Ultimate GPS Breakout - minor issue at high altitudes

For other supported Arduino products from Adafruit: Shields, accessories, etc.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
rbergerpa
 
Posts: 2
Joined: Sun Nov 18, 2012 2:14 pm

Ultimate GPS Breakout - minor issue at high altitudes

Post by rbergerpa »

Hack Pittsburgh did it's "C1" balloon launch on 11/11/12. The balloon carried an Adafruit Ultimate GPS Breakout Board using it's on-module logging feature.

It mostly worked well, but we discovered a minor glitch: at altitudes above 32,767 meters the recorded altitudes wrap around to negative numbers. By comparing the altitudes with the trend before and after the negative numbers, it appears the GPS calculated the altitude correctly, but the wraparound occurred when storing the value in the flash as a 16 bit signed number.

If we correct the negative numbers by adding 65536 we get values that make sense relative to the surrounding numbers.

Using this technique, we logged a max altitude of 34046 meters ( 111,757 feet )

Other Adafruit products were used on the launch and worked well:

Weatherproof 18B20 temperature sensor

Two Adafruit Data Logging Shields

Serail JPEG Camera (watch the Hack Pittsburgh site; we will add the pictures soon)

Robert Berger
Hack Pittsburgh member

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by adafruit »

is the bug in our parser or the NMEA output?

User avatar
wethaguy
 
Posts: 54
Joined: Sun May 06, 2012 9:00 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by wethaguy »

32,767...65,536. This has to be a valued stored as int when it should be unsigned int. It would more correct to make it a long, since it's technically possible to have a negative altitude (below sea level).

buprafisc
 
Posts: 11
Joined: Sun Dec 02, 2012 6:29 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by buprafisc »

Hello,
Sorry for my bad english but I'm French.
Could you tell me if Ultimate Gps Breakout is comptatible with Arduino Due ?

Thanks.

Thierry

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by adafruit_support_bill »

Yes. It will work with any 3.3v or 5v microprocessor.

buprafisc
 
Posts: 11
Joined: Sun Dec 02, 2012 6:29 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by buprafisc »

Thanks

Thierry

User avatar
rbergerpa
 
Posts: 2
Joined: Sun Nov 18, 2012 2:14 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by rbergerpa »

adafruit wrote:is the bug in our parser or the NMEA output?
I wasn't using the NMEA/serial output; the bug occurred when using the "log to internal flash" feature of the module, and then extracting the data with the MT3339 GPS PC Tool

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: Ultimate GPS Breakout - minor issue at high altitudes

Post by adafruit »

oh, yeah the internal logging stuff is hardcoded - it was not designed for use at high altitudes!

Locked
Please be positive and constructive with your questions and comments.

Return to “Other Arduino products from Adafruit”