Subject: Re: GPS45 normal vs. bat. save mode Newsgroups: sci.geo.satellite-nav References: <3tunel$12c@news.bu.edu> <3tv30g$bkh@ixnews4.ix.netcom.com> <3u3rtn$7q2@mujibur.inmind.com> <3u5vlj$2ke@news.bu.edu> Organization: In Mind International, Inc. Distribution: world Thomas P. Skinner (tom@engc.bu.edu) wrote: : thogard (thogard@inmind.com) wrote: : : It would be nice if there was a way to tell it to scan a specific : : satellite till its told to stop. : Can you explain what you mean by this? Why yes... What I would like to see is a feature where I can tell the little box that I want it to find satellite #6 or #20 or #1 since I know that one of the three is likely to be overhead. In fact the order it does it initail scan seems a bit odd. The orbits don't change all that much (in terms of inital fix) and if you have a position and a time and last years alimnac you can guess at what satellites are visable. If you can't find any of those, then try scaning those that are 45degrees away and repeat until you find one. Once you have one, you can guess at your position (ok so its withing about 1000 miles but thats beter than nothing). With that info you can uses your old almanac data (that is being updated since your now listening to one satellite) and guess at the next closest satellite. Once you have two you can determine if the user is telling the truth about the inital location and time. This method would work well for land based units. If your up in the sky or in orbit there are too many assumptions. Some of the problems: 99kt speed limit... It could be more waterproof. Some units arn't but you don't know till its too late. It I were building a product to compete with the G45 this is what I would add: *)durring acuistion telling it to look for 1,6,20 in that order since one of them is almost always overhead. *) correction of waypoints. find a point on a map, when you walk there press "mark" *) the rename feature could use some improvment I called a waypoint 485I66 and it should ahve been 495I66. *) it should have every feature a bike computer has (speed, distance covered, max speed, min speed) *) altitude on waypoints *) smarter power managment (i.e. autor turn off when the external power goes down, auto on every 15 min to get a fix, auto off after staying in once location for n minutes. All user selectable of course) *) marking waypoints on the map with the cursor. *) goto should only scroll through known waypoints. *) The battery level indicator should show battery level even if its on exteranl power. It chould show a hollow graph. *) remove that funny edge on the front of the case. It looks stupid and feels worse. *) A mark this point feature... Set the unit up, the mark feature and it averages until you tell it your moveing to the next point. *) a nice display showing that S/A is on/off (can you tell this?) *) an auto waypoint set at the units last known good position.