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Chapter 5 - Other Functions: Using the MORE key

Page 5-8

490 Echo Sounder Operations Manual Rev. B2

Archiving and

restoring snapshots

with a Zip disk

If your 961/962 has a zip drive installed, you can save up to 10
snapshots on each disk.

save

a stored snapshot onto a zip disk, from the

SNAPSHOT

screen, press the

CURSOR PAD

to highlight the desired slot,

and press

ARCHIVE

. A new screen appears displaying the 10

slots available on the zip disk.

Archiving snapshots screen (961/962 only)

Press the

CURSOR PAD

to select an empty slot on the disk,

and press

. The snapshot will be written to that slot on the

zip disk.

restore

a snapshot from a zip disk to any empty slot, from

the

SNAPSHOT

screen, press the

CURSOR PAD

to highlight

the desired empty slot, and press

RESTORE

. A new screen

appears displaying the 10 slots on the zip disk. Use the

CURSOR PAD

to select the slot containing the snapshot you

want to restore, and press

Summary of Contents for 490 Echosounder

Page 1: ...Northstar 490 Echo Sounder Operations Manual ...

Page 2: ...of the owner To be covered by this warranty the Northstar equipment must have been in normal use The warranty does not apply to units with defects caused by improper installation physical damage abuse tampering lightning or other abnormal electrical discharge or to units with defaced or altered serial numbers or to units repaired by unauthorized persons or repaired in a manner that violates Norths...

Page 3: ...ing the Echo Sounder Picture 3 1 The picture menu 3 2 Adjusting the gain strong echoes 3 2 Adjusting the clutter weak echoes 3 3 Adjusting the signal level weak echoes 3 4 Suppressing interference the noise limiter 3 5 Selecting the color bar hue and white level 3 6 Understanding Depth Settings 4 1 Viewing the seabed depth 4 2 Viewing the depth marker 4 2 Changing the depth settings 4 2 Setting th...

Page 4: ...undTrac 6 2 Marking fish as waypoints 6 3 Navigating to a past echo position 6 3 Setting the Alarms 7 1 Understanding the alarms 7 2 Setting the fish alarm 7 2 Setting the bottom alarm 7 4 Setting the temperature alarm 7 6 Troubleshooting 490 Operations 8 1 Troubleshooting the echo sounder 8 2 Checking the transducer 8 4 ...

Page 5: ...nual 1 2 Technical support 1 4 How echo sounding works 1 5 Powering the 490 on and off 1 7 Setting up the 490 1 7 This chapter introduces the Northstar 490 Operations Manual explains how to contact Northstar for technical support and service and describes the 490 s basic set up and power on off procedures ...

Page 6: ... marine technician To get started right away see Quick Start Using the Echo Sounder starting on page 2 1 Using this manual Organization Chapter 1 introduces you to the 490 echo sounder and to this operations manual Chapter 2 gives you a quick start introduction to get you started with echo sounding as soon as the 490 has been installed and configured Chapter 3 tells how to adjust the echo sounder ...

Page 7: ... Conventions Specific conventions are used to provide a consistent way to recognize certain information as follows is the universal symbol used for caution and warning information that pertains to your personal safety or pre vents damage to the 490 The CAUTION and WARNING boxes contain critical information please read them NOTE is the type style used for titles of reader notes These notes contain ...

Page 8: ...rn the unit to the Northstar factory for diagnosis and repair When describing an operating problem be as complete and accurate as possible Be sure to have your 490 s serial number available whenever contacting or corresponding with either your dealer or the Northstar factory The 490 s serial number is located at the top of the unit If you need help feel free to call the Northstar Service Departmen...

Page 9: ...h the serial number The 490 s serial number is located at the top of the unit The 490 should be shipped in a properly designed carton with packing material Please reference the RMA number on the outside of the carton Shipments to Northstar should be made to the following address Northstar Technologies 30 Sudbury Road Acton MA 01720 If you have overnight or second day shipping requirements please c...

Page 10: ...ent capable of 50 and 200 kHz The model 490 D is a 1000 watt dual channel echo sounder designed to be used with a transducer having dual ceramic elements one each for 50 and 200 kHz Figure 1 957 echo sounder system components below and Figure 2 961 962 echo sounder system components below show how the 490 connects to these navigators to enable echo sounding functions Figure 1 957 958 echo sounder ...

Page 11: ...talled by a qualified marine technician Your satisfaction with the system s performance will be greatly influenced by the practical knowledge and experience of the installer Unlike GPS or other marine electronics systems echo sounder installation is as much an art as a science The installation procedure includes setting up the following options the transducer s depth the speed and temperature 961 ...

Page 12: ...tain water temperature that you ve set To see or change any of the above settings press STAR several times until you reach the ECHO SOUNDER SETUP screen For details see Setup functions starting on page 2 12 Using the 961 962 Before starting you should double check that the 961 962 s Port 3 is set to the 490 option 1 Press STAR until you reach the SERVICE MENU screen 2 Press PORT SETUP 3 Press PORT...

Page 13: ...h More ECHO SCREEN Gain Clutter Noise Limiter Hue Signal level Return Shift Range Bottom box Return Alarms Advance Speed Snapshot A Scope Data Return Fish alarm Bottom alarm Temp alarm Return Bottom box Temp box Temp graph Speed Return Picture settings Depth settings More settings Alarm settings Data on screen Display Rename Archive Erase Return Snapshot ...

Page 14: ...y Zoom Depth More ECHO SCREEN Gain Clutter Noise Limiter Hue Signal level Return Shift Range Bottom box Return Alarms Advance Speed Video A Scope Data Return Fish alarm Bottom alarm Temp alarm Return Temp box Temp graph Bottom box Speed Return Picture settings Depth settings More settings Alarm settings Data on screen Video on Return Video setup ...

Page 15: ...ounder s picture 2 2 Using demo mode 2 4 Introducing the displayed information 2 5 Using automatic mode 2 6 Changing the frequency of echoes 2 7 Zooming in and out 2 9 Setup functions 2 12 This chapter shows you how to start using the echo sounder and explains several of the echo sounder s important features ...

Page 16: ...es using Northstar s exclusive SoundTracä feature To activate SoundTrac press the CURSOR PAD left or right on the ECHO screen The position marker appears controlled by the CURSOR PAD and movement of echoes to the left stops The data boxes at the bottom of the screen turn white and refer to the position marker rather than to your current position Press the green Depth Scale Depth box Water temperat...

Page 17: ...y keys to view the current alarms although you must press STAR to clear alarms that don t automatically clear The SAVE and MOB functions always work normally Moreover whenever you press either of these keys the corresponding SAVE or MOB waypoints will be displayed automatically on the echo sounder s picture as well as on the CHART screen after you press CHART Depth Scale Depth box Water temperatur...

Page 18: ...er of the ECHO screen To leave demo mode repeat this procedure selecting OFF instead of ON Displaying echo sounder data on the CHART screen You can overlay a smaller version of the echo screen onto the CHART screen For the 961 962 To overlay the echo screen 1 Press CHART to display the CHART screen then press OVERLAY 2 At the CHART OVERLAY SELECTION window press SHOW 490 Both chart views A and B w...

Page 19: ...side of the screen depth scale on the right side depth marker press the CURSOR PAD to scroll the marker down water temperature digital display if temperature sensor is connected can be turned off water temperature graph if temperature sensor is con nected can be turned off Navigation vessel s current lat lon on the SOUNDTRAC screen this lat lon indicates the position marker s location vessel s SOG...

Page 20: ...controls the gain and clutter settings You can always press AUTO on the ECHO screen to remove any manual settings you ve made and return to the standard automatic configuration Cruising or fishing Automatic mode has two variations autocruising and autofishing autocruising optimizes the gain and clutter for tracking the bottom with less emphasis on any fish in the water autofishing optimizes the ga...

Page 21: ...low You can choose from four settings for the transducer frequency 50 kHz displayed on a full screen 200 kHz displayed on a full screen 50 kHz on the left half of the screen and 200 on the right 200 kHz on the left half of the screen and 50 on the right There are two reasons why you might want to operate with your preferred frequency on the right side of the screen Table 2 50 kHz vs 200 kHz 50 kHz...

Page 22: ...til you display the desired frequency or frequencies The frequencies in use are shown pictorially on the tab just below the FREQUENCY key When you change the frequency echoes already on the screen don t change they just move off the screen as they are replaced by echoes at the new frequency A dual frequency screen is split into two halves separated by a gray vertical line in the center Adjusts the...

Page 23: ...and increase the amount of water seen You can choose from any of six depth scales for the magnified echoes These scales cover the same depths regardless of the scale of the original echoes The available scales are 15 30 60 120 240 and 480 when using units of feet Similar scales are available for the other depth units NOTE When zoom is in use only a single frequency is displayed Unzoomed echoes are...

Page 24: ... automatically locates the seabed and displays it on the lower left side of the screen normal echoes are displayed on the right side If the seabed moves out of the lower half of the screen for example if you travel into deeper water the 490 automatically repositions the bottom back into the lower half You ll see the zoomed image jump up or down from time to time as the 490 keeps the seabed display...

Page 25: ... sea bottom is flattened out and displayed in the center of the screen You can see any fish near the bottom as with the bottom lock zoom and also examine the seabed s composition Using marker zoom When you select marker zoom you can choose the part of the water column to magnify The top edge of the magnified area is determined by the location of the depth marker To move ...

Page 26: ...ng ZOOM repeatedly until you have cycled through all the zoom modes Setup functions Several setup functions are available to configure the echo sounder to your preferences CAUTION Be careful not to change any of the functions that are not described here unless you first read about them and understand their functions in the Northstar 490 Installation Manual Accessing the setup screen To access the ...

Page 27: ...e 2 13 961 962 echo sounder setup screen 957 958 echo sounder setup screen Entering numerical values When changing the numerical value of the echo sounder s settings you can either press the CURSOR PAD to increase or decrease the value or use the KEYPAD to manually type in the desired value ...

Page 28: ... that will be displayed on the temperature graph 1 Press the CURSOR PAD up or down to highlight the line containing the temperature scale 2 Press EDIT 3 Press the CURSOR PAD left or right to highlight C or F as desired then press ACCEPT 4 To change the endpoints of the scale press EDIT DATA 5 Enter the lower temperature limit using the KEYPAD 6 Press the CURSOR PAD to the right to highlight the up...

Page 29: ...aypoint type you want to change The line Fish controls fish waypoints The line Therm controls temperature waypoints The line Mark Wpts controls waypoints marked by the user 2 Press EDIT 3 Press the CURSOR PAD left or right to highlight the desired number of waypoints to be saved 4 Press ACCEPT Speed and temperature sensor setup These functions are set during installation The calibrations should no...

Page 30: ...ine and press EDIT to change an option Speed calibration is entered as a percentage from 99 to 99 to make the speed read lower or higher than the uncalibrated value NOTE You must enable the speed setting under the Data menu on the ECHO SOUNDER screen see Setting the ECHO screen data starting on page 5 4 Temperature is calibrated by entering the temperature error as a number of degrees from 99 to 9...

Page 31: ...hoes 3 2 Adjusting the clutter weak echoes 3 3 Adjusting the signal level weak echoes 3 4 Suppressing interference the noise limiter 3 5 Selecting the color bar hue and white level 3 6 This chapter explains the different ways you can adjust the echo sounder s picture including gain clutter the noise limiter white level and signal level ...

Page 32: ...nly the PICTURE key tab changes from green to yellow Changing the hue or adjusting the signal level has no effect on the operating mode the tabs stay green Adjusting the gain strong echoes The gain setting selects the echo strengths that will be displayed using the top color in the color bar the strongest echoes Any echoes stronger than this selection will use the same color and no detail can be d...

Page 33: ...isplay these echoes As you adjust the gain to obtain the best looking picture also watch the real echoes on the right side of the screen 4 Press RETURN to go back to the ECHO screen When you adjust the gain the color of the AUTO and PICTURE key tabs changes from green to yellow since the echo sounder is no longer in automatic mode Also a yellow tab appears under the DEPTH key indicating that the r...

Page 34: ...RE 2 At the PICTURE screen press CLUTTER 3 Press the CURSOR PAD left or right to adjust the clutter or use the KEYPAD to manually enter the desired clutter value The available settings range from zero minimum to nine maximum Clutter window 4 Press RETURN to go back to the ECHO screen When you adjust the clutter the color of the AUTO and PICTURE key tabs changes from green to yellow since the echo ...

Page 35: ...3 are all displayed using the same color 4 Press RETURN to go back to the ECHO screen Suppressing interference the noise limiter The noise limiter reduces the adverse effects of interference from other nearby echo sounders or electronic devices however the noise limiter may cause some very weak echoes to be made smaller or entirely eliminated since it removes any echoes that aren t sustained for a...

Page 36: ...oose any one of nine palettes of colors to represent the echo strengths from weakest to strongest Color bar 1 is the one most often used Color bar 2 is similar but with fewer colors to aid visibil ity under some conditions Color bars 3 8 are additional variations with different background colors Color bar 9 uses only a single color ranging from very dark to very bright Selecting the color bar hue ...

Page 37: ...back to the ECHO screen Setting the white level You can replace any single color in the color bar with white On the HUE AND WHITE LEVEL window press the CURSOR PAD up or down to select that color To remove the white level and return to using all the colors on the color bar press the CURSOR PAD down until the white level moves off the color bar ...

Page 38: ...Chapter 3 Adjusting the Echo Sounder Picture Page 3 8 490 Echo Sounder Operations Manual Rev B2 ...

Page 39: ... 2 Viewing the depth marker 4 2 Changing the depth settings 4 2 Setting the picture s shift starting depth 4 3 Setting the picture s range 4 4 This chapter explains how to override the system s auto matic depth settings and manually control the depth range shown on the screen and how to use the depth marker ...

Page 40: ...o move the box up and down press the CURSOR PAD 3 Press RETURN to go back to the ECHO screen The depth box can also be adjusted by pressing MORE then pressing DATA Viewing the depth marker You can use the depth marker to accurately measure the depth of an echo To display the depth marker a dashed horizontal line and move this marker up or down press the CURSOR PAD down Attached to the depth marker...

Page 41: ...s shift starting depth The shift setting adjusts the depth of the top edge of echoes pictured on the ECHO screen You can shift the entire pic ture up and down to start at the surface of the water or any other depth you choose To shift the picture 1 At the ECHO screen press DEPTH 2 Press SHIFT Shift window The SET SHIFT window shows a picture of the current shift settings and range The large white ...

Page 42: ...is win dow adjusts the depth at which the echo sounder picture starts relative to the surface of the water 3 Press the CURSOR PAD up or down to shift the picture or use the KEYPAD to enter the digits of the desired depth If you type the number on the keypad wait a moment for the system to enter the number 4 Press RETURN to go back to the ECHO screen Adjusting shift changes the AUTO and DEPTH key t...

Page 43: ...cho sounder picture relative to the depth of the water The white number in the black box indicates the current range setting 3 Press the CURSOR PAD up or down to adjust the range or use the KEYPAD to manually enter the desired depth 4 Press RETURN to go back to the ECHO screen Adjusting the range changes the AUTO and DEPTH sta tus tab from green to yellow since the echo sounder is no longer in ful...

Page 44: ...Chapter 4 Understanding Depth Settings Page 4 6 490 Echo Sounder Operations Manual Rev B2 ...

Page 45: ...ing the MORE key 5 2 Changing the advance speed 5 2 Displaying the A scope 5 3 Setting the ECHO screen data 5 4 Introducing snapshots 5 6 Setting up the video image overlay 5 9 This chapter describes all of the functions of the MORE key except for the alarms which are covered in Chapter 7 ...

Page 46: ...rs to the speed at which the vertical scan lines move from right to left across the ECHO screen There are five advance speeds plus the STOP setting which freezes the advance of all data 2 1 two identical lines of data are displayed for every ping 1 1 one line of data is displayed for every ping 1 2 one line of data is displayed for every two pings 1 4 one line of data is displayed for every four p...

Page 47: ...e lets you look closely at present or past echoes by horizontally magnifying the echo from each ping To display the A scope 1 Press MORE 2 Press A SCOPE to turn the A Scope on or off A scope on single frequency echo screen The A scope appears on the far right hand side of the screen magnifying the water column designated by the position marker ...

Page 48: ... on the right side of the screen A scope on dual frequency echo screen Using the A scope with zoom mode If you re in zoom mode the A scope magnifies the unzoomed echoes on the right side of the screen Setting the ECHO screen data Screen data refers to numeric and graphic information displayed on top of the echoes including bottom depth water temperature and speed through the water STW To access th...

Page 49: ...l medium large and huge Press the CURSOR PAD up and down to set the position of the box at the left edge of the screen Temperature box Press TEMP BOX key to set the size and location of the box displaying the water temperature white numbers on a black background Press this key again to cycle through the available sizes off small medium large and huge Press the CURSOR PAD up and down to set the pos...

Page 50: ... 961 962 s echo sounder screen You can store up to 10 different snapshots of echo sounder screens for later review These can be stored on floppy disk one snapshot per floppy or zip disk for permanent archiving The snapshot feature is not available in the 957 958 Taking and storing a snapshot To take a snapshot press MORE and then SNAPSHOT The echo sounder screen will be recorded at that instant To...

Page 51: ... CURSOR PAD to highlight the desired slot and press ERASE You ll be asked to confirm erasure by pressing YES The slot will be erased to make room for a new snapshot Archiving and restoring a snapshot with a floppy disk If your 961 962 has a floppy disk drive installed you can save one snapshot on each disk To save a stored snapshot onto a floppy disk from the SNAPSHOT screen press the CURSOR PAD t...

Page 52: ...s ARCHIVE A new screen appears displaying the 10 slots available on the zip disk Archiving snapshots screen 961 962 only Press the CURSOR PAD to select an empty slot on the disk and press OK The snapshot will be written to that slot on the zip disk To restore a snapshot from a zip disk to any empty slot from the SNAPSHOT screen press the CURSOR PAD to highlight the desired empty slot and press RES...

Page 53: ...screen To display the video image on the ECHO SOUNDER screen first press MORE then press VIDEO To change the transparency of the image while you re displaying the ECHO SOUNDER screen go to a different screen press the IN or OUT keys then return to the ECHO SOUNDER screen To change the size and placement of the image on the ECHO SOUNDER screen press the STAR key to display the VIDEO SETUP screen th...

Page 54: ...Chapter 5 Other Functions Using the MORE key Page 5 10 490 Echo Sounder Operations Manual Rev B2 ...

Page 55: ...viewing past echoes using SoundTrac Viewing past echoes using SoundTrac 6 2 Marking fish as waypoints 6 3 Navigating to a past echo position 6 3 This chapter describes how to use SoundTrac to view past echoes and how to navigate to any past echo positions ...

Page 56: ...th the CURSOR PAD the marker speed accelerates to quickly scroll to the desired location SoundTrac screen The lat lon of the position marker is displayed at the bottom of the picture along with the time elapsed since the ping and the distance and bearing from your present position to the marker assuming the navigator is providing position data As you move the position marker left and right these c...

Page 57: ... that you see at any past echo displayed on the screen To mark echoes as waypoints 1 At the ECHO screen press the CURSOR PAD to the left to move the position marker a dashed vertical line to the position of the echo 2 Press MARK A MARK waypoint immediately appears on the SOUNDTRAC screen and on the CHART screen Each marked echo becomes a waypoint named MARK stored in the waypoint database You can ...

Page 58: ...o a past echo position To go directly to a past echo position as long as the GPS is providing position data 1 On the SOUNDTRAC screen press the CURSOR PAD left or right to move the position marker to the desired posi tion then press GO TO The SELECTED CURSOR POSITION window appears 2 Press GO NOW The navigator creates a new temporary waypoint called COORD and returns to the SOUNDTRAC screen The CO...

Page 59: ...anding the alarms 7 2 Setting the fish alarm 7 2 Setting the bottom alarm 7 4 Setting the temperature alarm 7 6 This chapter describes the echo sounder s three alarm functions for fish bottom and temperature conditions the settings for each alarm and how to turn them on and off ...

Page 60: ... situations related to echo sounding you can set three alarms fish alarm seabed bottom alarm temperature alarm NOTE You also can set the echo sounder to automatically save FISH or THERM waypoints when fish or a certain temperature are detected if the fish or temperature alarms are on To automatically save these waypoints see Number of special waypoints starting on page 2 14 Setting the fish alarm ...

Page 61: ... echo strength level from 1 to 15 as represented on the vertical color bar Echoes received that are strong enough to be within the crosshatched area on the vertical bar will cause an alarm weaker echoes will be ignored Setting the upper and lower marker depths The fish alarm will sound only when there are echoes inside or optionally outside the upper and lower markers These markers are displayed o...

Page 62: ...ers If you set these markers as outside markers the fish alarm sounds when fish are detected outside of these markers To set the markers to inside or outside at the FISH ALARM window press INSIDE OUTSIDE MKRS to toggle between the inside and outside settings The setting is displayed in the tab below the INSIDE OUTSIDE MKRS key Turning the fish alarm on and off To turn the alarm on at the FISH ALAR...

Page 63: ...shallower than this depth the bottom alarm will sound To set the bottom level at the BOTTOM ALARM window press the CURSOR PAD up or down to set the depth or use the KEYPAD to manually enter the desired depth NOTE The 490 s depth indicator reflects the depth below your vessel s transducer not below the keel Ask your installer for the exact dis tance between your transducer and your keel This value ...

Page 64: ...rs automatically after 20 seconds and the alarm is reset Setting the temperature alarm When the temperature alarm is set an alarm sounds if the echo sounder detects that the water temperature has either risen above or dropped below the limit you ve set To set the temperature alarm 1 At the ECHO screen press MORE 2 Press ALARM 3 At the ALARM screen press TEMP ALARM The options on the TEMPERATURE AL...

Page 65: ...he lower limit window is highlighted in black 2 Press the CURSOR PAD up or down to set the temperature or use the KEYPAD to enter the desired temperature The temperature is displayed in the tab just below the SET LOWER LIMIT key Setting inside or outside temperature limits If you set the upper and lower temperature limits as inside limits the temperature alarm sounds when the temperature is detect...

Page 66: ...s Page 7 8 490 Echo Sounder Operations Manual Rev B2 The alarm When the temperature alarm sounds the message THERM is displayed at the bottom of the screen This message clears automatically after 20 seconds and the alarm is reset ...

Page 67: ...ual Rev B2 Page 8 1 Troubleshooting 490 Operations Troubleshooting the echo sounder 8 2 Checking the transducer 8 4 This chapter explains how to troubleshoot the echo sounder system before returning the equipment for factory service ...

Page 68: ...COND Contact Northstar Service to upgrade to the latest version of 961 962 software Change the Advance Speed setting Configure NMEA Port 3 for the 490 See the 490 Operations Manual GM490 for instructions 1 Check fuses and circuit breakers 2 Check power to 490 with a voltmeter 3 Verify that the data cable between the 961 962 and the 490 is properly wired and connected 1 Check transducer connector f...

Page 69: ...Second Change the Advance Speed setting Configure 957 Aux Port for the 490 See the 490 Operations Manual GM490 for instructions 1 Check fuses and circuit breakers 2 Check power to 490 with a voltmeter 3 Verify that the data cable between the 957 and the 490 is properly wired and connected 1 Check transducer connector for the proper wiring 2 If wiring is correct check transducer impedance with an o...

Page 70: ...er s documentation Do not return a transducer to North star If you need to return a transducer for service contact the man ufacturer directly for instructions Maintaining a transducer Do not expose a transducer to gasoline or clean it with strong solvents These can penetrate and degrade the housing If a transducer will be exposed to saltwater coat it with anti fouling paint to prevent sea growth T...

Page 71: ...0 D Dual Channel 50 200 1kW Alarms Fish seabed temperature Update rate 10 Hz maximum depends on water depth Auto modes Fishing and cruising Zoom modes Marker bottom bottom lock bottom lock center Features Mark present or past echo as waypoint 961 962 Go directly to any past echo A scope analyzes present or past echoes Navigation data shown at bottom of screen Demo mode for training ...

Page 72: ...terfacing Connects Northstar 961 962 GPS Chart Navigator Northstar 957 958 GPS Chart Navigator Northstar recommended or compatible transducer Other Transducer outputs protected against open circuit short circuit LED monitors input power and system status Physical characteristics Dimensions 10 x 6 25 x 2 5 inches Weight 2 pounds Environmental characteristics Temperature 25ºC to 60ºC operating tempe...

Page 73: ... White level Any single color Other Screen color palette Depth marker Position marker Zoom in out Shift Ranges 15 30 60 120 200 400 800 1000 2400 feet 5 10 20 40 80 150 300 500 800 meters Advance speed 1 8 to 2 1 Depth units Feet meters fathoms Installation calibrations Include speed temperature gain and transducer type Table 4 490 echo sounder features Continued ...

Page 74: ...Appendix A Specifications Page A 4 490 Echo Sounder Operations Manual Rev B2 ...

Page 75: ... instrument that uses sound waves to measure the depth of a body of water or an object such as a school of fish below the water s surface fathom A depth measurement that equals six feet or 1 83 meters of water gain The amount of amplification given to the received echo before it is displayed GPS Global Positioning System hue The gradations of a color interference The electromagnetic interruption o...

Page 76: ...e One nm is equal to 1 minute of latitude ping A pulse transmitted from the 490 echo sounder Also the act of transmitting a pulse from the echo sounder pinging SOG Speed Over Ground The actual speed of your vessel relative to the earth not the water tide The vertical rise and fall of water caused by the gravitational pull of the moon and sun transducer The device mounted through the hull to send a...

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