satellite accuracy and chart navigation?

John has a good point; an iPhone, for example, will give you your position either from the GPS or telemetry from the mobile network masts. But if you were outside, it would certainy use its GPS.

As John writes, a smart phone GPS is a simple one. For example, if you buy a TomTom bracket to put say in your car, it contains its own GPS receiver that increases the quality of the position finding.

Another factor is that, maritime charts are not necessarily updated to the WGS-84 standard used by the GPS. In the past, each country had its standard of geographical reference and maritime charts were drawn accordingly. When the GPS came in use, charts were printed with, in the margin, the WGS-84 correction to add or subtract. In places there could be differences of perhaps two hundred yards. But never a mile or so.

Are you sure you read the position correctly? Latitudes and longitudes can be read as degrees and fraction of degree, or degrees, minutes and fraction of minute, or degrees, minutes and seconds. Aviation still gives position as the latter while seafarers now use degrees, minutes and fraction of minutes.

Some smart phones get an approx. position by judging the signal strength from the nearest masts, not from the GPS system. So I'd guess the numbers were wrong.

Try again with a proper GPS device.

By "satellite numbers" I assume you mean GPS location. That is accurate to a yard or so.