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Jan 02, 2012, 09:18 PM
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yzguy's Avatar
since the LOS (or DIST) is already just distance, the angle to the plane would be easy to calculate. Is this in there somewhere already?
It would be nice to keep the plane at a certain angle to keep a good signal to the plane.
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Jan 02, 2012, 10:51 PM
Suspended Account
Quote:
Originally Posted by yzguy
since the LOS (or DIST) is already just distance, the angle to the plane would be easy to calculate. Is this in there somewhere already?
It would be nice to keep the plane at a certain angle to keep a good signal to the plane.
i did this before and calculated a minimum altitude to maintain 15 degrees in order to get good reception on a patch antenna.

http://www.youtube.com/watch?v=-sa7w4pbYv0
Jan 02, 2012, 11:02 PM
Suspended Account
obviously simple trig, but here is the work done for you



simply modify layout.h to move stuff and add/remove stuff
Jan 03, 2012, 12:25 AM
Registered User
Took some poking around but I got what I want. Just had to comment out a couple lines in layout.h
Jan 03, 2012, 01:15 AM
Expert
Quote:
Originally Posted by highviz
if you could direct me to the right file location to change...
looks like we need comment 2 lines in gps-nmea.h
gGpsLastData.speed *= 463;
gGpsLastData.speed /= 250;
Jan 03, 2012, 03:03 AM
Registered User
Thanks Redsonic - must have had tired eyes last night, as I could not find those lines, despite them being well commented.

- I'll take a drive with the unit today, to verify that we are really seeing a 1.85x error, before commenting those lines out. Rough calculations from time over distance during yesterdays flight seem to support it though.

Malcolm
Jan 03, 2012, 04:59 AM
Up up and away!
FpvKiwi's Avatar
Quote:
Originally Posted by yzguy
since the LOS (or DIST) is already just distance, the angle to the plane would be easy to calculate. Is this in there somewhere already?
It would be nice to keep the plane at a certain angle to keep a good signal to the plane.
Angle is useful but maybe arctan is expensive for the poor little AVR to calculate. In such case, glide number or whats-it-called should be good enough; 100 * height / dist
Jan 03, 2012, 05:38 AM
RC pilot by soul
Hey guys,

im trying to make a GPS unit from a LASSEN-IQ module (trimble) + Trimble antenna.

im wondering, do i need just the GPS antenna (on the right) or the complete antenna with amplifier (left) ?

please advise.
Jan 03, 2012, 10:38 AM
Registered User
I found a bit of private road and mapped the G-OSD II recorded speed against my satnav this afternoon:-



The speed display rolled over above 255 - but that won't be a problem for most!

Results are close enough to the predicted 1.85 x error, so I'll comment out the existing multiplication factor and see what happens....

Malcolm
Last edited by highviz; Jan 03, 2012 at 10:48 AM.
Jan 03, 2012, 12:59 PM
Registered User
That worked for the instantaneous speed. Now looks to be within 1 -2kph at normal flying speeds. Plenty good enough for me

The recorded stats however, are showing high figures on both speed and altitude. Of course I was not very scientific about things, so had changed the refresh rate to 4hz at the same time as making the speed changes. Guess I'll have to step back on one of those changes to narrow down the cause......

Malcolm
Jan 03, 2012, 04:30 PM
Registered User
yzguy's Avatar
Quote:
Originally Posted by FpvKiwi
Angle is useful but maybe arctan is expensive for the poor little AVR to calculate. In such case, glide number or whats-it-called should be good enough; 100 * height / dist
yeah, I was thinking fuctions like that might be to much, but actually now that I think about it, once you come up with an angle, like say 15 degrees, then the ratio of height to distance is constant for that angle (right? or am I remember this stuff wrong). So I can get that number, and just make the altitude blink if the ratio is below that number. The actaul angle does not matter, just if I am above or below it. This would be easy to add, and I can add comments for a few different ones. (and a minimum distance, who cares if you are less than 15 degrees LOS if you are 50 feet away)
Jan 03, 2012, 04:34 PM
Registered User
yzguy's Avatar
Quote:
Originally Posted by chatch15117
i did this before and calculated a minimum altitude to maintain 15 degrees in order to get good reception on a patch antenna.
yeah, that displays the minimum alt.... I was thinking more of an alarm, but displaying the number might be cool too.

another thought was just making a hard coded lookup table for the ratio of hight to distance, say in 5 degree increments. Not as accurate, but probably close enough.
Jan 04, 2012, 03:34 AM
Registered User
Quote:
Originally Posted by after.burner
Got my E-OSD to work! The reason for my problems: GPS Checksums were invalid 99% of the time @ 9600 baud. I switched to 4800 baud and everything works like a charm. Here is a patch that will make the satellite symbol blink if the OSD receives GPS data with wrong checksum.

Also I switched to 2 hz update rate on GPS and OSD. Judging from my ground test this is way more reactive than 1 Hz. I'll try to post a flying vid soon.
Nice patch!

I mentioned in my last post that I am using my GPS at 38400 (I don't get the choice to change that as I'm just sucking a feed going to my autopilot who is in charge.)

I've finally done some flying and while it does technical seem to work (numbers seem reasonable), it is very slow and sometimes does not update LOS, ALT etc for many seconds. Perhaps I still have transmission errors too but enough packets get through to make it kinda work. I'll try your patch and watch out for the blinking icon.

Perhaps there are still some serial bugs lurking in cl-osd?

Dave
Jan 04, 2012, 06:30 AM
Up up and away!
FpvKiwi's Avatar
Quote:
Originally Posted by yzguy
yeah, I was thinking fuctions like that might be to much, but actually now that I think about it, once you come up with an angle, like say 15 degrees, then the ratio of height to distance is constant for that angle (right? or am I remember this stuff wrong).
Yes, angle and height/dist ratio are equivalent. The problem with 100*height/dist is that it might become arbitrarily large if flying overhead. It gives the height you'd have if dist is 100m so maybe just write "99" or some other character if the angle is above 45 degrees.
Jan 04, 2012, 07:36 AM
RC pilot by soul
do the last versions of CL-OSD come with compass already ?
anyone got some videos with the compass on ?


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