[Loadstone] Feature suggestion: automatic database handling for external map data

Shawn Kirkpatrick shawn at loadstone-gps.com
Fri Nov 20 13:27:12 GMT 2009


I've thought of a similar approach for database management but there are 
some problems. First, splitting a database up this way would result in each 
database consisting of a large number of files. Even if you split by a 
single degree this still results in a lot of files. The phone's file system 
is fat 32 so a large directory will be slow to access.
I'm not sure the access would be much faster in the end. For a close point 
search it might be but you still have to search files as the search radius 
expands.
This does nothing at all for the downloading and importing, you still have 
to get data from somewhere and load it in to a database.
Splitting a database in to multiple files might happen at some point, it's 
just a question of how to do this and if it would be at all faster. Maybe 
each table gets its own file? Maybe a table with just the point's 
coordinates and a pointer to the rest of the information for faster 
indexing? The phone's database engine doesn't do joins so this limits the 
type of queries we can use. The database will have to be redesigned at some 
point but I don't know how the system will be optimized.

On Fri, 20 Nov 2009, arimo at iki.fi wrote:

> Hi
>
>
>  Now when LS can keep open severan databases i'll suggest following feature 
> for large  map databases loaded from OSM or similar sources:
>
> - Map data is divided into smaller rectangular areas, for example 1/100 of 
> degrees. This value could be user definalbe according  features of the phone 
> how densely area is populated with POIs. 1/100 degree will provide about 1.5 
> kilometers (almost a mile) visible points for each direction near the 
> equator.
>
> - The area where user currently is located and  it's eight adjacent areas are 
> kep open.
>
> - When user crosses the area boundary more than about 100 meters appropriate 
> databases areclosed and openet to reflect new location.
>
> - In exploration mode open /closed status is also update regularly.
>
>
> - User's own points are kept in separate database to  make it usable for 
> searches for longer radius.
>
> With scheme like this one can download much larger databases and let LS 
> automatically swithch between them instead of manually downloading  ,
> importing and opening separate database for different areas.
>
> Yes,  I know LS is open source but I'm not a Symbian programmer.
>
>
> -- 
> mr. M01510 & guide Loadstone-GPS
>
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