How to Efficiently Retrieve and Sort Nearby Locations from an SQLite Database Using Latitude and Longitude?

Getting the Nearest Locations with Latitude and Longitude in SQLite

Problem:

Retrieve locations from an SQLite database based on proximity to a given coordinate and sort them by distance.

Discussion:

To calculate the distance between locations on a sphere, the Haversine formula is commonly used. However, implementing this formula in SQLite often requires custom external functions, which can increase app size. Additionally, sorting data by a non-database column presents a challenge.

Solution:

1. Filtering Data Using Approximation:

• Calculate four points that form a rectangle around the target location with a specified radius.
• Use SQL operators to filter the database for data within this rectangle.

2. Determining Proximity and Sorting:

• Loop through the filtered data and calculate the actual distance from the target location using the Haversine formula or a simplified version.
• Use a custom adapter or implement a sorting algorithm within the app to sort the data by distance.

Additional Tips:

• Use a multiplication factor (e.g., mult = 1.1) when calculating the rectangle boundaries for a more accurate approximation.
• For performance optimization, consider precalculating the Haversine formula or using a dedicated library.

Conclusion:

This approach combines SQLite filtering with Java code to approximate and determine the proximity of locations. It avoids custom SQL functions and allows for the sorting of data based on a non-database column.

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