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From "Chris A. Mattmann (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SIS-51) Pluggable Distance Calculation
Date Tue, 31 Jul 2012 01:01:55 GMT

     [ https://issues.apache.org/jira/browse/SIS-51?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris A. Mattmann updated SIS-51:
---------------------------------

    Fix Version/s: 0.3-incubating
    
> Pluggable Distance Calculation
> ------------------------------
>
>                 Key: SIS-51
>                 URL: https://issues.apache.org/jira/browse/SIS-51
>             Project: Spatial Information Systems
>          Issue Type: Improvement
>          Components: distance functions
>            Reporter: Peter Karich
>            Priority: Minor
>             Fix For: 0.3-incubating
>
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> The distance calculation is done in several places. I think it shouldn't be a static
helper method instead it should be an instance which could be replaced by a more precise or
faster calculations:
> double distance(double latFrom, double lonFrom, double latTo, double lonTo)
> E.g. one could use euclidean distance, haversine calculation or a fast projection calulation
(https://github.com/karussell/GraphHopper/blob/master/core/src/main/java/de/jetsli/graph/util/ApproxCalcDistance.java
+ see test). 
> Also one should think about "normed" distances. I mean, if one does not need the actual
distance and rather needs to compare distances one could avoid parts of the distance calculation
and make it faster. e.g.:
> sqrt(deltaX*deltaX + deltaY*deltaY) then gets: deltaX*deltaX + deltaY*deltaY and the
comparisons of distances are still correct if done for all distances (eg. in a quad-tree).
This could be done with a separate normedDistance method or probably just the same and a different
implementation? Not sure ...

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