On Sectional Charts, what do the upside down V and M symbols indicate:
Thanks
The upside down V indicates a obstruction of 300 ft or higher from AGL level
the M indicates a group of obstructions 300 ft or higher from AGL level.
See page16 or page 30 of the link
The elevation of the top of the obstacle above Mean Sea Level (MSL) and the height of the structure (AGL) is also indicated (when known or can be reliably determined by a Specialist). The AGL height is in parentheses below the MSL elevation. In extremely congested areas, the FAA typically omits the AGL values to avoid confusion.