[FOSS-GPS] Mobile Robot Experimentation

Wed Sep 17 19:01:09 PDT 2014

Hello Felipe,

What do you mean by “process base versus CORS”?  Do you mean running rtknavi with the CORS as an input?

The Rover was operating within 30m of the base, but I can try it closer if that would help.

On the next test, I will let the Rover idle for a while before starting the test.  The antenna (or rather the steel plate) is the highest point on the robot (by about 30cm).  The base, however is rather low to the ground and I am trying to build something to elevate it more.

-Sean

From: foss-gps-bounces at lists.osgeo.org [mailto:foss-gps-bounces at lists.osgeo.org] On Behalf Of Felipe G. Nievinski
Sent: Wednesday, September 17, 2014 9:50 PM
To: foss-gps at lists.osgeo.org
Subject: Re: [FOSS-GPS] Mobile Robot Experimentation

before anything else, check what accuracy you get 

with the rover parked for a couple of hours. 

to isolate which one between rover and base 

is noisier, download data from the nearby CORS, 

then process your base versus CORS and your rover

versus CORS separately.

keep your base as close as possible to the rover.

that's the best way to mitigate iono delay 

without dual-frequency tracking data.

turn on the GPS on the rover for some time 

before it departs, as it should help with 

ambiguity resolution.

try to elevate the antenna above the body

of the robot, so as to minimize multipath 

and EM interference.

On Wed, Sep 17, 2014 at 6:06 PM, <foss-gps-request at lists.osgeo.org <mailto:foss-gps-request at lists.osgeo.org> > wrote:

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Today's Topics:

   1. Mobile Robot Experimentation (Sean Hyde)

----------------------------------------------------------------------

Message: 1
Date: Wed, 17 Sep 2014 17:05:35 -0400
From: "Sean Hyde" <sean.a.hyde at gmail.com <mailto:sean.a.hyde at gmail.com> >
To: <foss-gps at lists.osgeo.org <mailto:foss-gps at lists.osgeo.org> >
Subject: [FOSS-GPS] Mobile Robot Experimentation
Message-ID: <0ddc01cfd2bb$20551d40$60ff57c0$@gmail.com <http://gmail.com> >
Content-Type: text/plain; charset="us-ascii"

Hey Guys,

I've been playing around with RTKLib for a couple months now and have run
into some issues and I was wondering if anyone had any idea on how to
improve performance.

---Setup---

Base Station:

NVS08C on custom PCB using the receiver to power the antenna

Antenna is Taoglas Limited AA.161.301111
(http://www.taoglas.com/images/product_images/original_images/AA.161.301111. <http://www.taoglas.com/images/product_images/original_images/AA.161.301111.pdf> 
pdf)

Antenna is on a 12" x 24" steel plate

Connected via FTDI->USB to Rasperry Pi

Raspberry Pi runs str2str to send the data to Windows laptop running rtknavi
using wifi backhaul

Rover:

NVS08C on custom PCB using the receiver to power the antenna

Antenna is Taoglas Limited AA.161.301111
(http://www.taoglas.com/images/product_images/original_images/AA.161.301111. <http://www.taoglas.com/images/product_images/original_images/AA.161.301111.pdf> 
pdf)

Antenna is on a 18" x 18" steel plate

Connected via FTDI->USB to Rasperry Pi

Raspberry Pi runs str2str to send the data to Windows laptop running rtknavi
using wifi backhaul

The Rover setup is on a small mobile robot with a top speed of about 3mph.
It is in a city (Pittsburgh), but the sky is relatively unobstructed.

I'm running rtknavi in Kinematic mode using only GPS, L1+L2, 15deg elevation
mask.  The position that I input for the base station is a 5 hour average
(though it seems to have lost some precision when I pasted it?).  I have
tried both Continuous and Fix and Hold Integer Ambiguity Res.  I'll try to
attach screen shots of rtknavi.

Right now, it kind of works.  I can get relatively jitter-free floats and
occasionally fixes, but these fixes don't last long and I'm not sure they
are actually globally accurate (ie: if you restart the software, you may get
a fix, but it may be several meters from your last fix).  Sometimes a fix
goes away and never seems to come back.

I'm wondering if you guys have any suggestions to improve these results.

Better antennas? (Which ones?)

Trying to get better placement of the base station?

Different settings in rtknavi?

Continuous vs Fix and Hold?

Thanks!

-Sean

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