I use Sailsafe on my Sony Xperia Tipo
phone. There is a "pro" version with extra bells and whistles but I have found the basic version to
work well.
Some tips on best use if I may:
Make sure your
GPS is active before you drop your
anchor, it can take time to get that fix
Whenever possible update your "assisted" datafile as this will improve the accuracy
Activate the
alarm app as soon as you start dropping the
anchor not when it hits the seabed
Calculate the maximum circle including the length of your
boat then add a little extra for any accuracy degradation (not too much though)
Put your
phone in standby including Airplane mode and switch off any data or
wifi to improve
battery life. Like this my phone will watch over my anchor for 3 days. My
laptop dies after 6 hours and I have never got the
alarm to
work on my
chartplotter.
I also have a Bluetooth
GPS device with an associated (free) app so that I can leave the BT GPS on the roof sending a stronger signal to my phone in the
cabin. Not normally necessary but if your anchorage is heavily wooded you can lose the signal from the satellites as they get closer to the horizon. Extra signal strength from the few satellites overhead can improve accuracy or at least minimise the degradation.
aGPS is "assisted" in the same way that dGPS is. Differential GPS uses known signals from known
radio towers to improve the accuracy, assisted does it from cell towers. It's the same basic system we use in chartplotters that use sGPS or WAAS which is
Satellite Differential GPS using geostationary GPS satellites to improve the triangulation.
Why do I use an anchor alarm? Not because I don't trust my ability to set my anchor well or for it to hold but because it is an extra arrow in my arsenal to ensure a calm, restful nights sleep.
Keiron