Thread: HDS GPS performace

You may be expecting too much! According to Garmin "Newer Garmin GPS receivers with WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average" that is 10 feet and a lot depends on location and atmospheric conditions.

NO gps is going to give you "spot on" results. Only the military has access to something that accurate... they purposely dumb down civilian units to not read that accurately. As he said, 9-10 ft is really the best accuracy you can expect, under ideal conditions and reception.

You have to remember, the HDS units ARE the antenna. If you see something and mark it on your finder it marks the position of your finder when you saw the object. For example, you are trolling down the bank and see a brush pile and mark it on your bow unit. If you have a 20' boat and the transducer you were using was the LSS1 on the stern, then that is already 20' from the brush that you are going to be off. Under ideal circumstances with the 10' error, your best location is going to be up to 30' off, and thats on a good day. Using a handheld and holding it over the area is obviously going to deceive better results, but thats not the case. The HDS isnt any more inaccurate in my experience. You just have to pay attention to what your doing, and not mark your waypoint right on the brush pile.

What I have found is you need to mark your waypoint BEHIND where you saw it.... so for instance, dont put the cursor right on the pile, put it 20ft behind it the direction you came from. That would put it much closer to that acutal postion your unit was in when the brush passed under your boat. The left to right directions shouldn't be any different (for instance if your marking on side scan).. unless you were making a hard turn at the time.

Obviously the distance you put it from the object depends on the distance from the unit and the ducer. So if you mark it while idling at the wheel you may only put it back 10ft etc. Its still not perfect but it will definately get you closer than blindly clicking on your screen every time you see something.


Edit: None of this applies to "reading" your postion. When you log a waypoint its saved as a coordinate. Each unit on your boat stores that coordinate, and will base that navigation off of its own antenna. In otherwords, a waypoint you saved on the console units isn't going to be off any more if you read it on the bow unit than you would if you read it on the original console unit. The bow unit would use its own signal to get back to that "coordinate". You just have to remember to base your position on that object as the distance from the unit you are currently using to find it.

Thanks for the explanation TommyBass. I understand what your saying but it doesn't explain why when I marked the waypoint in my garage it wasn't based off what the transducer was seeing so it eliminated that margin of error. It would still drift 40+ feet from the waypoint. My $100 handheld doesn't do this.

Thanks Tenntomm, but my reply was more to people who were concerned / replying to you, not your original question directly As to that, they are not the most super sensitive receievers in the world. Obtaining a good signal in a garage is next to impossible on mine, but when out on the water I have no problem holding steady. Many gps units do not do well near any sort of building or object, even under tree cover. My Garmin handheld with the super sensitive antenna is the only one I can get good signal under heavy forests etc with. I wouldn't guarentee thats your problem, but I would think its a large possiblilty. I would say your irregularity is from cycles of brief signal strengths through your roof / garage door. Try it outside and see what happens.

I just ordered the LCG4000 antenna along with the 124-69 - Lowrance Network Starter Kit. I was finding it too hard to "Zero in" on my waypoints I had marked and I believe it is due to the refresh rate of the "in unit antenna". I hope it helps at least $250 worth. I plan to mount the antenna right above my LSS-1 transducer.

I also have a Garmin GPSMAP192 C that I've had for quite sometime now. I guess I should break down and install that thing too.

I dont know about the HDS units. I have an outdated LMS unit and dont ever have any problems finding my brush (waypoints), and it has an internal antenna. When I get close I idle with the zoom all the way in and go slow enough to allow the GPS to make boat location corrections.

TommyBass, you were right about the garage, i got a much better signal on the lake today. Another thing I cant fingure out is on the navioincs map I can only zoom in to 100ft . If I change the card to my lowrance hotmap I can zoom in to 50 ft. This made a big differnence in pinpointing waypoints. I wonder if I have something setwrong on the navionics. Also anybody know what Map Datum should be used for the navioincs card. I think mine is on the default WGS84

Originally Posted by Tenntomm

TommyBass, you were right about the garage, i got a much better signal on the lake today.

So you hit your waypoints closer?

Originally Posted by justinp61

So you hit your waypoints closer?

Yea it was much easier on the Lowrnace Hot spot chip because it would zoom in closer. I think this was most of the problem. Also I changed the overlay data to include Cross Track error and Distance to Destination, and even though I couldnt zoom any closer I could reference this information to see how far off I was.

Originally Posted by Tenntomm

Yea it was much easier on the Lowrnace Hot spot chip because it would zoom in closer. I think this was most of the problem. Also I changed the overlay data to include Cross Track error and Distance to Destination, and even though I couldnt zoom any closer I could reference this information to see how far off I was.

What & how does Cross Track error & Distance help, I know just plain distance but not other.......