[OT] Navigation systems
alex at tweedly.net
Thu Oct 17 19:32:25 EDT 2013
On 17/10/2013 16:57, Peter Haworth wrote:
> Thanks for the pointers eveyone. I have some reading to do!
I'll suggest some more reading :-)
I don't agree with some of the earlier posts. Navigation problems (i.e.
'best' route from A to B) is not equivalent to the Travelling
Salesperson Problem - it's considerably easier than that. It's a graph
searching problem, and so there are solutions which run in polynomial
time (whereas NP-complete problems like TSP don't). Best known approach
would be Djikstra's algorithm ( as used in in network routing, like OSPF
You could start with http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
though it's a pretty hard slog.
An easier intro is in http://en.wikipedia.org/wiki/Link_state_routing
and go down to the section on "Calculating the shortest paths" (and
don't get distracted by all the rest of the stuff link-state routing has
to deal with; in map/directions you don't need to dynamically detect
link failures and you don't need to spread info about them over the
network you are trying to use :-)
Or, jump to the answer ...
> Mike, I never made the connection between aircraft boarding and navigation
> before but you opened my eyes! Incidentally, Southwest now have a "clump"
> system layered on top of their no seat allocation rule. There are three
> boarding groups (A,B,C) and within those groups, numbers from 1-60 (or more
> for larger aircraft), with the group and number being assigned serially (I
> think) in order of time checked in. The numbers aren't seat numbers, just
> sequence numbers within the group. At boarding time, group A, numbers 1-30
> go first, followed by group A numbers 31-60, and so on.
> This all came about really because I'm using my Nexus 7 for navigation and
> it does not have the LTE option on it so I'm not on the internet when
> driving. I found a few apps that will provide navigation when not
> connected to the internet, which they do by downloading maps from an open
> source mapping project. Obvioulsy you have to get the necessary maps while
> you have an internet connection but after that, the apps use the gps in
> conjunction with the maps to figure out routes and navigate them.
> I guess Google maps allows you to save maps and work offline but I found
> that it has size restrictions that won't save maps that cover a large area.
> lcSQL Software <http://www.lcsql.com>
> On Thu, Oct 17, 2013 at 7:57 AM, Richard Gaskin
> <ambassador at fourthworld.com>wrote:
>> A good overview:
>> Richard Gaskin
>> Fourth World
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