CHICAGO, UNITED STATES - A suggestion box submission came in from a Lifeboat crew member questioning how you define the location of a rescue. On land a search may be defined at the point of abandoned car, a landmark, mountain top or starting car park. A sea search is a moving entity, it can move during the search with currents, tides and winds.
It would be useful to know the area of that search, overlay multiple searches, and the centre of the plot.
A search at sea, like on an open piece of land, might be over a large area rather than around a single point. So how do we plot that search... A square? A circle? A set of lines? A custom drawn area?
-Robin.
Note: We will soon support the import of GPS tracklogs from an activity too.
Share
and spread D4H :-)
Andy Waite
Tuesday, 17th June 2008
How about contours with the lines representing time advancement in, say, 1 hour intervals? e.g. for a sea search you might start with a 5km circular area, then over time expand that area and change its shape based on the wind direction and tide. A bit like http://www.mysociety.org/2006/travel-time-maps/ actually.
Ronanob
Tuesday, 17th June 2008
It'll be much better when AIS B units are fitted on all small vessles. That way the Search can be easily plotted by the partaking parties using the AIS live or Dolphin website. The Coast Guard have a new really advanced AIS system and their sites are incredible so they would no doubt be able to track the covered area to a very accurate degree.
Personally i would opt for a cone shape based on the last know position and tide / winds (with an extra cicrle around the last position).
admin
Tuesday, 17th June 2008
@andy - those travel maps are fascinating. Could be very interesting once you add in the data from the tracklogs.
@ronanob - The new AIS stuff is fantastic. It is already installed on all the commercial vessels (and most rescue ones). The cone/triangle is interesting - certainly good for prediction but may not be always the case. http://www.ican.nf.net/images/SAR-2.jpg
There's a lot of prediction/live-tracking software out there http://sarbayes.org/links.shtml
Charles Twardy
Monday, 23rd June 2008
Maritime planning methods and software account for drift. The new software is SAROPS. Here's one very nice live presentation: https://www.illipack.fr/SAR/p/STW06_D061018_H1400_I18010/breeze/index.htm
Skip right to slide 16 for initial position and distributions, and let it run from there.
admin
Monday, 23rd June 2008
Charles, SAROPS looks like a fantastic piece of software. Thank you for sharing that link. Keep them coming!
So, my question still remains - how do you best 'mark' the location of a sea search after a search. Let's say you had to display 100 incidents on a map, do you pinpoint the centre of each overall search area?
Charles Twardy
Thursday, 26th June 2008
admin, I think if the display can render it nicely and quickly, showing the search areas as alpha-blended polygons (or rectangles) would be nice. Maybe set alpha dynamically to 1/n?
At the other extreme, if we had to pick one point per search, I suppose I would say in order:
centroid of search effort/area, if available
initial planning point (IPP)
find location
BTW, I think we want to record at least the initial planning point and find location. That's because I'm hoping lots of people will use your site, and contribute the data for analysis.
Robin Blandford (DFH)
Thursday, 26th June 2008
Charles, ..... Admin Here (Robin).
I think you're suggestion of marking initial & find points is a great stop-gap for recording & analysing the effort from GPS tracklogs.
This will get into an upcoming release.
Ana Nelson
Tuesday, 1st July 2008
Slightly off topic, one of my all-time favourite books is Ship of Gold in the Deep Blue Sea by Gary Kinder, and my favourite part of that book is the discussion about how the team that eventually recovered the Central America after 132 years systematically pieced together tiny fragments of information in diaries, ships' logs, weather reports etc., and then organized that data into a coherent structure to calculate a search map with probability bands.
Obviously this wasn't a rescue scenario, it was salvage, and I'm sure technology has moved on in the intervening years, but it was a great description of the process.
Charles Twardy
Monday, 14th July 2008
Ana: it's a great book which I'm still reading. And the underlying theory of search is the same.
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