The Forester

D'you want a Lat/Long? My student is very well trained in Advanced Land Navigation and now knows how to produce GPS-quality co-ords without GPS!

I asked one of my military students about the map. He says it's at the REME regimental museum in Arbourfield.

Not so. A modern GPSR with WAAS enabled, is good to ±3m or better. With just a couple of minutes averaging this can easily be brought down to well below the 2.1m resolution of the GC.com DDMM.mmm format. The 3parameter datum shift used by systems such as Garmin and Magellan GPSrs induces an error of 7 metres or more.

The Foinavon oilfield, West of Shetland, is named after the mountain of the same name. It's pronounced FoynAvvon, with the emphasis on the second syllable Cheers, The Forester Former BP Survey Superintendent, Foinavon Field

Or buy a Magellan. Those have an option to display two different position formats simultaneously.

They come in two sizes.

The reason why retail level GPSrs and some apps such as GC.com's get OS co-ords so wrong is that most of them are using the oversimplified 3-parameter datum shift. By its very nature, that method cannot be accurate across the whole country. In central Scotland, for example, it's about 7 metres adrift. It's more than that elsewhere. If you want accurate conversions, such as to plot single metre precision co-ords on large-scale mapping such as www.magic.gov.uk, then you really need to use the full polynomial datum shift thingy, such as the one on the OS website. If you want to have that ability on your own GPSr for use in the field in your own general area, then you need to make your own three parameters (dX;dY;dZ) and select the user-definable datum shift option on the menu of your GPSr. Use a freebie package such as the NGA's GeoTrans to do the number crunching to find out what your local datum shift should be. Take some WGS84 co-ords which are reasonably central to your caching area. Anywhere within 10 or 20 miles is quite adequate. Look up the 3D Cartesian co-ords for that location on WGS84, then on Airy/OSGB36, subtract one from t'other and voila, you have your own bespoke datum shift parameters for injection into the user definable option on your GPSr. That will give you metre-accuracy conversions on your own GPSr within a fair distance of the centre of your geocaching area.

#4 looks like Local Hero. Scene-setting soundtrack was local radio station in Houston, Tx.

Woohoo! I've beaten Nediam for once!! It's Bawnmuff.

Is a sand lizard the same thing as a common lizard? Or are they two different species? Edited to suggest: Tor three different species of lizards with Common Sand Lizard being the third?

Smooth snake hasn't been mentioned yet.

The who is a Swiss guy; The where is Switzerland; The when ... my guess is 1960 The why ... because he could!

The seeds which are sometimes called sticky willow are Burdock.

Elizabeth Alexandra Mary Saxe-Coburg Gotha, aka Battenburg, aka Betty Windsor?

Still pants in the hinterland of lowland Scotland too. Forester Towers is just a LandSat7 blur on Google Earth and Local Live imagery is about 7 years out of date. Fortunately it's quite easy to insert one's own high resolution imagery overlaid onto Google Earth and georeference it to metric accuracy or better.

Blair/Browne/Beckett's worst nightmare has come to pass. The Pasdaran confiscated at least one Garmin Legend from the Navy/Marines and they've found that the waypoint and track data had not been deleted. They've downloaded the data and plotted it on a chart. Yes, the data really does appear to back up what the Iranians have been claiming and it appears that at least one of the attack craft really had strayed into Iranian waters. That daft photo of the Magellan Legend in the doorway of the Lynx has backfired on Whitehall in a really big way. They thought that it would be a clever distraction from the actual track of the RN/RM launches, but it has merely legitimised the Iranian claim that the identical GPSr now in Iranian hands is a genuine record of the craft's track. In an Arabic language press conference a Pasdaran officer shows the plot and says that the data recorded a 450 metre excursion into Iranian waters. As for the Lynx being unable to photograph the incident: that now looks a bit lame in view of the footage of the helicopter which is clearly taken from one of the Iranian launches and clearly shows at least one of the RN/RM launches. What is unclear from the Iranian video of the event is why the two British launches appear to have become separated from eachother. In the soundtrack you can clearly hear a British-sounding voice saying something less than complimentary about the people in the other British craft. It's a phrase which is not allowable in this forum, but alludes to what type of heads they have. There is clearly an object lesson in this development: if you want to deny where you've been, then for goodness sake delete the tracklog in your GPSr before doing so!

Yes. I don't understand quite what you are trying to say. Clearly, from the half mile discrepancy between the two sets of co-ortdinates issued by the FO/MoD, the inspected vessel had moved in the couple of days between the incident and the "evidential" photograph. What use is the photograph? It quite certainly doesn't indicate the position of either the Iranian boats or the RN/RM ones. It does nothing whatsoever to refute the Iranian claim the the RIBs strayed into the Iranian side of the boundary line. In fact, if anything the photograph suggest that the Brit side has an embarassing paucity of GPS tracking data with which to refute the Iranian allegation that our side strayed onto their side. There is no doubt whatsoever that Cornwall's surveillance radar data tapes will have recorded the positions of all of the six Iranian gunboats as well as the two Marine RIBs throughout the whole of the incident. The MoD presentation conspicuously omits the track taken by the RIBs when travelling from the mothership (Cornwall) to the target cargovessel. It simply plots the posiition of Cornwall and the position of the anchored "dhow". In lieu of tracking data, they simply published the rather lame and quite irrelevant GPS photo taken from the cabin door of the ship's Lynx. If the MoD was comfortable with the track taken by the boarding party, they would no doubt have shown that track and demonstrated its innocence. I think Whitehall has shot itself in the foot with that picture of the Garmin. They also grossly overstated the significance of the one digit typo in the Iranian Latitude, as if it in some way proves the innocence of the boarding party. Thus far there has been a lot of bluster from Beckett and Browne. Too much, perhaps. Even a simple matter such as where the detainees are being held became a very silly and petulant demand that Iran declare the location. You really don't need to have done the long course at Fort Monckton (I haven't!) to deduce that they are being held at Evin nick.

Quite apart from the fact that the co-ords are not in any way my co-ords, they are the co-ords shown on the Garmin. You are quite right that there's something fishy about those co-ords. There's a bust of 823m (that's about half a mile, in old money) between the co-ords reported to/by la belle Beckett and the co-ords shown on the screen of that Garmin. As evidence of whether the Royal Navy/Marines assault craft entered Iranian waters or not, the picture is totally useless and quite misleading.

The aircraft does have a GPS input to the inertial reference system, but that display is down low on a console between the two pilots. The propaganda photograph seems to have been taken purely for propaganda purposes, not as part of any actual military mission. There are several reasons why I don't believe that the photograph is anything like the incontrovertible proof that the gumment promised. I can't see any Iranian military vessels in the picture, nor even either of the two Marine rigid raiders. If the GPS imagery is purported to be relevant to the incident, I'd expect there to be some evidence visible in the picture. The target ship had two lighters (shallow draft barges) tied up alongside her at the time of being boarded by the Marines. I see no lighters in the image either. So, the picture doesn't show the time or the place of the incident. What does it show? Not much, I think. I guess we shouldn't expect much from the people who gave us the incontrovertible evidence of the Uranium shipments and the mobile anthrax laboratories and the babies being torn out of Kuwaiti hospital incubators and all that guff.

I must put my hand up in the air and admit a certain amount of guilt there! In 1985 during the IranIraq war, I was instrumental (no pun intended) in importing to Iran's Northern Gulf coast a NavStar GPSr for high-accuracy measurement of 'stuff' for defence work which was intended to make the Iraqi airforce/USnavy attacks against Iranian exports from Kharg Island more difficult. An irony was that I was working for a very Murricane company (Dick Cheney's favourite!) at the time. All open and above board, 'guv, honest!

Hee hee hee! Like many other geocachers, when I see co-ords I like to plot them on a good map or georeferenced satellite image to see the area and exact location that is being quoted. For that reason I plotted the Navy's Lat/Long onto the MicroStiff VirtualEarth. If you tilt your screen and/or play around with the image contrast on your monitor, you can actually see the seabed contours in this image. Those contours are highly relevant to the question of whose territorial waters were trangresssed by whom. In that part of the world, the international boundary between Iran and Iraq runs along what is called the thalweg. That just a fancy name for the middle of the river outflow's meandering course. The boundary runs along the centreline of the Shatt-el-Arab's course, not equidistant between its shorelines. For that reason, until recent troubles, there was an annual survey of the Shatt, all the way out to the conventional 12 mile territorial limit, to delineate exactly where the thalweg was at that time. Every two years or so, the surveys were used in bilateral conferences to re-demarcate the boundary between the two neighbours. Good fences making good neighbours an' all that. Take a gander at the latest(?) satellite picture and use your eye to follow what you think is the centreline of the NorthWest_to_SouthEast course of the deepest part of the outflowing Shatt. That is the bilaterally agreed (between the DeFacto governments of Iraq and Iran) boundary between Iranian and Iraqi territorial waters. Make your own mind up as to whether the little white cross at the RN Garmin GPS position of the dhow (if that deck is really a dhow) is on the Iranian or the Iraqi side of the centreline of that thalweg!

I've got a question for Legend users: Does that screenshot show the time/date of the fix? I've had a look at the exif metadata of that jpeg and it shows that the image was made by Photoshop Version 7.0 at 09:54:36 (BST?) this morning. Are we supposed to be as impressed with this piece of evidence as we were about the incontrovertible evidence that Iraq was stuffed full of weapons of mass destruction prior to being "liberated"?

Isn't it something to do with two-dice game? You have to declare the two numbers you expect before you throw the dice. The higher the numbers the higher the stakes: a five and six is the highest risk/reward number pair. A confused player who means to say "5 and 6" might inadvertedly say "6 and 7"., hence "at sixes and sevens" to describe someone who is confused. That was the explanation our English teacher gave us at school when we did Chaucer, anyway. Was she at sixes and sevens herself?

To do anything like a warm start your GPSr needs to 'know' its position to within about 500 miles. Here's why: Each satellite sends a data string called a 'navigational message'. That string of data is composed of 1,500 bits of data in 5 subframes. The transmission rate is extremely slow, only 50 bits per second which is about the same data rate as an old-fashioned telex machine. Your GPSr needs to know which satellites to 'look' for and to do this it needs to know which satellites are above its local horizon. If it doesn't have that data, it needs to read every part of every subframe of every navigation message from every satellite. As it takes 30 seconds to send the full message and as it must start at the beginning of the message in order to make any sense of it, the machine must wait until bit number 1 to start reading the rest of the message. Therefore it can easily take almost 60 seconds to read the message from a single satellite. If it misses so much as a single bit of data, then it has to start all over again. It has to do that for about 30 satellites, so you can see that it can easily take 15 to 30 minutes to orient itself within the sequence of navigation message datastreams for all the satellites that it knows about. Only after it has got all that data can it start to try to figure out which of the satellites to 'listen' to and start to compute a position. You can greatly speed up this process by inputting a start position that you know to be within a couple of hundred miles of where you actually are. This enables the machinme to make an intelligent guess as to which part of which navigational message it should pay attention to. If you switch the machine off in Newcastle, Tyneside and then back on again in Newcastle Australia, the machine is totally confused as it is looking for the satellites it expects to see in its old location. It's just a matter of luck when it will 'realise' that its estimated position is grossly in error and it starts to look at the bigger picture and start from scratch. That can be expected to take anywhere from 15 to 30 minutes and can take 30 to 60 minutes if it's getting a noisy signal which must be rejected if a checksum error occurs.

There's a cache at one of these oddities. This one is an Omani enclave located well within the UAE. Llivia is a little bit like that, except it's right on the Spanish border and in about 180° of the panorama I suspect that you'd see Spain from there.