I am interested in mobile navigation apps. I do not own a boat and when I rent one, I'd like to have some tool to locate myself on the water and keep me out of dangerous or shallow areas . At a minimum, it would show my position, Aids to Navigation, and charted water depth by using NOAA charts that are frequently updated. I am initially looking at free or inexpensive apps that have minimum or no cost associated with installing and updating charts.
After reading some comparisons online, I decided to try SEAiq USA for the iPad. It has many more features than my minimum requirements. It was easy to add NOAA charts that include the Potomac River and Chesapeake Bay. Using the app for about a week, it has already prompted me to get updates to the charts I have installed.
There is a free trial, and the cost to buy the iPad/iPhone version of SEAiq USA is only $4.95 which is intended for recreational use. Full details are available at http://www.seaiq.com. The least expensive option for Android devices is $49.
Other versions are available for Android, Mac and Windows computers and the pricing varies up to a $300 version intended for pilot use.
I have explored the app at home, but not on the water yet. The charts look very much like paper charts and it does take some practice zooming in and out to see the desired level of detail and the desired scale. After taking the Navigation class recently, it is quite interesting looking at the charts in this SEAiq USA app.
I will update this posting after using SEAiq while sailing.
Update: In July 2018, I did use my iPad with SEAiq on a Wednesday evening social sail. It worked great. I could see our speed and course and the position was accurate as verified as we approached and passed navigational aids. The only problem I experienced is that an iPad is difficult to view on a clear sunny day. I have to use something to shade the screen because even with the highest brightness setting, the sun can be too bright for the iPad to usable.
I am a fan of mobile navigation apps. There is great value having a system that you are familiar with and you know is up-to-date, neither of which is always the case with the charter boat integrated nav systems. Also, for boat owners, an I-pad with navigation software and a gps feed is much cheaper and easier to replace than an integrated system, though it is less robust and cannot usually be used to operate autopilots.
There are a lot of software packages out there, which one is really user preference. I have used both MXMariner and Navionics, but there are others that are fine too. I personally think Navionics is way overpriced for what it provides, but lots of people use it. The important things to consider are the charts and the position source.
The charts should be from a reliable source, which for marine navigation means either NOAA or the UK Hydrography Officer (called Admiralty charts). Many companies also make their own charts (Navionics for example) but these tend to be good in popular areas and less so in unusual cruising areas. Also, you need to know when the charts are updated and how often. NOAA and Admiralty charts are updated every week, so if you system only gets an update once per year you could be missing a lot of important information.
The second, and frequently mis-understood factor is the position data. GPS is a great tool for location, and you should use it. Any smartphone will provide position data with GPS-level of detail, but most of that is based on the phones position relative to cellular towers that have known locations. Many phones do not have independent GPS receivers, so once you are out of range of the towers (usually about 20 miles) they will no longer provide a reliable position. This may not be a concern in the Annapolis-Baltimore area where cell signals reach the whole way across the Bay, but in the Southern Bay and many other locations it can be perilous. Many phones can be bought with a receiver or have one connected by Bluetooth or wifi, at low cost to provide world-wide position precision.
The issue about reliability of GPS on a mobile device was one of my initial concerns. I had read about "gps assisted" modes that used cellular towers to determine position. I see notices in some apps "enable wireless networking to improve location accuracy". When reading the specs of some devices it was difficult to determine if the device actually had the capability to operate only with true satellite based GPS.
I decided to do a test of my iPad with cellular, wireless and bluetooth turned off (even removing the SIM just to be sure). I was happy to see that my iPad was accurately showing my location, course and speed while sailing. That should be a valid test of the GPS function for any device.
I do make sure that before sailing, I enable networking and check for updates to the NOAA charts and download them.
I believe that using the true GPS in mobile device is more of a battery drain than the "assisted" GPS that uses cellular and/or wireless networks. That has not been a problem since I have not sailed for more than 4 hours at a time yet.