To obtain your measurements Mr. Macon, you and your friend can employ online NOAA Navigation Chart 18649, Entrance to the Golden Gate. https://www.charts.noaa.gov/OnLineViewer/18649.shtml
You'll indeed discover that Mile Rocks Light is located one half mile from the shoreline of Lands End. Historically these rocks, among others, proved major navigational hazards to shipping. Prior to and even with navigational aides the entrance to San Francisco Bay is the scene of scores of vessel accidents.
How Mile Rocks earned their name is another question. While plying the main shipping channel profesional mariners and alert recreational skippers leave those hull ripping rocks at least a mile to the south to sail safely in or out of port. If after you’ve read the material I posted to you earlier you desire further information seek the book, "Guardians of the Golden Gate: Lighthouses and Lifeboat Stations of San Francisco Bay,” by Ralph Shanks and Lisa Woo Shanks. For a history of shipwrecks, a good bet is “Shipwrecks at the Golden Gate” by James Delgado and Stephen Haller. Unfortunately this book is out of print so browse used book stores or seek it through a public library.