Gps

[rdny041285]

Anybody know if a GPS receiver has to be installed facing a certain direction?

 

[tommays]

Re: Gps

No

But it may be hard to read and interpert some of the info it it was off enough

 

[bruceb58]

Re: Gps

The GPS doesn't care what position it is in. The GPS receiver calculates your direction by looking at your position over time.

 

[rdny041285]

Re: Gps

ok thanks....also would it be ok to mount it under the windshield or does it need a clear path to the sky?

 

[rndn]

Re: Gps

Under the windshield is fine as you may see many GPS systems for cars mounted on the dashboard under the windshield.

 

[Boatist]

Re: Gps

You will be able to get a 3 D Pasition, Latitude, longitude, and Elevation with it under the window. It takes 4 satellites to get a 3 D postion. These GPS Satellites orbit the earth in lots of orbits and are only 11,000 miles high. With 24 GPS birds usually will see 6 or more. Since you only need 4 should get a 3D position.

If you have an internal antenna that will be your best choice. Glass and soft tops like Canvas or Sunbrella have very little affect on the signal.

For the most accurate positions you also need to pick up one of the WAAS satellites. These Satellites are used to give your unit error correction information about the GPS birds and inprove it accurracy.
These Sattellites are in geoStationary orbits so must be over the equator and 22,240 Miles high so they are a little harder to pick up.

If your in the USA Northern States or Canada and want the most accurate postion then an external antenna is better. Without a WAAS Satellite the accuracy is about 30 feet. With a WAAS Satellite pickup the accuraccy is about 10 feet.

Since they moved the WAAS Birds around back in 2006 in the USA it has been a lot eaiser to pick up and have more birds. Still if your standing between the unit and the Southern sky you will block the signal. also if another unit lile a radio or depth finder is to the south of the gps it will block this signal. Any metal structure will also like block the signal if between the unit and the WAAS Bird..


Bodega Bay weather May 6 2008
Winds NW 320 Degrees True, 29.1 knots with gust to 35.0 knots, Sea Temperature 48.6 degrees F.
Seas NW 326 degrees true at 9.5 feet every 6 seconds, Swell steepness = Very Steep.
http://www.ndbc.noaa.gov/station_page.php?station=46013

 

[Chris1956]

Re: Gps

Boatist, I had thought Geostationary satellites were 22,500 miles high, over the equator.

 

[tnduc]

Re: Gps

You should mount your GPS so it is facing north.




Sorry, couldn't resist :redface: .

 

[Boatist]

Re: Gps

Chris1956
You are correct thank for the correction.

Geostationary orbits are useful because they cause a satellite to appear stationary with respect to a fixed point on the rotating Earth. As a result, an antenna can point in a fixed direction and maintain a link with the satellite. The satellite orbits in the direction of the Earth's rotation, at an altitude of approximately 35,786 km (22,240 statute miles) above ground. This altitude is significant because it produces an orbital period equal to the Earth's period of rotation, known as the sidereal day.

Bodega Bay weather May 6 2008
Winds NW 320 Degrees True, 29.1 knots with gust to 35.0 knots, Sea Temperature 48.6 degrees F.
Seas NW 326 degrees true at 9.5 feet every 6 seconds, Swell steepness = Very Steep.
http://www.ndbc.noaa.gov/station_page.php?station=46013

 

[Drowned Rat]

Re: Gps

Anybody know if a GPS receiver has to be installed facing a certain direction?

Yes, up.

 

[rdny041285]

Re: Gps

i have this fishfinder/GPS

http://store.humminbird.com/humminb...ombos/500-series/595c-combo/prod406320-1.html

and it came with this waas

http://store.humminbird.com/accessories/system-modules/gps-receiver/prod406340-1.html

i need to know where i can mount the waas....when i have it hooked up and i move it around it looks like the map rotates a little but i cant really tell which way is north and it doesnt always move when the waas is rotated...

 

[bruceb58]

Re: Gps

The map is not going to rotate until you actually move feet at a time. There is no magnetic compass in the GPS that tells you your orientation. It determines your heading by looking at your path over time.

Also, the round puck is your receiver. This includes that antenna for the GPS satellites as well as the WAAS. It just needs to have a clear view of the sky. A few obstructions will be fine. There is no orientation for mounting the puck

 

[rdny041285]

Re: Gps

ok thanks bruce....i will try to mount it somewhere with no obstructions but maybe under the windshield will be ok...i hope its waterproof...

 

[bruceb58]

Re: Gps

I have a similar puck that mounts under the windshield.

 

[45Auto]

Re: Gps

My GPS receiver is mounted inside my console. There is wood, fiberglass, and windshield between it and the sky. Doesn't bother it a bit.

 

[Boatist]

Re: Gps

45 Auto

What is your Latitude and how many WAAS Satellites do you pick up?

West Coast of the USA can see 4 but the farther North the harder they are to pick up and the lower on the horizon they are.

Middle of the contry can see 3

Notrh East can see 2


Bodega Bay weather May 11 2008
Winds NW 320 true at 33.1 Knots with Gust to 40.8 Knots, Water temperature 47.7 Degrees F
Seas 15.4 feet every 9 seconds, chop at 6.9 seconds, Wave steepness = Steep
http://www.ndbc.noaa.gov/station_page.php?station=46013

 

[rdny041285]

Re: Gps

not sure about those (how many waas satellites i pick up) where can i find that out....i live in jupiter.....south east florida.

 

[Boatist]

Re: Gps

In Florida you will have no problem picking up WAAS Satellites. You should be able to see 51 ANIK at 107 degrees West, 48 Panam at 133 degrees West and 35 AOR-W at 142 degrees West. All three of these satelites are over the Pacific now. Even AOR-W (Atlantic Ocean Region - West) is now over the Pacific ocean.

To see if you receive them go to the Satellite page screen and look for the numbers. Also on the satellite page many units will have a symbol to identify satellites as WAAS. Check your manual. Also if the link works you can click your postion on the map and it will give your Azimuth and Elevation.

Example for 51 ANIK the easiest for you to pick up it would be Azimuth 220 degrees and Elevation 46 degrees.

The hardest for you to see is #35 AOR-W at Azimath 252 degrees and elevation 18 degrees. So looking at you Satellite page with the top pointed North and you put a compass rose over the unit then at 252 degrees an one of the outer rings you should see 35. Or in general this would be WSW of your postion. 18 degrees above the horzion is eaiser to be blocked by trees or mountains to your West if your running in a mountain stream or lake.


# 51 at 46 degrees elevation or 46 degrees above the horzion should be easy to see still if you are standing between your GPS antenna and 220 degrees you body will block it. The farther North one goes the lower on the horizon the WAAS birds will be.

Existing WAAS satellite
*New WAAS satellite

One can readily determine the elevation and bearing of these satellites from your location from these URLs:
The below are listed from west to east.

Name GPS Series Location
POR #47 3F3 Pacific Ocean at 178.0?E@
http://www.lyngsat.com/tracker/inmar3f3.shtml

AOR-W #35 3F4 Pacific Ocean at 142.0?W@
http://www.lyngsat.com/tracker/inmar3f4.shtml

PanAm #48 Galaxy 15 Pacific Ocean at 133.0?W*
http://www.lyngsat.com/tracker/g15.html

Anik #51 F1R Pacific Ocean at 107.3?W*
http://www.lyngsat.com/tracker/anikf1r.html

Inmarsat #34 4F2 Atlantic Ocean at 53.0?W
http://www.lyngsat.com/tracker/inmar4f2.shtml

AOR-E #33 3F2 West of Africa at 015.5?W
http://www.lyngsat.com/tracker/inmar3f2.shtml

IOR-W #39 3F1 Indian Ocean at 064.0?E
http://www.lyngsat.com/tracker/inmar3f1.shtml

Bodega Bay Weather at Noon on May 12 2008
Winds NW at 310 Degrees true, 29.1 knots, Gust to 35 knots, Sea Temperature 46.7 degrees.
Seas Swells 13.1 foot at 8 seconds, Chop at 6.6 seconds, Wave Steepness = Very Steep

 

[rdny041285]

Re: Gps

thank you for all the information....not sure what most of it means but i will try to google some of it and try to figure it all out lol thank you.

 

[Boatist]

Re: Gps

Rdny

Sorry I did not mean to make it complicated.
GPS you need to receive 3 satellites to get a 2 D Position. This is latitude and longitude. This will pinpoint your location on earth.

The GPS satellites orbit earth about 11000 miles high. There are 24 GPS satellites in differents orbits to form a grid. Most GPS receivers today will have 12 to 16 channels. You need to recieve signals from 3 satellites to find you 2 D position, (Latitude and Longitude). If you are not in the bottom of a narrow cayon or under thick tree cover it very easy to receive 3 sattelites. So in a car thru the windows or in a boat thru the windows or thru a soft canvas of sunbrella top it very easy to receive 3 satellites.

To find a 3 D Position that will also include Elevation you need to receive 4 satellites again very easy.

With GPS Satellites your accuracy is about within 30 feet at best and Elevation about 100 feet. That very good but the FAA and of course the military need it to be better. When trying to land a airplane in the cloudes and fog would like to be in the center of the runway. So they added a few more satellites Called WAAS (Wide area augmentation SysteM).

These WAAS Satellites are in Geostationary orbits, Meaning they are like TV Satellites so are in the same postion all the time with respect to earth. Like your Sattellite TV dish. It points to a point in the sky where the TV satellites is.

To get a Satellite in Geostationary orbit it has to be about 22,240 miles high over the equator and orbit the earth in the same dirrection the earth turns. This means the farther North you go the lower in the sky the WAAS satellites are. The lower in the sky they are the more likely they are to be blocked by something on your boat or a tree or a hill. These WAAS Satellites are used to improve the accuracy of your GPS on your boat or car. With the WAAS Satellites error correction the accuracy improves to about 10 feet or 3 meters.

My last post was a list of the WAAS Satellites that can be seen from the USA.
Each one has a link and if you click on the link and scroll down the page to the world map then use your mouse to mark your position in the world it will tell you if you can see that WAAS satellite or if it is over the horzion. It will also tell you the AZIMUTH in degrees from your position and The Elevation Above the Horizon.

What it means is if your in the far Northern USA, Canada or Alaska and you need or want 10 feet accuracy of your GPS On your boat then you likely need to get an external antenna and mount it high enough that it will not be bocked by anything on your boat. On the other hand if your in southern states and the Western USA then you will have 4 WAAS satellites that are high in the sky and even with an internal antenna should pick up at least one WAAS Satellite and get 10 foot accuracy.


Bodega Bay Weather May 13 2008
Winds NV 320 degrees true at 23 knots with Bust to 27.2 knots. Water Temperature 48., degrees
Seas 7.9 feet every 8 seconds, chop 5.6 seconds, Wave Steepness = Steep