How to Efficiently Find the Nearest Locations in SQLite Using Latitude and Longitude?

SQLite: Obtaining Closest Locations Based on Latitude and Longitude

Introduction

When working with geospatial data, it becomes crucial to retrieve locations within a specific vicinity. In SQLite, this entails obtaining the nearest points to a given set of latitude and longitude coordinates. This article delves into various techniques for accomplishing this task.

Custom External Function for Haversine Formula

The Haversine formula is indispensable for calculating the distance between two points on a sphere. To leverage this formula in SQLite, you can create a custom external function. While Java implementations exist, they may introduce unnecessary dependencies on external libraries.

Latitude and Longitude Approximation and Database Filtering

As an alternative, consider filtering data using a good approximation. By computing four points within a radius of your central point (north, west, east, and south), you can determine which database records lie within this rectangular area. This step helps reduce the amount of data that needs to be processed in your Java code.

Calculating Derived Positions

The 'calculateDerivedPosition' method is used to determine these boundary points. By applying simple geometric equations, you can determine the end-points based on the desired range and bearing.

Query Creation

Once the boundary points are established, you can formulate a query using the COL_X (latitude) and COL_Y (longitude) columns, ensuring that only records meeting the criteria are retrieved.

Evaluating Within Circle

The filtered records represent points near your central point, but further processing is required to determine which of these are actually within a defined circle. Utilizing the 'pointIsInCircle' method, you can verify if each record meets this condition.

Calculating Distance

Finally, the 'getDistanceBetweenTwoPoints' method calculates the distance between your central point and each record to determine which ones are closest.

Conclusion

By combining these techniques, you can obtain the nearest locations based on latitude and longitude in SQLite without resorting to custom external functions. This approach ensures efficiency in both data retrieval and distance calculation.

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