Tracking Rothes and Mallachie

Thanks Alan

I think Rothes has just been extremely unfortunate with the weather. If she had started on migration when Rothie did then I've no doubt that she would have traversed the Sahara as briskly as he did. She has had to deal with sandstorms blowing her towards the coast where she is now encountering stiff northerly winds (which are forecast to continue). If you look at the pressure chart for Africa the winds must be lighter inland so her next few fixes will be really interesting (and enlightening as to where she ends up).

Rothes last fix only 80 yards from the road, the second last was 1200 yards. The figures are very approximate, since GE distorts the plots at close quarters, at least thats the way it seems. But it seems to discount one of my original concerns that we were tracking a vehicle, with Rothes being transported.

jsb

It had also occurred to me (though I was reluctant to say), that it would be possible for a vehicle to travel between the penultimate and latest points between the stated times.

But I think another indicator which shows this is not the explanation, is altitude. If you right-click on the latest point to reveal the properties, the altitude is 140m as you've said. But if you run the cursor over the area beside the highway where the point has been plotted, the altitude is around 72m ASL, for some distance around.  

On the other hand, if you assume there was a keying error as has been suggested above, and look at the altitude of the corresponding area, it's about 125m - so Rothes, roosting on a sand dune, could easily be at 140m.  

I guess tomorrow will reveal the answer.   

Unknown said:

jsb

It had also occurred to me (though I was reluctant to say), that it would be possible for a vehicle to travel between the penultimate and latest points between the stated times.

But I think another indicator which shows this is not the explanation, is altitude. If you right-click on the latest point to reveal the properties, the altitude is 140m as you've said. But if you run the cursor over the area beside the highway where the point has been plotted, the altitude is around 72m ASL, for some distance around.  

On the other hand, if you assume there was a keying error as has been suggested above, and look at the altitude of the corresponding area, it's about 125m - so Rothes, roosting on a sand dune, could easily be at 140m.  

I guess tomorrow will reveal the answer.   

SueC: I am interested in this, but have never looked at kml files much at all and not in this detail, so it is really for my own satisfaction. What I looked at is set out below. Please do not spend time on this unless you are really interested. Most people will think it is double-dutch.

I am assuming that the satellite and bird sat pack are calibrated in absolute height in metres. i.e height above sea level, regardless of whether the bird is flying or roosting. But RSPB have chosen the kml file format/treatment of this altitude as 'clamped to ground' which apparently means that Google Earth ignores the reading, except that it records it in the properties. (Incidentally this explains why we have seen the flightpath disappear into mountains?).

Link to GE kml reference re altitude.

MW Snaps

In the first one Rothes is near sea level, 7 metres altitude.

In the second one, which is the mysterious fix, the last we have, as said she is at 140 metres altitude and as you said the ground altitude is about 72 metres.

So in the first example she is on a rock or a structure, or in flight, beside the sea.

In the 1st June one, the last, she is probably in flight about 70 metres above ground level.. The proximity to the road would probably rule out a sand dune.

All this does not explain, why she is there in the first place however. Pleased to say, it seems to rule out any foul play.

Data updated on GE but still not sure what is going on?

I still don't understand the final position on 1st June, but it now seems clear that it didn't indicate anything sinister.

From 2nd to part way through the 4th, it seems Rothes felt the need to take a further break on the coast north of Nouadhibou - refuelling or waiting for a more favourable wind?  

During the 4th, she then set off again - does the easterly heading indicate that the wind direction still isn't ideal?  

Thanks SueC, That easterly track was a bit worrying but at least she has turned north to the latest fix on the 6th:

Well at least this looks a bit better. She is a young bird who has never  migrated North so this may account for  her indecision and  back tracking.  If she is not  following the same route she took to get to her winter home it is all new  territory for her. GodSpeed Rothes I hope you find your inner compus soon. Your fans are waiting for you in Scotland :)