Garmin Sonar Users: Tips for Shading Map Chart to Display Actual Shoreline and Shallow Areas While Navigating

Fursniper

Well-Known Member
If you have a Garmin sonar unit that has topo maps for inland lakes installed, it may allow you to shade the map chart for different depth ranges. Here are some tips on shading the map chart so it will correspond to the actual shoreline and highlight shallow areas to avoid while underway.

Map Chart Displaying Depth Zones in Wakeless Area Between Glen Canyon Dam and Wahweap Marina (April 8, 2019).



The bathtub ring (dry land) is shaded orange. The red area is from the actual shoreline to 70 feet deep. The blue area shows the depth between 300-500 feet deep to highlight the bottom of the channel. Navigation is set to "track up" not "north up" so direction of travel is always toward the top of the screen. The Garmin sonar unit I have updates my position on the map about 5 times/second.

To apply shading to the map chart, display the map chart, press the MENU button, and select CHART APPEARANCE. You can manually shade the map chart for multiple depth zones in a variety of colors and they are applied to the entire lake. Otherwise, the map chart will be all white. The settings for each depth zone are entered in feet below full pool. For example, the settings for the orange zone (bathtub ring/dry land) were to shade the depth between 1 to 130 feet and the settings for the red zone were 130 to 200 feet (actual shoreline to 70 feet deep). The map contour lines are in 10 foot intervals so don't expect the shading to be more accurate than that.

In the photo above, my direction of travel is north heading toward Wahweap Marina. My boat is near Anchovy Point on the left. I am approaching a narrow reef that is about 70 feet below the surface. In the center of the screen is a larger red zone which is where the hazard buoys are located inside the wakeless area and it shows a whale barely above the surface. The blue area is where the water is the deepest. The land area on the right side of the channel is Antelope Island.

Shading the map chart is a very useful tool for getting around on Lake Powell with the fluctuating water levels. It helps prevent colliding with whales because you can see where shallow areas are a mile away and know which way to steer to go around them. I avoid entering the red zones when underway. The blue highlights the bottom of the main channel so I do not need to search for main channel buoys.

When the lake water level changes, you can adjust the boundaries of the depth zones very easily with the boat beached on the shoreline. That way your map chart will correspond with the current water level. Way cool!
 
Last edited:

Pegasus

Well-Known Member
I have a Garmin sonar unit that came with mapping features that allows shading the topo map to corresdpond to current water levels and to shade shallow areas to avoid them while underway. I thought these tips would be useful to others.


Map chart photo showing wakeless area between the dam and Wahweap Marina (April 8, 2019).



I display the bathtub ring by shading it orange. The red zone is the area between the surface to 70 feet deep. I avoid the red zones when I'm underway. I shade the bottom of the main channel blue (300-500 feet deep) so I can see where it is without having to search for channel buoys. Navigation is set to "track up" not "north up" so my direction of travel is always toward the top of the screen. The Garmin unit updates my position on the map about 5 times/second.

To apply shading to the map chart, display the map chart, press the MENU button, and select CHART APPEARANCE. You can manually shade the map chart for multiple depth zones and they are applied to the entire lake. The topo map contour lines are in 10 foot intervals.

In the photo above, my direction of travel is toward Wahweap Marina. My boat is near Anchovy Point on the left. I am approaching a narrow reef that is about 70 feet below the surface. In the center of the screen is a larger red zone and this is where the hazard buoys are located in the wakeless area. The dark blue is the bottom of the channel where the water is the deepest. On the right side of the screen is Antelope Island.

I do not totally rely on the map chart to navigate, but it is a very useful tool for getting around on Lake Powell with the fluctuating water levels. I like it a lot and it has saved my bass boat from getting hit by sandstone torpedos going 50mph. :whistle:

When the lake level changes, you can change the upper and lower boundaries of the depth zones very quickly when you launch. Way cool!
Great informative post! What mapping software is this using?
 

Fursniper

Well-Known Member
My Garmin sonar unit (echoMAP CHIRP 53dv) came preloaded with the U.S. Garmin LakeVu HD maps which covers over 17,000 inland lakes of which 13,000 are HD lakes with one foot contours shore to shore.

I have not tried using it on other reservoirs yet. I don't know if going to Lake Mead and changing the settings there will change my settings for Lake Powell. If so, its no biggie. Its very quick and easy to adjust the shading on the map chart at the launch ramp to correspond to the current water level.
 
Last edited:
Top