Educate me on depth finders and GPS units

[MalcolmV8]

So I'd really like a depth finder on the boat so I can tell how deep or not so deep the lake is in questionable spots. This was my original interest which got me thinking about them. I figured well if I'm installing a unit it might as well have GPS too so I don't always have to pull out my phone and navigate when I'm on lakes I don't go to very often. Fish finder would be nice too.
Sounds simple. I start searching and wow there are hundreds and hundreds of devices out there and most cost a lot more than I was expecting. Humm I'm not really sure what features or items I should be paying attention to or why there's such a massive price gap. Units from $100 some to over $4k I see. Dang that's a big gap.

Is there something simple that does those basic features for a reasonable price?

 

[UncleWillie]

Re: Educate me on depth finders and GPS units

The included base maps in most units are good enough for navigation. The upgrade maps add more detail if needed.

Consider the HB386 as a place to start looking.

 

[MalcolmV8]

Re: Educate me on depth finders and GPS units

That unit seems pretty nice. I watched the video on the page which helped but I wish it had more details in the video and showed samples of what the GPS part looked like. So $300 is about what I'm looking at. I liked how it also includes water temperature. Pretty slick.

 

[UncleWillie]

Re: Educate me on depth finders and GPS units

A side by side comparison of the included Base Map Compared to the $150 HotMap Upgrade.
I would not buy the Upgrade map until you see if the included map is not satisfactory.
You can upgrade at anytime, discount suppliers are all over the web.



The included Maps are not all that bad!
The upgrade is sometimes overkill for many needs.

 

[Silvertip]

Re: Educate me on depth finders and GPS units

Just remember that the depth finder tells you depth where you ARE. It cannot see in front of you. If you are on plane and suddenly in shallow water the depth finder will sound off about the same time you are aground or on top of a rock. Set the shallow alarm to a safe depth so it sounds off when the depth reaches that point. Annoying, but the only protection.

 

[MalcolmV8]

Re: Educate me on depth finders and GPS units

A side by side comparison of the included Base Map Compared to the $150 HotMap Upgrade.
I would not buy the Upgrade map until you see if the included map is not satisfactory.
You can upgrade at anytime, discount suppliers are all over the web.

View attachment 207126

The included Maps are not all that bad!
The upgrade is sometimes overkill for many needs.

Yeah that upgraded map is way overkill for what I want. I just want the basic layouts so when on lakes I'm not overly familar with I can find my way back to the boat launch I used etc. Nothing overly fancy. My phone's GPS works great for that. Just a pain using the phone and watching for dry hands and don't drop it etc.

Just remember that the depth finder tells you depth where you ARE. It cannot see in front of you. If you are on plane and suddenly in shallow water the depth finder will sound off about the same time you are aground or on top of a rock. Set the shallow alarm to a safe depth so it sounds off when the depth reaches that point. Annoying, but the only protection.

Ah good to know. For some reason I thought the sonar was giving you the depth of an area around your boat, like a large radius. I will definitely play around with it cautiously and get a feel for it.

 

[UncleWillie]

Re: Educate me on depth finders and GPS units

... Ah good to know. For some reason I thought the sonar was giving you the depth of an area around your boat, like a large radius. I will definitely play around with it cautiously and get a feel for it.

The Base Maps are fine for navigating back to the dock and relocating fishing spots. :joyous:

The Wide" Beam Sonars are 60 degree beams. The sonar beam is as wide as the water depth.
That means in 10 feet of water it sees 5 feet Left, Right, Front, and Back.
With a 20 foot boat, the front 15 feet is a blind spot.
In 50 feet of water, a whale passing off the bow will not register on the sonar. :blue:

The high resolution 20 degree beams have less than an 18 inch radius at 10 feet.

 

[MalcolmV8]

Re: Educate me on depth finders and GPS units

Ah interesting. So does that 386 Humminbird have the wide beam or the narrow 20 degree? Reading the specs I'm not sure it says exactly. It says "dual beam plus" what ever that is?

 

[UncleWillie]

Re: Educate me on depth finders and GPS units

Ah interesting. So does that 386 Humminbird have the wide beam or the narrow 20 degree? Reading the specs I'm not sure it says exactly. It says "dual beam plus" what ever that is?

Dual Beam Plus has BOTH.
The 386DI has 3 frequencies, 4 beam widths up to 75 Degrees, and Down Imaging.

 

[JoLin]

Re: Educate me on depth finders and GPS units

I would not buy the Upgrade map until you see if the included map is not satisfactory.
View attachment 207126

The included Maps are not all that bad!
The upgrade is sometimes overkill for many needs.

Ditto that. I bought a Lowrance HDS-7 three years ago and the basemaps have plenty of detail for me. A friend gave me a Navionics 'upgrade' card that was several years old, and my basemap was better. Try what's built in before spending any additional money.

 

[dingbat]

Re: Educate me on depth finders and GPS units

Ah interesting. So does that 386 Humminbird have the wide beam or the narrow 20 degree? Reading the specs I'm not sure it says exactly. It says "dual beam plus" what ever that is?

"Dual beam" is a software function. All transducers produce a secondary, lower frequency (wider beam, lower resolution) as a side affect of the primary frequency. Whereas a conventional sounder would filter out the secondary returns as noise, the dual beams listens to both returns using software filters to ?fit? the secondary, lower resolution returns into a viable, higher resolution data package for display.

The rating method of the cone angle varies by manufacturer. The commercial fishing, naval industry and most of the marine recreation industry, provide beamwidth information by measuring the sound beam at ?3 dB. Hummingbird, however, provides beamwidth information measured at ?10 dB, giving the impression that their transducers have a wider beam field than the competitor, when in fact, they are the same.

The image on the left has a 20 degree beam angle at -3db. At -10db, the beam would be advertised as a 35 degree cone angle. At -30db, you're looking at a 60 degree cone angle.

 

[cetsa]

Re: Educate me on depth finders and GPS units

I found this website very useful: fish finder reviews

 

[dingbat]

Re: Educate me on depth finders and GPS units

I found this website very useful: fish finder reviews

These review sites just regurgitate the manufacturer's calms. They make no effort to set the record straight. One of the units claim cone angles of 60 and 120 degrees. Physically impossible for a single crystal transducer but the reviewer makes no mention of this. It's not until you read the small print in the back of the owners manual that the manufacturer comes clean on the claim.

The transducer provided with XXXX has beam angles of 15 and 45 degrees at 3dB. However, when this transducer is used with the XXX device, it can detect the smallest signals up to 60 and 120 degrees.


From the image above, a 120 degree cone angles is roughly -30db. How reliable is your cell phone with less than a 1 bar of signal?

 

[Silvertip]

Re: Educate me on depth finders and GPS units

Yeah that upgraded map is way overkill for what I want. I just want the basic layouts so when on lakes I'm not overly familar with I can find my way back to the boat launch I used etc. Nothing overly fancy. My phone's GPS works great for that. Just a pain using the phone and watching for dry hands and don't drop it etc.



Ah good to know. For some reason I thought the sonar was giving you the depth of an area around your boat, like a large radius. I will definitely play around with it cautiously and get a feel for it.

That's true when the boat is stationary. Remember that a boat moving carries the "sonar cone" at the same speed. To illustrate how the sonar cannot warn you in time of a problem, place a funnel upside down on a table. Place an object representing your boat on top of the funnel. Now place an object (any object) on the table and push the funnel toward it. You should be able to visualize that at a speed of 30 MPH for example, the sonar beam would hit the obstruction only moments before the boat struck it. The faster you are going the less time there is to react and at anything above idle speed, you simply do not have time to avoid the obstruction. Therefore you set the "SHALLOW ALARM" to a depth that when reached sounds the alarm. Since depth generally changes gradually, you would be able to see the gradual change and the depth alarm would alert you so you can slow down. Obviously obstructions like rocks, wing dams, ridges, pilings, old bridge piers, etc represent instant depth changes so that issue is still present. But those hazards on navigable waterways are usually marked so they can be avoided.

 

[MalcolmV8]

Re: Educate me on depth finders and GPS units

Thanks guys. In reading reviews and trying to educate myself on them I see there's this feature called "down imaging" which looks like they use sonar to generate an image of what it looks down below. It almost looks like a photo film original used to print pics (pre digital cameras). I'd never seen that before but after seeing it wow. It's now up there on the "must have" features lol. I'm not sure if it's as good as the reviews or manufactures claim it to be but wow it looks nice. That steps me up to the Humminnbird 386 DI which is $450. However I see the close competition is the Lowrance Elite 4 DSI which is only $350 and has the down imaging and I believe everything else I wanted. Are the Lowrance units good too? I've noticed the Humminnbird units on display in my Marine shop which gives the impression they are "name brand" or at least decent quality.

 

[MalcolmV8]

Re: Educate me on depth finders and GPS units

Well I ended up picking up a Lowrance Elite 4 DSI. Used it all weekend for the first time and loved it. The down imaging is pretty interesting. Having depth, water temp, and mph on the screen at all times is great. Thanks for the help guys.