Newsgroup sci.geo.satellite-nav 30438

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	Has anyone found out how this works yet? The few points I would like
to know are:
	1. What is its sampling interval?
	2. Does it reject any data based on signal strength or satellite
geometry?
	3. How does it determine the error?
	The best way of testing its performance would be to measure a
known point such as a trig station.
-- 
* Andrew Walker         *
* Department Of Physics * e-mail -- ajw01@uow.edu.au
* Wollongong University *
* Australia		*

Does the garmin 12XL have all the trip functions that the GPS II has?
eg ave speed, trip distance, etc
thanks
brian

Yes, seems to work though the accuracy leaves a bit to be desired. I used it
to locate some places I've camped at (in the oz bush) and I was impressed 
that it found some of the places. But, the lat/longs were 'rounded' and
compared to my gps fixes (especially for rockholes etc), were off by 5km or
more - not tooooo good when you're trying to locate a spot in a 4wd and your
view of the world (via your eyes) is limited to a few hundred metres. Good
topo maps (rather expensive to collect enough for good coverage of areas of
oz) is still the way to go. That's what I do when going 'bush', carry a whole
bunch of them with me, along with my gps and ruler and calculator with simple
program to convert lat/long to offset on a map page. Then just punch in 
the lat/long of the top left corner of the map and enter in the gps reading.
Out comes the offset from the top left corner - draw some lines and you know
where you are. Be nice to have a CDROM of oz topo maps and a laptop - but
I can imagine how long that would all last when covered in dust in the 
bush... I guess you could use it all as kindling for the night campfire.
To tell the truth, having a gps has taken some of the fun of being lost out
of my camping trips... Used to go out bush with just the Shell maps - now
that was an adventure...
george.
Fly Boy (sorry@too.dangerous) wrote:
: On Tue, 28 Jan 1997 03:11:34 +1100, kaya  wrote:
: >Where to get or download lat/long data for Australia?
: >
: >Thanks!
: www.dma.gov/gns is the USA NIMA's Geo Name Server. Coverage is
: worldwide.

Look at my page, I have several links to such sites under the mapping
section. http://www.blkbox.com/~hub
Tim
William Bowser wrote:
> 
> I know this has been on before but I lost all my bookmarks and need to
> find some areas via longitude - latitude and know there is a url that
> does that but cannot remembe can someone help please..? Thanks
> 
> --
>         <<>>
> 
> **The Media's handling of all matters, domestic
> and foreign,is hopelessly inept and always dangerously
> misleading...**

When returning to anchored gear bouys my Loran C seems better than my GPS.
The LAT/LON on GPS is certainly more accurate than the Loran, but in
repeatedly guiding you back to a fixed location (disregarding LAT/LON) the
Loran gets you closer more often than the GPS. Why?

What is the algorithm used to determine that you have reacheda waypoint?
The interest is purely academic... Since it isdifficult to reach a
waypoint EXACTLY, and an exact hit israrely needed I was wondering how
GPSs dealt with this.

river5@peachnet.campus.mci.net writes:
>I hope I'm wrong!  -But as far as I can determine, the EE cannot
>down/up-load waypoints and routes, because there isn't a cable
>available and the software hasn't been developed...  I probably should
>have elaborated at least THIS much;
Perhaps it would be useful to distinguish three different categories:
1. Cannot upload/download waypoints (routes, tracks, whatever) because
   there is no serial port at all, or the firmware in the GPS just does
   not support it.  (e.g. Magellan 2000)  This limitation is permanent.
2. The GPS supports upload/download, but the necessary cable and/or
   software is not yet available.  (e.g. Eagle Explorer).  This limitation
   is (we hope) temporary.
3. Upload/download work now: the GPS supports it, cables and software are
   available, people have done it.  (e.g. all the Garmin small handhelds)
	Dave

Dave Martindale wrote:
> 
> river5@peachnet.campus.mci.net writes:
> >I hope I'm wrong!  -But as far as I can determine, the EE cannot
> >down/up-load waypoints and routes, because there isn't a cable
> >available and the software hasn't been developed...  I probably should
> >have elaborated at least THIS much;
> 
> Perhaps it would be useful to distinguish three different categories:
> 
> 1. Cannot upload/download waypoints (routes, tracks, whatever) because
>    there is no serial port at all, or the firmware in the GPS just does
>    not support it.  (e.g. Magellan 2000)  This limitation is permanent.
> 
> 2. The GPS supports upload/download, but the necessary cable and/or
>    software is not yet available.  (e.g. Eagle Explorer).  This limitation
>    is (we hope) temporary.
> 
> 3. Upload/download work now: the GPS supports it, cables and software are
>    available, people have done it.  (e.g. all the Garmin small handhelds)
> 
>         DaveDave, I am new to GPS i was going to buy a Eagle Explorer becuase I want 
to down load the way points and post process the data to a D_GPS file to 
be as accurate as possiable to know where I was. I am trying to map a 
wood lot with out paying the full price of a survay.
Am I out of luck?
ED F

Marian Holton writes:
	USCG DGPS services provide range and range rate correctors.  
	The range rate correctors allow the mobil receiver to 
	interpolate between DGPS updates.  ALso, the USCG services 
	transmit single satellite messages, scheduled such that 
	satellites with a high rate of change in their range error 
	are transmitted more frequently.  (If memory serves me 
	correctly these are Type 9 messages).  This message type was 
	added to allow better service; atmospherics were causing the 	
	conventional messages (all satellites in view) to fail parity 
	checks because they were long and the baud rate is low.  
	Addition of the Type 9s increased the likelihood of the 
	corrctors getting through to the user.
Fine. I now have two more key questions:
	(1) How muxh of this information is currently used by
	the low-end (Garmin, say) DGPS receivers?
	(2) How is this DGPS output being integrated into the
	the primary receiver such as the 12XL?
Capt FIDO (My interest is nautical)

nite_owl wrote:
> 
> What is the algorithm used to determine that you have reacheda waypoint?
> The interest is purely academic... Since it isdifficult to reach a
> waypoint EXACTLY, and an exact hit israrely needed I was wondering how
> GPSs dealt with this.
The Garmin units consider that you have reached a waypoint when you have
crossed a line through the point which is perpendicular to the course
from the previous waypoint (or from your initial position, if you
manually selected the waypoint with GOTO).  So, as soon as you cross the
"finish line" of your current leg, Garmin units signal that you've
reached the waypoint (and select the next one on the route - if there is
one).
This has caused many people (including myself) initial confusion when
using waypoints.  If I'm very far off-track, the unit might signal that
I'm approaching a waypoint when I'm still very far from it.  However,
I've decided that if I were navigating in a boat or a plane, where
staying on-track is a matter of some importance, but crossing the
waypoint *exactly* is not very important, that the way the software
functions is actually the correct thing to do.
I don't know what units other than Garmin do.
-- 
J. Giles
Ricercar Software

Tom Pettit wrote:
> 
> I've got a Garmin 45 with rev 2.41 firmware.  It works fine with
> Waypoint +, and Gardown 7.  But, on both a Toshiba laptop and my
> desktop, I only get the "Aquiring Satellite" window, then a notice that
> nothing was found, even though the 45 is locked onto four or more sats
> and it happily 3Ding.  I've tried GARM/GARM, NEMA/NONE, NEMA/NEMA on the
> garmin settings and G45 and generic NEMA on the SA4 settings.
> 
> Any Ideas?  Delorme has not answered my two emails.
> 
> Thanks in advance,
> 
> Tom Pettit
Hi Tom,
I have tested a G-45 (not the xl) on my toshiba 2150cdt laptop and it
works fine.  You might try some terminal program such as Procomm.  Set
it up for 4800,N,8,1 (or whatever you use).  You should immediately see
the data flow into your laptop when the garmin is locked.  Be sure if
you are using windows,  to set the windows comm port settings correctly.
Joe

The best way to understand it is to itemize the sources of error:
E(user)		error caused by the user's equipment
E(atmosphere)	error caused by atmospheric conditions
E(system)	error caused by other systematic error
E(SA)		error caused by SA
Turning off SA eliminates E(SA), the largest component of error.  Use of
DGPS corrects E(SA) and E(system), and may reduce E(atmosphere).  Use of
dual frequency measurements largely corrects E(atmosphere).
However, none of these help E(user).  On consumer receivers it is between
10 and 25 meters.

BOEING377 wrote:
> 
> When returning to anchored gear bouys my Loran C seems better than my GPS.
> The LAT/LON on GPS is certainly more accurate than the Loran, but in
> repeatedly guiding you back to a fixed location (disregarding LAT/LON) the
> Loran gets you closer more often than the GPS. Why?
Loran transmitters don't move, and are not subjected to Selective
Availability.  So, you may not get accurate readings from a loran unless
you've carefully calibrated it.  But you will get more reliably
repeatable readings from it. 
Any measuring device has three properties: accuracy, reliability, and
precision.  To say that it's cold at the north pole is probably
accurate, but not very precise.  To say that it's 71.23 degrees
Fahrenheit at the north pole is very precise, but probably not very
accurate.  Reliability is a matter of whether you get the same reading
for the same conditions each time.  You can be precisely reliable (you
get the same reading to lots of digits each time you make the same
measurement) without being very accurate.  This is the case you have
discovered.  What everyone wants (and the reason most people confuse
these three qualities) is something which is reliably accurate to lots
of precision.  Failure of any of these qualities is pretty much a mark
against any measuring tool.
-- 
J. Giles
Ricercar Software

Arthur,
I read your post when I came home today and immediately hooked up my
Explorer to a 12V power supply and turned the light on (it was set on
Group
M so I could verify the power supply was hooked up and operating
properly,
also the Light delay was already set to 240 sec).  I set the unit
down and
went to have dinner.  I came back after 26 minutes (I timed it with a
stopwatch) and the backlight was still on.  The unit was in the
middle of
my house and never aquired any birds, but my previous experience with
the
backlight was in my truck with the unit tracking my position on the
plot
screen.
Is it possible that since you have an older version of the manual
that you
may also have an older version of software in your EE?  My SYS INFO
screen
says OCT 24 1996  VERSION 1.3 .  My Manual is 988-0129-57 Rev A.
Can anyone else confirm or disprove my observation using software
version 1.3 or later?
-- 
Jeff Kaiser
JKaiser1@aol.com
Arthur Schwartz  wrote in article
<5clcv1$kbo@usenetz1.news.prodigy.com>...
> Bob <_pmw5_@cornell.edu> wrote:
> >
> >Jeff Kaiser wrote:
> >> 
> >> The Eagle Explorer backlight will stay on continuously if the
unit is
> >> hooked up to an external power supply and the Light Delay is set
to 
> 240
> >> sec.  I found this out by accident this morning on the way to
work.  
> I
> >> hooked up the external power cord (a homemade cobbled version)
and set 
> the
> >> light delay to 240 sec fully expecting to have to hit the PWR
button 
> every
> >> 4 minutes.  I was pleasantly suprised that the light stayed on
for my
> >> entire 1 hour commute.  When Light Delay was set to 5 or 10
seconds 
> the
> >> unit operated normally (as if no external power was connected)
and 
> shut the
> >> light off in the indicated amount of time.
> >> 
> >> Another interesting backlight feature is that when you have
external 
> power
> >> to the unit and you have the light set to 5 or 10 sec anytime
you hit 
> a key
> >> (MENU, MODE, etc.) the backlight comes on so you can see the
menus you 
> are
> >> navigating through.  This is all without hitting the PWR button 
> (supposedly
> >> the only way to turn on the light).  This most likely works on
all 
> settings
> >> but I only tried 5 and 10.  This feature is very helpful at
night and 
> does
> >> not interfere with the display quality during the day.
> >> 
> >> I think both of these features were well thought out and
executed, 
> but
> >> poorly documented in the manual.
> >
> >Can you set it to 0. If you can, maybe it'll stay on forever.
> >-- 
> Hello All,
> 
> About the backlight staying on with external power hooked up and
the unit 
> set to 240 delay, (WRONG) ! I have external power hooked up on
mine, I 
> even used mine with no batteries in it and it of course showed a
full 
> charge. But the backlight "DID" go off after 4 minutes. Even Eagle
told 
> me the backlight will surley go out after 240 seconds with external
power,
>  so who ever made the post will have prove it and also tell Eagle
their 
> wrong.
> 
> Also, the backlight has no "0" setting at all.
> 
> Later, Art!
> Orlando, Florida USA
> 

Hi,
I have heard the samr thing but was wondering why then the 12xl has a
best position of, I think 29 meters with DGPS while my 175 book claims
1-5 meters with differential. This might be a software limitation and
I'd be surprised if they didn't have the same RF front end.
Now, to speak towards the receiver's ability. If we differentiate the 
antenna from the receiver/tracking engine, then we can describe each
fairly. 
First a disclaimer. There seems to be a tremendous difference from
unit to unit in Garmins ability to receive and hold signals. I have
had numerous Garmin units, and compared many more head to head. Some
will have almost full signal strength from DOH satellites, while other
units of the same model will show only 1/2 strength. 
The ability of the tracking engine in the 175 is very impressive. Once
it has an SV it is amazing how much blockage it takes to lose lock. 
I have had reflected signals inside tunnels hold lock, as well as from
my second floor apartment in a three story building with attic. The
175 acquires roughly 2/3 of the visible SV's immediatly after power up
and is usually tracking them within a minute. Compared to the
38/40/45/75
this is outstanding performance. If lock is lost due to total blockage
like a tunnel, the 175 reacquires signal very fast indeed. If the total
blockage has been less than four minutes then lock happens within five
seconds after seeing the SV's again.
But where the 175 falls flat on it's face, and Garmin should be really
ashamed of it's self is in the quality of the internal antenna. There
is nothing inherantly wrong with patch antennas, Garmin has used them
for several years now, as does Eagle. The problem lies in the disclaimer
above. Some units perform much better than others when it comes to
signal
strenght and my unit is in the bottom of the heap. I had a 40 with twice
the gain on the internal antenna, and a 38 that wouldn't lock except 
in the middle of the desert with several SV's nearly overhead. My 175
will certainly lock in an urban environment but not in a forrest. With
the addition of a GA-27 external amplified antenna this situation is
totally reversed. Even low elevation SV's are at the top of the signal
bars and the big game becomes to try and lose lock, anywhere. It is
truely amazing what that little amplifier can do! And Garmin should
be truely ashamed they didn't build the internal antenna with an amp.
Note, this may NOT apply to any other 175, but it's been my experiance
with
Garmin over the years that roughly 1/2 the units are RF "hot" while the
others are lukewarm to cool. I have seen and heard the same things with
the old Garmin 45's too. Some were much better than others at signal
strength. I believe the patch amplifiers only draw 55MA and that is
small
enough price to pay. 
I really love the 175. If it had the HSI compass of the smaller units
and an amplified antenna it would be a truely great gps. 
david
cd@ricochet.net
Todd Marshall wrote:
> 
> I've just learned that the Garmin 12XL has the same receiver engine as
> the Garmin 175. Has the 175 been out for a while and do people have
> experience on it's locking ability? My interest is performance in Oregon
> forests.
> /Todd
-- 
There exists no problem that cannot be solved
by the proper application of high explosives.

I am getting ready to add a GPS page to my Ag. News website and wanted
to know if anyone knew of any Ag. related GPS websites.  Any information
would be appreciated.  Either e-mail me at ctsimms@unity.ncsu.edu or
stop by my homepage, the URL is
http://www4.ncsu.edu/~ctsimms/web/index.htm , and leave me a message in
my guestbook.  Thanks, Chris.

I would like to know the number for the K-Mart in Raleigh that has the
12XL. The K-Marts I called throughout NC today did not have ANY Garmin
products. Only Magellan.
On the other hand Wal-Mart carries Garmin and Magellan, but no
12XL's....yet.
GSW  wrote in article
<5cj6oe$rtb@lastactionhero.rs.itd.umich.edu>...
>     Somewhere someone is not telling the truth...  Kmart is based out
> of Southeast Michigan, Troy as a mater of fact. I have contacted
> a woman who is named Sara Bishop, she is apparently in charge of
> purchasing for the Sporting Goods departments at Kmart throughout
> the USA. She told me that Kmart does not purchase any products from
> Garmin, and that they do not carry the GPS 12XL. She told me they once
> were able to make special purchases but with the new president at Kmart
> they can no longer do that, so everything goes through her. I told her
> that I had two people tell me they purchased these at Kmart, and she
> told me to tell you that I heard it from the horse's mouth... Kmart
> has not purchased any Garmin products.
> 
>    If you people have purchased Garmin stuff at Kmart, apprently it is
> not authorized by Kmart as a whole. Maybe you should call Sara and tell
> her that your Kmart does sell them...  she would probably be interested
> to hear from you, her phone number is...
> (810) 637-0310
> 
> 
> In article <32ecfcba.37053280@news.rdu.bellsouth.net>,
> Sam Cederas  wrote:
> >	A friend of mine went to KMART in Raleigh, N.C. and bought the
> >12XL yesterday.  I own a GPS4000, but the point is I know KMART sells
> >them bk he bought one.  It was like $279.
> 
> 
> 

   Joe, I respectivly submit that you are likely to be wrong. How do you
come by your knowlege of GPS and DGPS? As I have said before, I don't 
claim to be a expert, but the majority of information I have seen goes
against what you are telling us. Let me submit to you something I have
just gotten off of the Garmin webstite that appears to give a very differnt
picture then what you paint. If Garmin really is not describing things
correctly I think someone should try and point that out to them...
  This is some text taken from the Garmin International web site...
"How accurate is GPS, really? A typical civilian GPS receiver provides
60 to 225 feet accuracy, depending on current status of selective
availability, number of satellites available and the geometry
of those satellites. More sophisticated and expensive GPS receivers,
costing several thousand dollars or more, can provide accuracies within
a centimeter by using more than one GPS frequency.  However, a typical
civilian GPS receiverUs accuracy can be improved to fifteen feet or better
(in some cases under three feet!) through a process known as Differential
GPS (DGPS). DGPS employs a second receiver to compute corrections to the
GPS satellite measurements. How are these corrections provided to your
GPS receiver? There are a number of free and subscription services
available to provide DGPS corrections. The U.S. Coast Guard and U.S.
Army Corps of Engineers (and many foreign government departments as well)
transmit DGPS corrections through marine beacon stations. These beacons
operate in the 283.5 - 325.0 kHz frequency range and are free of
charge. Your only cost to use this service is the purchase of a DGPS Beacon
Receiver. This receiver is then coupled to your GPS receiver via a
three-wire connection, which relays the corrections in a standard serial
data format called TRTCM SC-104U."
   My posistion stated simpler is I beleive that Sam was simply indicating
that simply taking two cheap GPSs and using one at a fixed location to
gather some distance and vector error of that GPS, then using that
figure to try and correct the accuracy of a second GPS, is not possible.
I do not beleive that Sam was trying to say what Joe is saying...
     I really would like to hear from some of the experts on this
subject. If what Joe is telling us is true then what other companys
like Garmin are tellig us, borders on false advertising.
In article <32EE8723.672A@bellsouth.net>,
Joe Mehaffey   wrote:
>GSW wrote:
>> 
>>    After re-reading what Sam had said a few posts back, I don't beleive
>> what Joe is telling us is entirely true, or at least it is misleading...
>> 
>No..  Unfortunately,  my statement is  accurate.  DGPS CANNOT MAKE A GPS
>RECEIVER WITH BASIC INTERNAL ACCURACY OF 15 METERS BECOME ACCURATE TO
>(SAY) 1 METER BY ADDING 1 METER DGPS.
[snip]

K4ZDZ wrote:
> 
> G-45 wanted. Will trade Toshiba T1200 Laptop. E-Mail me for details.
> 
> Jim (K4ZDZ@aol.com)
I have a 45 xl 9 mo. old. I just bought the 175 . With all the
acessories ( about $110 worth), I'll sell it for $225.   Barry

Aurthur,
I read you post when I came home today and immediately hooked up my
Explorer to a 12V power supply and turned the light on (it was set on Group
M so I could verify the power supply was hooked up and operating properly,
also the Light delay was already set to 240 sec).  I set the unit down and
went to have dinner.  I came back after 26 minutes (I timed it with a
stopwatch) and the backlight was still on.  The unit was in the middle of
my house and never aquired any birds, but my previous experience with the
backlight was in my truck with the unit tracking my position on the plot
screen.
Is it possible that since you have an older version of the manual that you
may also have an older version of software in your EE?  My SYS INFO screen
says OCT 24 1996  VERSION 1.3 .  My Manual is 988-0129-57 Rev A.
Can anyone else confirm or disprove my observation?
Arthur Schwartz  wrote in article
<5clcmc$2jeu@usenetz1.news.prodigy.com>...
> SUBJECT: Re: Eagle Explorer (alarms and waypoints) 
> "Ronald M. Wilson"  wrote:
> >
> >
> >
> >Arthur Schwartz  wrote in article 
> >> 
> >> Well the manual is wrong on a couple of things. The manual states that
> 
> >> the backlight is adjustable from "0" to 240 seconds when the unit 
> itself 
> >> goes from 240 to 5 seconds with no "0". 
> >
> >Art,
> >	You're right, but I think the argument about whether the delay 
> actually
> >goes from 5 to 240 seconds or 0 to 240 is immaterial now.  According to
> >Jeff Kaiser's post entitled "EE Backlight will stay on continuously" 
> from
> >1/24/97, the EE's backlight will stay on indefinitely if you set the 
> delay
> >to 240 seconds and the unit is on external power.  He tried it with a
> >makeshift external power connection and the backlight stayed on.  The
> >manual says that it will shut off after 240 seconds even on external 
> power.
> > While this is an error in the manual, it is an error in your favor.
> >
> > 
> >> Also the manual states that the unit has "Audible tones and sounds", 
> the 
> >> unit does not have any audible tones or sounds. 
> >
> >I went back and checked the ALARMS section in my EE manual on pgs.
38-39.
>  
> >In my copy it doesn't say anything about audible alarms.  It says "You 
> can
> >set an arrival alarm to flash a warning message ...".  I took that to 
> mean
> >the display would have a message flashing on it for an alarm.  Maybe 
> yours
> >is an earlier version which contained more errors than mine?  I hear 
> the
> >Lowrance version (Global Nav 200) of the EE is supposed to have audible
> >alarms.
> >
> >[SNIP]
> >
> >-- 
> >Ron Wilson  
> >
> Hello all,
> 
> About the backlight staying on with external power hooked up and the unit
> set to 240 delay, (WRONG) ! I have external power hooked up on mine, I 
> even used mine with no batteries in it and it of course showed a full 
> charge. But the backlight "DID" go off after 4 minutes. Even Eagle told 
> me the backlight will surley go out after 240 seconds with external
power,
>  so who ever made the post will have prove it and also tell Eagle their 
> wrong.
> 
> Also, You have a revised manual. If you look at the back cover of your 
> manual in the lower right hand corner, you will see a number with the 
> word (Rev or Revised) near it. Mine only has the number. 
> 
> Later, Art!
> Orlando, Florida USA
> 
> 
>  
> 
> 
> 

> If nothing else this is going to force
> me to investigate the matter further myself... Sometimes I think these
> newsgroups are just around to make me learn more on my own, and not
> trust people on the groups...
--
Yes YEs YES!  How right you are. Trust peoples observations but not
their "facts". The USCG has a web pagu up dealing with DGPS. 
http://www.navcen.uscg.mil/
Get the facts from them. 
Some "facts" I will share with you. 
1)  The farther you are from a diff. beacon, the less precision you will
    have. 
2)  The better your GPS and the better your DOP the better DGPS
    precision you'll have.
3)  I am researching this too and am going to buy a beacon receiver
     when the data cable is made for my system. I have read and 
    believe the following with regards to mid-range equipment
    ala 12xl/175/magelleon 4K 5K, and some others. 
    If you are within 35-50 kilometers, have no obstructions, have
    a strong DGPS signal and low interference/multipath/ionispheric
    delays, you may get 5 meters. If you are within 25K of the
    station, 2 meters on a good gps will be possible. 
4)  With postprocess averaging you might get this down by a 
    power of 5 - 10. With epherimis post processing, close
    beacon, good gps clock, good fortune and the eyes of
    luck smiling on you, 10cm is possible.
So take a look at their web page and decide for yourself! Just
remember GPS quality and beacon distance are the overriding concerns
here.
Good luck!!!
david
cd@ricochet.net
-- 
There exists no problem that cannot be solved
by the proper application of high explosives.

  Apparently it varys from one GPS to another. My Eagle AccuNav Sport
has limits that you can set, and you must come closer then the limit
before it determins you have arived. The limit of the AccuNav Sport
for arivial can be set from .01 to 9.99, mile or meters depending on
what units your using at the time.
  I know that Garmin does this differntly...
In article <17B0410E57S86.MOISEFF@UConnVM.UConn.Edu>,
nite_owl  wrote:
>What is the algorithm used to determine that you have reacheda waypoint?
>The interest is purely academic... Since it isdifficult to reach a
>waypoint EXACTLY, and an exact hit israrely needed I was wondering how
>GPSs dealt with this.

 I just saw this amazing receiver and am wowed by its many features.
Micrologic has finally produced the killer GPS. Garmin and Eagle lookout!
I hope somebody has a review of one in actual field conditions. (I saw it
in a large building ­­ no signal)

What experience does anyone have with the new USGS DRG's?
What software do they work weel with? Particularly packages that will
interface with With a Trumble Scouctmaster.
-- 
Terry S. Arnold
2975 B Street
San Diego, CA 92102
USA
tarnold@cts.com
(619) 235-8181 (voice)
(619) 235-0016 (fax)

Hi There,
        Has anyone experienced any ambiguous altitude readouts with the
MentorPlus/Rockwell R100 GPS NavCard??
                      Thanx,
                           Bob

In article <32e2a4ab.17362871@netnews.worldnet.att.net>, Tom Orle (orle@postoffice.worldnet.att.net) wrote:
|droring@aol.com (Droring) wrote:
|
|>Jack, Do you know where I can find SA4 for $25.00, It's around $45 in
|>Southern CA.
|
|$25 is the UPGRADE price from the old SA3 - so, to answer your
|question: Buy SA3 - then you can get SA4 for $25!! 
  So, pay $65-70 ($40-45 for SA3.0 plus $25 for the upgrade, which requires
that you send in your SA3.0 CD, as I recall) when all you need to pay is $45
for SA4.0 flat out?  Am I the only one that this doesn't make sense to?
Randy Davis
randy@agames.com

For someone who has their very own 12XL manual handy:
What does the manual say is the possible accuracy, using the 12XL and a 
DGPS unit.
success,
Roland

I'm going to break down and pay for a data cable to hook my 45XL to my
Mac but Garmin only makes data cables suitable for PCs.  I figure I'll
have to hack a cable from an old Mac/modem cable I have.  
How do I connect the cable to the DIN cable?  Has anyone seen on the web
a diagram showing how to wire up a cable for a Mac?
I've checked out a couple sites but have only found pin outs for PC
applications.
Thanks for any help.
-- 
Greg Smith
greg.n.smith@worldnet.att.net

In article <5cldl2$ffp@maze.dpo.uab.edu>, Trip@uab.edu says...
...snip...
>Are you sure the altitude was the same?  Pressure altitude is not what
>a GPS measures.  
  But it can approximate it using interpolation and and a table of Mean 
Sea Level (MSL) versus WGS-84 ellipsoid altitude corrections indexed by every 
10 degrees of latitude and longitude.  The Rockwell chipset firmware in the
Tripmate should have inherited this capability from the original 
Rockwell Collins GPS receiver software.
_______________________________________________________________________
Robert S. White                    -- an embedded sys software engineer
WhiteR@CRPL.Cedar-Rapids.lib.IA.US --long/cheap alternate I-net address

Joe Mehaffey wrote:
> Thus,  if ( for instance ) your GPS receiver is specified to have 15
> meter accuracy (exclusive of SA) (Please see the specs in your manual.)
> then if you get a DGPS service (such as DCI) offering 1 meter DGPS
> correction information,  you can expect something like 16 meter maximum
> error (about 52ft.).  If you purchase 10 meter correction DGPS
> corrections then you can expect errors to about 25meters RMS.  Now about
> 90+ percent of the time,  your errors will be LESS than 25 meters,  but
> here I am talking about what you can expect WITH RESPECT TO
> SPECIFICATIONS.  This is MUCH better than the 100 meter RMS errors you
> should expect with a standard low cost GPS.
> 
I'm not so sure about this either. The part whereb DGPS service can not
correct a position beyond the capability of the receiver is true enough,
but are we sure that a 10 meter DGPS service add 10 meters of
uncertainty
on top of the receivers built in minimum precision?
Here is how I understood it. 
Add one meter DGPS to a 15 meter receiver gets you 15 meters.
Add 10 meter DGPS to a 15 meter receiver gets you 15 meters.
Add 10 meter DGPS to a 5 meter receiver gets you 10 meters.
I am not so sure about the 90% of the time factor either. I
understood DGPS to offer it corrections 100% of the time. Though
your receiver may not have to DOP to take advantage of the corrections
at all times.
> If you want higher accuracy in your GPS,  then you will have to purchase
> equipment with higher specified accuracy.  DGPS cannot and does not
> compensate for design compromises in low cost GPS units!
True. But it helps.
> 
> Joe Mehaffey
-- 
There exists no problem that cannot be solved
by the proper application of high explosives.

And courtesy of Kevin Ricks, 1-28-97.    hmws99a@prodigy.com-- 
This is my BASIC program. You may need to fix the ASCII line draw
characters. They did not translate through my email editor. I think I
am displaying all of the data sentences, but may have missed one or
two?
Kevin
-----
REM TRIPMATE GPS RAW DATA DISPLAY PROGRAM
REM written by Kevin Ricks 1-28-97.    hmws99a@prodigy.com
REM    (QBASIC - DOS )
REM Tripmate must already be initialized with the SA4 program so that
REM it starts with the correct Lat and Long. Time and Date are not
needed. REM The Tripmate seems to store the last lat/ long in a NVR.
Time and REM date are not stored when Tripmate is powered down, but
doesn't seem REM to matter.  The correct GMT will show up 1st then the
Date (1 or 2 sats). REM When tracking (3 or more sats) you will see
the LAT and LONG begin to fluctuate. REM The V in the $GPRMC string
will change to A. etc. REM Don't let your Windows 95 screen saver come
on or the program will abort.
CLS
OPEN "com2:4800,n,8,1,CD0,CS0,DS0" FOR RANDOM AS #1     'kick start
COM CLOSE #1 'For some reason Tripmate does not always start on the
1st try.
OPEN "com2:4800,n,8,1,CD0,CS0,DS0" FOR RANDOM AS #1      'start again
PRINT " Waiting for Tripmate to respond.  Press CTRL BREAK to exit "
10 LINE INPUT #1, rec$
    IF NOT MID$(rec$, 1, 1) = "$" THEN 10   ' Wait for 1st string
LOCATE 1, 1: PRINT "
        "
LOCATE 4, 1      'These 3 lines are stored in the Tripmate
PRINT rec$;             '1st line is ID string
LINE INPUT #1, rec$     '2nd line - $GPRMC. Contains previously
initialized Lat, Long. LOCATE 5, 1 PRINT rec$
LINE INPUT #1, rec$     '3rd line - $PRWIZCH. Sats. all 0s
LOCATE 6, 1
PRINT rec$
LINE INPUT #1, rec$     '1st "ASTRAL" 'This will repeat forever until
ASTRAL is sent back to Tripmate. LOCATE 7, 1 PRINT rec$
PRINT #1, "ASTRAL"      'Send word "ASTRAL" to Tripmate
LOCATE 1, 1: PRINT "   Press ESC to exit  "
LOCATE 10, 5
PRINT "        Clock      LAT           LONG               Date"
LOCATE 11, 5        REM - ASCII graphics line draw characters below.
PRINT "       UÄAÄÄ¿   UÄÄÄAÄÄÄÄÄ¿ UÄÄÄÄÄAÄÄÄÄ¿           UÄÄAÄ¿ "
DO
        LOCATE 12, 5
        LINE INPUT #1, rec$  'read GPS string from Comm port
        gps$ = MID$(rec$, 2, 71)           'parse out LF.
        IF LEFT$(gps$, 6) = "$GPRMC" THEN PRINT gps$
        LOCATE 13, 5
        IF LEFT$(gps$, 6) = "$GPGGA" THEN PRINT gps$  'similar to
        $GPRMC, includes ALT. # of Sats etc. This does not show up
        until you are tracking.
        LOCATE 16, 5
        IF LEFT$(gps$, 8) = "$PRWIZCH" THEN PRINT gps$
        LOCATE 17, 5
        IF LEFT$(gps$, 6) = "$GPGSA" THEN PRINT gps$  'lists Sats
        being tracked etc.
        IF LEFT$(gps$, 6) = "$GPGSV" THEN     'not sure what these
        lines do.
              sv$ = MID$(rec$, 11, 1)
              IF sv$ = "1" THEN LOCATE 20, 5: PRINT rec$
              IF sv$ = "2" THEN LOCATE 21, 5: PRINT rec$
              IF sv$ = "3" THEN LOCATE 22, 5: PRINT rec$
        END IF
LOOP UNTIL INKEY$ = CHR$(27)    '27 is the ASCII code for ESC.
CLOSE #1
Kevin Ricks
DSP Solutions Inc.
1157 San Antonio Rd.
Mountain View, CA 94043
(415)919-4067 voice
(415)919-4040 FAX
newbury@erols.com
newbury@tec.army.mil
"Have HP100LX, will travel"

		I recently stated that a friend of mine was able to
purchase a 45xl at Kmart.  I stand corrected...he just told me it was
at
WalMart.  Sorry for incorrect info.  
	Anyway....point is that yes it is available at WalMart.

> I'm wondering if it would be possible to get very accurate
> direction and distance readings between 2 points using 2 handheld
> GPS units.
This has come up a couple of times before. Your reasoning is flawless - the
main problem is the filtering software in the receivers that is designed to
make the reading more stable. This is easy to check - just look at two
receivers side-by-side if the show the same reading drive around the block
with one then look again.
I am working on commercial solution to this problem that I can't disclose
now but I expect to test it during March/April - cost should be in the
region of $AUD300 if it works. 
The filtering is not the only source of error between two cheap receivers
but it is the major one. 
Ian Bailey
baileyi@msn.com

In article <5cjm0p$vsi@news.cis.okstate.edu>, gcouger@tacoma.ceatlabs.okstate.edu (COUGER GORDON) wrote:
>How is the checksum calculated on a NEMA message? I have tired XORing 
>the charecters togeather its close but not quit right. 
Here's some code I used that seem to work correctly -- at least the mapping 
programs I fed it to seemed to enjoy it.
unsigned char gpssim_checksum( char *s )
   {
   unsigned char  sum=0;
   char           c;
   while ( '*' != *s )
      {
      c = *s;
      sum ^= c;
      s++;
      }
   return( sum );
  }
/*
	Lee Lindquist		lindquist@ibm.net
*/

In article <5cjm0p$vsi@news.cis.okstate.edu>, gcouger@tacoma.ceatlabs.okstate.edu (COUGER GORDON) wrote:
>How is the checksum calculated on a NEMA message? I have tired XORing 
>the charecters togeather its close but not quit right. 
One of the GPS programs in Peter's Bennett file area includes source.  I know 
that I found the checksum calculation there, but I don't remember any more
specifics.  Once you do find it, it's trivial.
/*
	Lee Lindquist		lindquist@ibm.net
*/

I see that there is a current explosion in handheld GPS receivers on the
market.
I have a Garmin 40, and my biggest complaint is that although altitude
is calculated, it is not saved when you store as a waypoint.  Since I
hunt in mountainous areas, this would be useful.  I also have a
paragliding friend who needs a receiver that stores altitude with each
waypoint.
Do any of the current receivers do this?
thanks
swest