Go to google maps and switch to the satellite view. Put your cursor where you want to measure from and right click. A menu will pop up, select the last item labeled "Measure Distance". Then left click on the spot you want to measure to and it will give you the distance. You can also keep adding more waypoints and even join them all together to get an area measurement.
Depends on where you're measuring from but it looks to me to be about 515 feet.
Thanks Piscivore, great idea, works great. I ended up using the gps functions to place a pin in my starting location and destination, keeping note of the longitude & latitude coordinates it provided. Then entering them as my travel points as if I were walking. I got 500 feet between my points of interest.
Now I can practice in an open field with measurement points mimicking standing on a slippery rock and not moving my legs while casting a 3 oz plug without hooks.