GPS MISCONCEPTIONS

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msinger said:
CapnBob said:
By itself, indicating 12-13 satellites doesn't necessarily mean it's GLONASS enabled.
So, how do we figure out if it's GLONASS enabled?

The chip in the Phantom (mentioned above) is the Ublox NEO-6Q chip, which does not receive GLONASS.
There is another Ublox chip, the NEO-7N which is GLONASS enabled: GPS L1 C/A, GLONASS L1 FDMA

Hmmm. I wonder..

viewtopic.php?f=27&t=16846
 
I was wondering that as well. I have "GPS Plan" app on my iPhone and it shows up as well. Before I fly I check to see what I'm receiving on the phone, assuming its the same ones that I see on the DJI app when I launch. Anyway, I will almost always see more 'satellites' on the DJI app then is indicated on the GPS plan app so i assumed the bird was connecting to them..am I wrong?
 
Well there you go. I was loathe to take the shielding off and have a look. Shame really.

I got the Phantom as it was plug and play rather than the faff most of my toys are so I didn't want to play. Got me thinking though. I have an Adafruit Ultimate GPS board here that uses the the MTK3339 chipset. This chip has onboard flash and can datalog every 15 seconds for 16hours. Might be fun to try.
 
Something else I haven't seen mentioned in relation to GPS is the augmenation systems to improve accuracy. I got my facts wrong on GLONASS so this is probably redundant as well. In the US you have WAAS to improve accuracy and here in the EU we have EGNOS. This is meant to improve accuracy of the positioning but again is poor in urban environments. Unlike GPS these are geostationary.
 
wildpalms said:
Something else I haven't seen mentioned in relation to GPS is the augmenation systems to improve accuracy. I got my facts wrong on GLONASS so this is probably redundant as well. In the US you have WAAS to improve accuracy and here in the EU we have EGNOS. This is meant to improve accuracy of the positioning but again is poor in urban environments. Unlike GPS these are geostationary.

The problem with WAAS is, it's a ground-based system. With the issues we have with LOS space-based hardware, imagine the glitches with ground-based hardware. Think FM radio multipath "picket-fencing". Think LORAN. Yuck.
 
I have a Garmin hand held that receives both GPS and GLONASS, and an older model Garmin that receives only GPS. One day I ran both of them alongside my P2V - the Garmins about a foot off the ground, the P2V on the ground. The newer Garmin was seeing 9-10 GPS and 6-7 GLONASS (total 15-17) while the older Garmin was seeing the same 9-10 and while the P2V was receiving a total of 8-9 satellites. I concluded that the P2V receives only GPS satellites.
 
CapnBob said:
wildpalms said:
The problem with WAAS is, it's a ground-based system.

I think you've confused WAAS with something else. WAAS is a refinement of GPS. Basically it provides data (via satellites) to GPS receivers so that they can compensate for small variations in the signals from the GPS satellites. It's not a radio-based navigation system like LORAN.

-- Roger
 
Roger, I am not confused. WAAS is indeed a "Wide Area Augmentation System ". However, It is a GROUND BASED system. As LORAN was. Multipath was then and is now an issue. I believe you are confused. RADIO and MICROWAVE are the same thing, Different frequencies. As is visible light, and infrared, and ultraviolet.. It's all electromagnetic radiation.
 
CapnBob said:
Roger, I am not confused. WAAS is indeed a "Wide Area Augmentation System ". However, It is a GROUND BASED system. As LORAN was. Multipath was then and is now an issue. I believe you are confused. RADIO and MICROWAVE are the same thing, Different frequencies. As is visible light, and infrared, and ultraviolet.. It's all electromagnetic radiation.
+1
WAAS is indeed a ground based system.
 
CapnBob said:
I found the spec sheet on the NEO-7:

http://www.u-blox.com/images/downloads/ ... 003%29.pdf

And this is for the NEO-6 series:

http://www.u-blox.com/images/downloads/ ... 003%29.pdf

Notice the last bullet under "Highlights"
•Backward compatible with NEO-6 and NEO-5 families



Looking into this..

Bob, if you find that we can replace our old GPS chips in the Phantom with the NEO-7, please start a new thread on that. I've flown in the polar regions, and that is where GLONASS really helps. I would switch my chip in a heartbeat if I knew it would work on my P2V+
 
What exactly do you mean by 'ground based'.

WAAS is a hybrid.

True the receivers are ground based to determine the GPS errors but the correction data/signals come from satellites.

So as far as as the GPS engine is concerned transmission is satellite based therfore there is no 'picket fencing' or similar transmission interruptions.

In fact, the FAA labels it a SBAS ('Satellite Based Augmentation System') differentiating it from a GBAS augmentation system.
 
CapnBob said:
Roger, I am not confused. WAAS is indeed a "Wide Area Augmentation System ". However, It is a GROUND BASED system. As LORAN was. Multipath was then and is now an issue. I believe you are confused. RADIO and MICROWAVE are the same thing, Different frequencies. As is visible light, and infrared, and ultraviolet.. It's all electromagnetic radiation.

WAAS had a ground-based component which collects the data on the GPS satellites, but it transmits the data to geosynchronous satellites which send the data to GPS receivers. It's not a radio-based navigation system like LORAN.

http://en.m.wikipedia.org/wiki/Wide_Are ... ion_System

-- Roger
 
CapnBob said:
See previous post. I was confusing WAAS with a project I worked on years ago. I stand corrected.
I hate getting old.

Sorry, I didn't mean to hit you when you were down. :)

But, I entered my post while the other one was being posted. And, I thought the Wikipedia link was still useful.

Getting old ,.. older ... isn't all bad. I have three ... wait, let me think ... one, two, three ... yes, three wonderful grand kids now. And, I can now afford cool toys like the Phantom 2 Vision.

-- Roger
 
WAAS uses a network of ground-based reference stations, in North America and Hawaii, to measure small variations in the GPS satellites' signals in the western hemisphere. Measurements from the reference stations are routed to master stations, which queue the received Deviation Correction (DC) and send the correction messages to geostationary WAAS satellites in a timely manner (every 5 seconds or better). Those satellites broadcast the correction messages back to Earth, where WAAS-enabled GPS receivers use the corrections while computing their positions to improve accuracy.

see: http://en.wikipedia.org/wiki/Wide_Area_ ... ion_System
 

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