Question

I want to build database with sql server 2008 that include columns of gps coordinate-

latitude 

and

longitude

and i want to build a query that will be something like :

"Give me all rows that are within 5(for example) metres of this coordinate"

It is possible in c#??

Answer 1

C# really isn’t the problem, the problem is the database itself. MS SQL Server 2008 and higher has spatial support as described in this article:

http://msdn.microsoft.com/en-us/magazine/dd434647.aspx

Without using spatial extensions, you’d have to manually calculate the bounding box yourself (which would probably include points > 5 meters from the coordinate.) Then you’d have to restrict the results to make sure they are within 5 meters of the point in question.

Here’s a little pic of the manual (ie. somewhat painful) calculation:

---------------------
|        ^          |
|     +5m lat       |
|                   |
|-5m lon *   +5m lon|
|                   |
|     -5m lat       |
|        v          |
---------------------

The (*) is the point in question. The problem with doing the calculation manually is that the points near the corners of the box are (probably) > 5 m away from the (*) point. You could calculate the bounding circle, but that’s going to increase the complexity of your SQL query.

So – in short – you really need a DB with spatial support.