Another possibility would to have the 400 points on a server, and then just upload your own position and let the server do all the calculations. /Smartass
On Sep 4, 11:11 am, Neil <[email protected]> wrote: > Hi Martijn > > I did it like this: > > private double[] getBoundingBox(final double pLatitude, final > double pLongitude, final int pDistanceInMeters) { > > final double[] boundingBox = new double[4]; > > final double latRadian = Math.toRadians(pLatitude); > > final double degLatKm = 110.574235; > final double degLongKm = 110.572833 * Math.cos(latRadian); > final double deltaLat = pDistanceInMeters / 1000.0 / degLatKm; > final double deltaLong = pDistanceInMeters / 1000.0 / > degLongKm; > > final double minLat = pLatitude - deltaLat; > final double minLong = pLongitude - deltaLong; > final double maxLat = pLatitude + deltaLat; > final double maxLong = pLongitude + deltaLong; > > boundingBox[0] = minLat; > boundingBox[1] = minLong; > boundingBox[2] = maxLat; > boundingBox[3] = maxLong; > > return boundingBox; > } > > The code is copied from mini_osm.py which you can find > here:http://gagravarr.org/code/ > > Regards > > Neil > > http://l6n.org/android/ > > On Sep 4, 10:39 am, Martijn van der Plaat <[email protected]> > wrote: > > > Thank you Gary, > > > Is it true that, when i use SQLite and not the Google App Engine, the > > first algorithm in that GeoBOX story is good enough, because i dont > > use App Engine? > > > SELECT * > > FROM Business > > WHERE Lat > (position_lat - d) AND > > Lat < (position_lat + d) AND > > Lon > (position_lon - d) AND > > Lon < (position_lon + d); > > > Last thing i need to know is how to calculate the variable "d" in the > > above query, if the box is -say- a 1 mile radius. > > > Greets, > > Martijn > > > On 4 sep, 08:48, gjs <[email protected]> wrote: > > > > Hi, > > > > There is a description about a GeoBox algorithm & some python source > > > code located here - > > > >http://code.google.com/appengine/articles/geosearch.html > > > > Regards > > > > On Sep 4, 6:42 am, String <[email protected]> wrote: > > > > > This is a common problem in GIS. I'd suggest doing a simple check for > > > > whether each point is within a simple lat/lon box - that should be > > > > fast enough with only 400 points, and should narrow down the list > > > > enough to be able to check the distance on just those few. > > > > > If you're doing this a lot, put the data in SQLite with indexes on lat > > > > & lon; that way you can do this initial "box" query easily & > > > > efficiently. > > > > > String > > > > > Martijn van der Plaat wrote: > > > > > > Dear all, > > > > > > In my application I have a list of +400 GPS coordinates which I > > > > > retrieve from addresses. The application should give me the top X > > > > > nearest coordinates based on my current location. > > > > > > This application is possible (I think) with the distanceBetween > > > > > function. But (I think) the application is really inefficient when i > > > > > iterate through the list of 400 coordinates and check the distance > > > > > within a certain time interval. > > > > > Another option is (I think) the proximityAlert function? All > > > > > coordinates are loaded in this function and when my current location > > > > > comes in the radius of a coordinate an alert is given. But the > > > > > downside of this solution (I think) is the high memory usage which > > > > > implies a short battery life of the Android phone? > > > > > > Please can anybody help me to make the right decision? > > > > > > Greets, > > > > > Martijn --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
