[FOSS-GPS] RTKLib and uBlox 7

[Michele Bavaro]

If I may, I'd like to add to the subject.

- There are rumors about uBlox releasing soon a "7P" engine which should 
support RAW data output. I am expecting it to be pin compatible with 6 
generation.

- Using a SuperStarII on the UAV and a NEO6P as a base station.. sounds 
very much like the other way around? If you use RTKLIB, there is no 
point in streaming DGPS corrections to the Novatel receiver (assuming 
RTKLIB converts the UBX to the "right" RTCM messages 1, 2, 3 and 9). 
RTKLIB onboard will do better than code differential by using a loose 
"kinematic" solution (carrier-phase based). Also "6P" has a crystal as 
onboard clock, which is known to be not great in terms of accuracy and 
phase noise. A TCXO ("6T") is supposed to be better, but really the 
Novatel should be the "base".

- LEA6H accepts RTCM (code corrections) input as far as I know, an so do 
"6T" modules. "6P" modules don't, since they offer inbuilt "PPP" capability.

- How do you time-tag the UAV pictures with GPS? I am pretty sure that 
"T" modules have a EXTINT0 pin which records "events" in the digital 
domain and causes the module to output a message with a very accurate 
(sub-us) time-tag. You may refer to chapter 1.7.3 of NEO6 data sheet 
(GPS.G6-HW-09005) and message UBX-TIM-TM2 for more details.

Cheers,
Mic



On 21/08/2013 16:34, Brent Fraser wrote:
> Weber,
>
>   Well I really don't NEED to; it's more of an experiment to see if it 
> will improve the performance of the UAV (likely more trouble than it's 
> worth), or if it will improve the positioning quality of the imagery 
> acquired from the UAV (it might).
>
>   Currently I've got a uBlox Lea-6H 
> (http://www.canadadrones.com/3DR-GPS-LEA-6-p/3dr-gps-lea-6.htm) 
> supplying positions to the autopilot, but it has no raw data input(?) 
> or output capability so the positions are likely in the +/-3m range (I 
> really need to test that too).
>
> Best Regards,
> Brent Fraser
>
> On 8/21/2013 12:15 AM, Weber wrote:
>> Tomoji, thank you for the reply. For the moment I intend to work with 
>> their 6T model.
>>
>> Brent, this may sound a stupid question but as I am moving from 
>> industrial cameras development to UAV electronics, I have a lot to 
>> catch up:
>>
>> Why do you need to input corrections into the onboard GPS receiver?
>> What I've read on RTKLib docs about RTKNAVI dataflow, it only takes 
>> inputs from the rover/basestation GNSS receivers.
>>
>> Weber
>>
>>
>> Em Wednesday, August 21, 2013 2:04:46 AM, Brent Fraser escreveu:
>>> Weber,
>>>
>>>   Interesting.  I'm planning to use RTKlib to implement RTK on my UAV
>>> using an old Novatel SuperstarII on board which supposedly will take
>>> corrections on its Com2 port (we'll see).  For the base station, I'll
>>> use a ublox Neo-6p
>>> (http://www.csgshop.com/product.php?id_product=103). And hopefully the
>>> RTCM corrections can be transmitted via MAVlink on 3rd telemetry
>>> radios....
>>>
>>> Best Regards,
>>> Brent Fraser
>>>
>>> On 8/20/2013 2:52 PM, Weber wrote:
>>>> Hi all,
>>>>
>>>> Anyone has any experience about trying to make the uBlox 7 receiver
>>>> work with RTKLib?
>>>>
>>>> Any expectations of how complicated/'how much code editing' it would
>>>> require?
>>>> The intention is to implement a RTK solution for UAVs.
>>>>
>>>> Thanks,
>>>>
>>>> Weber
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