What UV did next

On 21 January after nearly six weeks at the Gulf of Cintra UV moved on. It was a windy afternoon gusting over 30 knots or 55 kph from the NNE. So with a tailwind, here is his route.

UV heads south

UV heads south

Paul has provided lots of figures and graphics; UV’s overall speed averaged 46.7 kph with a maximum of 105 kph. He travelled 314.2 km from his overnight roost on 20 January to the last fix at after 19.00 GMT on 21 January. His highest altitude was 993m above sea level and much of his journey was at altitudes over 300m. Here are the graphs.

UV travel Cintra to Nouadhibou

UV travel Cintra to Nouadhibou

A final graphic shows his approach to his final spot with extensions to the ground giving a clear sense of his altitude.

UV approaches his overnight spot via a bit of time over the sea

UV approaches his overnight spot via a bit of time over the sea

He roosted in an area not far from an oil refinery and just into Mauritania; the peninsula is shared between Western Sahara to the west and Mauritania to the east. UV flew past  Nouadhibou, the second largest city in Mauritania perhaps best known as the world’s largest ship graveyard! Not because of coastal wrecks but because over 300 vessels have been dumped in the area. The upside of the rusting hulks is that reefs have formed providing breeding grounds for fish. UV will like that bit!

However, he is not at all used to more populated areas and it is unlikely he will choose to stay. (Famous last words in the osprey world!) Even the light pollution may have disturbed him as he was moving around a little as the last data points were collected.

So where next and will it be another stopover?

 

This entry was posted in Blue UV, Migration, Osprey updates and tagged , . Bookmark the permalink.

3 Responses to What UV did next

  1. thehutts says:

    I like the last map; an interesting perspective on the flight. GPS heights are notoriously less reliable than horizontal position – could some of the peaks and troughs in the graphs be due to altidutinal errors? Sally

  2. It is true that the vertical components of a given position are slightly less accurate (not necessarily less “reliable”) than the horizontal components, due to the relational geometry of the system. However, this is a matter of degree. The vertical dilution of position (“VDOP”) at 95% and 65% confidence levels can be established mathematically, and we have these figures for each recorded point on UV’s track. At the times illustrated during his approach to Capo Blanco, this would have represented a maximum overall error of +/- 4.55 metres altitude. Since UV’s recorded height at this time was over 400m ASL, I regard the proportional effect of VDOP as being insignificant for the purposes of mapping his flight path.

    It is a curious attribute of the GPS positioning system that a receiver which is moving returns more accurate readings than one which is stationary for any extended period. The technical reasons for this are beyond the scope of any answer which would not send our readers into a deep and restful sleep.

  3. thehutts says:

    Thanks for that clarification Paul. As an ex land surveyor I studied GPS technology when it was in its infancy many years ago now and I appreciate what you say about not boring the readers! Your efforts with the data are much appreciated – it is great that you and Joanna have devoted so much time to making sense out of what the trackers are telling us and presenting it in such away that the layman can picture what the ospreys are upto. Sally

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