TO DO THIS: SEE PAGE(S): Turn the unit on or off. 4 Adjust screen backlighting. 6 Enter data and select options. 3 Learn how to operate the units function keys. 1 Mark your present location as a waypoint. 44 Go to a destination. 53 Create and use a route. 57 Pan using the map arrow. 23 Zoom in or out on the Map Page. 24 Reconfigure the Map Page display. 25 Adjust Sonar settings. 33 Reconfigure the Sonar Page display. 36 Access the Main Menu. 67 Change units of measure (statute, nautical, metric). 85 Change the displayed time (zone). 86 View tide information. 73 View celestial information. 74 Set Alarms. 90 Use the Find function. 65 View a unit message. 106
(ZOOM) OUT Key The OUT key adjusts the map scale to display a larger area with less detail. (Zooms out) (ZOOM) IN Key The IN key adjusts the map scale to display a smaller area with more detail. (Zooms in) PAGE Key The PAGE key selects the main pages in sequence and returns display from a submenu page. QUIT Key The QUIT key returns the display to the previous page and, when entering data, it restores the previous value (cancels data entry). ARROW KEYPAD The ARROW keypad is used to select (Highlight) menu options and enter data. It also controls cursor movement on the Map Page. ENTER/MARK Key The ENTER/MARK key selects a highlighted menu option. When entering data, it allows you to initiate entry, and then to accept the selected value(s). It also marks the current location as a waypoint when pressed and held for more than one second. MENU Key The MENU key displays a menu of available options for the current page. Press twice (or press and hold for more than one second) to display the Main Menu. NAV/ MOB Key The NAV key displays the Go To and Follow navigation menu. MOB (Man Over Board) actives the Man OverBoard navigation feature when pressed and held for more than one second. FIND Key The FIND key activates the find function to search for nearby items and user waypoints. POWER/ BACKLIGHT Key The POWER/ BACKLIGHT key turns on/off the unit and and adjusts the display illumination/contrast. Multiple presses toggle the units backlight between maximum, user-set, and minimum brightness levels.
Getting Started Keypad Usage

Arrow Keypad

Power Key Always press and release a key to perform its primary function. Press, hold for more than one second, then release the ENTER/MARK , NAV/MOB, and MENU keys to activate their secondary function.
Getting Started Selecting Options
The GPSMAP 178/178C Sounders advanced keypad system is designed to allow for fast, convenient selection of navigation options and data entry. The Getting Started Tour introduces you to the keypad and provides a hands-on lesson in using the GPSMAP 178/178C Sounder. We strongly encourage you to follow the Getting Started tour before using your unit for actual navigation. The GPSMAP 178/178C Sounder Quick Reference Guide contains helpful tips on using the unit and performing various navigation tasks.

Selecting Options and Entering Data
You can select and activate options and enter data to customize the GPSMAP 178/178C Sounder to fit your requirements. You can use the ENTER/MARK key and ARROW KEYPAD to select options, enter names and numbers in data fields, and activate your selections.
Options Menu with highlighted option. Use the ARROW KEYPAD to highlight the next option. Press ENTER/MARK to activate.
To select and activate an optional feature:
1. With any page displayed, press the MENU key to pop-up the options menu. The options menu displays a list of optional features which are specific for that particular page. To select any feature on the list of options requires movement of the cursor, which is identified as highlighting, selecting or choosing an item in a list or a field (box) on a page. 2. Use the ARROW KEYPAD to move the cursor (highlight) up and down a list or up, down, and sideways on menus. 3. Once you have moved to the desired selection, press the ENTER key to either activate the feature or the MENU key to pop-up a sub-menu or list of yet more feature options. Repeat this process to select an option from the list or press the QUIT key to return to the previous setting. The QUIT key moves backwards through these steps or back to the main page you started on.
To select and activate a function button:
1. When moving about a page with function buttons, like the New Map Waypoint Page, you observe functions such as Delete, Show Map, and OK. To activate the function, highlight the desired button and press the ENTER key.
Pop-up list of options for a highlighted field.
Naming a waypoint or placing any sort of data that has not been predefined requires the use of both the ARROW KEYPAD and the ENTER/MARK key. To enter a name or number in a data field:
1. Once you have accessed a page with programmable data fields (e.g. Waypoint Edit) you can use the ARROW KEYPAD to move the cursor (highlight) to fields on the page. Use the UP/DOWN arrows to move up or down and the LEFT/RIGHT arrows to move sideways. 2. Pressing the ENTER key with the field highlighted begins the process for entering data in the form of alphanumeric characters. 3. Use the ARROW KEYPAD UP/DOWN arrows to cycle through numbers 0 to 9, plus/minus symbols, blank space, and the alphabet. Pressing and releasing the keypad moves you character by character through the list. Pressing and holding the keypad moves you rapidly through the list. 4. Use the ARROW KEYPAD LEFT/RIGHT arrows to move to the next character on the line or backwards to edit characters. If there are more than two lines of data, keep pressing to the RIGHT to drop down to the next line. 5. When data entry is completed press ENTER to accept data, then move to the next programmable field. Not all data fields are programmable, such as the date and time. When moving about a page with these fields, the cursor skips over them.

1. Press the MENU key twice for the Main Menu. Press Up or Down on the ARROW KEYPAD until the GPS tab is highlighted, then press the MENU key once. 2. Use the UP or DOWN arrow of the ARROW KEYPAD to highlight the Start Simulator option and press ENTER. Choose No to the retail demonstration and press the ENTER key. 3. Press the ENTER key to confirm the Running Simulator message that appears at the bottom of the display. Simulating appears at the top of the Main pages.
Getting Started Simulator Mode
While in Simulator mode, a Running Simulator message appears after 2 minutes of inactivity. Now youre ready to continue the rest of the simulated tour. Keep in mind that the GPSMAP 178/178C Sounder does not track satellites in simulator mode, and this mode should never be used for actual navigation. All the waypoint and route planning done in simulator mode is still retained in memory for future use.
A Running Simulator message appears after 2 minutes of inactivity.
Getting Started Main Pages/ Map Page

Main Pages

The Map Page is one of six main pages used in the GPSMAP 178/178C Sounders system. The six main pages are the Map Page, Map/Sonar Split Page, Sonar Page, Compass Page, Highway Page, and Active Route Page. All pages are linked together in a simple chain, which allows you to scroll through the pages in either direction using the PAGE and QUIT keys.

Map Page

Map/Sonar Split Page

Sonar Page

Compass Page

Highway Page

Active Route Page
The GPSMAP 178/178C Sounders Map Page combines digital chartplotting with a user-selectable display of navigation data and a built-in worldwide database. It is also the page you use most to create and edit waypoints and routes. Before we take off on our practice route, lets take a brief look at its various features and displays. The map display shows your boat as a triangle marker on an electronically generated chart. Geographic names, roads, markers and buoys that are provided by the optional BlueChart or MapSource data are also shown. It also displays your track, routes, and nearby waypoints. An on-screen cursor lets you pan to other map areas, determine the range and bearing to a position, and perform various waypoint and route functions. The data window, located at the top of the page, provides a user-selectable display of various navigation data, including speed over ground, distance to the next navigation point, compass ribbon, and current position coordinates. The current map scale setting is located at the bottom right of the page.

Press ENTER/MARK after entering the name.
You can choose from a list of useful symbols. There are two Diver Down waypoint symbols to select from: the International and U.S. versions.
The waypoint is now stored in memory. Note that waypoints may also be created graphically from the map display or by manually entering position coordinates. Each of these techniques is described in the reference section of this manual.

Going to a Destination

GPS is all about marking positions as waypoints and navigating to them using the receivers steering guidance and map displays. Weve already seen how to use the ENTER/MARK key to store your present position, so its time to move on to the fun partgoing to a destination. The NAV/MOB key, located on the keypad above the QUIT key, is the primary tool used to select a destination waypoint, TracBack, or a route to navigate. The NAV key can be used in two primary ways: Pressing NAV once displays a list of options from which you can select Go To Point, Follow Route, Follow Track, or Stop Navigation. Highlighting an on-screen waypoint or map item as a destination directly from the Map Page and pressing NAV allows you to graphically select points to Go To. For our simulated trip, youre going to select a pre-programmed tour route using the first method. This also shows how the MENU key is used throughout the GPSMAP 178/178C Sounder system to provide tab style options and functions. Lets start by changing the position to where the practice route is located. To change the GPSMAP 178/178C Sounder position in simulator mode:
1. Press the MENU key twice to display the list of Main Menu tab items. 2. Use the UP or DOWN arrow of the ARROW KEYPAD to highlight the Setup tab, then LEFT or RIGHT to highlight the System submenu tab. 3. Highlight Set Position in the simulator setup window and press ENTER. 4. From the Initialize Position Page, press the MENU key. You see Enter As Text highlighted, then press ENTER. 5. On the Enter Position window, press ENTER then use the ARROW KEYPAD to enter N3456.800, W07624.066 and press ENTER when done, then press QUIT to return to the Map Page.
Getting Started Using the NAV Key
Text entry for simulator position.
For future practice, you may skip steps 4 and 5 and point to a location from the Initialize Position Page.
Getting Started Simulated Tour
To activate the practice route stored in memory for navigation:
1. Press NAV. The option list page appears. (If you were selecting a single waypoint to navigate to rather than a route, you could highlight the waypoint on the map, press NAV and then press ENTER.) 2. Use the ARROW KEYPAD to highlight the Follow Route option. Press ENTER to confirm. 3. The Select Route Page appears, with the GPSMAP TOUR route highlighted. 4. Press ENTER then highlight Activate and press ENTER again.
To zoom in to a closer map scale:
1. Repeatedly press the IN key until the 3 nm scale displays.

Reference Map Page: Cursor
When the cursor reaches the edge of the map, the unit may pause as it loads new map data.

Using the Cursor

The cursor allows you to pan away from your present position and scroll to other map areas around the world (even outside of your current detail coverage). As you pan past the edge of the current map display, the screen actively scrolls forward to provide continuous map coverage. You see an hourglass symbol by the pointer while the unit is busy drawing new map detail. To move the cursor:
1. Press the ARROW KEYPAD to move the cursor in an up, down, left or right direction.
As you move the cursor, the distance and bearing from your present position to the cursor is displayed in the data window, along with the cursors position coordinates. Keep in mind that when the cursor is stationary, the distance and bearing from your present position changes as your boat moves. The cursor may also be used to snap to on-screen waypoints and map items, allowing you to review a selected position directly from the map display. To select an on-screen waypoint or map item with the cursor:
1. Use the ARROW KEYPAD to move the cursor to the desired waypoint or map item (if there are several waypoints grouped closely together, zoom in closer for a better view). 2. When a waypoint or map item is selected, it becomes highlighted on screen, with the name and position displayed. Press ENTER to show details of the map item. When using BlueChart or MapSource data, additional information tabs appears. Use the ARROW KEYPAD to highlight the individual tabs to display the information and additional options.
Move the cursor over an item on the map to highlight it.
Additional information tabs. Pressing ENTER/MARK while highlighting a map item brings up additional details and options. Option buttons
Reference Map Page: Cursor and Zooming
To eliminate the cursor and re-center your position on-screen:

1. Press the QUIT key.

The cursor may also be used to create new waypoints directly from the map. To create a waypoint with the cursor:
1. Use the ARROW KEYPAD to move the cursor to the desired map position. 2. Press the ENTER/MARK key and the New Map Waypoint window appears. If the cursor is on a map item, you get a new window with details about the item when ENTER/MARK is pressed. Press ENTER again on the highlighted Create Wpt option. 3. Press ENTER to confirm the new waypoint using the default three-digit name and symbol.

NOTE: COMPASS, HIGHWAY, POSITION, SONAR, and WATER TEMP. LOG are only available on Large and Huge sized data fields.
Turn Declutter On/Off toggles between showing spot soundings and map outlines for easier viewing.
Choose the type of data you wish to display.

Map Setup Menu Options

Reference Map/Sonar Split Page
The Map/Sonar Split Page combines the Map Page on the left half with the Sonar Page on the right by default. The menu options for this page are the same as the Map Page. Any setting changes made from the Map/Sonar Split Page will also affect the Map Page. One additional option is that you may adjust the size of the split left or right. Size Split enables width adjustment of the Map/Sonar Split Page. You may adjust the size of the map/sonar split window anywhere from 1/3 to 2/3 width from the edges of the screen. To resize the Map/Sonar Split Page:
1. From the Map/Sonar Split Page, press MENU. 2. Highlight Size Split and press ENTER. 3. Use the ARROW KEYPAD to move the horizontal double-arrow LEFT or RIGHT until the desired vertical width line shows, then press ENTER.
You may resize the split to the left or right.
The Sonar Page is where your GPSMAP 178/178C Sounder becomes a powerful fishfinder. Fish are displayed as colored arches (178C), arches (178) or as fish icons in three different sizes. Thermoclines are shown as shades of blue (178C) or as a grayscale (178). The sonar display may also be set to show a split screen view of a zoomed portion of the sonar, bottom lock (display scaled from the bottom up), or a combination of these options (see pg. 34). For example, you may choose to show dual frequency at a 2X zoom (Dual 2X) on one half and normal range dual frequency (Dual) returns on the other half. The current display mode is displayed at the bottom of each sonar display. For more information on understanding sonar and the display, see page 14 and Appendix G.

Reference Sonar Page

The Adjustment Menu allows direct access to the settings and features most commonly used on the Sonar Page. The currently selected option appears in the upper left of the display. To select an adjustment option from the Sonar Page:
Press MENU and highlight Adjustments to see a list of all options and their current settings.
Reference Sonar Page: Adjustment Menu
Adjustment Menu Options R ange sets the display depth range used for viewing. The unit can be set to automatically track the bottom or set to a user-specified depth range. Auto mode displays the most information possible while continuously showing the bottom. Z oom used to quickly select a display zoom scale or split the display. When a scale other than No Zoom is selected, the Adjustment Menu displays a new selection labeled View. Split screens display the same frequency (50kHz, 200kHz, or Dual) on both sides. The Zoom setting is divided into six display levels:

View Adjustment

Gain Adjustment

Target Level Adjustment

Whiteline Adjustment

Frequency Adjustment

Reference Sonar Page Options
N oise Reject helps filter unwanted noise from the graph. The Noise Reject tool can be turned Off, set to Normal (automatically adjusts for optimum viewing), or to a fixed 1-100% setting. Increasing the Noise Reject setting decreases the sonars sensitivity. At high Noise Reject settings the unit may not show all fish or structure. To turn the Noise Reject Off, press the ARROW KEYPAD DOWN until the setting bar is all the way at the bottom of the range and reads Off. S croll adjusts the rate that the graph scrolls from right to left. If you are sitting still or the graph is moving too fast, slowing the scroll rate, or pausing it can be beneficial.
Sonar Page Options The GPSMAP 178/178C Sounders Sonar Page features a menu page that provides access to additional functions and to layout and data field options. To display the Sonar Page options:

Depth Line Adjustment

Noise Reject Adjustment

Scroll Adjustment

The following options are available: Adjustments lists the Adjustment Menu options and their current settings (see page 15). To change an Adjustment setting:
1. On the Adjustment options list, use the ARROW KEYPAD to highlight the desired option and press ENTER. 2. Use the ARROW KEYPAD to make the desired change and press ENTER.

Sonar Page Menu Options

how/Hide Pointer allows you to reference sonar items and mark underwater waypoints. This S makes it easier to find and use an object such as a stump for a future fishing location. When using this feature, the Sonar Page pauses. The pointer does not move off the paused display and cannot show an area that has scrolled off the screen. The depth is updated while the display is paused, but the unit does not show any new sonar data until the standard Sonar Page is resumed. You may see a discontinuity from where the sonar information stops to where it starts again.
To mark an underwater waypoint:
1. From the Sonar Page, press MENU, highlight Show Pointer and press ENTER to pause the screen movement. 2. Use the ARROW KEYPAD to move the cursor onto the target (underwater drop off, stump, etc.) you want to mark. The data window at the top of the screen displays the cursors depth, coordinates, and bearing and distance from your current position. 3. Press and hold ENTER/MARK. The New Waypoint Page appears with the waypoints coordinates, default three-digit name, and pointer depth automatically filled in. 4. To change the name, symbol, or depth, highlight the appropriate field and press ENTER. Make your changes and press ENTER when done. 5. When done, move the field highlight back to the OK prompt and press ENTER. 6. To return to the standard Sonar Page, press QUIT; or press MENU, then highlight Hide Pointer and press ENTER.

1. Highlight the desired field and press ENTER. 2. Use the ARROW KEYPAD to edit/enter the data. To drop to the next line, press to the right on the ARROW KEYPAD. Press ENTER when done.
Reference Editing Waypoints
On the Waypoint Review and Waypoint Edit Pages, you may also delete the selected waypoint, view the waypoint on the map, and move the waypoint on the map. To delete a waypoint:
1. On the Waypoint Review/Waypoint Edit Page, use the ARROW KEYPAD to highlight Delete and press ENTER. 2, With OK highlighted, press ENTER again to confirm the deletion.
Symbol Name Comment Depth Coordinates Waypoint Edit Page Water Temperature
To view and move a waypoint on the map:
1. From the Waypoint Review/Waypoint Edit Page, highlight Show Map and press ENTER. The waypoint is highlighted on a map screen with an information window that shows the waypoint name, position and distance and bearing from your current position. 2. To move the waypoint, press ENTER. A MOVE label now appears under the cursor arrow. It may be necessary to use the IN and OUT keys to zoom the map. 3. Use the ARROW KEYPAD to move the waypoint to a new position. As you move the cursor around the map display, the information window at the top changes to show the distance, bearing, and position of the map cursor (in relation to the waypoints original position), and a description of where the cursor is on the map. If you wish to stop the move process, press QUIT. 4. With the pointer at the desired position, press ENTER. To return to the Waypoint Edit/Waypoint Review Page, press QUIT.
On the Show Map map display, an additional option is available by pressing MENU: Point to on Map Page returns to the highlighted waypoint on the main Map Page (exits the Waypoint Review/Waypoint Edit Page). 49

Reference Waypoint Lists

Submenu Tabs

Waypoint Lists

The GPSMAP 178/178Cs Main Menu Page features two waypoint submenu tabs, User and Proximity, that let you manage a large number of waypoints quickly and efficiently. The submenu tabs also provide a continuously updated proximity waypoint alarm function that can be used to define an alarm circle around submerged hazards, shallow waters, etc. To access the waypoint submenus of the Main Menu:

Proximity Waypoint List

The Proximity submenu of the Points tab lets you define an alarm circle around a stored waypoint position, and can be used to help you avoid reefs, rocks, or restricted waters. Up to ten waypoints may be listed, with a maximum alarm radius of 99.99 nautical or statute miles or kilometers. If a proximity alarm circle overlaps with an existing alarm circle, the message Proximity Overlaps Another Proximity Waypoint appears. Since the unit only alerts for one of the overlap points, use caution when navigating in these areas. If you enter an alarm circle overlap, you are only alerted to the closest proximity waypoint.
To add a proximity waypoint:
1. Use the ARROW KEYPAD to highlight an empty space on the Proximity list and press ENTER. The Find screen appears. Highlight Waypoints and press ENTER. 2. Use the ARROW KEYPAD to highlight the desired waypoint from the By Name or Nearest tab lists. The Waypoint Review Page appears for the selected waypoint. 3. With OK highlighted, press ENTER to confirm. The distance field is now highlighted. 4. Press ENTER to begin entry of the proximity radius. 5. Use the ARROW KEYPAD to enter a distance value (to 99.99 units) and press ENTER.
To turn proximity alarms on or off:
1. Use the ARROW KEYPAD to highlight the field below Proximity Alarm and press ENTER. 2. Select the desired ON or OFF setting and press ENTER.

Proximity Waypoints List

The following options are available from the Proximity submenu of the Points tab: Delete Alarm removes selected waypoint from proximity list. Delete All removes all waypoints from proximity list.
To display the waypoint menu options:
1. Using the ARROW KEYPAD, highlight the Proximity tab and press MENU.

Proximity Circle

Proximity Waypoint
To clear one or all proximity waypoint(s) from the list:
1. Use the ARROW KEYPAD to highlight the proximity waypoint to clear and press MENU. 2. To clear a single alarm, highlight the Delete Alarm option and press ENTER. 3. To clear all proximity waypoints, select the Delete All option and press ENTER.
A dashed circle appears showing the alert boundary for the proximity waypoints.
4. Use the ARROW KEYPAD to highlight the OK prompt and press ENTER to confirm.
Using the NAV key, the GPSMAP 178/178C provides three ways to navigate to a destination: Go To Point, Follow Route, and Follow Track (TracBack). Once you are actively navigating, you see a straight line that always runs from your current location to the destination on the Map Page. The easiest method for selecting a destination is the Go To function, which lets you select a destination point, then quickly sets a direct course from your present position. If you highlight a point on a list or the map and press NAV, Go To <point name> appears in addition to Go To Point. The Go To function can be accessed from any list of points or graphically from the map display. To activate a Go To from a point list:

Reference Route List Page
To deactivate (stop navigation) of a route:

Route List Page

The GPSMAP 178/178C Route List Page (Route tab of the Main Menu) displays all the routes currently stored in memory, along with a descriptive name for each route. By pressing MENU while on the Route List Page, the following menu options appear: New Route (page 57), Copy Route, Delete Route, or Delete All. To select and follow a route:
1. On the Route List page, use the ARROW KEYPAD to highlight the desired route and press NAV. 2. With Follow <route name> highlighted, press ENTER. Highlight Activate or Invert and activate and press ENTER.
If you highlight a route name from the Route List and press NAV, the name automatically appears.
To deactivate (stop following) the route:
To copy or delete a route:
1. From the Route List, using the ARROW KEYPAD, highlight the route you want to copy or delete and press MENU. 2. Choose either Copy Route or Delete Route and press ENTER and with OK highlighted, press ENTER again to confirm a deletion. Copy uses the same route name with an additional number, starting at 1, at the end of the route name.

To delete all routes:

1. From the Route List, press MENU. 2. Highlight Delete All and press ENTER. With OK highlighted, press ENTER again to confirm.

Route List Options Menu

Reference Route Review Page
Route Name Data Fields Route Points Data Totals

Route Review Page

Once you have created a route, the Route Review Page allows you to edit a selected route. To access the Route Review page:
1. Press MENU twice and highlight the Route tab. 2. Highlight the name of the route you wish to review and press ENTER.
The Route Review page also allows you to enter a 15-character name for any listed route. By default the name includes the first and last waypoints in the route. To enter a custom route name:
1. From the Route Review page, highlight the name field and press ENTER to begin editing. 2. Use the ARROW KEYPAD to enter the desired name and press ENTER when finished.
Once you are on the Route Review Page, you may review the route points (waypoints or map items) one at a time from the list. To review individual route points:
1. Highlight the desired point and press ENTER. 2. On the Point Review window, you may choose Next (highlight the next point on the route list), Show Map (show the point on a map window), or Delete (permanently delete the waypoint from the unit) and press ENTER. If the route point is a user waypoint, you may edit any of the waypoint properties on the Waypoint Review Page (see pages 48 for details).

1. Use the ARROW KEYPAD to highlight desired submenu tab of the Alarm Tab. 2. Highlight the field below the alarm name you wish activate and press ENTER. 3. Change the mode to the desired setting and press ENTER. 4. Highlight the next field to the right and press ENTER, then enter the desired settings and press ENTER to finish. 5. If you want the alarm to display and beep until acknowledged, highlight the Persist box and press ENTER to place a check mark in the box.
Reference Main Menu: Alarm Tab
Main MenuAlarm Tab (Nav Submenu)
Main MenuAlarm Tab (Sonar Submenu)
Appendix A Antenna Installation
Installing the GPSMAP 178/178C
The GPSMAP 178/178C must be properly installed according to the following instructions to get the best possible performance. To complete the installation, youll need the appropriate fasteners and a 1 x 14-thread marine antenna mount available at most marine dealers. (If you have a GPSMAP 178/178C with an internal antenna, skip to the next page.) When in doubt, seek professional assistance.

Mounting the GPS Antenna

Suggested locations for mounting the GA 29 antenna.
The antenna should be mounted in a location that has a clear, unobstructed view of the sky in all directions to ensure the best reception. Avoid mounting the antenna where it is shaded by the boats superstructure, a radome antenna, or mast. Keep the antenna away from the path of a radars beam. Sailboat users should avoid mounting the antenna high on the mast to prevent inaccurate speed readings caused by excessive heeling. Most marine VHF and LORAN antennas do not seriously degrade the GPS antennas reception. Never paint the antenna or clean it with harsh solvents. The Garmin antenna screws directly onto any standard 1 x 14-thread antenna mount. If you need to raise the antenna to avoid shading, try using a 1 x 14-thread extension mast available at most marine dealers. To install the GPS antenna:
1. Screw the antenna directly onto the 1 x 14-thread mount. 2. Route the cable to the mounting location of the display unit. Use appropriate tie-wraps, fasteners, and sealant to secure the cable along the route and through any bulkhead or deck. 3. Once the GPSMAP 178/178C unit has been installed, connect the cable to the antenna connector on the back of the display unit. Make sure that you turn the antenna cable connector 1/4 turn clockwise to lock the cable into place.
It is possible to route the coaxial cable either through or outside the antenna mount. It is possible to remove the BNC connector on the coaxial cable and shorten the coaxial cable to ease installation, however, doing so voids the antenna warranty. If the BNC connector is removed it must be replaced with a new solder-on or crimp BNC (RG 58 or 59 compatible) connector.

Hex Nuts

Washer
Appendix A Wiring and Interfacing
You can download a copy of Garmin's proprietary communication protocol from the Help and Support section of our web site at www. garmin.com
Connecting the Power/Data Cable
The power/data cable connects the GPSMAP 178/178C to 10-35 volt DC system and provides interface capabilities for connecting external devices. The color code in the diagram below indicates the appropriate harness connections.

To Transducer

Note: During a typical installation, only the Red and Black wires are used. The other wires do not have to be connected for normal operation of the unit. Replacement fuse: AGC/3AG - 2.0 Amp

To Unit

(red) + 10-35 VDC (black) - Ground (Power/Data) (blue) Port 1 Data OUT

DC Power Source

Complete information concerning NMEA & RTCM formats and sentences is available for purchase from NMEA at: NMEA Seven Riggs Avenue Severna Park, MD 21146 U.S.A. 410-975-9425 410-975-9450 FAX www.nmea.org Radio Technical Commission For Maritime Services (RTCM) 1800 Diagonal Road, Suite 600 Alexandria, VA 22314-2480 U.S.A. 703-684-4481 (Info Only) 703-836-4229 FAX www.rtcm.org

(brown) Port 1 Data IN

Pin 11 - Yellow (Alarm) Pin 15 - Red (DC Positive)
Pin 14 - Green (TX COM 2)
(white) Port 2 Data IN (green) Port 2 Data OUT

Autopilot/ NMEA Device

Pin 13 - White (RX COM 2) Pin 18 - Black (Ground) Pin 17 - Blue (TX COM 1) Pin 16 - Brown (RX COM 1)

(yellow) Alarm Low

Beacon Receiver or DSC VHF

(Cable View)

Alarm Relay 100ma max coil current

TX+ RX+

Interfacing
The following formats are supported for connection of external devices: Garmin proprietary Differential GPS (DGPS), NMEA 0183 version 3.01, RTCM SC-104 input (version 2.0). The following are the sentences for NMEA 0183, version 3.01 output: Approved sentences GPBWC, GPRMC, GPGGA, GPGSA, GPGSV, GPGLL, GPBOD, GPRMB, GPRTE, GPVTG, GPWPL and GPXTE. Sonar SBDDBT, SDDPT, SDMTW, and SDVHW Proprietary sentences PGRME, PGRMZ, and PSLIB.

Transducers

The transducer acts as the eyes and ears of your new sonar. Proper transducer selection and installation are critical to the operation of your unit. The transducer transmits sound waves toward the bottom in a cone shape. The larger the cone angle, the larger the coverage area at a given depth. A wide cone angle transducer works best in shallow water. The wide cone angle provides a large coverage area, but at a decreased bottom resolution. In deeper water this can result in a large dead zone where fish cannot be seen. A narrow cone angle transducer is better suited to deep-water installations. The narrow cone angle provides a smaller viewing area (compared to a wide cone angle transducer at the same depth) with improved bottom resolution and a smaller dead zone. Dual frequency transducers give you the best of both wide and narrow cone angles. The GPSMAP 178/178C is packaged with and without a transducer. Depending on which transducer you select, you will have either single or dual frequency performance. Since many mounting locations vary, there are a variety of standard and optional transducers, and accessories which are available. See your local Garmin dealer or contact Garmin to help you in your selection of optional transducers and accessories.

Appendix G Understanding Sonar
This fish is currently in a dead zone and is not detected by the sonar. The fish is in the coverage area of the transducer, but remember the first strong return sets the bottom level. The fish is eventually detected when the first strong return sets the bottom level below the fish.
Appendix G Transducer Coverage

Transducer Coverage

The area covered by the transmitted sound waves is determined by the cone angle of the transducer and the water depth. Cone angles may vary between different types of transducers. For example, a 50kHz frequency may provide a wide 40 cone angle, with a coverage width that is approximately 2/3 of the water depth. As shown in the sidebar, the 40 cone angle (50kHz frequency) approximately covers the area of a 20 foot diameter circle at a 30 foot depth. A 200kHz frequency may provide a narrow 10 cone angle, with a coverage width that is approximately 2/10 of the water depth. As shown, the 10 cone angle (200kHz frequency) approximately covers the area of a 6 foot diameter circle at a 30 foot depth. When using the GPSMAP 178/178C in Dual frequency mode, the unit transmits both 50kHz and 200kHz signals at the same time. The Dual frequency capability of the GPSMAP 178/178C allows you to have a large coverage area and still retain good bottom resolution. When in Dual frequency mode the unit uses the narrow cone angle (200kHz) to display detailed bottom information, keeping Dead Zones to a minimum, and the wide cone angle (50kHz) for the large coverage area. Fish returns from the wide and narrow beams appears differently on the display. The wide beam tends to show longer fish returns than the narrow beam.
200kHz - 10 Cone Angle 72" coverage at 30'
50kHz - 40 Cone Angle 20' coverage at 30'

Wide Cone Angle

Narrow Cone Angle

Understanding the Graph

It is important to understand that the unit does not display a 3-D representation of the underwater environment. The unit can display multiple things at the same time, but cannot determine where the return originated only when it was received. Examples 1 and 2 provide a look at the underwater world from a top view, and illustrate how these views would be displayed on the graph. On both graphs it appears the fish and tree are side by side as shown in Example 1. However, when we look at Example 2, we see that the fish can be several feet from the tree. It is important to remember that the sonar cannot determine where in the coverage area the tree or fish are, only that the returns were received at the indicated depths in the same time frame.
Appendix G Understanding the Chart
Enlarged Transducer View Branches