PostGIS change column type varchar => geometry

Question

I have a Postgres database with PostGIS extension on it. Also, I have a table with column lat with type (varchar 40). Column values are like this:

52.1432514
52.1431855
52.1431586

I want to convert the whole column to geometry type. When I do ALTER TABLE m_copy ALTER COLUMN latitude TYPE geometry USING (latitude::geometry); I see an error:

ERROR: parse error - invalid geometry
SQL state: XX000
Hint: "52.1432514" <-- parse error at position 11 within geometry

What am I doing wrong and what is the right query?

P.S Also I have a lon column. Maybe it is better to combine that columns?

Answer 1

You probably should just create a new column and I would suggest if you are new to PostGIS, you probably want to use geography instead of geometry. So somethng like

ALTER TABLE m_copy ADD COLUMN geog geography(POINT,4326);
UPDATE m_copy SET geog = ST_SetSRID(ST_Point(longitude,latitude),4326)::geography;

If you decide to use geometry, just replace the geography (and geog) with geometry and geom