Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_202_115 ( id number, "station" text, "distance from wellington" text, "height above sea level (m)" text, "opened" text, "closed" text, "notes" text )

### Question ###
how much higher is the takapu road station than the wellington station ?

### Accurate SQL ###

SELECT (SELECT "height above sea level (m)" FROM table_202_115 WHERE "station" = 'takapu road') - (SELECT "height above sea level (m)" FROM table_202_115 WHERE "station" = 'wellington')