title: new row for relation "venues" violates check constraint "enforce_srid_latlon"
body: <p>I'm getting the following error when I try to create a new venue that is location aware.</p>
  
  <pre><code>ActiveRecord::StatementInvalid: PG::Error: ERROR:  new row for relation "venues" violates check constraint "enforce_srid_latlon"
  </code></pre>
  
  <p>This is the method I follow to recreate the error.</p>
  
  <pre><code>v = Venue.create(:latlon =&gt; "POINT (43.245332 -85.4352332)")
  v.save
  </code></pre>
  
  <p>I did notice that in my migrations, I did not set the :geographic => true property for t.point :latlon. Could that be what's causing my problems? If so, how do I set that flag to true on a column that already contains data?</p>