum off (forward spotter used the wrong datum) the desired target ?


-John

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Projection is how you distort the earth's shape into a flat map. UTM (Universal Transverse Mercator) which the military uses extensively, is one projection and is really useful for most people and thus, very popular. The military eschews confusing technicalities in favor of wider understanding. Soldiers grasp UTM.

Consequently, most data that you may import from commercial sources will have UTM coordinates and WGS84 for the datum. A cautionary attribute to remember is that UTM has serious problems when changing zones. It can shift you tens or hundreds of meters. Coincidentally, New Orleans is on one such UTM seam. During the search & rescue operations the struggle to use a common coordinate system was very serious source of frustration for anybody trying to coordinate rescue. The City of New Orleans uses State Plane and most fed agencies use UTM. Coordinate conversion results in drastically different errors depending on whether the State Plane is converted to Zone 15 or 14, and then used in the other Zone. because of the Zonal Boundary issue, NOLA had previously elected to remain with State Plane rather than shift to the UTM system recommended by HSA. So when FEMA showed up and when the 82nd Airborne showed-up, it was a freaking nightmare of mutual incomprehensibility.

A high quality GPS will allow you to change projections and datums. There are dozens used throught the world and in the USA, most states have their own projections and coordinate systems. Do a search on "State Plane Coordinates" and you'll be deluged with mutually exclusive possibilities. In Louisiana we use two Lambert polyconic projections: LA North and LA South. I'll bet Texas has several and goodness knows what Alaska does -- just look at the longitudinal convergence and imagine all of the UTM zones they must deal with -- ugh.

Folks interested in this and good at math would love the field of geodesy.

B

Has Selective Availability (SA) been implemented in portions of the Persian Gulf?

The GPS satellites send encrypted and unencrypted information. Encrypted signals (called P-Code) are used exclusively by folks who have the special decoder ring in their GPS. It is a chip that quits working after a certain amount of time, which requires periodic chip exchange. That's so if the enemy should get their hands on an enabled system, that system would automagically cease operation. The most common GPS used by ground forces is PLGR or "plugger". It is extremely reliable and ruggedized and simple to use. All of this info is in the public and you can read it all over the internet.

The other signal from the satellite is unencrypted. However, the military can institute SA at the equivalent of the flip of a switch. This downgrades the timing signal. Using differential correction it is possible to regain most of the lost accuracy, but it cannot be corrected fast enough to target a missile, for example. In fact, you lose lock at a fairly slow highway speed.

Now I imagine that the UK forces have the equivalent of a PLGR and so, are unimpeded by SA. I sincerely doubt that the Iranian forces have a PLGR equivalent, so if they use GPS, it is probably a Garmin equivalent, subject to SA.

What if somebody was dicking-around with SA in the Gulf area? The UK folks would be deriving correct nav positions. The Iranians would be deriving bogus navigation but (unless they checked the data stream) might believe they were getting good stuff.

Just a thought.

B

someones lasic surgery hadn't quite healed yet...

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It would be interesting to consider a scenario in which we rachet the Iranian border halfway through the Zagros Mts. and begin to administer their oil fields.

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Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14

I have little doubt that the British were, where they say they were.

But lets agree with Iran for a moment, lets say they were 500 yards as they claim inside their waters. So what? Does that mean its ok to capture them and hold them hostage?


The whole argument is total nonesense. The Iranians grabed them, they should just admit they wanted some hostages and move on to more fruitfull discussions.

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More relevant to me would be the question of what the hell the frigate these sailors were off of was doing. Evidently not much in the way of support if a couple of Rev Guard patrol boats can intercept their "away teams". What the hell has the RN come to?

- Peter.

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Yeah, what happend to the old RN? 200 years ago the Brit's would have sent a few ships to shell their coast, and maybe block and shell a few ports.

Sadly times have changed.

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Yep. I'm betting standing orders interfered with rapid response. That's the danger of having poor political support AFTER politicians order a war. The military gets engaged and the pols, mindful of polls, leave them hanging.

B

I read that the small boats were ordered not to defend themselves with their weapons. Have no idea if that is a true story or not. Goofy enough to be true. Maybe they didn't want to contaminate the gulf with spent shell casings...

Bot, can you explain how a GPS can be affected by the datum issue? If it gives you lat/lon, isn't there only 1 set on the world for that pair? I understand the theory of datums etc. but not how they apply to a GPS. The GPS system know what spot you are on the ground. It converts it to lat/lon (for example). Are you saying the same lat/lon could exist in multiple locations depebdinbg on which datum you are using?

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^^^I agree with the above remarks. They just got bored. "I'm all out of money, do you take hostages?"

I'm not surprised. These acts have happened before. They have a word for it in criminal law------"prior similars".

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