Here are two links with a number (14 and 15) of chart apps. Hard to tell which one(s) are suitable for your specific use. They claim to rival paper charts and chartplotters.
I did some research on this a few years ago. I ended up with an Ipad, Navx and Navionics charts.
Not 100% coverage but I have coverage for the standard round-the-world trip, (via Panama / Suez Canal and Singapore) plus N. Europe, Persian/Arabian Gulf and both coasts of North and South America.
I spend about $800 on charts. That includes one year of updates. I didn’t update after that because I don’t use it to navigate the ship.
I was not aware that Navionics had coverage beyond North America. It doesn’t even have most of Mexico.
I’m not prepared to spend $800 for electronic charts. I’d just like to have a few small scale ocean and coastal charts, perhaps 30 charts, they don’t need to be official, that give very general world coverage.
I looked at trying a newer version of navionics on a newer iPad last year and was saddened to see they wanted recurring licensing payments for the charts. My bare bones system I use now on a first gen iPad gives me an AIS overview from the comfort of my rack which comes in handy when working with new mates. I don’t need a very accurate chart, but traffic info is very handy
WiFi and a little makeshift pilot plug setup. It works pretty well since the pilot plug is almost directly above my cabin. WiFi through steel and concrete is a bitch.
I got lucky, when the bridge deck was all torn up for installing the ECDIS someone had the correct wire dropped though the deck. The WiFi router is on my deck but wired up to the AIS.
I found out about it after everything was buttoned back up.
I have an AIS “WiFi antenna” that I can mount to some AIS units. A lot of AIS units don’t have a port for attachment. Once in awhile I come across about with the electronics on a WiFi that I can connect to. It’s rare for me to be on a boat with a pilot plug.
I was downbound from Portland Or one time, had a high-stepping pilot. After we let-go, dropped the tugs and got up to speed he asked me where I went to school, guess he didn’t like my answer because he seem a bit standoffish after.
On the way down the river, Willow Lower Range to be exact, I noticed we were too far to the right. I’d slumped down in my chair a bit but I bolted upright and told the pilot looks like we are too close on my side.
He told me that I wouldn’t know where we were in the river.
I thought what a flaming eff’n a$$h0le. I went down to my office where I had INavX running and brought the iPad up to the bridge. I took a screen shot and showed it to the pilot. So he says, well ok, I started the turn a little late.