Garmin Radar
- Thread starter TyBoo
- Start date
Well, maybe I used too simplistic a term. I think it uses barometric pressure as part of the calculation much as would a barometric altimeter. I readily admit I don't understand all I know about the thing. How do the "decent" GPS units supply altitude? There is a way to calibrate the thing - I just haven't found it yet.
The GPS and radar are networked in the same unit. I don't know who talks to what, but they seem to get along pretty well. It will overlay the radar on the chart, and display waypoints on the radar screen, so I guess they communicate.
The GPS and radar are networked in the same unit. I don't know who talks to what, but they seem to get along pretty well. It will overlay the radar on the chart, and display waypoints on the radar screen, so I guess they communicate.
I think you will like that thing once ya diddle with it a bit. TyBoo":c7yezlli said:
Altitude is calculated the same way position is calculated - by triangulation to the satellites' positions (which are known to high accuracy). Your position in 2 dimensions can be found in principle with just two GPS sattelites. Your position in 3 dimensions takes a minimum of 3. Of course, the accuracy goes way up with more data (e.g. more satellites). My guess is that you're not getting very many satellite fixes due to blockage by trees etc. in your current location so that the elevation accuracy is not that good. The Garmin units will report the accuracy in your position (indicated by a green circle around the boat) but I'm not sure if they report the accuracy in the elevation.
Elevation is a bit harder to calculate accurately unless your antenna is picking up satellites that are relatively low to the horizon. E.g. if you just get satellites mostly straight up, elevation will not be accurate. There is a page where you can see the position of the satellites that are being recd' relative to the horizon. I bet most of the ones you have a lock on in that parking spot are mostly overhead. The elevation accuracy (and hence reported elevation) will also change over time since not all GPS satellites are in geostationary orbit.
Mike – if your altimeter uses barometric pressure for the altitude, there is no way of calibrating it, so it will always show your altitude without resetting it every day. I am an ex-pilot and altimeters on the planes I flew had to be reset all the time as we were flying. The sea level barometric pressure is always entered into the setting and the difference in the pressure, is how your altitude is indicated.
Satellite altimeters do not have this limitation, but also do not have the accuracy of barometric altimeters. If a satellite altimeter maintains an accuracy rate within 50’ you are lucky. A cheep barometric altimeter will be accurate within 2’.
I have an altimeter in my truck and it has a reset button on it, so each morning I hit the reset button and the altimeter is reset for my given altitude. The only time the reset button works, is when I am at a known altitude of 195’ (the altitude of my garage). Otherwise I have to enter the sea level barometric pressure for my location, to get the altitude of my given location.
Satellite altimeters do not have this limitation, but also do not have the accuracy of barometric altimeters. If a satellite altimeter maintains an accuracy rate within 50’ you are lucky. A cheep barometric altimeter will be accurate within 2’.
I have an altimeter in my truck and it has a reset button on it, so each morning I hit the reset button and the altimeter is reset for my given altitude. The only time the reset button works, is when I am at a known altitude of 195’ (the altitude of my garage). Otherwise I have to enter the sea level barometric pressure for my location, to get the altitude of my given location.
Thanks, Roger. When checking the sattelite lock, the minimum has been 7 and one time it had 10. The most it will use is 12.
As for the elevation, it seems I have read that hikers/climbers prefer the barometric altimeter to the GPS calculations for accuracy. I could probably find where I read it if it matters, but it wasn't interesting enough to me at the time to study in depth. It was on the internet, though - so it has to be true! The other Garmin on board shows the elevation varying from -3 to +6 where she sits. As you can see in the first pic, the receivers for the two units are side by side (and generously out of the lower 12.5º vertical radar trajectory). To tell you the truth, I have never bothered to display the elevation data because I am always at sea level or <50' above. When a guy can see the beach, he don't much need any more info.
It sure got the house color wrong, though.
Well, the thing is, I have the labels that big so I don't have to tip my head back far enough to look at them through the bottom of my glasses.
As for the elevation, it seems I have read that hikers/climbers prefer the barometric altimeter to the GPS calculations for accuracy. I could probably find where I read it if it matters, but it wasn't interesting enough to me at the time to study in depth. It was on the internet, though - so it has to be true! The other Garmin on board shows the elevation varying from -3 to +6 where she sits. As you can see in the first pic, the receivers for the two units are side by side (and generously out of the lower 12.5º vertical radar trajectory). To tell you the truth, I have never bothered to display the elevation data because I am always at sea level or <50' above. When a guy can see the beach, he don't much need any more info.
It sure got the house color wrong, though.
Well, the thing is, I have the labels that big so I don't have to tip my head back far enough to look at them through the bottom of my glasses.
And thank you, Dave. Now I don't need to keep looking for a way to claibrate it. The cheapo Garmin eTrek I have has a place to enter a known elevation to base its calculations on. That's what I was looking for on the big feller. Is that what you mean by reset?
If all you smart guys really want to help me understand something that bugs me, then tell me why during the earthquake a couple years back that made the floor in the huge building at work undulate like the CR bar and the pillars move like the old rubber pencil gag did not cause the concrete to bust? Too weird. I was talking about that again today with a guy who saw the same thing in another building. All we can figure is that it was an illusion, but I swear there were 3' swells in the foot-thick concrete.
If all you smart guys really want to help me understand something that bugs me, then tell me why during the earthquake a couple years back that made the floor in the huge building at work undulate like the CR bar and the pillars move like the old rubber pencil gag did not cause the concrete to bust? Too weird. I was talking about that again today with a guy who saw the same thing in another building. All we can figure is that it was an illusion, but I swear there were 3' swells in the foot-thick concrete.
AstoriaDave
New member
February of 2001, I think. I was in my garage, and there was some settling under a footer, and I got some cracks in a foundation -- not critical, though. House was new April 2000, and is still here, cracks and all!TyBoo":phyh6lgz said:
That bending in the concrete is typical, and if not too extreme, will not crack it. Even concrete can bend a little without breaking. You've probably seen pre-stressed concrete bridge supports in transit on a flatbed trailer -- which come with a hump in them, purposely, so when they are loaded, they will be flat.
Uh oh. There's another gadget that will work with the new Garmin. AIS - Automatic Identification System. All ships over a certain tonnage are required to transmit location and other info, and for about $300 I can get a receiver unit that will display the info on the new line of Garmin chartplotters (and probably others).
A friend of mine just got the system installed on his boat and posted some screen shots here on a local fishing board. There are a lot of cool gizmos out there, but this one is cool and useful. Imagine planning a long trip and being able to see what ships will be coming around the corner long before you get there.
One of these days maybe................
A friend of mine just got the system installed on his boat and posted some screen shots here on a local fishing board. There are a lot of cool gizmos out there, but this one is cool and useful. Imagine planning a long trip and being able to see what ships will be coming around the corner long before you get there.
One of these days maybe................
I just received one of the new Garmin antennas. I have a 4212 chartplotter and the antenna has two wires for power and an ethernet plug for the back of the chartplotter. Couldn't get much easier than that. I plunked it on the roof and fired it up in the driveway. Seems to work, although I don't know what I'm looking at on the screen. I just used little alligator clips for power for the test. It only draws about 3.5 amps and it's supposed to work down to near 10 volts, so it's not too fussy about the power connection, at least for a brief test.
I need to mount the antenna properly and then daytime test on the water so I can learn to interpret the display. I could hear it spinning up to speed because everthing else was dead quiet out in the driveway. It ratchets up in several RPM steps, judging by the sound. Sounds like a quiet digital tone generator. Kind of musical. I doubt I'll hear it with the engine running or radio noise or water noise. Also it's not going to be just lying on the roof like tonight.
I carry kayaks on the roof on a Yakima rack setup, so I'll try to adapt to that rather than put more holes in the roof. That's my plan for the moment, anyway. I may give up and buy a pedestal, but I want to try custom first.
Once I get to where I can judge the performance, I'll post a report. It might take a couple weeks. I paid a little extra to get the High Definition (HD) version. Better performance or better marketing?... Beats me.
Jeff
I need to mount the antenna properly and then daytime test on the water so I can learn to interpret the display. I could hear it spinning up to speed because everthing else was dead quiet out in the driveway. It ratchets up in several RPM steps, judging by the sound. Sounds like a quiet digital tone generator. Kind of musical. I doubt I'll hear it with the engine running or radio noise or water noise. Also it's not going to be just lying on the roof like tonight.
I carry kayaks on the roof on a Yakima rack setup, so I'll try to adapt to that rather than put more holes in the roof. That's my plan for the moment, anyway. I may give up and buy a pedestal, but I want to try custom first.
Once I get to where I can judge the performance, I'll post a report. It might take a couple weeks. I paid a little extra to get the High Definition (HD) version. Better performance or better marketing?... Beats me.
Jeff
Gene Morris
New member
Jeff;
I have had a Garmin radar unit since Oct 2006. It is hooked up to a 3210 plotter/network. The radar works great with a 36nm range. I have XM connected to the network. When the plotter is on, the radar is powered up and the sonar is active. The only thing that I will do different is install manual switches so that we can turn power to the radar and sounder off when at anchor. I'm not sure what the power draw is however, it has to be more efficient with the power off at the units.
Gene
I have had a Garmin radar unit since Oct 2006. It is hooked up to a 3210 plotter/network. The radar works great with a 36nm range. I have XM connected to the network. When the plotter is on, the radar is powered up and the sonar is active. The only thing that I will do different is install manual switches so that we can turn power to the radar and sounder off when at anchor. I'm not sure what the power draw is however, it has to be more efficient with the power off at the units.
Gene