[Loadstone] Distance Calculation
shawn at odyssey.cm.nu
Sat Feb 17 00:57:59 GMT 2007
It's true that data you can get commercially would have the needed
information. However, loadstone is free and open source so this means that
we're not going to implement features that require the user obtain
commercial data in order to use.
You wonder how the database works with half a million points? I don't know,
I wouldn't even consider loading that much data in to it, the results would
be very slow I'd guess. The way comercial gps units do all this is one of
two ways. In the case of a dedicated unit the programs they run can be
optimized to the specific hardware and don't have to worry about doing
anything else. In the case of some phone products like wayfinder they do a
lot of there calculations on an external server. This requires you to have a
data plan to use. This may go in to loadstone at some point but we'd like to
avoid that for a while until the costs of data plans become somewhat
reasonable and having one is the norm rather than an acception. This is the
case in some places but not everywhere.
As for inporting points, the accuracy column is used in approach distance
calculations. The satellites column is mainly informational and the priority
column is used to indicate private, restricted, or deleted. If you're
converting points it's best to leave this at 0 unless the data is something
you don't want to put out on the general point share site. In that case
you'd set priority to 2. You only need to do this in the case of commercial
data that can't be freely distributed.
On Fri, 16 Feb 2007, Hasan Karahasan wrote:
> Hello Shawn,
> you wrote:
>> Well, that would be kind of nice but not very practical at the moment. For
>> one thing, we really don't have that much detail about the streets.
> Maybe not freely available, but if someone necessarily needs these data he
> will obtain it commercially and convert it to the Loadstone database. So
> this should not be the reason for not implementing a way distance
> calculation algorithm.
> The most
>> important thing would be we just don't have that kind of computing power
>> the phone.
> I am not sure how the loadstone database engine behaves with half a million
> points on typical fones. Wondering how commercial navigation products can do
> this even with a visual map that scrolls with you.
> By the way: I would like to import some points I have gathered myself from
> some other sources. Again: The data was not created by loadstone but comes
> from somewhere else. When I export my data into an ascii file I can see that
> the column for accuracy is always 1 and priority is 0. And what about the
> satelites column? Are these columns already used for some calculations.
> Otherwise I could simply use fix values for them.
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