dave and jaime

calculations inside a gps are done using the satellite as the center with the users(ie gps) position on the surface of a sphere of radius equal to the distance to the sat as computed from the time recieved. as more sats are locked 'onto', there become several spheres and your position would ideally be the center of the overlap region/volume. in actual fact there is no global standard as it regards to datums. datums only have a value when coordinates are applied to maps, to my knowledge maps are rarely produced in wgs84 and local datums are generally used.

while the default for gps units is generally wgs84 and decimal degreee, the gps doesnt do any type of translation unless you actually change either the coordinate display format or the datum, and then the 'translation' is only for stored data not the displayed data. the datums are simply a mathematically description of the earths surface projected onto a flat sheet of paper, once the gps gathers info, that is timing and location/elevation, from the sats it simply inputs the data into the correct formulas and outputs a position. why wgs84 is the default with decimal degree ill never understand. most mapping is based on either nad27 or nad83 while degrees are pretty useless to convert positions to distance. professionally ive never seen any type of degree format used, actually impossible with survey instruments, nor have i ever encountered wgs84, even though its essentially nad83, as being the datum of choice on any construction project.

the holes arent for allowing air to exchange(as noted warm moist air colling would essentially allow it to rain inside unit) rather they are located in prxomity tio a diaphram that prevents the case from imploding when there is a drop in pressure. to meet the 'water-proofness' the case must also prevent the exchange of air. bottom line--unit is defective and if in warrenty ought be replaced

one way of doing this is to view the route and track files in a text editor like notepad or word(simply save word files as txt files also works) etc. and change the file headers and the extension name to make the track file 'look'(use cut and paste) like a route file. you can also make point files using a text editor, the infomation you need to generate the files is in the technicial section of ozis help.

i dont use the handheld version, but the pc version using qnav png topo map images and the results are pretty good. ozi for the pc uses text files for waypoint, routes etc and are asily editted, and manipulated. i also have used elevation data to generate 3d map images, using the ozi 3d addin, again with great results.

to say that the gps cant tell you how far away the sat is isnt totally correct. it is possible to extract the timing info and thus use other methods to determine the distance of the sat from the reciever. to do this you also need misson planning software and good knowledge of the units propreity info. to clarify the gps altitude issue, elevation is determined using the geiod info upon which the datum is based. the datum is a mathematicial defination of the surface of the earth which is imperfect. in my humble opinion this info is pretty useless (either derived from a barometer or by sat calculation) unless tied to known control or you have good knowledge of the geiods definations and shortcomings.

2 points: 1)if you dont specify the reciever is it really a gift? 2)what in the department, and employees referenced here?

making the gps more accurate is not the correct way to describe the waas 'process'. ideally waas corrections represent a correction for the systematic errors due to the conditions in atmosphere by using known control points. these corrections are valid only if the conditions in your area closely match the conditions in the area surronding the local wgrs(area of ~150mi radius). personally i wouldnt expect waas to improve accuracy to such a degree that it is essential, and in fact with the variables concerning enviroment i would expect non-waas would be much stable over time.

that depends on the type of antenna system used. patch antenna(etrex etc) like to be laid flat however quad-helix( most magellan, garminv etc) ought to be verticial, and may not pick up signals of flat.

not to nitpick but: 1)do not lay magellan quad helix based recievers flat. this almost prevents reception. should be verticial. 2)assuming meridian menus are similar to my gps315, try to inilitiaze from a known coordinate. within a couple of degrees of location would be quite sufficient. post back to update your progress.

I don't think possessing a lottery ticket as a minor is a problem...they just cannot buy or cash them in. I really doubt anyone would ever get in trouble for this. according to our provincial laws, which i believe are the same across canada except quebec(civil vs common laws), under age possesion of lottery is essentially the same as possesion of alcohol etc. while i believe the laws concerning lottery tickets is geared more towards gambling, vlt machines and casinos, never-the-less though possesion, not necessarily purchasing or cashing, by minors is illegal. btw think your local bingo game, there are age restrictions listed but rarely followed.

normally there would be some kind of activity monitor from within the software package (counting percentage of total comm completed) when communication is happening. i dont think i know of any software package that can detect an idle serial device without pinging the port....native usb devices however could well be different though.

the epe is the estimated error due to mathematicial calculations. it is not related errors picked up via signal transfer to the gps from the sats or other 'external' influences.

my understanding is, as mentioned above, is that the errors picked up due to instability of the earths orbit would be small in relation to other ionospheric interferences. eventually these errors would be eliminated once the earths rotation stablized by reprogramming the system parameters re:orbitial info. im unsure as to the longterm effect, i would think that we are essentially behind rotationally due to the quake by milliseconds and correction isnt possible or even necessary. the other types of error that could be introduced would be actual physicial movements of the earth. here there are 3 options: 1)actual land mass movement, generally slips/thrusts 2)alteration of the earths shape 3)mass wasting of the contential landmass ive heard numbers of as much as 40m horizontal movements on some south pacific islands, this type of error would only affect mapping and other documented land positions, the gps would infact give the correct 'new' location. the mass wasting of the landmass has been documented, and depending on quanties could introduce errors specifically in elevation and possibly with the estimate position errors function. i have not heard any statements as to the post event shape of the earth, however, i would think that the amount of change in shape would intorduce less errors than those picked by the geoid representation of the earth. since this magnitude event has only been recorded 3 or 4 times we are in unknown territory and most scientific statements are educated guesses based on what we know. one thing i havent heard yet is the effect on sea level, anyone?

The operative word here is "known". Most benchmark waypoints are "scaled" by someone sitting at a desk with maps and the benchmark description. I find that they are often 100 to 300 feet off. But occasionally you can find markers that are just about spot on. Not sure what that process is called on the benchmark page but it is fun when the marker shows up exactly when the goto says 0 feet. that depends on the type of benchmark. some are for verticial control and those may have been scaled from a map or other source. try finding a horizontal control marker--those have known coordinates to the millimeter.

id also look at the fact that the item was listed at another price below $379. also it was said earlier about consumer protection, you need to look at contract law, which you had with them. threaten them and file in small claims court if need be.

not to nitpick.... but: "...we could not do anything to stop orders from...", i dont realy think this is your problem, rather they offer a product, you acepted, they charged to completed the transaction. i threaten to go to small claims if they refuse, and if they then refuse id go to small claims(not sure about your system but here you could also charge them for the filing fee).

CAN THEY DO THAT? HERE IN CANADA I DONT THINK THEY WOULD BE ABLE TO DO IT, ONCE THE ACCEPTANCE IS SENT(NOT NECESSARILY RECIEVED) THE CONTRACT IS BINDING. INTERESTING.... sorry for shouting....

these can work great or can go in the tank from the get-go. i participate in several with work for construction/survey gear and enjoy the ability to 'test' gear. count me in.

sorta related, my gps315's beeper has gone down in volume about 50% and now sounds only muffled.

unfortunately i shouldve checked my list before saying i had it. however here is a link to the listing i use. maybe the datum youre about to use may have an equivilancy on the list. if you find anymore post back.

if your geko has the ability to accept a use grid/datum than this would be the best route. there are anumber of sites that have posted the parameters for individual datums. if you cant find a complete listing i have one and can email it to you.

a couple of points: 1)the epe is only a measure of error contined within the mathematicial computations of position. epe does not have any dependance on weather and only indirectly depends on sat geometry. 2)ground level weather supposedly does not affect, however disturbances in the ionosphere do affect the gps. 3)if testing units side-by-side i doubt there would be any direct rf interference due to the levels of rf noise we are dealing with. 4)as for difference in testing units side-by-side, as was said earlier the clocks in gps (quartz based) are measuring nano seconds. minor varitions, data signifant figures, and quality would account for much more than the 20-50' of 'error' we see. 6)all esitmates of location ffrom a gps are based on the ellipsoid model that the current datum is based on, this model is only an approximation of the earths surface and this modeling also introduces errors into the calculation. nearly everyone here is using the gps for point position using the ca code, if results are within 20' of the known value the system has done its job. if greater acccuracy is desired differential position is necessary or using the p code.

i cant understand why south of the border law enforcement insists on wasting resources detonating caches due to the overactive imagination of untrained eyes without confirmation. all inate risks aside, the officers responsible ought be disciplined just as they discharged their sidearm in an unjustified manner. by contrast, last week our local police force removed 'misplaced' commercial explosive from the entrance way of a local elementary schol without blowing the side of theb building up. from the patriot act to the overacting law enforcement, its a wonder that total chaos hasnt erupted yet...

it would be interesting to post the same questions to a group that use gps professionally and compare the results. im pretty sure that the sample of gps users that posted wouldnt qualify as a random sample representative of the population of gps users as a whole.