Amazing how far [-]satellite navigation[/-] GPS has come. Early seventies on board the research ship RV Vema, we had an antenna mounted on top of the mast, sucker weighed about 80 lb, had radials and a vertical sticking out of it for 3 feet. The receiver was 19" rackmount classified device with seals on it. With all sorts of rules on who can see it.
The pre-rocessor was another rackmount with about 40 plug in cards with discreet transistor flip flops, outputting data to a Freiden tape punch. Which produced typically an 10 foot long tape with holes in it representing the satellite orbit, ID, time etc.
To actually get the data, the receiver's speaker was always on. THe watch standers in the electronics lab had trained ears for the faint whistle, of the satellite coming up the horizon. When heard the nearest tech would leap to the control head and press the oscillator tune until the local oscillator matched the satellite doppler, and lock onto the signal. Then the receiver would track the doppler shift until the satellite disappeared over the far horizon.
During the satellite pass the Frieden punch would be clankin out the the punched tape with the satellie data.
At this point all we knew was that we had sat. data.
Now came the processing part. The good old DEC PDP8 with 2 Kilobyte of memory was standing by, or running some other program. We set the toggle switches on front panel to tell computer that it is to expect a program. Now, feed the program tape int the reader, hit the go paddle (switch), and the machine would read a punch tape with the proper holes, which had the satellite navigation program.
This completed, the PDP 8 would beep,indicating it was ready to accept data. Now we loaded the previously punched data tape ftrom the last satellite pass, hit the go toggle, and for 20 ro so minutes be rewarded with an entertaining sequence of flashing lights on the front panel as the computer was processing the data.
At the end of twenty minutes or so the winking blinking lights would stop for a moment, then the computer started to output the fix (our location) on a teletype machine. with a great amount of clanking.
THus we received four lines of data with latitude, longitude, confidence level and estimated time of next satellite pass. The fix was typically good for a 10 to 12 mile radius.
After all this we walked over to the chart table and plotted our location. And got on the intercom to the bridge and read them the fix.
Anyone for the good old days
??
I now have a laptop in my suburban with Street Atlas, a surplus Rockwell GPS receiver, a puck antenna on the roof and can navigate on the go.
I like this newer version better.
