What's the best way to store co-ordinates (lon

Question

I'm designing a table in SQL Server 2008 that will store a list of users and a Google Maps co-ordinate (longitude & latitude).

Will I need two fields, or can it be done with 1?

What's the best (or most common) data-type to use for storing this kind of data?

Answer 1

The way I do it: I store the latitude and longitude and then I have a third column which is a automatic derived geography type of the 1st two columns. The table looks like this:

CREATE TABLE [dbo].[Geopoint]
(
    [GeopointId] BIGINT NOT NULL PRIMARY KEY IDENTITY, 
    [Latitude] float NOT NULL, 
    [Longitude] float NOT NULL, 
    [ts] ROWVERSION NOT NULL, 
    [GeographyPoint]  AS ([geography]::STGeomFromText(((('POINT('+CONVERT([varchar](20),[Longitude]))+' ')+CONVERT([varchar](20),[Latitude]))+')',(4326))) 
)

This gives you the flexibility of spatial queries on the geoPoint column and you can also retrieve the latitude and longitude values as you need them for display or extracting for csv purposes.

Answer 2

Store both as float, and use unique key words on them.i.em

create table coordinates(
coord_uid counter primary key,
latitude float,
longitude float,
constraint la_long unique(latitude, longitude)
);

Answer 3

Take a look at the new Spatial data-types that were introduced in SQL Server 2008. They are designed for this kind of task and make indexing and querying much easier and more efficient.

More information:

• MS TechNet: SQL Server 2008 Spatial Data Types,

• MSDN: Working with Spatial Data (Database Engine).

Answer 4

I don't know the answer for SQL Server but...

In MySQL save it as FLOAT( 10, 6 )

This is the official recommendation from the Google developer documentation.

CREATE TABLE `coords` (
  `lat` FLOAT( 10, 6 ) NOT NULL ,
  `lng` FLOAT( 10, 6 ) NOT NULL ,
) ENGINE = MYISAM ;

Answer 5

SQL Server has support for spatial related information. You can see more at http://www.microsoft.com/sqlserver/2008/en/us/spatial-data.aspx.

Alternativly you can store the information as two basic fields, usually a float is the standard data type reported by most devices and is accurate enough for within an inch or two - more than adequate for Google Maps.