Converting LinestringM to Polygon PostGIS

Question

I'm working with PostGIS and plotting polygons on a Google Earth plugin. I've found a few examples via Google on how to convert a LinestringM to a Polygon for rendering, but none of them, including the PostGIS docs, define very well the params for a LinestringM. Can someone identify what's happening here? Specifically, I need to know what each of the four params of LinestringM are supposed to represent.

Snippet:

....
parameters.put("wkb_geometry", "ST_MakePolygon(ST_GeomFromText('LINESTRINGM(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)'))");
....

Answer 1

A LINESTRINGM is a linestring with three dimensions: x, y and m (measure). The LINESTRINGM in your example is wrong because it's only defined by x and y. Instead this is how it should look like:

--measured line --
SELECT ST_MakePolygon(ST_GeomFromText('LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)'));

Compare: http://www.tokumine.com/postgis/

Specifically, I need to know what each of the four params of LinestringM are supposed to represent.

If I understand you correctly, you're referring to the four points that make up the line.