Garmin GPSMAP 178C Owners Manual - Page 124

Understanding the Graph, contour

Get Garmin GPSMAP 178C - Marine GPS Receiver PDF manuals and user guides
UPC - 753759043544
View all Garmin GPSMAP 178C manuals
Add to My Manuals
Save this manual to your list of manuals

Page 124 highlights

Appendix G Understanding the Graph F Whiteline can also help you to determine the type of bottom structure that is displayed on the chart. By determining the hardness of the structure, you can make a better informed decision on the type of structure. Whiteline The GPSMAP 178/178C can help you to determine if the bottom is hard or soft. When the sonar soundwaves are reflected back by the bottom, a hard bottom returns a stronger signal than a soft bottom. A thin whiteline indicates a softer bottom while a thick whiteline indicates a harder bottom. Normally, a red/dark line is used to show the point where water meets the bottom. This line follows the bottom contour, along with any significant objects lying on the bottom. The unit uses the whiteline function to make this bottom layer information easier to distinguish. With the GPSMAP 178/178C, active whiteline helps accentuate where strong signals are located, which make bottom type determination easier. The example to the right shows the bottom return with and without the whiteline activated. Structure is hard- probably a rock or stump Structure is soft- probably a mud pile Hard Bottom Whiteline 114 Soft Bottom Example 4. Whiteline Turned Off

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
  • 134
²²µ
Appendix G
Understanding the Graph
Whiteline
The GPSMAP 178/178C can help you to determine if the bottom is hard or soft. When the sonar
soundwaves are reflected back by the bottom, a hard bottom returns a stronger signal than a soft bottom.
A thin whiteline indicates a softer bottom while a thick whiteline indicates a harder bottom. Normally,
a red/dark line is used to show the point where water meets the bottom. This line follows the bottom
contour, along with any significant objects lying on the bottom. The unit uses the whiteline function to
make this bottom layer information easier to distinguish.
With the GPSMAP 178/178C, active whiteline helps accentuate where strong signals are located,
which make bottom type determination easier. The example to the right shows the bottom return with
and without the whiteline activated.
F
Whiteline can also help you to determine the type of bottom
structure that is displayed on the chart. By determining the
hardness of the structure, you can make a better informed
decision on the type of structure.
Structure is hard—
probably a rock or stump
Structure is soft—
probably a mud pile
Example 4.
Whiteline Turned Off
Hard Bottom
Whiteline
Soft Bottom