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Garmin GPSMAP 421S Chartplotter/Fishfinder



The GPSMAP 421s is a compact chartplotter that features an ultra-bright 4 in (10.16 cm) QVGA color display along with an improved high-speed digital design for increased map drawing and panning speeds. It's ready to go with a built-in, satellite-enhanced worldwide basemap and an easy-to-use interface designed to help you navigate the open waters with ease. The GPSMAP 421s also accepts BlueChart® g2 Vision® cards for added features and functionality such as high-resolution satellite imagery, 3-D views and Auto Guidance technology.

View Satellite-enhanced Worldwide Basemap

The GPSMAP 421s basemap contains worldwide satellite images in place of traditional maps. The GPSMAP 421s also comes standard with a high-sensitivity GPS receiver for superior satellite tracking and quicker acquisition times. In addition, the GPSMAP 421s can receive U.S. graphical weather data via optional GXM 51 satellite receiver/antenna. And with an SD™ card slot, it's easy to add additional maps without connecting to a computer.

Get Sonar

The GPSMAP 421s comes with a powerful dual-frequency transducer that clearly illustrates depth contours, fish targets and structures whether you're fishing in freshwater or off the coast. The GPSMAP 421s also is NMEA 2000®-certified for easy connectivity with sensors, instruments and future marine offerings.

Add Extras with BlueChart g2 Vision

With the optional BlueChart g2 Vision SD card, you can add a whole new dimension of exceptional features to your chartplotter.

  • MarinerEye view and FishEye view provide you a 3-D perspective of map information, both above and below the waterline.
  • High-resolution satellite images and aerial photographs help you orient yourself in unfamiliar areas.
  • Auto Guidance technology searches through all relevant charts to create a route you can actually follow — one that avoids obstacles, shallow water, buoys and other obstructions.

Physical & Performance:

Unit dimensions, WxHxD: 5.7" x 5.0" x 2.7" (14.5 x 12.7 x 6.9 cm)
Display size, WxH: 2.4" x 3.2", 4.0" diagonal (6.1 x 8.1 cm, 10.2 cm diagonal)
Display resolution, WxH: 240 x 320 pixels
Display type: QVGA display
Weight: 1.3 lb (590 g)
Waterproof: yes (IPX7)

Maps & Memory:

Basemap: yes
Preloaded street maps: no
Ability to add maps: yes
Accepts data cards: SD™ card slot
Waypoints/favorites/locations: 3,000
Routes: 100


CANet® compatible: no
Supports AIS (tracks target ships' position): yes
Supports DSC (displays position data from DSC capable VHF radio): yes
Audible alarms: yes
Tide tables: yes
Sun and moon information: yes
3-D map view: yes (with optional BlueChart g2 maps)
Dual-frequency sonar capable: yes
Dual-beam sonar capable : yes
Split-screen zoom: yes
Split-screen sonar/gps: yes
Ultrascroll® (displays fish targets at higher boat speeds): yes
See-thru® technology (exposes fish hidden in cover): yes
Fish Symbol ID (helps identify fish targets): yes
AutoGain Technology (minimizes clutter, maximizes targets): yes
Whiteline (indicates hard or soft bottom): yes
Adjustable depth line (measures depth of underwater objects): yes
A-scope (real time display of fish passing through transducer beam): yes
Bottom lock (shows return from the bottom up): yes
Water temperature log and graph: yes
Water temperature sensor included: yes


Frequency: dual freq: 50/200 kHz
Transmit power: 500 W RMS
Voltage range: 10-32 Vdc
Maximum depth: 1500 ft

What's in the Box:

  • GPSMAP 421s*
  • Tilt/swivel mount
  • Protective front cover
  • Power/data cable
  • Documentation

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