Explanation of Satellite Skyplot?

Taras D shared this question 38 days ago
Answered

The Satellite skyplot is explained here. However, I'm trying to understand the meaning of the satellite numbers. Do they correspond directly to what is seen here?

http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm

In addition, do Android phones support Wide Area Augmentation System (WAAS)? If they do, is it used automatically by Locus Map?

Comments (3)

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Good day Taras,

numbers should really match values you see on NSTB web page. As I see, it matches well.

WAAS/EGNOS

Usage of WAAS/EGNOS or any other system that improve location by supply pre-computed data is not known to me. From what I remember from school, these services need to deliver to device certain data, that are then used for little bit different computation of location than from raw GPS data received from satellites. So this also means, that support for these services should be software-based and not hardware-based (so no special hardware should be needed, most probably only new Android 7+, which support direct access to received GNSS data).

I remember on this topic https://www.gsa.europa.eu/news/new-free-software-toolkits-bring-egnos-accuracy-and-integrity-smart-phones where are information about "EGNOS toolkit": SDK for developers to support EGNOS augmented data, but seems that project is dead? Hmm.

So, from my personal point of view (not validated info): no common Android device use any kind of augmentation like WAAS or EGNOS to improve location data now.

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Trimble is one of biggest creators of equipment for surveyors and seems they have a software solution for this: https://catalyst.trimble.com/ . Hmm this brings me to offer to use their SDK directly in 3rd party apps like Locus Map, interesting ...

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Ah, I've found out that Trimble Catalyst depends on subscription fee (not a big problem), but also on hardware antenna (a lot worst). So not a solution.

If you find out anything more about this EGNOS/WAAS stuff, let me know, I'm interested in progress in this area as well, thanks.

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My device is SBAS capable (Moto X4/Snapdragon 630), and LocusMaps displays the three SBAS PRNs (131, 135, 138) in the signal strength plot, but not in the sky plot. This matches what the GpsTest app shows, which is only C/No values for the SBAS satellites, but not elevation and azimuth. I believe one of two things is occurring: either its the GNSS chipset hardware in my phone not providing these values for SBAS satellites, or the Android GNSS Raw Measurements API does not support these values for SBAS satellites. This could also be indicative that the hardware chipset only uses these PRNs as a source of corrections, and not an additional ranging signal. The SBAS elevation/azimuth would have to be computed from the SBAS broadcast message type 9, which contains the satellite's XYZ position.