fixing GPS altitude accuracy

If you’ve ever used your GPS navigation system in your vehicle or just on your smartphone you know it can pinpoint your location dead on in horizontal space. The same can not be told for altitude though. GPS is not very accurate when it comes to figuring out how high you are. This has been known issue since GPS has been around but finally some research scientists are bringing a solution to the table.

Dorota Grejner-Brzezinska, a professor Ohio State University and her colleagues at University of Warmia and Mazury in Poland are developing a software that can bring centimeter accuracy to altitude calculations. It is quite complicated but in the heart of the problem is the atmospheric changes that effect the time it take for GPS signals to reach ground based receivers. So her and her team tested receivers tested some GPS receivers at different altitudes and distances from each other - and tested their in-house software. One of their algorithms provided accurate location, including the height of the receivers, 97% of the time…

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LightSquared has no solution to GPS interference problem

Coalition to Save Our GPS has ripped apart the press release from LightSquared that announces a ‘solution’ that is really not a solution at all. Here are a few snippets from the coalition’s press release [pdf]

  • LightSquared’s claim that lower band operations would be largely free of interference for non-high precision GPS users is simply not true.
  • Even LightSquared admits that operation in the lower MSS band will not solve the interference problem for high precision uses. It fails to note that the harmful interference rate is 94 percent and the critical importance of those high precision users.
  • LightSquared’s proposal to “reduce” its permitted operating power actually represents an increase in power above the levels shown to create interference in recent tests.
  • LightSquared is still proposing to operate in the upper MSS band in the future, despite overwhelming evidence of massive interference and no credible support for any future technical solution.

Lightsquared buys more time to turn in GPS test results

LightSquared just got granted a two-week extension by federal regulators to turn in their report on tests that will determine whether their proposed high-speed wireless network would interfere with GPS signals all over the U.S.

The group studying the potential interference is mandated by the FCC is controlled by LightSquared but includes industry professional from GPS makers and users, and even federal agencies that rely on GPS technology.

LightSquared asked for more time to file their results which raises more questions whether the FCC will allow them to proceed with their new 4th generation wireless network that could compete AT&T and Verizon’s own networks.

The heart of the story is that GPS makers and users claim super powerful LightSquared towers (40 thousand of them) would interfere with relatively weaker GPS signals that would use a band that sits right next to GPS frequency.

The latest so far is that FCC gave LightSquared approval in January to build the system, but they have to stay on hold until GPS interference claims are resolved.

GPS and GLONASS integration

There’s an interesting article on GPS World from Javad Ashjaee. Javad started his GPS engineering career at Trimble Navigation, 1981-1986; was the founder and president of Ashtech Inc., 1986-1995; founder and CEO of Javad Positioning Systems, 1996-2000, which he sold to Topcon Corporation in 2000. He is currently president and CEO of Javad Navigation Systems.

In the early days of my frequent travels to Russia, the KGB probably suspected that I was a CIA agent — and the CIA probably suspected that I was a KGB agent! I would not be surprised if both the CIA and KGB monitored every bit of my travels and activities. After some years, the San Francisco airport authorities stopped interrogating me for my activities in Russia any time I came back home. Perhaps because of their deep investigations, I earned the trust and friendship of both sides, and their confidence that I had nothing in mind other than helping to integrate GPS and GLONASS.

DeLorme inReach two-way satellite communicator

This is DeLorme’s new two-way satellite GPS communicator. It is called DeLorme inReach and this device you see up here works on it’s own, with DeLorme PN-60W, or with any Android smartphone. It gives you global coverage using the Iridium satellites.

One of the biggest advantages of having two-way connectivity when you’re out in the wilderness (and in serious trouble) is that once you request emergency help you’ll get a feedback from search and rescue services telling you that they’re on their way.

Straight from DeLorme’s blog:

When using the device as a standalone, you will be able to send tracking locations as well as three different messages you’ve created ahead of time. SOS messages can be sent to search and rescue and they’ll be able to respond by triggering a change in the SOS LED on the inReach device to let you know that they heard you and are taking action.

Pairing the DeLorme inReach with either a PN-60w or an Android device allows you to type up to 160 characters and send your message to friends and family using either e-mail or SMS text message addresses. Don’t worry about building your contact list ahead of time anymore, you can send messages to new addresses right in the field. Communicate important information, change your plans, or just check in to let everyone know that you are okay. Send your message to Twitter and Facebook or a shared map to let them watch your progress and send you a message.

Here are some other details - You’ll have to wait until October to get a DeLorme inReach. It will cost you $250. The cheapest messaging plan is $10/month and you’ll need at least one year of service. The device is IPX7 waterproof and it floats. Battery tests are still in progress but the device has shown the ability to send messages up to 7 days. Lot’s of other details here.

India ready to put navigation satellite in orbit

India is really close to putting a new navigation satellite in orbit. The multi purpose satellite will be carried into orbit on an Ariane 5 mission from the French Guiana - which should be on May 11th if all goes well.

The satellite is called GSAT-8 and will weigh 3150kg and have a payload power equaling 5300 Watts. It carries 18 Ku-band transponders for various communication tasks but also carries GPS aided Geo Augmented Navigation payload - also known as GAGAN.

It is expected to have a lifespan of 12 years.

Save Our GPS (from 4G signals)

Back in February we talked about Garmin and Trimble’s report on interference to GPS signals that will be caused by the proposed 40,000 LTE network transmitters. The issue is still going on - and there is even a group: “Save Our GPS”, a coalition of industry leaders and companies that are trying to make FCC re-think their decision.

FCC granted a waiver allowing LightSquared - the company behind the proposed 40,000 ground transmitters - to repurpose the satellite spectrum right next to GPS signals (1525 MHz—1559 MHz vs 1559—1610 MHz) which could result in severe interference with the low powered signals that reach us from the orbit.

LightSquared will be competing with ClearWire to wholesale bandwidth for LTE (long term evolution) starting with a few markets third quarter of this year and covering 250 million Americans by the end of 2015. Even though the company says their launch schedule is still on track they now have to meet a few FCC mandates.

It is not only the Save Our GPS coalition but even Department of Defense and Department of Transportation that is voicing their concerns since GPS receivers are used for many things in their line of work (9 uses of GPS…). So now LightSquared is investigating the issue through an FCC-mandated working group; namely the United States Global Positioning System Industry Council (USGIC).

Jeff Carlisle, VP of LightSquared, says the company is cooperating with government agencies to address any potential problems with their GPS systems.

“We are sensitive to concerns about potential interference which is why we have fully committed ourselves to a comprehensive process that will ensure our network can coexist with GPS devices and agreed to only launch commercial operations when this process is completed to the FCC’s satisfaction.”

SkyTraq GLONASS/GPS receiver

SkyTraq of Taiwan just recently announced a receiver that is both compatible with GPS and GLONASS satellites. The dual purpose GLONASS/GPS receiver only measures 25mmx25mm in size and can function as a drop-in replacement to upgrade any GPS receiver into a GLONASS/GPS receiver (of course you’d need a dual frequency antenna too) making it suitable for manufacturers that want to update their lineup.

SkyTraq’s new receiver boasts 29 second cold start TTFF (time to first fix), -145dBm cold starting and -159dBm navigation sensitivity. It can 12 track channels for GPS-only mode, 12 channels for GLONASS-only mode, and 24 tracking channel when combined. It actually combines multipath detection and mitigation algorithm to provide tracking in difficult urban canyon and deep foliage environments…

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China is close to having their own satellite navigation network

China has been planning a network of GPS satellites for a while now. It is called Beidou and it is definitely taking a long time. Currently they have 4 or 5 satellites in this constellation which provides very little coverage while acting as a pilot for the whole project. The latest news report that the Chinese will launch somewhere between 12 and 14 satellites into orbit in the next few years which will get them a regional navigation positioning system. and by 2020 they will have more than 30 satellites for global coverage.

Being one of the biggest economies in the world, China no longer wants to rely on USA’s Navstar for their economy and defense system. USA keeps access to their GPS satellites open - and it provides location information for almost all the GPS receivers on Earth. However America may choose temporarily turn off this service in case of a national emergency - which really is very unlikely.

how to get GPS status updates

Do you need to know how those GPS satellites are doing in orbit? Are they in good working condition? There’s a way to get updates on their status - from the actual source: the U.S. Coast Guard Navigation Center. There you can click on the link that says Consolidated Nav Info select the sections you want to get updates on and click on continue. And you’ll get something like above - with status of each 32 satellites.

If you want to get emails about the status of GPS satellites you can also subscribe to NANU List Server. This way you will get an update within 60 minutes of the Air Force notifying of a change to the GPS constellation.

Do you know another way of getting updates on GPS status? Do the satellites tweet? Please share.