Passive radar reflector - anything better than Echomax?

Refueler

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I was with S&A Geophysical, which became Horizon Exploration. The vessel was "Oil Hunter"; a converted stern trawler. I still have sharp memories of retrieving the cable while waves were washing up the stern shute! Trisponder systems were the gold standard for position fixing at the time; again, I used such a system in 1983 (Motorola, I think); the Transit system was used to fix two of the base stations.

That was the beauty of Syledis .... it was a self contained triangulation system. CGG was very closely connected to French Military and it was not unknown when shooting in North Sea - when back in hbr - to be asked to run short cable in a Fjord or coast to look for unusual returns. Later we found out - we were looking for submarines - usually a Soviet ...
We believe we detected one in Hardanger Fjord ...

Sicily - one of the boats was sent down there and the Chef de Mission and guys went ashore to place the Transponder on the Spot Height marks - all agreed with authorities.
BUT ..

First spot height marker had a house illegally built on it .. so we 'rented' the roof and offset the geostats by the house height !!

Second spot was up a hillside that was a 'Mafia' area ... so we had to BUY the cart and donkey to get the gear up there ... pay the local Don a silly fee .. then 'donate' the cart and donkey back to him ... we also had to pay for him to provide 'guards' for the first two ...

Third was placed without any hassle !

Libya ... shooting along the coast - Libya provided a guard boat that basically kept us out of mined areas. They wouldn't give us the area co-ords .. so we would be shooting and then get called ... don't go there etc.
One day the guard boat motors off without any word of goodbye or anything .. we carry on shooting - praying no mines .
Shortly after - a manky fishing boat appears and heads towards us. We get out the Flare gun as usual after making the usual VHF calls ... FB keeps coming - so the Chef de Mission wants to fire the gun instead of me ... (as 'drivers' we usually did all that .. ) .. so he goes out wheelhouse door ... cocks the pistol ... and fires - but as he fired - he dropped his hand ...

The flare instead of going up up and away ... arcs beautifully down onto the deck of the fishing boat ... causing everyone on board to scatter - while this flare bangs around the deck trying to find way off !
Finally the flare fizzles out and the 'crew' appear from their hiding places ... couple of them go to a manky old tarpaulin and drag it off ... a bloody 50 cal machine gun gets pointed at us and all the shouting arabic ...
We hastily called Libyan Control and managed to defuse the situation ...

Yep - it was our replacement guard boat !
 

jamie N

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Down memory lane, no-one's mentioned Decca Pulse8. I've spent many hours searching the seabed for 'something' that was positioned using it.
The surveyor would tell me that he was suffering from 'tropospheric scatter', which didn't explain to me why ALL hydrographic survey types ARE odd.
Apologies to all of the exceptions on this thread.....
 

AntarcticPilot

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That was the beauty of Syledis .... it was a self contained triangulation system. CGG was very closely connected to French Military and it was not unknown when shooting in North Sea - when back in hbr - to be asked to run short cable in a Fjord or coast to look for unusual returns. Later we found out - we were looking for submarines - usually a Soviet ...
We believe we detected one in Hardanger Fjord ...

Sicily - one of the boats was sent down there and the Chef de Mission and guys went ashore to place the Transponder on the Spot Height marks - all agreed with authorities.
BUT ..

First spot height marker had a house illegally built on it .. so we 'rented' the roof and offset the geostats by the house height !!

Second spot was up a hillside that was a 'Mafia' area ... so we had to BUY the cart and donkey to get the gear up there ... pay the local Don a silly fee .. then 'donate' the cart and donkey back to him ... we also had to pay for him to provide 'guards' for the first two ...

Third was placed without any hassle !

Libya ... shooting along the coast - Libya provided a guard boat that basically kept us out of mined areas. They wouldn't give us the area co-ords .. so we would be shooting and then get called ... don't go there etc.
One day the guard boat motors off without any word of goodbye or anything .. we carry on shooting - praying no mines .
Shortly after - a manky fishing boat appears and heads towards us. We get out the Flare gun as usual after making the usual VHF calls ... FB keeps coming - so the Chef de Mission wants to fire the gun instead of me ... (as 'drivers' we usually did all that .. ) .. so he goes out wheelhouse door ... cocks the pistol ... and fires - but as he fired - he dropped his hand ...

The flare instead of going up up and away ... arcs beautifully down onto the deck of the fishing boat ... causing everyone on board to scatter - while this flare bangs around the deck trying to find way off !
Finally the flare fizzles out and the 'crew' appear from their hiding places ... couple of them go to a manky old tarpaulin and drag it off ... a bloody 50 cal machine gun gets pointed at us and all the shouting arabic ...
We hastily called Libyan Control and managed to defuse the situation ...

Yep - it was our replacement guard boat !
Despite my early experience with marine seismic, most of my navigational work was with airborne survey, during the 1980s. A lot of that was recording as much as possible and then post-processing it to get the best position. Accuracy was very variable! The trisponder I mentioned didn't output a position - it output the ranges to the transponders. It was great fun doing the spherical trig to convert them to positions - especially when I found that the surveyed position of one transponder was incorrect - it turns out the survey team, 2 Norwegians and a Brit, had used the time from the Brit's watch in their setting up, and hadn't realized it was set to BST, not Norwegian time! I was very proud that I managed to detect the problem and back calculate the approximate location of the transponder, which have them the clue they needed to identify the cause.

The good news is that the locals didn't run a protection racket - polar bears are much less sophisticated!
 

Refueler

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Down memory lane, no-one's mentioned Decca Pulse8. I've spent many hours searching the seabed for 'something' that was positioned using it.
The surveyor would tell me that he was suffering from 'tropospheric scatter', which didn't explain to me why ALL hydrographic survey types ARE odd.
Apologies to all of the exceptions on this thread.....

I miss Decca .... OK so it didn't have the range of Loran C ... or even A ... but it was accurate enough to bring VLCC's up the channel ... for Europoort / Rotterdam Pilots to use the Red lane that ran up the Mass channel to bring ships in ... (nicknamed on their high detail processing machine 'Brown Lane' ... ).

I still have a Decca Ruler somewhere ....

On one of my boats many years ago - I had the Nasa Decca machine - with Lat Long display ... but never could get it to work reliably.
 

Refueler

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Despite my early experience with marine seismic, most of my navigational work was with airborne survey, during the 1980s. A lot of that was recording as much as possible and then post-processing it to get the best position. Accuracy was very variable! The trisponder I mentioned didn't output a position - it output the ranges to the transponders. It was great fun doing the spherical trig to convert them to positions - especially when I found that the surveyed position of one transponder was incorrect - it turns out the survey team, 2 Norwegians and a Brit, had used the time from the Brit's watch in their setting up, and hadn't realized it was set to BST, not Norwegian time! I was very proud that I managed to detect the problem and back calculate the approximate location of the transponder, which have them the clue they needed to identify the cause.

The good news is that the locals didn't run a protection racket - polar bears are much less sophisticated!

Like I say - with Syledis - we could tell when the rigs skidded the tower ... so we would call up the Radio guy on the rig and tell him they had just skidded !!
 

Refueler

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Isn't that in The Guns of Navarone and also Hot Shots Part Deux?


Jokes apart ... it wasn't funny at the time !

I've been close to a 50 cal twice and I am not comfortable with it ... that Libya incident and second was in Cotonou WAF.

The Gulf War escorts and guys I rode with at times had lighter stuff ..... :)
 
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PilotWolf

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I miss Decca .... OK so it didn't have the range of Loran C ... or even A ... but it was accurate enough to bring VLCC's up the channel ... for Europoort / Rotterdam Pilots to use the Red lane that ran up the Mass channel to bring ships in ... (nicknamed on their high detail processing machine 'Brown Lane' ... ).

I still have a Decca Ruler somewhere ....

On one of my boats many years ago - I had the Nasa Decca machine - with Lat Long display ... but never could get it to work reliably.

Except at twlight or in storm!

We had a separate plotter and receiver- never remember them agreeing!

I think we had paper rolls for the plotter?

Red/green/purple lanes IIRC?

I also think my first skipper - I was 16/17 put red lighting in the wheelhouse but then found you couldn’t see the red lines on the chart!

W
 
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Refueler

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Chartroom l
Except at twlight or in storm!

We had a separate plotter and receiver- never remember them agreeing!

I think we had paper rolls for the plotter?

Red/green/purple lanes IIRC?

I also think my first skipper - I was 16/17 put red lighting in the wheelhouse but then found you couldn’t see the red lines on the chart!

W

Chartroom lighting !! Extendable arm lamps with orange glass in .. awful things !

First intro I had to Decca was talks from my Father - he was an RAF Navigator during WW2 and talked about its development and passing into civvy world. He moved into CAA and Nav was his main field along with safety and Accident investigation.
Joined ship and in front of me was the Decca machine with 4 analogue dials .... Master .. Red ... Green ... Purple ... and you had to read them quick to get the numbers !!
Few years later - WOW auto reading Decca and auto plot !! Then Maas Pilots brought the 'Brown Box' on board ... plugged in to the back of our Decca unit ... and it displayed how many metres of channel centre line we were going into Europoort .. not an insignificant matter when you have 300,000 ton tanker under your feet.
The auto then was linked to a chart table (a glass affair) with a travelling light dot under ... you placed chart on - referenced the corners - much as you do with a Yoeman - but this was only fitted to Lightering Vessels who stayed close enough to land (it also accepted Loran and some early ones had another electronic feed - name escapes me now but it was never universally adopted ... EDIT : OMEGA !).

Memories !!
 
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