response 1 of 87:

Nov 13 21:03 UTC 1994

I've entered this item to see if there are other GPS users here, who
could share information on the use of GPS units. I have purchased the
Garmin GPS-40, which is very compact (9 oz), and has good battery life.
I have a number of immediate questions about GPS:

1. Do GPS units differ significantly? The GPS-40 can acquire up to 8
satellites (I've had it up to 7), and can record 250 waypoints on 20
reversible routes. Are there any significant differences between units
in what counts - sensitivity and navigational accuracy?

2. By how much do "remote" antennas improve sensitivity (in addition
to allowing the GPS unit itself to be used within a vehicle or building)?

3. I have been observing the "dither" - the "Selective Availability
Program" variations. What is the pattern on this? If regular sampling
is done of instantaneous position, do the means converge to an unbiased
estimate? What is the effect of the DGPS accessory on the RMS error?

4. The GPS-40 will take battery power, and has a data-in/data-out port
(one wire each, plus gnd and 5-9 v power). The unit supports numerous NMEA
interface formats. What are these? (The manual writes of "approved
sentences" such as GPBWC, GPGLL, etc, and "proprietary sentences" (PGRME,
etc).) There is a "PC Kit" available, for interfacing to a PC, but I do
not yet know what capabilities this can offer (perhaps the averaging
I spoke of above?).
  
Well, that's enough for now - especially considering that there may not
be many other GPS "micros" users here.

response 3 of 87:

Nov 14 06:58 UTC 1994

Get a GPS, Mike, and we can correlate. I should probably get to the
bookstore and find _GPS for Dummies_ - the GPS-40 Owner's Manual,
like most, leaves a lot to be desired, and cites no other sources.

response 5 of 87:

Nov 15 06:39 UTC 1994

The Manual doesn't make a lot of things clear. I think I better get to the
library, and look for better explanations of theory and practice. Sounds
like I should contact Ms. Hose, too. Say, isn't anyone else here on Grex
into GPS? 

response 7 of 87:

Nov 15 17:12 UTC 1994

The GPS lets you find yourself *on* the topo map. After bashing through
the north woods for a few miles of cedar swamp (no relief), its nice to be
able to locate yourself on the map (especially if you are looking for a
particular lake, or other feature). It would also be useful when driving
the forest two-tracks. I'll be using it as part of a geographic-feature
inventory for one of the National Forests in MIchigan.

Border's Books also has an assortment of Michigan topos, though they don't
seem to maintain it too well. 

response 9 of 87:

Nov 16 02:38 UTC 1994

re 7: Cedar swamps, eh?  Counting deer in winter bedding areas?

response 11 of 87:

Nov 16 06:06 UTC 1994

Re #9: no, I'd be reconnoitering holes in the ground. I stay out of the
woods during deer season! 

I took a turbogopher trip and did a veronica on gps, and found all sorts
of dregs of old gps exchanges. There is a newsgroup on the topic.  There
is obviously a lot to this, with a lot of professional use of DGPS hooked
to computers. So, here I am, a newbie again! 

Thanks for the tidbit, omni: I'll navigate there ASAP. Can you give me its
Lat/Long? 

response 13 of 87:

Nov 16 13:22 UTC 1994

 It is a *very* short street and this is why you may not have seen it before.

I don't have the lat/long, sorry rane ;)

response 15 of 87:

Nov 17 18:01 UTC 1994

I have a gut feeling that map store closed last winter or this spring.

response 17 of 87:

Nov 18 07:23 UTC 1994

I telephoned Geography on Winewood. They are open 12-6, Tuesday to
Saturday. They carry maps. They don't have anything about GPS (didn't
know the acronym). They were friendly, but didn't seem to know how
to answer my question about what they carried in addition to topos 
(MI only, by the way)...maps, they said.

response 19 of 87:

Nov 29 05:21 UTC 1994

I have found the GPS "Mother Lode". It is the CANSPACE anonymous ftp
archive at unbmvs1.csd.unb.ca (in directory pub.canspace). The following
is the $README file from the archive: (warning! long). 

                        *********************

This directory is intended as an archive for discussions on the CANSPACE
list.  Created for Prof. Richard Langley on March 4, 1991. 
 
                          CANADIAN SPACE GEODESY FORUM
 
The Canadian Space Geodesy Forum (CANSPACE) is a computer-communications-
based information dissemination and discussion group that was established
several years ago as an aid to improving communication among scientists
and engineers working with the techniques of space geodesy.  Messages
consisting of news, comments, questions, and answers are exchanged among
forum participants by means of a LISTSERV list.  LISTSERV is an electronic
mail utility running on a BITNET computer that allows a message to be
"exploded" (sent simultaneously) to a list of individuals simply by
sending the message to the list address.  The address of the Canadian
Space Geodesy Forum is canspace@unb.ca (or canspace@unbvm1.bitnet). 
 
Any topic related to the space geodetic techniques (Navstar Global
Positioning System (GPS), Glonass, Transit, very long baseline
interferometry, satellite laser ranging, satellite altimetry, etc.) may be
discussed.  Questions are particularly encouraged.  Daily postings of
information bulletins include GPS satellite constellation status reports
(Department of Defense Notice Advisories to Navstar Users) and reports of
solar and geomagnetic field activity. Information concerning satellite
launches and orbital elements is posted regularly.  Although initially
intended to link Canadian geodesists and geophysicists together, CANSPACE
now has a wide international subscriber list and is open to all. 
 
CANSPACE is directly accessible through computers on the Internet/BITNET/
NetNorth/EARN networks.  CANSPACE is also accessible from other networks
such as CSNET, UUCP, SPAN, etc. through various gateways.  Individuals may
also communicate through commercial telecommunication and information
services such as MCI Mail, CompuServe, and the American Institute of
Physics' PINET, or through the various bulletin board systems on the
FidoNet network. 
 
How to Subscribe
----------------
To subscribe to CANSPACE it is necessary for you to send an e-mail message
to listserv@unb.ca (or listserv@unbvm1.bitnet but NOT to the CANSPACE
address itself) with the following text in the message body: 
 
SUB CANSPACE your name
 
Once you are a subscriber, you may post a message to CANSPACE simply by
sending the message to canspace@unb.ca.  The message will be automatically
distributed. 
 
Setting the Topics Option
------------------------- 
CANSPACE makes use of the LISTSERV "topics" option.  The subject headers
of postings optionally contain a three-letter designator.  These
designators (identifiying the organization responsible for the information
in the posting) are "topics" identifiers that allow you to specify which
kinds of CANSPACE postings you would like to receive.  You do not have to
receive all postings from CANSPACE -- you can select which groups you
would like to receive. 
 
At the moment, there are four topics:
 
DOD:   for the GPS Constellation Daily Status Report from USNO (DoD NANUs)
GSC:   for the Daily Geomagnetic Forecast and Review from GSC
STD:   for the postings from the Solar Terrestrial Dispatch
OTHER: for everything else that is posted to the CANSPACE list.
 
Initially, CANSPACE subscribers are automatically registered for all four
topics.  If you wish to change the topics to which you are subscribed, you
will have to send an e-mail message to LISTSERV@unb.ca (DO NOT SEND IT TO
CANSPACE!). The form of the message is as follows: 
 
SET CANSPACE TOPICS: xxxxx
 
xxxxx may be the list of all topics you wish to receive or one or more
topics preceded by a plus sign (+) to add a topic to or a negative sign
(-) to drop a topic from your current list.  For example, to drop the
GSC's Daily Geomagnetic Forecast and Review and keep the other topics,
just send the following: 
 
SET CANSPACE TOPICS -GSC
 
Signing Off from CANSPACE
-------------------------
To remove yourself from the list, send the following message to
listserv@unb.ca: 
 
SIGNOFF CANSPACE
 
Further Information
-------------------

All CANSPACE messages are archived in monthly notebooks that may be
retrieved or searched using the LISTSERV database function.  An archive of
related information files is also maintained on a computer at UNB (not the
computer running LISTSERV).  Among the many files included are a brief
description of GPS, tables showing the present status of the GPS and
Glonass satellite constellations, and a 1,000 item GPS bibliography. 
Files may be retrieved via anonymous FTP.  Connect to unbmvs1.csd.unb.ca
(131.202.16.2) and change the working directory to PUB.CANSPACE.  E-mail
to FTP gateways are available for those who are not able to do
computer-to-computer file transfers directly.  The files are also
available via the Gopher server on unbmvs1.csd.unb.ca.  See the file
ARCHIVES.GOPHER.ACCESS for further information. 
 
CANSPACE is maintained at the University of New Brunswick as a free
service by Richard Langley and Terry Arsenault.  They can be reached
directly by e-mail addressed to se@unb.ca or by phone at (506) 453-4698 or
by fax at (506) 453-4943. 
 
If you have any difficulties in accessing CANSPACE or want more
information on the use of LISTSERV facilities, consult your local computer
communications resource person or contact the Department of Geodesy and
Geomatics Engineering at UNB. 
 
Richard B. Langley (lang@unb.ca)
Geodetic Research Laboratory
Dept. of Geodesy and Geomatics Engineering
University of New Brunswick
Fredericton, N.B.
Canada  E3B 5A3
                        **********************

response 21 of 87:

Dec 17 12:18 UTC 1994

Per Rane's request, this is now linked between micros and travel.

response 23 of 87:

Jan 2 07:21 UTC 1995

I finally took GPS on the road (with my wife driving, I could run the
Garmin-40 through its tricks). Just held out under the windshield it
quickly acquired 6 satellites, and reported ground speed and direction
with a lag of ca. 4 seconds. The speed was reported to 0.1 mph, much more
accurate than the speedometer. I had set a waypoint at where am staying,
and "navigated" home with the GPS. It continually reported which way to
head, the (beeline) distance, and the ETE (estimated time enroute). Of
course, in a car, one can't just head cross country (!), but even though
we followed the roads, the ete counted down so well that the last second
was counted as we turned into the driveway (it also showed that turn). I
can see why it is taking over boating and flying navigation. I understand
some cities have equipped all their buses with GPS, and radio links, so
the dispatcher knows where every bus is and its direction and speed,
essentially instantaneously.