Google Earth now has a ‘historial images’ tool, which on my mac is in the form of a clockface-meets-arrow icon, and brings up a tool looking like this:
Moving the slider lets you change the date of satellite images.
Somewhat wonderfully for sailors on the River Blackwater, and seemingly also for most of Essex and Suffolk, a couple of the recent series of images seem to have been taken at spring tides, both high and low.
For shallow draught dinghy cruisers, happy to dice with a mudbank or two, this lets you now plan new routes thanks to the offer of accuracy with which a nautical chart can’t compete.
For example, to the south west of Bradwell Waterside, on the River Blackwater in Essex, there is a large mudflat, through which flows a narrow and winding channel known as St Lawrence Creek.
At anything other than high or low tide, this route is a bit iffy, since it’s hard to know when you’re in the channel when the whole mudflat covers with water, albeit not to a depth to let you sail safely.
This is a shame, as it’s a nice shortcut home to my base at Bradwell Waterside, where I keep my 14 foot Wanderer sailing dinghy.
Here’s the Navionics chart of the St Lawrence creek:
Now, here’s the same area at spring low tide from Google Earth, complete with a series of waypoints which I then use on my GPS to let me follow the channel whatever the state of the tide.
Following this route carefully means I don’t have to worry about my rudder hitting the bottom were I to stray onto barely-covered mudbanks at mid-tide.
To be fair, there’s no need to follow this route at or near high tide, shown below, as there’s enough water everywhere. But at mid tide, it’s a reassurance that you won’t hit the bottom.
I’ve tested the route a couple of times mid-tide, and am happy to share waypoints if anyone’s interested (YMMV, mud shifts etc).