Hi Yan, onboard large ships, you will find 2 or three GPS, all located on the top deck, above the wheelhouse. More and more frequently, one or 2 of these will be a differential GPS, to get a better accuracy, around 3 meters. With GPS alone, you get around 7 meters. The GPS are very rarely used in conjonction. ONe is for the electronic chart, one for AIS (Automated Identification System) and a spare. Jacquelin Hardy I work on ships. "Yan.L" <waters@starhub.net.sg> a �crit dans le message de news: df850db4.0406090812.4e8f7865@posting.google.com...> Is one GPS receiver enough to get the precise position? Or we need to > use multiple GPS receivers, for instance, four GPS receivers installed > on bow, tail, port and starboard, respectively? > > If we use four GPS receivers, how to manipulate the GPS information > collected by these four receivers to get the precise position of the > ship?
GPS Navigation for Ship - Single Receiver or Multiple Receivers?
Started by ●June 9, 2004
Reply by ●June 9, 20042004-06-09
Reply by ●June 9, 20042004-06-09
> Is one GPS receiver enough to get the precise position? Or we need to > use multiple GPS receivers, for instance, four GPS receivers installed > on bow, tail, port and starboard, respectively? > > If we use four GPS receivers, how to manipulate the GPS information > collected by these four receivers to get the precise position of the > ship? >As far as the position of the ship, I don't think you will get more accuracy with more receivers. Things like differential GPS and WAAS, which is a form of differential, will give you more accuracy. If it is heading that you want, FURUNO makes a GPS based heading indicator. Go to www.furuno.com and look at the Satellite Compass selections. John Bell www.smallboatgps.com
Reply by ●June 9, 20042004-06-09
Yan.L wrote:> Is one GPS receiver enough to get the precise position? Or we need to > use multiple GPS receivers, for instance, four GPS receivers installed > on bow, tail, port and starboard, respectively? > > If we use four GPS receivers, how to manipulate the GPS information > collected by these four receivers to get the precise position of the > ship?Airborne and ground-based vehicles also use inertially enhanced GPS -- basically you have a small inertial measurement unit (three gyros and three accelerometers) and a GPS receiver feeding a computer. The GPS provides good quality low-frequency data, the inertial measurement unit provides good mid-frequency data, and you implement a great big Kalman filter in the computer. These systems can provide _very_ good positional data. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●June 9, 20042004-06-09
On 9 Jun 2004 09:12:01 -0700, waters@starhub.net.sg (Yan.L) wrote:>Is one GPS receiver enough to get the precise position? Or we need to >use multiple GPS receivers, for instance, four GPS receivers installed >on bow, tail, port and starboard, respectively? > >If we use four GPS receivers, how to manipulate the GPS information >collected by these four receivers to get the precise position of the >ship?A good single GPS should be able to handle the job for you. Any current unit should give you 3-5m accuracy in most conditions on water. Don't know that there's much need for more accuracy than that in a boat. You "may" want to invest in a small additional self-contained waterproof handheld GPS as a backup for the main unit mounted in the boat. Besides giving you a good backup device should something happen to the main GPS, having a good portable is handy for non-nautical uses as well!
Reply by ●June 10, 20042004-06-10
"John Bell" <johnbell.nospam@cfl.rr.com> wrote in news:1tLxc.92624$Ol3.56335@twister.tampabay.rr.com:>> Is one GPS receiver enough to get the precise position? Or we need to >> use multiple GPS receivers, for instance, four GPS receivers installed >> on bow, tail, port and starboard, respectively?One receiver will give you the precise position of the antenna. On some ships I've landed on, there can be a couple or three football fields length from one end to the other. The question is what point on the ship do you need to know the position of, and why? If you know the position of the antenna, and know the bow is a certain distance away from it, then you know the position of the bow, with perhaps some arithmetic required.
Reply by ●June 10, 20042004-06-10
Stan Gosnell schrieb:> need to know the position of, and why? If you know the position of the > antenna, and know the bow is a certain distance away from it, then you know > the position of the bow, with perhaps some arithmetic required.No, you don't. The bow may be rotated around the antenna by any number. The only thing you do know is the distance. - Carsten -- Audio Visual Systems fon: +49 (0)2234 601886 Carsten Kurz fax: +49 (0)2234 601887 Von-Werth-Stra�e 111 email: audiovisual@t-online.de 50259 Pulheim / Germany WGS84:N50�57'50.2" E06�47'28.5"
Reply by ●June 10, 20042004-06-10
Carsten Kurz wrote:> No, you don't. The bow may be rotated around the antenna by any number.And for some numbers it could be quite fatal... :-) Best regards Preben
Reply by ●June 10, 20042004-06-10
Carsten Kurz <audiovisual@t-online.de> wrote in news:40C86C4A.761C9FE4@t-online.de:> > > Stan Gosnell schrieb: > >> need to know the position of, and why? If you know the position of the >> antenna, and know the bow is a certain distance away from it, then you >> know the position of the bow, with perhaps some arithmetic required. > > No, you don't. The bow may be rotated around the antenna by any number. > The only thing you do know is the distance.Well, you certainly should know the bow heading. Even if the ship is stationary, the magnetic compass shows which way the bow is pointing. That's elementary stuff. Anyone going out in even a relatively small boat without a mounted compass is mortally stupid. Large ships do not set sail without working compasses.
Reply by ●June 10, 20042004-06-10
Stan Gosnell schrieb:> Well, you certainly should know the bow heading. Even if the ship is > stationary, the magnetic compass shows which way the bow is pointing. That's > elementary stuff. Anyone going out in even a relatively small boat without a > mounted compass is mortally stupid. Large ships do not set sail without > working compasses.A dual GPS/antenna attitude determination device is exactly what you would need to overcome the shortcomings of a magnetic compass. That's the whole reason for the OP's request. - Carsten -- Audio Visual Systems fon: +49 (0)2234 601886 Carsten Kurz fax: +49 (0)2234 601887 Von-Werth-Stra�e 111 email: audiovisual@t-online.de 50259 Pulheim / Germany WGS84:N50�57'50.2" E06�47'28.5"
Reply by ●June 10, 20042004-06-10
Stan Gosnell wrote:> "John Bell" <johnbell.nospam@cfl.rr.com> wrote in > news:1tLxc.92624$Ol3.56335@twister.tampabay.rr.com: > > >>>Is one GPS receiver enough to get the precise position? Or we need to >>>use multiple GPS receivers, for instance, four GPS receivers installed >>>on bow, tail, port and starboard, respectively? > > > One receiver will give you the precise position of the antenna. On some > ships I've landed on, there can be a couple or three football fields length > from one end to the other. The question is what point on the ship do you > need to know the position of, and why? If you know the position of the > antenna, and know the bow is a certain distance away from it, then you know > the position of the bow, with perhaps some arithmetic required.If you know the position of one point on the ship, then using the ship's heading, you can calculate the position of any other point on it. If you know the positions of two points on the ship, you can calculate its heading. Beyond that, what do you mean? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
