GPS + Glonass Using the Best of Both Worlds

10 I 12 TELIT WHITE PAPER
GPS + Glonass
Using the Best of
Both Worlds
Jupiter SL869
Jupiter JN3
Jupiter SE880
IMPROVE TIME-TO-FIRST-FIX
GET MORE ACCURATE POSITIONING
ENHANCE TIME IN NAVIGATION
COLLECT MOST RELIABLE PROBE-DATA
TABLE OF CONTENTS:
EXECUTIVE SUMMARY
1.
2.
3.
3.1.
3.2.
4.
4.1.
4.2.
4.3.
5.
GPS and GLONASS Technology Background Information
Restrictions of GPS-Only
Combining GPS & GLONASS
Test studies in Los Angeles,
London and Johannesburg
Central Findings
The Telit difference
Telit Jupiter SL869
Telit Jupiter JN3
Telit Jupiter SE880
About Telit
10 I 12 TELIT WHITE PAPER
EXECUTIVE SUMMARY
At the end of 2011 the Russian government announced that GLONASS,
the Russian Global Navigation Satellite System (GNSS), is fully operational and has global coverage. Experts at Telit decided to test what
impact this has on satellite navigation and positioning. They conducted
tests in Los Angeles, London and Johannesburg to see the relevance of
GLONASS for the whole world. The results clearly showed that the
combination of GPS and GLONASS improves positioning tremendously.
Especially in urban canyons with huge skyscrapers the receiver had
the ability to track at least four satellites and thus calculate a fix –
which was impossible to guaranty using only GPS. Thanks to the SL869,
a newly released Global Navigation Satellite System (GNSS) module
from Telit that has access to both GLONASS and GPS, blind spots
were reduced and navigation performance was radically improved. This
white paper shows the test set-up and examines the results. For the
future further tests are planned.
3
1. GPS AND GLONASS TECHNOLOGY
Radio-based Global Navigation Satellite Systems
(GNSS) are part of our daily life for navigation, surveying and mapping. Although there are several GNSS
like the European Galileo or the Chinese Beidou, the
US GPS is the most popular one providing global coverage and used widely in navigation systems. Today
there are 31 GPS satellites that are operational, plus
3-4 decommissioned satellites that can be reactivated
if needed.
Since October 2011 the Russian GLONASS has been
fully operational with 24 satellites in orbit plus four in
reserve and one currently undergoing trials. This is
not only an alternative to GPS but, even more, the
completion of a combined GPS/GLONASS system
where there are in total 55 fully operational satellites
in outer space in different orbits (see picture 1). For
satellite navigation at least 4 satellites are needed to
determine a position solution: three to provide the
data for each space axis (x, y and z) and one to provide
the time sent. The more satellites that can be tracked,
4
the more accurate the fix will be. In theory this is possible with GPS-only as there should always be at least
5 satellites visible anywhere on the Earth’s surface. If
there is an unobstructed view of the sky even 12 satellites can be visible. But often there are buildings,
trees, mountains or clouds blocking some of the GPS
signals, and the GPS receiver is unable to obtain a
position fix.
10 I 12 TELIT WHITE PAPER
2. RESTRICTIONS OF GPS-ONLY
further in urban environments. This makes it a real
challenge to isolate them from background noise.
To overcome the limitations of GPS-only navigation,
the Telit engineers decided to launch a combined solution of GPS and GLONASS. The fact that there are
now in total 55 satellites operating in different orbits
covering the whole globe must have an impact on navigation and should provide advantages.
Especially in mega-cities with many skyscrapers, satellite signals are often lost. For fleet management as
well as for other types of tracking applications this
condition can be unacceptable. In addition there are
further restrictions of GPS-only navigation: GPS satellites orbit the earth from a distance of 20,000 kilometers. Their signals are barely -130 dBm once they
reach a terres-trial receiver, and are degraded even
Picture 1:
Orbits of different GNSS
Orbital period
GALILEO
GPS
Geostationary
Earth Orbit
20 hours
Compass
MEO satellites
GLONASS
15 hours
10 hours
5 hours
Radius of
orbit
40 Mm
Iridium
30 Mm
20000
miles
20 Mm
10 Mm
10000
miles
15000 mph
Height above
sea level
Hubble
10 Mm
ISS
25000 km/h
20 Mm
10000
miles
30 Mm
20000
miles
20000 km/h
10000 mph
15000 km/h
Orbital speed
5
Orbital speed
15000 km/h
10000 mph
20000 km/h
miles
20000
miles
10000
15000 mph
25000 km/h
ISS
miles
10000
miles
20000
3. COMBINING GPS & GLONASS
3.1. Test studies in Los Angeles, London and
Johannesburg
In February 2012 the Telit GNSS engineers decided to
run a field test comparing the navigation accuracy of
GPS only receivers and GPS+GLONASS receivers. The
team did seven test tracks between 11:00 a.m. and
3:00 p.m. in Downtown Los Angeles. They tested
several standard GPS only units in comparison to the
Jupiter SL869, Telit’s new GNSS module which processes both GPS and GLONASS signals. The results
were always very similar: Combining GPS and GLONASS
provided much more accurate and better positioning
possibilities instead of GPS only – see picture 2.
The picture shows a single test track. The red line represents GPS only. It shows that during the test track
there were several instances where GPS was not able
Picture 2:
Tracked way in Los Angeles. Green
shows the route which was driven with
GPS & GLONASS receiver, red the same
route with a standard GPS-only receiver.
6
to determine a position solution. With a GPS+GLONASS
receiver this didn’t happen – the receiver never lost
the signal. Furthermore there is a huge difference in
the accuracy of ground track.
With GPS there were several meters tracked off-road,
means the track was not on the street but next to it.
With GPS+GLONASS the positioning was very accurate and it didn’t happen at all.
Tracked way in Los Angeles.
10 I 12 TELIT WHITE PAPER
A similar study was conducted in London on March,
20th 2012 monitoring the number of satellites used
by a GPS-only receiver and by a GPS+GLONASS receiver. The findings were the same as in Los Angeles: Because of signal blockages in London caused
by five story buildings, the number of tracked GPS
satellites dropped below four (picture 3). Thus the
GPS-only receiver lost its fix point. This happened
three times, of which the time around 3:00 p.m. was
the most critical one. At that time the receiver had
no track for app. 20 minutes.
Tracked satellites.
10
The third test was conducted in Johannesburg, South
Africa to verify the availability and advantages of GPS
and GLONASS in the southern hemisphere. The results in South Africa were similar to the results in
London and Los Angeles: With approximately 18 satellites used for the fix with GPS and GLONASS in
comparison to 6-8 satellites with GPS-only, not only
does the number of visible satellites double, time in
navigation improves and a fix is virtually guaranteed.
8
7
Tracked satellites.
6
5
4
20
3
18
2
1
0
00:00
03:00
06:00
09:00
12:00
15:00
18:00
21:00
24:00
Number of Satellites
Number of Satellites
9
The same test tracking was done with GPS+GLONASS.
It showed that there are always more than 4 satellites
in track. A fix is virtually guaranteed (picture 4). In
addition even up to 15 satellites were tracked in the
middle of London were it wasn’t possible to track
more than 8 satellites with GPS-only. That nearly
doubled the available satellites.
16
14
12
10
8
6
4
2
0
Picture 3:
The picture shows the number of satellites
00:00
03:00
06:00
09:00
12:00
15:00
18:00
21:00
24:00
Picture 4:
that were in track in London March, 20. Dark
The picture shows the number of satellites
green shows times where the number of
that were in track in London March, 20 with GPS
satellites drops below 4.
+GLONASS. The number never drops below 6.
7
3.2. Central Findings
Thanks to the addition of GLONASS, the number of
tracked satellites never drops below six in the
tested environments, and the problem of lost
satellite coverage, especially problematic in urban
canyons with tall buildings, is dramatically reduced. Furthermore the test showed that also the
accuracy of positioning is significant improved. In
addition the team noticed an improved time-to-fix
which is for example vital for Stolen-Vehicle-Recovery
where it is crucial to locate the vehicle no matter
where it is. Accessing the combined GPS/GLONASS
constellations is thus a major step forward in navigation, providing the best satellite geometry to obtain the most accurate position possible more often
– not only in Russia but all over the world. Finally,
this enables a more accurate positioning, a better
“pinning” of a person, a car or an asset’s true location
on a digital map.
GNSS Satellites Used
20
18
GPS Satellites Used
Number of Satellites
16
Number of Satellites
10
8
6
14
12
10
8
6
4
2
0
4
0
5
10
15
20
25
30
2
0
0
8
5
10
15
20
25
30
35
40
45
50
55 60
Minutes
35
40
45
50
55 60
Minutes
Picture 6:
Number of satellites used for the position
Picture 5:
fix with GPS and GLONASS during the same
Number of satellites used for the position fix
hour in Johannesburg, South Africa. The
with GPS-only receiver during one hour in
visible satellites doubles, positioning is
Johannesburg, South Africa.
significantly improved.
10 I 12 TELIT WHITE PAPER
4. THE TELIT DIFFERENCE
4.1. Jupiter SL869 GNSS modules
In Los Angeles the Telit team tested the Jupiter SL869,
a new series of GNSS modules from Telit. These
tests clearly showed that the SL869 maximizes the
performance over GPS alone by utilizing both the GPS
satellites plus the GLONASS. The results are: Higher
percentage in navigation, faster acquisitions and more
precise and accurate position.
The Jupiter SL869 is a state-of-the-art 32-channel
global navigation module able to receive, track and
navigate using the entire spectrum of GNSS systems
available in the world: GPS, GLONASS and QZSS,
furthermore it is Galileo and Beidou ready.
The extreme low profile and small size of the LCC
package enables the design of ultra-compact applications. The solution cost and required space is significantly reduced. With its ultra-compact design and
extended temperature range, the Jupiter SL869 is a
multi-constellation receiver that is ideal for low,
medium and high-volume M2M combined applications and mobile/tracking data devices. The results
are: Higher percentage in navigation etc.
Jupiter SL869
GPS | GLONASS
16 x 12.2 x 2.4 mm
Equipped with a powerful yet power saving processor,
the module provides all the GNSS information via NMEA
standard protocol on a serial interface. The Telit Jupiter
SL869 can efficiently retrieve the correct position in
harsh environments using multiple GNSS constellations and SBAS as well as real-time ephemeris data.
4.2. Jupiter JN3 GNSS module
Although the combination of
GPS and GLONASS provides huge advantages, there
are also price differences. So in cases where a very
accurate position is not needed, but cents make a difference to a competitor, a GPS-only module would be
sufficient. Therefore Telit provides the Jupiter JN3
which is pin-to-pin compatible to the SL869. So customers need only one design for the two alternatives
and can migrate whenever needed to one or the other
without any problems.
The Jupiter JN3 is a state-of-the-art 48-channel GPS
module with high sensitivity, extremely low power
consumption, and extended ephemeris predictions for
fastest TTFF. Coupled with a Telit GSM/GPRS module,
the Jupiter JN3 represents the ideal wireless+GPS
solution in terms of total cost effectiveness and
Jupiter JN3
GPS
16 x 12.2 x 2.4 mm
9
time-to-market readiness. The extreme low profile
and small size of the LCC package enables the design
of ultra-compact applications. The solution cost and
required space is significantly reduced. With its ultracompact design and extended temperature range, the
Telit Jupiter JN3 is the perfect module for low, medium and high-volume M2M combined applications and
mobile/tracking data devices. Thus Telit can always
provide the perfect module for every need.
Original size
4.7 x 4.7 mm
4.3. Jupiter SE880 – the smallest GPS receiver in
the market
Telit offers the smallest GPS receiver in the market,
the SE880, which is ideally suited for applications
in the commercial, industrial, and consumer segments including wearable and handheld devices.
DE910-DUAL
Also Telit’s DE910-DUAL features a GPS and
GLONASS receiver that improves time for navigation and tracking performance in limited sky
environments as well as additional benefits descripted in this White Paper. The DE910-DUAL
is a 3G CDMA 1x EV-DO Rev A module with built
in GNSS receiver that is part of the Telit’s xE910
Family. The family features a single, compact
form factor that is interchangeable on any regional cellular network and across technologies, delivering ubiquitous, cost-effective coverage for m2m applications.
The miniature 4.7x4.7mm LGA (Land Grid Array),
SiRFstarIV™-based receiver module employs leading 3-D component embedding technology to achieve
best-in-class performance in all dimensions critical
for regular or size-constrained GPS applications.
Because of this extreme sensitivity with -148dBm,
the 48-channel receiver can reduce cold start Timeto-First-Fix (TTFF) by more than 3 minutes. In addition it allows class-unique achievements such as a
one-satellite acquisition of UTC (typically 4 are required) and fix acquisition with minimal sky-visibility
– garages, urban canyons, etc. Even indoor fixes are
possible in less than 200 seconds.
For more information about the
Telit xE910 family please visit
www.telit.com or check the
QR-code.
10
DE910-DUAL
CDMA | 1xEV-DO Rev.A
28.2 x 28.2 x 2.4 mm
Jupiter SE880
GPS
4.7 x 4.7 x 1.4 mm
10 I 12 TELIT WHITE PAPER
Telit’s Jupiter SE880 includes all components necessary for a fully functioning receiver design requiring
only a 32 KHz external crystal for its time-base and
TCXO to complete the design, along with antenna,
power and data connections adequate to the integrator’s needs. The SE880 receiver module was conceived to shorten Time-to-Market and to make the
chipset-versus-module decision an easy one to
make for device integrators. Integrators can attain a
working SE880-based design in as little as a week
versus several months when starting from a chipset
reference design.
In addition the Jupiter SE880 has a multi-filter system
which includes not only the traditional SAW filters typical in GPS receiver designs but also a 2.4 GHz notchfilter capable of nullifying the jamming effects of highenergy radio devices such as Wi-Fi hot-spots, Bluetooth
systems, and others, which greatly affect a GPS receiver’s ability to resolve timid satellite signals in the hostile radio environment where they need to operate.
Other distinguishing features of the Jupiter SE880 include an extended operating temperature range
wherein noise-versus-gain performance is linearly
balanced throughout the range with class-leading
sensitivity stability particularly at the extremes of -40
and +85°C – critical for applications such as sports
watches and OEM automotiv navigation systems. For
more information about the Telit
SE880 please visit www.telit.com or
check the QR-code.
5. ABOUT TELIT
Telit Wireless Solutions is a brand of Telit Communications PLC (AIM: TCM), an enabler of machine-to-machine (M2M) communications worldwide providing
wireless module technology, M2M managed services
and value added services, including connectivity. Exclusively dedicated to M2M with more than 12 years of
experience in the market, the company constantly enhances its technology leadership with six R&D centers
across the globe. Telit offers an extensive portfolio of
the highest quality cellular, short-range RF, and GNSS
modules, available in over 80 countries. By supplying
scalable products that are interchangeable across
families, technologies and generations, Telit is able to
keepdevelopment costs low and protect customers’
design investments. In addition, Telit is the only module
provider in the market today to offer a value added
services bundle including connectivity dedicated to
simplifying the deployment of M2M applications.
Telit provides unmatched customer support and premier design-in expertise through its 25 sales and support offices, a global distributor network of wireless
experts with more than 30 Telit-designated Competence
Centers, and its online Telit Technical Support Forum.
Telit technology enables organizations to wirelessly
collect, process and respond to real-time data creating new efficiencies and revenue opportunities as
well as societal and personal benefits. Further
information about Telit and its products can be found at
www.telit.com.
11
Contact
EMEA
Telit Communications S.p.A.
Via Stazione di Prosecco, 5/B
34010 Sgonico (Trieste), Italy
Phone: +39 040 4192 200
Email: EMEA@telit.com
Latin America
Telit Wireless Solutions Inc.
Rua Cunha Gago, 700 – cj 81, Pinheiros
São Paulo – SP, 05421001, Brazil
Phone: +55 11 3031 4051
Email: latinamerica@telit.com
North America
Telit Wireless Solutions Inc.
3131 RDU Center Drive, Suite 135
Morrisville, NC 27560, USA
Phone: +1 888 846 9773
Email: northamerica@telit.com
APAC
Telit Wireless Solutions Co. Ltd., APAC
12th floor, Shinyoung Securities Building
34-12, Yeouido-dong, Yeongdeungpo-gu
Seoul, 150-884, Korea
Phone: +82 2 368 4600
Email: APAC@telit.com
www.telit.com/ebook
www.telit.com/facebook
www.telit.com/techforum
www.telit.com/twitter