GPS and ThinkPad

[scoundrl <scoundrl@vnet.net>]

For those good folks who made suggestions about the problems I was having 
coupling my machine to a GPS receiver- many thanks.

The problem was not with the TP755, but was in the documentation of the 
linking software.  One person gently suggested that I RTFM.  Well, I did 
RTFM and the problems turned out to be NITFM <grin>.

***for those interested, the following is a description of the setup and how 
it works***

I have an Eagle Accunav Sport hand held GPS receiver.  There are four 
pins on the back.  One is a common, one is an NMEA-183 input, one is for 
supplemental power and the last is for NMEA-183 output.  The input pin is 
for coupling the GPS to a differential LORAN receiver for increased 
accuracy.  The output pin outputs an ASCII stream that includes 
longitude, latitude, time, date and altitude of the receiver.

Software from DeLorme Mapping accepts the input stream from the serial
port of the Thinkpad and slaves the street map program MapExpert (on CD
ROM) to the output.  The result is that the street map stays centered on
the laptop's screen as the laptop is moved around- as in a plane, car or
boat.  The refresh rate is adjustable, such as every 2-3 seconds and a dot
or "breadcrumb" can also be left on the map every so many updates. 

For those not familiar with MapExperty/ Street Atlas USA (DeLorme), it is
a CD ROM that contains every street, alley, road, highway, lane, river,
creek, town, airport. . .etc. in the USA, including Alaska and Hawaii. 

The end result is incredible. By fastening the little GPS receiver to the 
back of the 755CD's screen and sticking the GPS's antenna (a little plate 
about 2" square) to the windshield, I can see where I am and where I've 
been anywhere I drive in the continental USA.  When coupled with a 
trip-planning CD Rom, such as MapNGo (also by DeLorme), I can plan a 
vacation trip and see where I am as I travel.  

Accuracy of the GPS is degraded by our government, except in time of war, 
so that a terrorist couldn't use it to guide a cruise missile or to guide 
an airplane as a cruise missile.  This degradation of the accuracy is 
presently in the +-50' or so range.  That means your "trail of 
breadcrumbs" might wander from one side of the road to the other- but who 
cares?  Without the degradation of the GPS accuracy, accuracy in the 
10-15' range could be expected.  However, by coupling the GPS to a Loran 
Differential beacon, accruacy of about 10' is expected even with the 
degradation of the GPS signal.  

Another side benefit of the GPS receiver is that you have an incredibly 
accurate time displayed for setting your watch <grin>.

Thanks again to the good people who sent me their suggestions.  DeLorme's 
support folks came through by having me set the baud rate to 4800 
from the 9600 recommended setting (ITFM) and changing one other variable.  
Now- my next task is to get the modem working.

Tom


Thomas A. Gauldin       Here's to the land of the longleaf pine,
Raleigh, NC             The summerland where the sun doth shine,
BSRB45A on Prodigy      Where the weak grow strong and the strong grow great,
FAX (919) 676-1404      Here's to Downhome, the Old North State.