Thread: Humminbird GPS In-Depth...

I believe you get much better accuracy with more than 4 satellites. On our survey grade GPS, we could possibility get a 3D fix with only four satellites but we would have to be in a wide open field. When in vegetation or close to vegetation we need 10-12 satellites to keep a fixed position. In the field or on a boat the higher number of satellites will not only improve accuracy in calculations, it will help keep the accuracy when you may lose connection with a satellite. What happens when the motor gets in the way when your boat turns or you go into a small creek channel that is vegetated with large trees on both sides of your boat... You will most likely lose the signal to some satellites and keep the others.

In order for our survey grade GPS to reach sub-centimeter accuracy... It has fixed base stations it communicates with through radio waves on top of cell phone towers. This further increases the horizontal accuracy of the calculations. If only four satellites would give these type results then that would be great.. But it does not. There is always room for an increase in accuracy.

You mentioned earlier that there were not enough satellites to possibility connect 12 satellites at one time.. Have you thought about the Russian's GLONASS (21 satellites plus 3 spares) or Europe's Galileo (27 satellites plus 3 spares - Not active yet)? The US satellites (GPS - 24 operating satellites) are not the only satellites in orbit. Our survey grade GPS uses both US GPS satellites and GLONASS satellites. Along with the corrections made from the base stations in order to get the desired results.

GLONASS - Summary
ESA - Navigation - The future - Galileo - What is Galileo?
Global Positioning System

Also, the added accuracy of more satellites can stem from the location of the satellites. If all the satellites were closely grouped together then your accuracy would be poor. The further they are spread out the better the accuracy. Also, how can the average of 12 calculations not be better than the average of 4 calculations? Doesn't the standard deviation improve with the increase in calculations (or in this case satellites)? How about WAAS.... Why was WAAS needed if 4 satellites were accurate enough?

Navigation Services

There are many things that can cause variations in results with GPS measurements such as solar flares... When this happens with 4 satellites being averages to get the results the results would be off. Now when you have 12 satellites and you have a solar flare that affects one... the average is much better which improves accuracy.

Four satellites is a minimum requirement to get results... In the case of satellites, more is always better.

DoubleG

Originally Posted by DoubleGobble00

I believe you get much better accuracy with more than 4 satellites. On our survey grade GPS, we could possibility get a 3D fix with only four satellites but we would have to be in a wide open field. When in vegetation or close to vegetation we need 10-12 satellites to keep a fixed position. In the field or on a boat the higher number of satellites will not only improve accuracy in calculations, it will help keep the accuracy when you may lose connection with a satellite. What happens when the motor gets in the way when your boat turns or you go into a small creek channel that is vegetated with large trees on both sides of your boat... You will most likely lose the signal to some satellites and keep the others.

In order for our survey grade GPS to reach sub-centimeter accuracy... It has fixed base stations it communicates with through radio waves on top of cell phone towers. This further increases the horizontal accuracy of the calculations. If only four satellites would give these type results then that would be great.. But it does not. There is always room for an increase in accuracy.

You mentioned earlier that there were not enough satellites to possibility connect 12 satellites at one time.. Have you thought about the Russian's GLONASS (21 satellites plus 3 spares) or Europe's Galileo (27 satellites plus 3 spares - Not active yet)? The US satellites (GPS - 24 operating satellites) are not the only satellites in orbit. Our survey grade GPS uses both US GPS satellites and GLONASS satellites. Along with the corrections made from the base stations in order to get the desired results.

GLONASS - Summary
ESA - Navigation - The future - Galileo - What is Galileo?
Global Positioning System

Also, the added accuracy of more satellites can stem from the location of the satellites. If all the satellites were closely grouped together then your accuracy would be poor. The further they are spread out the better the accuracy. Also, how can the average of 12 calculations not be better than the average of 4 calculations? Doesn't the standard deviation improve with the increase in calculations (or in this case satellites)? How about WAAS.... Why was WAAS needed if 4 satellites were accurate enough?

Navigation Services

There are many things that can cause variations in results with GPS measurements such as solar flares... When this happens with 4 satellites being averages to get the results the results would be off. Now when you have 12 satellites and you have a solar flare that affects one... the average is much better which improves accuracy.

Four satellites is a minimum requirement to get results... In the case of satellites, more is always better.

DoubleG

Hey ask Garmin. I just repeated what I was told. I understand how the gps system works and I am aware of the European and Russian systems. Don't trust them though.

It is my understanding our (USA) "new" satellite constellation will have a new frequency band (L5) with more power and accuracy.

There is a point where more is not better as most will agree. It is more of a "selling gimmick" than a functional practicality.

I and others would rather HB fix the donut issue than hawk satellite counting.

Hahaha... Yeah I would like the donut issue to go away also... That is aggravating. Especially when your GPS says 2 feet of error.

I still believe more is better. There is no way to get 2 foot of error from 4 satellites... unless you had base station corrections but I still don't see that happening. I will say this.. I have the 50 GPS system.. Out of the 100 or so waypoints I have marked, it puts me right back on top of them every time. I never tried the 16 GPS system...

DoubleG

now days GPS is more important than your fish locator as most of us sink some kind of condo's

Originally Posted by DoubleGobble00

Hahaha... Yeah I would like the donut issue to go away also... That is aggravating. Especially when your GPS says 2 feet of error.

I still believe more is better. There is no way to get 2 foot of error from 4 satellites... unless you had base station corrections but I still don't see that happening. I will say this.. I have the 50 GPS system.. Out of the 100 or so waypoints I have marked, it puts me right back on top of them every time. I never tried the 16 GPS system...

DoubleG

Hi DoubleGobble00- thanks for your imput on this subject been interesting to say the least-good fishing to U

Originally Posted by DoubleGobble00

Hahaha... Yeah I would like the donut issue to go away also... That is aggravating. Especially when your GPS says 2 feet of error.

I still believe more is better. There is no way to get 2 foot of error from 4 satellites... unless you had base station corrections but I still don't see that happening. I will say this.. I have the 50 GPS system.. Out of the 100 or so waypoints I have marked, it puts me right back on top of them every time. I never tried the 16 GPS system...

DoubleG

the HB 50 receiver advertises accuracy withing 2.5 meters and my Garmin 76 12 channel advertises less than 3 meters. This is what I am saying, not that you get 2 feet accuracy from 4 satellites.

Good points you bring out.

I have a hundred dollar handheld unit, not a $10,000 surveyor unit.

Oh I got ya....

Maybe I should bring the survey unit out in the boat with me... and compare the data... Hmmmm.. Boss man would be happy if I dropped his GPS in the lake though... Better not try it but would be interested to see what the survey grade unit picks up conpared to the GPS50.

DoubleG

Originally Posted by DoubleGobble00

Oh I got ya....

Maybe I should bring the survey unit out in the boat with me... and compare the data... Hmmmm.. Boss man would be happy if I dropped his GPS in the lake though... Better not try it but would be interested to see what the survey grade unit picks up conpared to the GPS50.

DoubleG

To DoubleG Do it the other way around take the HB in the field with you. up here in IL we have made 997 units portable for use in ice fishing,run them off little 8ah sealed batteries from Cabelas about $19.00 with charger. walk on ice & let it lead u to spot to drill fish hole, then stick ducer in water & spin it on a 5 gal bucket and get reading just like in boat. Heck I have found some good structure by poking in old ice holes during week when most folks are working.