OT (GPS)

I know GPS systems get their info from satellites but how do the sats. get their info???

As far as what information the GPS satellites are merely transmitters. They are stationed in a precise geo synchronus orbit around the earth and the GPS receiver on the ground receives those signals and then calculates your position based on triangulation

The first one I ever used was the size of a shoebox and accurate to within 1/4 mile. Now they are in your cell phone and accurate to inches. There are now 32 to 35 GPS satellites in the constellation at the present time. It works on the same principle as the old celestial navigation did only infinitely more precise.

This is the GPS setup on one of our tractors we use. It is tied into the fertilizer application system on the planters. At the beginning of the year we update it with the soil analysis we have taken over the winter so we know exactly what part of the field needs fertilizer and how much. The days of just applying fertilizer everywhere is over. With the costs of diesel fuel and fertilizer you have to be more efficient. The fields are loaded into the system, soil analysis updated and crop to be planted entered and it will almost drive the tractor for you. Its the same way with what you see on your GPS screen. All that is, is a database that has been uploaded by someone like Google and the satellites tell your receiver where you are in relation to the signals they are transmitting and that is then shown on the screen. We also do the same thing with planted pine trees, I will fly over them in an ultralight taking pics and then they are loaded onto a laptop with a color mapping program and from the color of the pine needles we know which sections of trees need to be sprayed for Pine Beetles, which trees are stressed from lack of water or to much water.

And I could not even have an AM radio on the 8N. LOL Although, I did on occasion see piston engine fighters practice dog fights and several times hear a sonic booms from jets.

I had playing cards in the spokes of my bicycle held on with clothes clips

You might want to check the terminology. I think geo-synchronous orbits are for satellites just over 22,000 miles from the Earth and positioned over the equator, at that altitude they orbit one time every 24 hours, so from the Earth they always hover over the same spot on the equator. Dish and Direct-TV are good examples, weather satellites that take cloud and rain shots are usually these types.

The GPS network uses 24 active (some more are up there but held in reserve) satellites in orbits in varying planes, none of which (I think) are over the equator. This plan is just based on geometry in order to have at least four "visible" to your GPS receiver at any time. They broadcast a very accurate clock (time signal) and all are synchronized to several decimal places in seconds, and a trigonometry chip in your receiver calculates your location, and your altitude if you have that feature.

Me, too. I wish I had all the Mickey Mantle and Yogi cards that I wore out!

Aint that the truth flying down the road, my hair ripping in the wind, my lips curled back in a defiant sneer and 4 new playing cards in the spokes

You are right I stand corrected. They are indeed in a much lower orbit but the last time I checked there were 32 but that may have changed.

There are over 30 GPS satellites that orbit earth 2 times a day at approx 12,000 miles (20,000 Km) above Earth's surface. These satellites communicate with ground base stations across the globe that basically track their movements and confirm where they should be. The satellites also transmit signals down to GPS receivers, this information is what your GPS receiver uses to get positioning among other things like speed, bearing, altitude etc.

A receiver needs to communicate with at least 3 satellites to work, but will normally lock onto 4 or more. The more satellites it can communicate with, the more accurate information will be. The satellite signals are sent with specific timing with extreme accuracy using atomic clocks, your GPS device then knows how long it takes for these signals to reach it and can figure out location based on trilateration with multiple satellites.

what I don't know is how the info is fed (like maps) to the sats. in other words how does a paper map get to your GPS ?

The map info is already in your device, whether a hand-held or a car/tractor/boat receiver. The GPS signal is just broadcasting time, and your device interprets and displays it according to the specs it was designed for.

I understand that but how does the info get from the physical location to a signal on/in a device?

(quoted from post at 11:53:37 04/18/17) I understand that but how does the info get from the physical location to a signal on/in a device?

Click to expand...

aps get in via the USB port on the GPS device. Some think that you need to shrink them & roll into a tiny map so that you can shove them into that tiny port. They really do get in via that port though.

(quoted from post at 15:00:27 04/18/17)

(quoted from post at 11:53:37 04/18/17) I understand that but how does the info get from the physical location to a signal on/in a device?

Click to expand...

aps get in via the USB port on the GPS device. Some think that you need to shrink them & roll into a tiny map so that you can shove them into that tiny port. They really do get in via that port though.

Click to expand...

:lol:

it truly is impressive how small we've managed to make data. the machine i learned on was the size of a refrigerator - which included a whopping 50 meg of hard drive storage and an even more impressive total of 48K RAM. yes, that's K.

i shudder to calculate how much space that would require to match my modest flash drive's 8 gig capacity.

There are mapping services that photograph various places and convert that to digital images that are then sold on the corporate market. (Probably many intermediaries are doing various tasks.) For example, there are firms that take or buy aerial photographs and sell them to a firm that re-sells the photos to most county tax offices and they provide GIS mapping services for county tax assessments, real estate firms, and average citizens that take the time to use it for property research. Many overlay topo charts and other features depending on how sophisticated that county wants to be. If you buy a GPS/Sonar for a boat, the company has bought data like that (very specific to lakes and rivers in a certain region) and converted it to a format they load into the device they sell to you for your boat. When in use, the device interprets the four (or more) GPS satellite signals the device is receiving a signal from, links that to the installed map diagram and you see that on a screen. The guys that dreamed up all this get a lot of high marks from me! Way above my pay grade.

thanks!