Success using GPSout with Garmin aviation handheld GPS

[captaingps]

Peter,

I just signed on to this forum to send you some feedback on GPSout. Before I begin, let me compliment you on a job well done.

I got GPSout to work with FS 2004 using both a Garmin GPS III Pilot and GPS 196. I set the .ini file to “sentences=AV400”, the .ini comments had it as the singular “sentence” for AV400. To get the GPS to use the GPSout data, I set the protocol to “Aviation In” and put the GPS into the simulator mode.

After getting it to work, I did some quick flying; but I did not spend much time with it. There seems to be a slight lag in things like heading changes compared to the real GPS. However, this is just a quick unsubstantiated observation. Overall, it worked great!

I did a couple of very quick tests. I changed the weather in FS to a 36 knot crosswind and the GPS correctly showed TRACK rather than heading. The vertical speed and VNAV functions also appeared to work correctly.

I tried a couple of the other protocols offered by GPSout hoping that GPSout could be used with a non-aviation GPS. Obviously, I changed the protocol on the GPS, changed the gpsout.ini, and restarted FS. I had no success getting a non-aviation Garmin 76 to work. Likewise, I had no success with the Garmin 196 or III Pilot using other protocols other than “Aviation In.”

It would be cool if there where a way to make non-aviation GPS work also. Perhaps there is a way to do it with the Garmin protocol. If you are interested, it is published at http://www.garmin.com/support/commProtocol.html. It might take some double secret undocumented command.

I am not sure if I will get back to this forum. I just signed up to post this message. However, you are welcome to e-mail me at handheldgps@hotmail.com. My website is http://www.cockpitgps.com. I have a book on using GPS for flying, hence my interest in getting GPS to work with Flight Simulator.

Again, my compliments on your program.

Thanks,

John Bell

[Pete Dowson]

I got GPSout to work with FS 2004 using both a Garmin GPS III Pilot and GPS 196. I set the .ini file to “sentences=AV400”, the .ini comments had it as the singular “sentence” for AV400.

Ah, a typo -- thanks, I'll fix that.

There seems to be a slight lag in things like heading changes compared to the real GPS.

The default update rate is 1 second so you could try faster, though most GPS's only seen to read the values that infrequently even if you send them more often. Another factor is the serial speed. The default NMEA standard of 4800 bps is rather slow considering the data is in plain text formats and so longer than would be necessary for pure binary data. With a message length of, say, 80 characters, it takes a sixth of a second just for the transmission. Even small lags like that can be noticeable.

I did a couple of very quick tests. I changed the weather in FS to a 36 knot crosswind and the GPS correctly showed TRACK rather than heading. The vertical speed and VNAV functions also appeared to work correctly.

Great!

I tried a couple of the other protocols offered by GPSout hoping that GPSout could be used with a non-aviation GPS. Obviously, I changed the protocol on the GPS, changed the gpsout.ini, and restarted FS. I had no success getting a non-aviation Garmin 76 to work. Likewise, I had no success with the Garmin 196 or III Pilot using other protocols other than “Aviation In.”

From what I've seen there aren't many GPS units designed to allow NMEA input, only output. If they did allow NMEA input then it should have worked. You say you changed the GPS protocol, but are you certain it was to something accepting NMEA? All the Garmin units I've seen support NMEA out but only RTCM (or similar) in -- the latter isn't a GPS type output but an external antenna encoding for more accurate positioning. The contents are more like raw information from which the GPS can compute things. I can't get into that.

It would be cool if there where a way to make non-aviation GPS work also. Perhaps there is a way to do it with the Garmin protocol. If you are interested, it is published at http://www.garmin.com/support/commProtocol.html. It might take some double secret undocumented command.

I've got all the documents. The "Garmin protocol" is for transfer of waypoint and routing information, and digital maps for those units which support them. I've not found any real-time position infomation capabilities that way.

Regards,

Pete

[Mgarmy]

Just wanted to confirm that the Garmin GPSmap 196 is indeed working without any problem. I hooked up the standard cable to COM2, configured the GPS ini file and started FS where the GPS synchronized itself perfectly with FS.

What was not working is the trip logging which the 196 has after you takeoff and land at different airports. It will usually show you how long the trip took, distance and amount of landings. I wonder where such data is supposed to come from?

Nevertheless, it works like a charm!

Thanks for your great product and efforts.

Mannie

[Pete Dowson]

What was not working is the trip logging which the 196 has after you takeoff and land at different airports. It will usually show you how long the trip took, distance and amount of landings. I wonder where such data is supposed to come from?

Sorry, I've no idea. You'd think the stuff it does get would be enough? If you find out, please let me know!

Regards,

Pete

[captaingps]

Peter,

A couple of more notes: I just flew some approaches and some flights from KORL to KMCO with the Garmin 196. I found when flying from KORL to KMCO, the 196 started off right down the runway but drifted off by a couple of hundred feet by the time I reached KMCO. The GPS would show me on runway 17 when I was off in the grass a couple of hundred feet to the east in flight simulator. I also noticed some strange behavior in that TRACK would go blank. However, I still had a valid value for TURN, which is the difference between TRACK and BEARING.

I tried changing the com speed above and below 9600, but 9600 appears to be the only valid speed.

My guess was that for some reason the 196 was using the speed and distance from gpsout and not updating the position as often. This is my possible guess for the drift.

Going to the GPS page on the actual 196 and turning the simulator on and off seemed to quickly align the GPS position to the Flight Simulator.

I changed the interval to 200 milliseconds. This seemed to work much better based on another flight from KORL to KMCO. The normal GPS update rate on the 196 in actual operation is 1hz (1000 milliseconds), but the 200 millisecond update rate from gpsout seems to be better.

On the last flight from KORL to KMCO, I put in a 36 knot easterly wind. The GPS guidance seemed to work correctly.

As another post observed, the 196 does not record flights in simulator mode. It also does not record tracks either. I did not remember to check the trip menu, but judging by the behavior of the 196 in the normal simulator mode, this does not work either. The GPS III Pilot does record tracks, but I do not believe that the trip computer functions work. This appears to just be the way that Garmin designed the receivers and has nothing to do with gpsout. For use with Flight Simulator, I don’t see any loss in utility.

If I get the chance in the next couple of weeks I will try to do some more checking to confirm or disprove that the 200 millisecond interval made a difference. I will also check the III Pilot.

Again, my compliments on such a cool program!!!!

John Bell

[Pete Dowson]

I found when flying from KORL to KMCO, the 196 started off right down the runway but drifted off by a couple of hundred feet by the time I reached KMCO. The GPS would show me on runway 17 when I was off in the grass a couple of hundred feet to the east in flight simulator.

Compare the Lat/Lon coordinates. The runway positions in FS are not all that accurate in many cases. Check that the map you are using in the GPS agrees with the scenery in FS.

Going to the GPS page on the actual 196 and turning the simulator on and off seemed to quickly align the GPS position to the Flight Simulator.

Oh, right. In that case strike the above! :)

I changed the interval to 200 milliseconds. This seemed to work much better based on another flight from KORL to KMCO. The normal GPS update rate on the 196 in actual operation is 1hz (1000 milliseconds), but the 200 millisecond update rate from gpsout seems to be better.

At 9600 that's probably getting close to the fastest you can get in any case. There's 74 bytes (I think) in each AV400 transmission. 9600 async allows only 960 bytes per sec max, 192 bytes in the 1/5th second you allow. At 100 msecs the blocks could start looking continuous and/or would back up in the PCs buffer.

As another post observed, the 196 does not record flights in simulator mode. It also does not record tracks either. I did not remember to check the trip menu, but judging by the behavior of the 196 in the normal simulator mode, this does not work either.

This is confirmed by our other contributor here.

Regards,

Pete

[Mgarmy]

Both,

Just wanted to tell how much the use of FS as well as my understanding of my GPS has changed since I managed to make it work with FS. As a die hard VFR pilot who either uses conventional IFR procedures or VFR charts to get around flying I recently bought my GPS only to come to the conclusion that it has to many functions which can only be tested for useability during real flight. This resulted several times in stranges attitudes while trying to work the controls and GPS at the same time. Now after several flights using FS I managed to configure my GPS in such way that it presents the information I need during various stages in flight accross the different screens so that it all makes sense. I managed also to get the data displayed on the GPS map to reflect much better to what VFR/GPS paper charts are showing. All this without stepping into my airplane wasting time and endagering myself by fiddeling around with all the hidden GPS features which do not make sense unless you see them work for real.

Thanks both for all of your efforts figuring things out and giving as the technology to make it all work!

Mannie

P.S

200 Msec works indeed better. What I also noticed is that drift is mostly caused when pausing FS for a while.

[Pete Dowson]

200 Msec works indeed better. What I also noticed is that drift is mostly caused when pausing FS for a while.

Sounds like the GPS is doing some extrapolation, then, assuming you can't actually stop the aircraft dead in the air! :D

It must be a bit puzzled when you release the pause!

Regards,

Pete

[captaingps]

Pete,

Have you contacted anybody at Garmin with regard to using the Garmin format rather than the aviation format? If not, send me an e-mail at johnbell@cfl.rr.com with your e-mail address and I will see if I can find anything out. Not that I have any special connections, but I may have someone that I can write to.

It would be great to be able to use a non-aviation handheld GPS with Flight Simulator.

Thanks,

John Bell

[captaingps]

Pete,

I did some more playing with the drift issue that I had previously mentioned. I really have not discovered much new; however, I though that I would take a couple of minutes and post what I did find. It appears that the simulator mode of the GPS may integrate the speed and track over time to reach a position. Thus, the position appears to drift a little flying from place to place. Perhaps the GPS position does not change until it disagrees with the GPS position from GPSout by some error value. I don’t know beyond relatively uninformed speculation.

For example, I started off down the runway and hit pause on FS about halfway down the runway. The GPS continued straight ahead based on its track and speed at the time of the pause. At about the end of the runway, the GPS position jumped back to the point that I hit the pause. To be able to jump back to the paused position, the GPS must be getting updated positions from GPSout.

Changing the GPSout rate to 200ms appears to make the drift diminish just because the update rate for the speed and track is faster. For some reason, the effect seems less when the simulator is flown back to the airport of departure. Perhaps the way FS calculates groundspeed in the context of the curvature of the earth may be a factor.

Although, it would certainly be better if GPSout combined with the GPS did not exhibit this behavior, it is not a big deal. I rate the significance of this as a minor issue at worst and is probably more a function of the internal software of the GPS than it is of the GPSout program. Where the user might notice this is that if the GPS to navigate to the runway threshold instead of the airport, he may find that the threshold and the GPS position are several hundred feet off. Generally, the GPS will show the aircraft traveling right down the center of the runway in real life. However, I have seen it off in real life were the GPS track shows the aircraft just off of the side of the runway even though the aircraft was on the runway. Thus, there is a certain “reality” introduced by the error.

The very simple work around is to quickly stop and restart the simulator mode on the GPS. A good time for this might be when approaching the airport.

As always, submitted in the context of humble constructive feedback as opposed to being a complaint.

John

[captaingps]

Both,

Just wanted to tell how much the use of FS as well as my understanding of my GPS has changed since I managed to make it work with FS.All this without stepping into my airplane wasting time and endagering myself by fiddeling around with all the hidden GPS features which do not make sense unless you see them work for real.

Mannie,

Hopefully I am not violating good taste by suggesting my book, Cockpit GPS. Considering that it is a free download at http://www.cockpitgps.com , I think that it is within the bounds of good taste to post the information here. There is a link to voluntary payment, feel free to ignore that – most people do. However, definitely sign my guestbook or send me feedback if you get something of value from it.

I find the most useful core fields on the map display to be TURN, OFF COURSE, and DISTANCE to NEXT. You can also try the HSI display on the map page, but go the HSI or panel page, press menu, and change the bug to read BEARING instead of TO COURSE.

I find a feature that many GPS users miss out on is the ability to edit a route using the map. Create a route from origin to destination. From within the route, press MENU and select Edit on Map. Move the cursor to the route until it turns to dashed lines and then press ENTER. Now you can drag the route where you want it. Press ENTER when you get it where you want it. You can also create the whole route in a similar manner rather than just modifying the route. Most Garmin mapping GPS receivers, both aviation and non-aviation, have a version of this feature.

John Bell

[Pete Dowson]

I rate the significance of this as a minor issue at worst and is probably more a function of the internal software of the GPS than it is of the GPSout program.

GPSout can only relay the information it gets from FS.

I don't notice this sort of "error" when using moving map type programs -- e.g. Jeppesen FliteMap -- which is what GPSout was designed for (i.e. to emulate a GPS rather than provide simulated input to one).

I think the error is simply a function of the GPS, entirely, and probably a result of some algorithm intended to deal with temporary losses of signal -- as in cars when passing through tunnels or through tree-lined avenues. It simply refuses to believe that the aircraft can suddenly stop dead. Understandably.

Regards,

Pete

[captaingps]

I think the error is simply a function of the GPS, entirely, and probably a result of some algorithm intended to deal with temporary losses of signal -- as in cars when passing through tunnels or through tree-lined avenues. It simply refuses to believe that the aircraft can suddenly stop dead. Understandably.

Pete,

Here is my guess as to why the GPS position and the Flight Simulator position drift apart: I think that the GPS mode uses the position when the GPS simulator mode is started. After that it calculates the position based on the cumulative effects of speed, track, and time. Without GPSout and Flight Simulator, the user moves the rocker pad to adjust the track and speed and then the GPS position moves accordingly. The altitude on the GPS does seem to get an update from GPSout.

Thus, I see this whole issue as a function of the GPS internal software relating to the GPS simulator mode rather than the dead reckoning mode, which is meant to handle a lost signal. I certainly would not fault GPSout. In fact, I really do not fault the internal functioning of the GPS either, using the GPS in simulator mode with GPSout is an added bit of functionality that you have managed to coax out that it was really not designed for.

I do think the re-alignment trick is useful for anybody flying an instrument approach using Flight Simulator and one of the Garmin handhelds for reference using GPSout.

One reason that I am responding to your response is that I fear that my spending several posts on the issue may have inflated the importance of the issue rather than merely reflecting my interest in the matter.

The other thing that I want to do is once again express my admiration and appreciation for GPSout. I am not an active simmer, but I have thought that being able to interface a handheld GPS with Flight Simulator would be a fantastic training tool. You have figured out how to do it with GPSout and it works great.

Once again, thanks,

John Bell