GPS in Aqua Map: how it works and what it shows you

Your position on the water is the single most important piece of information any navigation app gives you, and it all starts with GPS. Aqua Map connects to your device's internal GPS and compass sensors to show exactly where you are on the chart, in real time, and it gives you a few different ways to view that position depending on how you like to navigate.

This page walks you through how GPS works in Aqua Map, the three display modes you can switch between, and how to read the info box that appears once your GPS is active.

A quick note on GPS accuracy

Most smartphones and tablets have a built-in GPS chip, but not all of them do. Some devices, like WiFi-only iPads, don't have internal GPS hardware. In that case, Aqua Map will estimate your position using WiFi and cellular data instead. This works fine for general reference, but it's not accurate enough to rely on for actual navigation.

If precise positioning matters for what you're doing, whether that's threading a narrow channel or anchoring close to a reef, always check that you're getting a real GPS fix rather than a network-based estimate. Aqua Map can also connect to an external GPS device over a Wi-Fi connection for even more reliable positioning, which is worth considering if your device doesn't have built-in GPS.

The three GPS modes

Managing GPS in Aqua Map comes down to a single button in the upper left corner of the map. That same button also shows you which mode is currently active, so you always know how the map is behaving without digging through menus.

Tap the button and it cycles through three modes, one after another:

Not centered . The map stays where you left it and doesn't automatically follow your GPS position. This mode kicks in automatically whenever you pan or zoom manually, except when you use the plus and minus buttons in the scale box. It's useful when you want to look ahead on the chart or check something without losing your current view.

North-up mode . The map continuously re-centers on your GPS position, with cartographic North fixed at the top of the screen. This is the classic chart-plotter view many mariners are used to. One thing to know: if your Perspective View setting (found on the Settings page) is set to Automatic, Perspective Mode will be disabled while you're in North-up mode.

Heading-up mode  . Like North-up, the map keeps following your GPS position, but now it also rotates so the top of the screen always points in the direction you're actually moving, either your Course Over Ground (COG) or your compass heading (HDG). Your position is placed slightly below center rather than dead center, so you get a better view of what's ahead of you rather than what's behind. If Perspective View is set to Automatic, this is the mode that will switch Perspective Mode on.

If you want the map to actively follow you as you move, North-up or Heading-up are the modes to use. Not centered is really a manual browsing mode.

One more icon worth knowing: if you see a small overlay icon on the GPS button itself , it means your position is coming from an external GPS device connected over Wi-Fi, rather than your device's built-in sensor.

Reading the GPS info box

Once GPS is active, a small info window appears on top of the map. It's compact, but it packs in the data you'll actually use while underway.

Here's what you'll find in it.

• GPS quality , shown as a color-coded indicator. Green means a good, reliable fix. Yellow and red mean lower quality, which can translate into real inaccuracies in your displayed position, so it's worth keeping an eye on this rather than assuming your dot on the chart is always exactly right.
• SOG (Speed Over Ground), your boat's speed relative to the earth's surface, not the water. If you've set your boat type to "Sail" on the MyBoat page and you're actively following a route, SOG automatically alternates with VMG (Velocity Made Good), showing your effective speed toward the next waypoint rather than your raw speed over ground.
• COG (Course Over Ground), the actual direction your boat is moving, which isn't necessarily the same as where your bow is pointed.

In most US canals and rivers, you'll also see a third figure appear in the info box: the Mile Marker (MM) that corresponds to your current GPS position, a handy reference if you're navigating waterways where mile markers are the standard way locals and charts describe location.

Why this matters beyond the basics

GPS is the foundation everything else in Aqua Map builds on. Your position feeds into route planning, anchor alarms, AIS collision detection, and how weather data is matched to your exact location. A good, stable GPS fix isn't just about the dot on the screen looking right, it's what makes every other safety feature in the app trustworthy.

If you're navigating in areas where signal can be inconsistent, offshore, in canyons, near tall structures, it's worth pairing your device's GPS with Aqua Map's official offline nautical charts, so you're never left without a reliable picture of where you are, connection or not.