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Description of the task:
-Describe what kind of output comes from the Matlab code that processes 
the GPS data
-Note any files, resources that are in the project for further info

Please update the issue with any progress you've made.

Original issue reported on code.google.com by c.shi...@gmail.com on 27 Oct 2009 at 5:13

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One of the functions used in Matlab is the acquisition function; this function 
finds signal parameters for all 
available satellites in the data.
 acquisition(longsignal, Settings) were longsignal is the 11 ms raw data, and Setting are  established by typing 
initSettings().
The postnavigation functions converts the ECEF (Earth-Centered & Earth-fixed) 
coordinates into UTM (Universal 
Transverse Mercator) coordinate system, a grid-based method of specifying 
locations on the surface of the 
Earth. 

Original comment by eidyn...@gmail.com on 27 Oct 2009 at 10:06

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So running the Matlab Code is easier than I thought; after playing with it for 
a long time I figured out that all 
we need to do is:

1) call the function initSettings()
2)Run the code in the file postprocessing.m, which already calls the functions 
needed (acquisition, tracking, 
and postnavigation functions). Remember the last function converts coordinates 
from the WGS84 system to 
the UTM coordinate system.

I tried to run the code with the sample capture from the previous team , and 
Matlab could not detect any 
GNSS signals, so we probably need to get a new sample of data. 

Original comment by eidyn...@gmail.com on 10 Nov 2009 at 6:58

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I took the SiGe chip and the antenna with me during the weekend and captured a 
lot of data samples that 
actually worked. I am attaching the final figure from the Matlab code, which 
gives the coordinates; I put them in 
google maps and google earth to verify that they were correct.

Original comment by eidyn...@gmail.com on 24 Nov 2009 at 5:24

Attachments:

• coordinates.jpg

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File used to capture data.

Original comment by eidyn...@gmail.com on 31 Dec 2009 at 7:39

Attachments:

• GN3Sv2.exe

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From Adrian, our GPS guru...

Tell them to look into research papers with the following keywords:

Snapshot GPS
microGPS from JPL
GDGPS and APPS from JPL
TIDGET from NAVSYS

Specifically, the problem that they need to address is this:

Navigation solution requires pseudoranges and ephemerides from four satellites. 
Satellite acquisition provides 
you with code phase and Doppler shift. With only one second of data, it is not 
possible to do tracking or 
obtain the satellite ephemerides. Luckily, you can obtain the ephemerides after 
the fact from places online 
(e.g. IGS). You can also obtain atmospheric corrections too (e.g. GDGPS).

The tricky part of this project is that the code phase gives you a very 
accurate distance (pseudorange) to the 
satellite, but with an inherent ambiguity. It is like measuring the distance 
from Livermore, CA to Salt Lake City, 
UT and reporting that the distance is x meters and 12 centimeters. You know the 
distance to a good accuracy 
(the code phase), but the code phase repeats over and over and over. This is 
known as the integer millisecond 
ambiguity. Be careful when referring to GPS papers, because they will sometimes 
discuss the "integer 
ambiguity" but that refers to the carrier phase. Usually, you can resolve the 
integer millisecond ambiguity 
simply by looking at the navigation message broadcast by the satellites. That 
message reports when the data 
was sent (referred to as Time of Week or TOW) to an accuracy of about six 
seconds, if I recall correctly. By 
knowing the rough position of the satellites, you can resolve the integer 
ambiguity.

Try looking into this topic and seeing if you can understand the problem. You 
want to translate CODE PHASE 
to PSEUDORANGE. This can be done either by observing the TOW or by solving for 
the integer ambiguity with 
additional data in post processing.

Once you have valid pseudoranges, it is very easy to calculate the GPS 
navigation solution.

Some links: http://www3.sympatico.ca/craymer/geodesy/gps.html

-----Original Message-----
From: Eidy Carvajal [mailto:eidy.carvajal@utah.edu]
Sent: Tuesday, January 19, 2010 11:11 PM
To: Paradise, Steven
Subject: RE: Weekly report, 19 January

Steven,

I did not write this code, it is a piece of the MATLAB code that was provided 
to us at the beginning of the 
project. I believe it came with the book "A software defined GPS and Galileo 
receiver".
The "status" is the mode of the tracking channel,  "off" meaning there is no 
signal to track and "T" meaning 
the channel is in tracking state.

I have performed several tests with different data sizes that I captured (from 
1 sec to 40 sec) and this are the 
results so far:
For a 40 seconds sample, able to obtain the satellites information during 
acquisition, code and carrier 
tracking for each channel, and finally the navigation solutions. 
For 32 and 16 sec, the satellite's acquisition and tracking.
For a 1 sec, only the satellite's acquisition. (that was the table we sent you).

I would like to be able to obtain navigation solutions with any size of data,  
what step would you recommend 
next?
Thank you for help and time,

Eidy

________________________________________
From: Paradise, Steven [sparadi@sandia.gov]
Sent: Tuesday, January 19, 2010 6:07 PM
To: Eidy Carvajal
Subject: FW: Weekly report, 19 January

Eidy,

Excellent job.  Did you write this code yourself, or did you get it somewhere?  
Also, what does the "status" 
mean?

Thanks,

Steven

Original comment by eidyn...@gmail.com on 25 Jan 2010 at 6:59

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