Coverage planning usually require complex and expensive tools to predict wave propagation using terrain models.
However since many years, Roger Coudé has developed a planning software for amateur radio, implementing the Longley-Rice model and using public terrain height maps. This software can also be used to make a prediction of broadcast coverage, including the use of directional antenna systems and VHF band III. It requires some time to get used to the way of working, but is definitely worth the effort.
Example for FM broadcast coverage prediction:
Transmitter maker Nautel has on their website a coverage prediction tool that can be used after registration:
It appears to be based on the Radio Mobile website by Roger Coudé. The limitation is that the antenna directivity diagram cannot be included, but for omni-directional transmissions this is quite handy.
To generate the antenna pattern model from specification documentation one can use the antenna pattern editor from