Old ground revisited...

[puddlepirate]

Yesterday I went again to Rendlesham forest to visit the farmer's field and to take a trip across to Orford Ness to view the lighthouse close up. Not sure why because I felt I already knew the answer but I thought I could be wrong and IR might be right. From the edge of the field there is only one substantial dip in the tree line. When standing in the picnic area, i.e. where the small wooden table and benches are placed at the corner of the field, it can be clearly seen that beyond this dip is an area of tree lined high ground that blocks the view to the coast. Further to that, i did a bit of reading on perspectives and why an object appears smaller the farther one moves away from it. The reason is to do with 'angle of view' and is simply explained by the formula: angle of view (v) = height of object (h) divided (/) by distance from the object (d). The light is 28m high (see Reeds Nautical Almanac) and the distance from the field to the lighthouse is 5.5 miles or 8800m (see OS Explorer map 212). Therefore the angle of view of the lighthouse for someone standing at the corner of the farmer's field is: 28/8800 = 0.003 deg. Thus even with a clear line of sight to the lighthouse, it would be a tiny speck on the horizon. Secondly, from the corner of the field the lighthouse lies on a bearing of 093 deg and not the 110 deg mentioned by Halt.

It transpires that this difference is quite significant because if you follow a route on 110 deg you pass along the southern edge of Oak Wood (which borders the south side of the farmer's field) then to the north of Capel St Andrew and across Butleyferry Farm (any animals here? Pigs perhaps?). The land drops steadily towards the coast (no high ground to block the view) and passes between two areas of high ground to the north and south before crossing Orford Ness at Havergate Island, some distance to the south of the lighthouse. The area of sea off Havergate Island is frequenly used by ships waiting to enter Harwich - in fact there was a large container ship there yesterday afternoon, apparently at anchor about a mile off the coast. Skippers do not want to waste money so rather than enter Harwich at Christmas and have to pay harbour dues whilst they waited to be unloaded/loaded after the holiday, they would probably have anchored off. At night they would display navigation lights - port (red), starboard (green) and masthead (white). Ships also swing about their anchors so the lights would move. At Christmas some of the crew might have let off fireworks - or there could have been a distress flare. If there was a ship in distress then at least one helo would have been scrambled to assist. But why does any of this matter? It matters because it could mean that Halt was not in Rendlesham forest as such but in Oak Wood. Not being familar with the forest, he might not have known the difference. If this is correct then it could mean the site Halt and his men checked for radiation was actually somewhere else.

I've posted some images from yesterday's trip on Flickr - not sure if this link will work but nothing ventured etc... http://www.flickr.com/photos/powfoto/se ... 052588878/

[stephan]

Hi puddlepirate

very good point with the lighthouse. If the angle of view is that small it couldn't have been it. Another good reason to discard this possibility.

The formula you used is taken from trigonometry: tan a= opposite side / adjacent side

(with a = angle)

on a calculator you usually have to push the shift key plus tan in order to calculate the angle. You have to consider the relative altitudes if you want to know the actual angel, i.e. the altitude (resp. sea level) of the location you are standing on and the altitude (resp. sea level) of the bottom of the lighthouse. If your location is 28 meters high the angle would be 0 degrees. If the location was higher the angle would be negative and if it was lower it would be bigger than the angel on a same level of lighthouse/ your location. If the altitudes are the same the angle would be (according to the furmula above) 0.1823°- still very small!

Thus the correct formula to use in this case would be:

tan a = (altitude of lighthouse + (altitude of bottom of lighthouse resp. sea level) - (altitude of your locaton resp. sea level)) / distance
= (28m + a1 - a2) / 8800

if you want to calculate for the height of your eyes ''e'' (e.g. 1.8 m if you are about 1.9 m tall and in a standing position) this would be even more exact and the formula would be:

tan a = (28m + a1 - (a2 + e))



I don't know the altitudes of the lighthouse (a1) and the altitude of the point from where you would have to look (a2) (the point where the witnesses stood), perhaps Google Earth can be used to determine those values.

[lcdvasrm]

The first formula was very correct for small angles. The only error was that the result from the formula is in radians .

[stephan]

The first formula was very correct for small angles. The only error was that the result from the formula is in radians .

yep because tan a equals approximately a for small angles. But the difference of the altitude could also be important. Say the lighthouse would stand on a hill it would appear higher than if it stands on the ground (relative to your location). And of course the stuff that's in between also can play a role

[puddlepirate]

It's something to do with the way the human eye sees distant objects and the reduction in height (or width) caused by perspective, e.g. when you look along a railway line, the lines appear to converge in the distance - which of course they don't. The angle of the lines at the point of convergence is the angle of view. Using trigonometry, if you took the distance from the lighthouse in metres and multiplied that by Tan A (the opposite angle) you should arrive at an answer of 28m but over 5.5 miles (8800m) the angle is too small. The Tan tables start from an angle of 1 degree and using Tan of 1 deg (0.0175) over 8800 metres gives a lighthouse height of 154 metres (less the height of the observer and assuming both observer and object to be on level ground).

Anything between the observer and the object would be similarly (apparently) reduced in height due to perspective, e.g. if a hill of only 15m was between the observer and the lighthouse but was much closer to the observer than the 28m lighthouse, the hill would block the view of the lighthouse. You can easily prove this by holding a postage stamp or something similar at close range then look at a building in the distance, the stamp could block your view of the building yet it is obviously many, many times smaller.

[puddlepirate]

Don't know if this link will work but the image was taken on Orford Ness, near to the Black Beacon with the lighthouse in the background. There is approximately 1Km between the beacon and the lighthouse yet even at this relatively close range the lighthouse appears much smaller due to the effect of perspective. Imagine how small the lighthouse would appear to be from 5.5 miles (8.8 Km) away.

http://www.flickr.com/photos/powfoto/4918021432/

Anyway, enough of that. If Halt was seeing lights on a bearing of 110 from the vicinity of the corner of the farmer's field then he was looking at something else.

[stephan]

I just watched your photos, great stuff, puddlepirate

another funny thing with distant objects is that they seem to ''move'' when you move especially when you have something much closer like trees in the foreground. So if one walks through a forest traversing little scrapes (not the Rendlesham one, as we know they did NOT see the lighthouse!!) at night and then sees the light of a distant lighthouse it will appear moving ''through the trees'' bopping up and down and blinking. One who's not a trained observer might indeed interpret that as an UFO. However, only if he doesn't stop walking and noticing that the light stops whenever he stops. This way he'll soon realize that the light is ''static''.