SQL Server Latitude/Longitude Storage: Decimal or Float?

Determining the Appropriate SQL Server Type for Double Values

When mapping C# double properties that represent latitude and longitude values to SQL Server, the optimal data type is crucial for ensuring precision and accuracy. While SQL Server does not have an explicit double type, this article compares the suitability of decimal and float data types for this purpose.

Precision Considerations

For latitude and longitude values, high precision is essential.

• Decimal(x,y): This data type represents fixed-point decimal numbers, providing exact representation and eliminating rounding errors.
• Float: This data type uses floating-point arithmetic, which can result in approximations and loss of precision, especially for very large or small numbers.

C# Double vs. SQL Server Float

In C#, double is a 64-bit floating-point type. The equivalent in SQL Server is float, also a 64-bit floating-point type. Tests have shown that double and float exhibit 100% compatibility in representing binary numbers, providing no significant difference in accuracy.

Float(24): A Compact Alternative

For latitude and longitude values, which typically require only five decimal places of precision, the float(24) data type can be a suitable alternative. It offers a compact representation, using only 24 bits, while still providing sufficient accuracy for most scenarios.

Decimal(8,5) vs. Float(24)

Decimal(8,5) offers higher precision than float(24), with eight digits before the decimal point and five digits after. However, for latitude and longitude values with limited range and precision requirements, float(24) provides an efficient solution.

In conclusion, when storing double values representing latitude and longitude in SQL Server, float(24) or decimal(8,5) is recommended. Float(24) offers a compact representation with sufficient accuracy, while decimal(8,5) provides higher precision for more demanding scenarios. The choice depends on the specific precision requirements of the application.

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