Key
| Heavy Anti-Aircraft site |  | Z Battery |  |
| Site No. | Name | OS Grid Reference |
| H12 | Nacton Heath | TM 203 417 |
| H14 | TM 214 444 | |
| H16 | TM 141 403 | |
| H18 | Grove Farm | TM 164 467 |
Coding sequence integral with Harwich & Martlesham
Gun Strengths
Overlord & Diver
| Dates | 3.7 inch static | 3.7 inch |
| Mar 44 | 4 | 16 |
| Apr 44 – Aug 44 | 8 | 8 |
| Jan 45 | 8 | 0 |
Heavy AA Regiments known to have occupied sites in this GDA
| Dates | Units |
| Jun 40 – May 41 | 99 Heavy Anti-Aircraft Regiment |