# USRP for GPS

**URL:** <https://www.ruby-forum.com/t/usrp-for-gps/212450>\
**Category:** GNU Radio\
**Created:** [October 3, 2011, 5:01pm UTC](https://www.ruby-forum.com/t/usrp-for-gps/212450 "2011-10-03T17:01:46Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\
**Post date:** [October 3, 2011, 5:01pm UTC](https://www.ruby-forum.com/t/usrp-for-gps/212450/1 "2011-10-03T17:01:46Z")

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hi,

i was wondering whether the usrp can be used as a “gps receiver”. if so,

1. how can i achieve this?

2. any link you could provide for me to read?

3. what daughterboards should be used?

4. Can the usrp be used with OpenGTS (for example) for tracking (usrp as  
a gps receiver)?

thanks in advance,  
walter

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**Author:** ![w\_barnes](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f08c70/32.png) [@w\_barnes](https://www.ruby-forum.com/u/w_barnes)\
**Post date:** [October 3, 2011, 8:52pm UTC](https://www.ruby-forum.com/t/usrp-for-gps/212450/2 "2011-10-03T20:52:47Z")

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Hi Walter,

My group is using the USRP to record raw RF data at GPS and GLONASS  
frequencies. We do all of our signal processing in post right now, but  
are  
interested in developing a stand alone receiver. If you search the  
mailing  
list you’ll find some other folks who are implementing GPS receivers on  
the  
FPGA. What kind of performance metrics are you hoping to obtain? As  
far as  
the daughter boards go, we use the RFX1200 and RFX1800. I’ve also heard  
of  
people using the SBX.

I have no answer to your question regarding OpenGTS: I’m fairly new to  
this  
system as well. If you’re going to do real time tracking your best bet  
is  
probably to modify the FPGA for performance considerations. Hope this  
helps!

Ryan

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**Author:** ![w\_barnes](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f08c70/32.png) [@w\_barnes](https://www.ruby-forum.com/u/w_barnes)\
**Post date:** [October 3, 2011, 8:57pm UTC](https://www.ruby-forum.com/t/usrp-for-gps/212450/3 "2011-10-03T20:57:43Z")

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Hi Ryan,

Thanks very much for your answer! You mean you are inetersted in  
developing a stand alone receiver “with” the USRP?

I’m sorry, what do you mean by performance metrics?

thanks again,  
Walter

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<div class="post-metadata">

**Author:** ![w\_barnes](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f08c70/32.png) [@w\_barnes](https://www.ruby-forum.com/u/w_barnes)\
**Post date:** [October 4, 2011, 6:38pm UTC](https://www.ruby-forum.com/t/usrp-for-gps/212450/4 "2011-10-04T18:38:00Z")

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Walter,

Currently the receiver that triggers our USRPs to record the RF data is  
quite expensive. We don’t use all of its features, but it has a few key  
parameters that are used in our trigger threshold calculation. If we  
deploy  
this same system to another location we’d like to have a USRP function  
as  
the trigger. In that sense we are interested in using the USRP as a  
GNSS  
receiver, but our goal isn’t to get a position solution.

As far as performance metrics go, you need to define a few parameters  
for  
your receiver before settling on the USRP as a host. The two that pop  
into  
my mind right away are: 1.) which GPS signal(s) do you want to use and  
2.)  
how many channels do you hope to track? If I recall correctly, there’s  
a  
thread somewhere on this list where a group used the old USRP1 and  
modified  
the FPGA to do 4 channel tracking with fast acquisition.

Regards,  
Ryan