What’s E6 HAS? – Information

A dive into Galileo’s free corrections service, which places the “quad” in “quadband.”

A few of our latest merchandise have been described as able to quadband reception, just like the RTK Postcard and LG290P Breakout board. What units these aside from our different multiband recievers? Like our different high-precision PNT merchandise, they’re able to L1/L2/L5 reception. Nevertheless, they take it a step additional by having the ability to obtain information from the Galileo constellation’s E6b band.

In 2018, the European Area Company started a undertaking known as “Excessive Accuracy Service” (HAS). The aim of this undertaking was to make elevated accuracy GNSS accessible globally by broadcasting corrections straight from every satellite tv for pc in real-time. Since then, new GNSS receivers have been designed which might be able to receiving and using these corrections, such because the Unicore UM980 and the Quectel LG290P.

Regular GNSS has a peak accuracy of round 1.5 meters, primarily because of the uncertainty of modifications to the service part as alerts propagate via the ionosphere. With the intention to get higher accuracy than this, the GNSS alerts must be augmented by “corrections”. HAS gives corrections by transmitting them on the E6b band alongside their commonplace GNSS alerts.

So, how does HAS work?

HAS corrections are designed to be used in a Exact Level Positioning (PPP) algorithm; a typical use case for PPP could be establishing a really excessive accuracy place for a Everlasting Base Station. Conventional PPP works by having a community of floor stations monitoring satellite tv for pc broadcasts, computing the error in GNSS satellite tv for pc broadcasts (and different parameters), and creating corrections for these errors. To compute a corrected place utilizing PPP, a sequential estimation algorithm is used, equivalent to an Prolonged Kalman Filter, with the objective of discovering the next output values:

• Receiver place (ECEF X, Y, Z)
• Receiver clock offset
• Tropospheric zenith delay
• Service-phase ambiguities

There are a variety of parameters that must be corrected for after the bottom station community has noticed the GNSS alerts:

• Satellite tv for pc orbit corrections: These refine the published ephemeris information to offer extra correct satellite tv for pc positions.
• Satellite tv for pc clock corrections: These enhance the accuracy of satellite tv for pc clock offset info.
• Satellite tv for pc biases: These embody code and part biases for supported Galileo alerts.
• Atmospheric corrections: Not presently accessible; the complete service will embody atmospheric (at the least ionospheric) corrections, significantly for the European Protection Space.

The drawbacks of PPP are the period of time and infrastructure it requires. The very best high quality PPP consequence is just accessible 12-16 days after the only level information has been collected. The CSRS Fast PPP has centimeter stage accuracy just like RTK, however just isn’t accessible till 12 hours after the top of the day the only level information was captured on. For actual time, excessive accuracy operations, RTK continues to be your best option.

A singular function of HAS is that these correction messages are computed for every satellite tv for pc within the Galileo constellation by a floor station, then uploaded to every respective satellite tv for pc the place they’re then broadcast alongside the usual GNSS alerts. This permits receivers to run the PPP algorithm in real-time, so long as they’re able to receiving the HAS E6b band, and so they have the flexibility to run the PPP algorithm. Along with HAS E6-B satellite tv for pc broadcast, HAS PPP corrections will be obtained via their Web Information Distribution channel; this distribution channel capabilities very like NTRIP; you present credentials, and PPP corrections are piped to your machine over the web utilizing NTRIP.

HAS is an incredible achievement on this manner; corrections accessible practically worldwide, no base station or NTRIP community required. However, there are some downsides; the accuracy is comparatively unhealthy in comparison with RTK (however nonetheless adequate for a lot of use-cases), the method is considerably gradual (5-Quarter-hour for PPP convergence), and it’s delicate to sudden velocity fluctuations.

What {hardware} is suitable with Galileo E6b-HAS?

SparkFun sells just a few merchandise which might be in a position to obtain HAS corrections.

SparkFun RTK Torch

GPS-25662

The RTK Torch is your one-stop store for high-precision geolocation and GIS wants.

SparkFun RTK Postcard

GPS-26916

The SparkFun Postcard is a compact dev board for high-precision PNT wants that mixes the Quectel LG290P GNSS RTK with an E…

Beneath is an inventory of HAS enabled receivers.