What Is Geography Data Type?


Larry Thompson

What Is Geography Data Type?

When it comes to data types in computer programming, the geography data type is a specialized format that represents spatial data. It allows developers to store and manipulate geographic information such as points, lines, and polygons. This type of data is particularly useful for applications that deal with mapping, location-based services, and geographical analysis.

Defining the Geography Data Type

Geography data types are typically found in database management systems (DBMS) that support spatial capabilities. These systems provide built-in functions and operators for working with geographic data. The geography data type stores information about the Earth’s surface, including its shape, position, and attributes.

Working with Points

A point is one of the simplest types of geographic objects that can be represented using the geography data type. It consists of a single location defined by its latitude and longitude coordinates. For example, a point could represent a specific address or landmark on a map.

To define a point in SQL Server:

  • Create a new column with the geography data type.
  • Use the POINT function to specify the latitude and longitude coordinates.
    Name VARCHAR(50),
    Coordinates GEOGRAPHY

INSERT INTO Locations (ID, Name, Coordinates)
VALUES (1, 'Statue of Liberty', geography::Point(40.6892, -74.0445, 4326))

Working with Lines and Polygons

The geography data type can also represent more complex geometric objects such as lines and polygons. A line is a series of connected points representing a path or route, while a polygon is a closed shape with multiple points defining its boundary.

To define a line in SQL Server:

  • Create a new column with the geography data type.
  • Use the LINESTRING function to specify the sequence of latitude and longitude coordinates.
    Name VARCHAR(50),

INSERT INTO Routes (ID, Name, Path)
VALUES (1, 'Route 66', geography::LineString(
    geography::Point(34.0522, -118.2437, 4326),
    geography::Point(35.4676, -97.5164, 4326),
    geography::Point(41.8781, -87.6298, 4326)

Geographical Analysis and Spatial Queries

Once geographic data is stored using the geography data type, developers can perform various spatial queries and analysis. These operations can help answer questions like finding the nearest point of interest or calculating distances between locations.

Example of spatial query:

FROM Locations
WHERE Coordinates.STDistance(geography::Point(37.7749,-122.4194,4326)) <= 10000 -- Find locations within 10 kilometers of San Francisco


The geography data type is an essential tool for handling spatial information in programming. By leveraging this specialized format, developers can store and manipulate geographic data with ease. Whether it's mapping applications or location-based services, the geography data type provides the necessary functionality to work with spatial information effectively.

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