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GPS City Q&As » Marine GPS » Garmin GPSMAP 421s Sounder with Dual Frequency Transducer Q&As

Garmin GPSMAP 421s Sounder with Dual Frequency Transducer: Collection of Water Depth (7 replies)

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Original Question

Collection of Water Depth

› Garmin GPSMAP 421s Sounder with Dual Frequency Transducer

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Adam
corner brook, NL

Original question asked on Oct 9, 2012, 12:24pm

Can you collect water depth information with this unit? If so, what is the accuracy of the depth measurements? Will the depth points have x, y, and z coordinates?

Jordan
GPS City

Reply #1 on Oct 10, 2012, 9:26am

The only way to collect depth data on a Garmin GPSMap 421S or similar unit is to place a waypoint. Depth will be added to a single waypoint. Depth will not be added to a track point. You can also buy a eternal NMEA 1083 data logger to collect that information from the NMEA feed.

The Lowrance HDS units will log depth for making maps. I have used the Lowrance HDS 10 and have seen that function in the unit.

Adam
Corner Brook, NL

Reply #2 on Oct 10, 2012, 12:17pm

Ok, if I collect a series of waypoints, then the resulting points will have a depth attribute linked to it? What is the level of accuracy associated with the depth readings?

Adam
Corner Brook, NL

Reply #3 on Oct 11, 2012, 10:46am

Do you also know where I can find a NMEA 0183 Data Logger to go with this unit?

Jordan
GPS City

Reply #4 on Oct 11, 2012, 1:58pm

I made a few phone calls and there is no guaranteed accuracy spec for the transducers. People online have mentioned they get a few inches accuracy.

Sorry we do not carry a NMEA data logger. Any serial data logger will work. Here is an example (not a recommendation) www.brig-elec.com/ Check out the DogCatcher serial data logger.

Jordan
GPS City

Reply #5 on Oct 11, 2012, 2:03pm

I still highly recommend the Lowrance units for logging depth data, specially if you are making a map. They just launched a new program today for making your own marine maps called "Insight Genesis"

One thing to note for Lowrance products is that they do not have Canadian Topo coverage for inland lakes in areas without Navionics coverage. Garmin has the ability to use Garmin Topo maps for lakes without chart data.

Adam
Corner Brook, NL

Reply #6 on Oct 12, 2012, 5:06am

Thanks so much for the help. 1 last question. I will be using the GPS unit in a small watercraft with an ourboard motor. I notice that these units do not have battery. What alternatives do I have for a power source for these units? Also, is there satellite coverage on the Lowrance units (i.e. for inland ecosystems)?

Jordan
GPS City

Reply #7 on Oct 12, 2012, 7:37am

The draw back to Lowrance is the lack of inland information in Canada. A lot of lakes will be covered under Navionics but not all. That is where Garmin is better because they can use topo mapping to supplement the lake maps for areas that are not covered. Both units don't really do satellite images. The Garmin maps have some satellite images on the marine charts but they are generally for harbors only. You will only be able to get that info with the Garmin.

If you do not have power on your boat I suggest a motorcycle 12VDC battery. They are about half the size of a car battery so they are easier to port around. I have an older boat and normally hook my electronics to a separate motorcycle battery instead of the battery that starts the motor.

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