Lakemaster accuracy of roads

[ameyers41]

I was able to pick up the '06 version of the MN Lakemaster chip to use with my Lowrance Expedition. The street detail is great. However, it seems like the accuracy is off by almost an entire block when I'm at my house, even outside, where I'm getting a decent signal and my EPE is only at 34 feet.

Is there something I need to do to calibrate the unit or the card itself? Any thoughts?

[nluchau]

If Schweady chimes in he might be able to give you more information.

Nick

[schweady]

Enough already...

"Success is 10 percent inspiration and 90 percent perspiration." -- Thomas Alva Edison (a very schweady sort of guy)

Seems like I noticed that right after getting mine, and it seemed like almost a block off, too. (Isn't that what we all do first thing?.. sit out on the deck at home in the freezing cold and wait for it to find enough satellites to tell us we're sitting out on our deck at home?) I can't remember if it had any effect, but I know that somewhere along the line I initialized my gps. In Advanced mode, hit 'Menu' twice > GPS Setup > Initialize GPS > move the cursor crosshairs to where you think you're at. See if that does it.

Some inaccuracy is caused by the unit constantly dropping off and picking up sattelites as they fly overhead... Fun useless exercise: turn it on and let it acquire your position then let it sit for a while. When you come back to the unit, it's amazing how much 'traveling' you did. Especially if you zoom in closely, you'll see a zig-zag trail being laid down as the unit readjusted to your 'new position.' In your cae, what's continues to be a mystery is still being off that much when the EPE is down to 34 ft... ??

[Big Pine Walleye]

It seems to me that the more you are zoomed in that the further you may be off! I agree with Schweady...last night we were sitting in the parking lot at work seeing how far we would move without moving (man we need some ice!) and we moved 12 feet without moving the truck!

[MJCatfish]

Alien abduction attempt? How do you know you weren't moving ?

[Augusta]

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Alien abduction attempt? How do you know you weren't moving

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[ameyers41]

Thanks. Glad it's not the chip, GPS, or me (USER ERROR). I'll try your suggestion Schweady.

Such a cool, fun toy, but kind of frustrating marking the home waypoint on the next block up...

Thanks again.

[Jim Almquist]

Quote:

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Thanks. Glad it's not the chip, GPS, or me (USER ERROR). I'll try your suggestion Schweady.

Such a cool, fun toy, but kind of frustrating marking the home waypoint on the next block up...

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Maybe your GPS is trying to tell you to move north

[Sutty]

I noticed the same thing when I turned mine on for the first time today. I am not too worried about being off a block at home but I am worried about it being a block off on the lake...

[hanson]

I don't think any GPS unit has really good accuracy when you are standing still. The accuracy of the unit will really go up when you are slowly moving in one direction.

Some of the roads on the Lakemaster chip are off, either because roads were re-routed during construction or they are using older maps for certain areas. The more you drive around the state with your unit, the more you'll notice this.

[Sutty]

As long as I can drive to the edge of a flat or some structure on the lake I don't care who's house I drive home to

[ameyers41]

Thanks! Hansen - I tried this while driving home, not stationary, so I think the signal was okay. Based on feedback, it sounds like the roads are just off on the map, not anything to do with having to calibrate the unit. Just hope the lakes are a little more accurate. I'll find out the first time I'm on the ice!

[RandyR]

In general you will get a more accurate location reading on open water because the sky is unobstructed (unless you are on a river or near shore). You will also get a more accurate location if you are moving instead of standing still. On the water my unit regularly aquires a WAAS signal which can greatly enhance the accuracy of indicated position. It isn't unusual to have a location accuracy estimate of 16 feet or less (as calculated by the GPS receiver) when there is a WAAS signal present. At home or in the truck there is a much higher probability that at least some of the satellites will be obstructed from a line of sight view, which is required to obtain the GPS and WAAS signal.

WAAS (Wide Area Augmentation System, I hate acronyms!) is fairly new, about three years old, added as an aircraft navigation enhancement to refine the accuracy of GPS signals.

The more signals your receiver can find, the more accurate the location shown. I have also noticed that for some reason the GPS signals are stronger in the evening hours. (Anyone else notice this? Does anyone know why?)

The roads on the LakeMaster chip come from the same data on the MapCreate software sold by Lowrance as a mapping software utility for their handheld and larger receivers that are able to utilize MMC/SD cards (chips) to supplement the low resolution and crude map data that is on the permanent memory of the unit.

From my experience the road data accuracy ranges from great to awful. Freeways , state highways, county roads and local streets all have errors that I have found, but overall it is usually close to reality.

[Duffman]

I deal with digital roadbases everyday at work. There's only a couple of vendors out there that produce the source data for most of the industries digital roadbases. And parts of these roadbases are being updated 4 times a year, from adding roads to shifting roads to better reflect the accuracy of the roadbase. I've seen roads shift anywhere from less than a foot to 3/4 of a mile between roadbase releases, there is still plenty of inaccuracy out there. It's not that the GPS is inaccurate, it's probably a case where the source data is inaccurate.