Another study I am carrying out is how much benefit the availability of
Glonass satellites really brings. Low-cost dual constellation GPS-Glonass standalone receiver are starting to show up in the market:
Skytraq released the S4554GNS-LP and the S2525G2F, and
NVS is soon coming out with their
NV08C.
Well, I assembled a few S455GNS-LP on a carrier board:
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Figure 1: Kopeke10 USB GPS-GLonass receiver |
..and drove in the countryside doing some tests.
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Figure 2: Test drive with two dual constellation antennas: a non-branded one (20EUR, left) and a Tallysman TW2400 (80EUR, right). |
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On the left antenna I had:
- a S1315F-RAW
- a S4554GNS-LP
on the right antenna I had:
- a uBlox LEA-5H evaluation kit
- a S1315F-RAW
- a S4554GNS-LP
So that I would make sure to test my receivers with both antennas and compare them against a good reference. Some preliminary results are shown below.
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Figure 3. The roundabout is always good to test how much filtering the PVT solution has. Considering that Google Earth might not necessarily be super-accurate, all the receivers perform pretty well. |
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Figure 4. Driving under a big junction does not affect the receivers very much. Well done! |
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Figure 5. Uhm? What the heck is that? The Skytraq receiver obviously picked up quite a bit of multipath from the South-East building when I stopped. The good LEA-5H -on the same antenna- did not make a move, and neither the other S4554GNS-LP. |
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Figure 6. Approching a parking slot just after the road bends, running along a bunch of trees. Multipath has again an interesting different effect on the receivers. But I am more likely to have parked where the uBlox said :) |
I will soon add some results in urban environment, where having twice as many satellites should make a real difference.
EDIT 26/08/2011:
Recently, I went out again to compare data from the Sytraq S455GNS-LP and a NVS NV08C-CSM which I soldered onto a carrier board called Denga10 (shown below). The antenna was a low-cost GPS/Glonass magnet-mount patch.
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Figure 7. Denga10 carrier board for NV08C-CSM GPS/Glonass receiver. |
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NVS provides easy software to manage their receivers and translate what is a unconventional NMEA stream:
$GPGGA,203211.00,4340.7619,N,01020.8364,E,2,14,00.8,002.0,M,47.9,M,,*59
$GPRMC,203211.00,A,4340.7619,N,01020.8364,E,00.00,218.2,020811,,,D*5B
$GPGSV,4,1,13,03,65,155,48,06,53,140,47,11,32,282,44,14,24,117,41*7D
$GPGSV,4,2,13,16,19,193,46,18,22,048,41,19,77,307,49,22,58,066,48*7B
$GPGSV,4,3,13,24,21,268,41,32,14,210,40,33,33,214,43,37,38,164,41*7A
$GPGSV,4,4,13,39,37,159,00*48
$GLGSV,2,1,06,66,55,046,46,73,09,307,24,74,05,353,20,81,52,106,38*6C
$GLGSV,2,2,06,82,62,338,44,83,12,313,01*6D
$GNGSA,A,3,03,14,19,06,24,32,22,16,11,18,,,01.3,00.8,01.0*16
$GNGSA,A,3,66,73,82,81,,,,,,,,,01.3,00.8,01.0*10
$PORZD,A,002.8*36
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Figure 8. Navis converter to generate a KML from the GPS/Glonass NMEA output of the NV08C-CSM |
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Also Skytraq is working hard and recently added a GNS Viewer to their software in order to allow customers to quickly evaluate what is again a non conventional NMEA stream:
$GNGNS,203211.170,4340.7630,N,01020.8350,E,AA,16,0.7,14.1,45.7,,0000*53
$GNGSA,A,3,03,06,22,14,18,19,24,32,11,16,,,1.1,0.7,0.9*23
$GNGSA,A,3,66,81,82,73,65,74,,,,,,,1.1,0.7,0.9*25
$GPGSV,3,1,12,19,77,308,49,03,65,155,49,22,58,067,48,06,54,141,46*7B
$GPGSV,3,2,12,11,32,283,44,14,24,118,40,18,23,049,41,24,21,268,40*71
$GPGSV,3,3,12,16,19,194,46,32,14,210,40,28,02,333,,08,00,299,*79
$GLGSV,3,1,09,82,62,338,44,66,56,047,47,81,52,106,37,83,12,314,15*6C
$GLGSV,3,2,09,73,10,307,24,74,06,354,32,65,05,030,32,88,03,125,*6D
$GLGSV,3,3,09,80,00,261,*51
$GNRMC,203211.170,A,4340.7630,N,01020.8350,E,000.0,221.9,020811,,,A*7B
$GNVTG,221.9,T,,M,000.0,N,000.0,K,A*1B
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Figure 9. Skytraq GNS Viewer. |
Some results are shown below. Seems that the NVS tends to filter a bit too much. Luckily it's possible to upgrade the firmware of these receivers and hopefully NVS has already worked on it to improve accuracy.
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Figures 10. The NVS receiver tends to filter too much compared to the Skytraq. |
EDIT 07/12/2011: NVS released recently a new firmware for their NVS08C-CSM. I will update Denga10 and have another test session very soon!
Questions?
To be continued (again),
Michele