NMEA Mapper 3D

User Guide

Connect your boat, record depths into your own 3D map of the seabed, and use the sonar, marks, catch log and bite times, on iPhone, iPad and Android.

Last updated: 20 October 2026

• Quick startYour first five minutes
• Connect your boatNMEA over Wi-Fi
• The screenCard, buttons and gestures
• Chart and seabedBasemaps, seamarks, 3D
• Recording depthsRecord, background, tracks
• Depth sonarHistory, scroll back, alarm
• MarksAdd, edit, share, GPX
• TracksYour trips and their depths
• Go to a markDistance, bearing, arrival
• Catch logCatches and insights
• Bite timesCalendar, sun and moon
• Depth and tideTransducer, keel, tide
• Layers and displayColours, contours, night
• Settings and adsOptions, Remove ads
• Tips & questionsAnswers to common issues
• SupportQuestions and ideas

Quick start

1. Join your boat’s Wi-Fi. Connect your phone or tablet to the Wi-Fi of your NMEA gateway, multiplexer or chartplotter. The app finds the data by itself: the status at the top left of the instrument card changes to NMEA · live.
2. Check the depth. The instrument card shows the depth, speed over ground (SOG) and heading (HDG). Tap the depth to switch between metres, fathoms and feet.
3. Set your transducer. Open ☰ › Depth and tide and enter how deep your transducer sits below the waterline, so depths are measured from the surface.
4. Press Record. Tap the red Record button on the instrument card and drive over the area. Depths are saved to your map only while recording. After a few seconds, tap Seabed at the top to see the bottom take shape in 3D.
5. Mark a spot. Tap the yellow button at the bottom right, choose what it is, and tap Save mark.

Connect your boat

What you need

• An NMEA 0183 source that sends over Wi-Fi (TCP or UDP): a Wi-Fi gateway or multiplexer, or a chartplotter or fishfinder with Wi-Fi NMEA output.
• An NMEA 2000 network works through a gateway that sends NMEA 0183 over Wi-Fi.
• For recording, the feed must include depth and GPS position.

Auto detect

With ☰ › NMEA connection › Auto detect (the default), the app tries the usual gateway addresses and ports on the boat’s network until it receives data. Most gateways are found within seconds.

Set it by hand

• TCP: enter the Gateway IP and Port from your gateway’s manual (for example 192.168.4.1 and 10110), then tap Connect.
• UDP: enter the port your gateway broadcasts on, then tap Connect.

Tap the status at the top left of the instrument card to see the details: the source, how many sentences arrive per second, and the last position, depth and heading.

Without NMEA GPS

If your boat’s feed has no position, the app uses your phone’s GPS to show where you are (the status reads Phone GPS). Marks, catches and bite times work as usual, but depths are recorded only with GPS from your boat’s NMEA feed, which is more accurate and matches your sounder.

The screen

Compass bar (top)

Shows the direction the map is facing (VIEW) and your heading.

Instrument card

• Status: NMEA · live, Phone GPS or Searching…. Tap it for the connection details.
• Depth: large, with a trend arrow and the last two minutes as a small graph. Tap the depth to change the unit; tap the graph to open the depth sonar.
• SOG and HDG: speed over ground and heading.
• Position: open it with the arrow at the top right of the card. Tap it to switch between degrees and minutes, decimal degrees and UTM.
• Next bite: the next bite period and how long until it starts.
• Record: starts and stops recording depths.

Buttons

Gestures

• Drag with one finger to move the map, pinch to zoom.
• Twist two fingers to turn the map.
• On the seabed, drag two fingers up or down to tilt the view.

Chart and seabed

The chart

• Choose a street chart or a satellite map in ☰ › Layers › Basemap.
• Seamarks adds buoys, lights and harbour marks from OpenSeaMap.
• Recorded areas outlines everywhere you have recorded depths.
• Areas you have viewed are kept on your device, so they still show without a connection.

The 3D seabed

• Tap Seabed at the top to see the bottom in 3D, built from your own recordings. Between nearby soundings the app fills in the bottom; areas you haven’t recorded stay flat.
• Tilt with two fingers, twist to turn, pinch to zoom. Your marks stand on the bottom at their depth.
• From the chart, tap one of your tracks and choose Seabed here to dive straight to that point.
• Tap Chart to come back to the surface, or zoom out and tap Surface.
• The colour scale at the bottom left shows the depth range in view.

Recording depths

1. Tap Record on the instrument card. It changes to Stop with a blinking dot, and the card gets a red frame.
2. Drive over the area. A row on the card shows the time, the distance and how many depths have been saved, and the tide being taken off (see Depth and tide).
3. Tap Stop. A summary shows what was recorded; Resume carries on if you stopped by mistake.

• Depths are saved only while recording, and only with GPS from your boat’s NMEA feed.
• Short spikes from the sounder are filtered out, and each depth is stored at the moment and place it was measured.
• The 3D seabed of a new area appears a few seconds after its first depths.
• Driving lines a few tens of metres apart gives the most detailed map.

With the screen off

Recording carries on when the screen is off or you use another app. The data received in the meantime is added when you return to the app, with each depth at the time it was measured.

• iPhone and iPad: the app needs location access to keep running in the background. If it is off, the card warns you and recording pauses in the background.
• Android: a Recording depths notification shows while recording. Allow notifications for the app when asked.

Depth sonar

Open it by tapping the depth graph on the instrument card, or with ☰ › Depth sonar. On a phone held upright it opens at the bottom of the screen; in landscape and on tablets, at the side. The arrow button fills the screen.

• The newest depth is at now, with older readings scrolling left. Choose 1 min, 2 min or 10 min.
• Minimum and maximum depth and the water temperature are shown at the top.
• Right of now, faded: the bottom ahead along your course, from your recorded map.
• Your marks sit on the profile where the boat passed over them.
• Touch the upper half to see the depth at that moment, how long ago and how far back it was, with a pin on the map. Show on map moves the map there.
• Drag the lower half left or right to scroll through the whole history. Back to live returns to now.
• Mark here adds a mark at the boat, or at the moment you are looking at.

Shallow alarm

Turn it on and set the depth in the Shallow alarm row of the sonar. When the water gets shallower, a red banner appears under the compass, the depth turns red, and the phone beeps and vibrates every few seconds until the water is deeper again. Tap the banner to silence it. The alarm works with the sonar closed.

Marks

Add a mark

1. Tap the yellow button at the bottom right. The New mark card opens.
2. Where: At the boat, or Map point to drag the map and place it exactly.
3. What is it?: Pin, Fish, School, Hotspot, Wreck, Rock / reef, Anchor or Hazard. For fish, choose the species.
4. Add a colour, a note and tags such as Good bite, Bait fish, Structure or Snag.
5. Tap Save mark. The depth at that spot is filled in from your recordings.

Use a mark

Tap a mark on the map to see its type, depth, date and position, and the live distance and bearing from your boat. From its card: Go to, Log catch, Edit and Share.

All your marks

☰ › Marks and tracks lists your marks, sorted by Newest, Nearest or A–Z and filtered by type.

• Export GPX saves every mark in one GPX file through your share options.
• Import GPX shows what a file will add before importing it, and can be undone.
• Show marks on map hides or shows them all.

Tracks

Every recording becomes a track. Find them in ☰ › Marks and tracks › Tracks, with the date, duration, distance and number of depths.

Tap a track on the map to see the depth saved at that point and when, with the distance and bearing from your boat. From its card:

• Whole track zooms out to show all of it.
• Seabed here dives to the 3D seabed at that point.
• Hide takes it off the map; it stays in the list.
• Share sends it as a GPX file with its depths.
• Delete removes the track after asking first. The depths it added to your map stay.

Go to a mark

Tap a mark and choose Go to. A bar shows the distance and bearing to the mark, your course and speed, the time to go, and whether to steer left or right. Tap Stop on the mark’s card to end it.

When you arrive within the arrival radius, the app plays a sound and vibrates. Set the distance units (nautical miles, kilometres or miles), the radius, and the sound and vibration in ☰ › Navigation. Test alert plays it.

Catch log

Log a catch

Hold the yellow button (at the boat), or tap Log catch on a mark’s card.

• Add a photo (take one or choose one), the species, length and weight. Tap a value to change its unit. + Add fish adds your own species.
• Add the bait, whether it was released, a note, and whether to mark the spot.
• Depth, water temperature, bite period, time, moon and place are filled in for you.

Your catches

☰ › Catch log lists your catches, newest first, filtered by species, with your personal bests marked PB. Tap one to show it on the map, edit or delete it.

The Insights tab finds the patterns: catches by hour, how many fell in bite periods, by moon phase, the depths each species was caught at, and the baits that worked.

Bite times

Fishing calendar

☰ › Fishing calendar shows each day of the month rated from one to four, with its moon phase. Tap a day to see:

• a 24-hour timeline with the major and minor bite periods, dawn and dusk, the sun and moon, and your catches;
• the best times, each with Remind me, which sends a notification 15 minutes before, even with the app closed;
• sunrise, sunset, moonrise and moonset;
• your own catches on days with the same moon.

Times are worked out for your boat’s position, or the last one known.

Sun and moon

☰ › Sun and moon shows sunrise and sunset, civil, nautical and astronomical dawn and dusk, moonrise, moonset, how much of the moon is lit, and the next eclipse.

Depth and tide

Open ☰ › Depth and tide.

Transducer

• Fore / aft and Port / starboard: where the transducer is, measured from the GPS antenna. The app uses this to place each depth exactly.
• Transducer depth: how far below the waterline it sits.

Depth readout

• Depth shown from: Surface, Transducer or Keel.
• Keel draft: from the waterline to the lowest point of the boat.

Tide

Recorded depths are saved to chart datum, so recordings from different days and tides fit together.

• Auto: the tide is predicted from the nearest tide station, where one is within 100 km.
• Manual: enter the tide height now, above chart datum. Update it every hour or two.
• Off: no tide correction, for lakes and waters without tide.

Layers and display

Open ☰ › Layers.

• Basemap: Chart or Satellite.
• Seamarks, Recorded areas and Marks: show or hide them.
• Seabed colour: Depth colours or a Textured bottom.
• Contour lines: every 1 to 100, in metres, feet or fathoms.
• Display: Day, Dusk (dimmed) or Night (dim red, to keep your night vision).

Settings and ads

Open ☰ › Settings.

Remove ads

The app is free with a small banner ad. ☰ › Remove ads removes it for good with a one-time purchase. There’s no subscription. Restore Purchases brings it back on a new device, and Privacy options changes your ad consent where that applies.

Tips & questions

The status stays on Searching.

Check that your phone is on the boat’s Wi-Fi and that the gateway is switched on. Some phones leave a Wi-Fi network that has no internet; choose to stay connected when asked. On iPhone and iPad, check Local Network access for the app. If Auto detect doesn’t find your gateway, enter its address and port by hand in ☰ › NMEA connection.

There is a position but no depth.

Your sounder must send depth (DBT or DPT) to the Wi-Fi feed. On some chartplotters NMEA output to Wi-Fi has to be turned on in their settings.

Nothing was recorded.

Depths are saved only while Record is on and only with GPS from your boat’s NMEA feed. With Phone GPS, nothing is recorded.

The seabed is flat.

The 3D seabed shows only where you have recorded. Record over the area, and give a new area a few seconds to appear.

My depths don’t match the chart.

Set your transducer depth and choose where the depth is shown from in Depth and tide. In tidal waters, turn on the tide correction: charts show depths at chart datum.

Recording stopped when the screen was off.

On iPhone and iPad, allow location access for the app. On Android, allow notifications and don’t restrict the app’s battery use.

The map is blank without a connection.

Only areas you have already viewed are on your device. Look over the area while you are online before you go out.

Support

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