Question

I have a geographic polygon created as follows

DECLARE @polyString as varchar(max);
SET @polyString = 'POLYGON((' + @eastAsString + ' ' + @northAsString +',' + @westAsString + ' ' + @northAsString + ',' + @westAsString + ' '+@southAsString +','+ @eastAsString + ' ' + @southAsString +',' +@eastAsString +' ' +@northAsString +'))';

DECLARE @g geography;
SET @g = geography::STPolyFromText(@polyString, 4326)

I would like to find the centre lat/long of the polygon? Is this possible inside sql server?

Answer 1

You can use the EnvelopeCenter() method of the geography type.

DECLARE @polyString as varchar(max);
SET @polyString = 'POLYGON((' + @eastAsString + ' ' + @northAsString +',' + @westAsString + ' ' + @northAsString + ',' + @westAsString + ' '+@southAsString +','+ @eastAsString + ' ' + @southAsString +',' +@eastAsString +' ' +@northAsString +'))';

DECLARE @g geography;
SET @g = geography::STPolyFromText(@polyString, 4326)
SELECT @g.EnvelopeCenter().ToString()

It would be helpful to define what exactly you mean by center of the polygon, because there are different ways of defining it.