Is this Class G Airspace? So it's been about a decade since I got my private pilot cert and almost as long since I got to fly. My map reading is a little rusty. 

I'm trying to fly my drone at a local park and it's warning me that I'm in Class D airspace. I've marked on the map where the park is.



If I'm reading this correctly, then I should be in Class G airspace up to 700ft AGL

Am I missing something or is this probably just a bad GPS signal on start? 

I'm not getting repeated warnings so I think it's a bad signal but I figured a prudent pilot would check.
Provided the drone is flying where the red dot is, you are correct and Class G extends from the surface to 700 ft AGL.  If you really wanted to play it safe, call the tower at KBKL to establish two way radio comms before flying there.