700 GNSS Channels VS 184 Test (Part 1 of 3)

The Trimble 12i has 672 channels, the Emlid Reach RS2 has 184, the Carlson Brx7 & Stonex S900A have 800. What are GNSS channels & why are they important?

Tracking a locked on satellite signal is one thing, and for that one task you normally use a channel. To actually find that signal and lock on is another thing altogether! Without going into too much detail, channels serve more than one purpose. They:

• Speed up satellite acquisition
• Reduce power consumption
• Reduce the likelihood of losing a 3D fix even in harsh environments
• Provide better sensitivity, allowing fixes in places where previously we would struggle
• Provide better positioning accuracy?

Essentially the more channels the better.

Today we are looking at part 1 of my detailed test between the $6,555 700 channel Stonex S700A & the $3,720 184 channel S580 their entry level models of their lineup.

In part 1 of the test we looked at both of these using just SBAS as the correction service. In Parts 2 & 3 we will be using a local Stonex S980A as a base paired with an Intuicom RTK Bridge so it is able to talk to the S700A & S580.

What is SBAS?

SBAS is a regional network of ground and satellite system that works to boost the accuracy and dependability of GPS and GNSS data. The increased accuracy is critical for aviation and is widely used by the geospatial industry for increased accuracy in navigation and mapping.

What does SBAS stand for?

SBAS stands for satellite-based augmentation system.

How does SBAS work?

SBAS uses stationary land-based GNSS monitors to calculate GNSS position errors caused by atmospheric and ionospheric disturbances, satellite orbit errors, and inaccurate clocks. Each of these errors causes delays in timing, which result in position errors for a receiver.

To calculate?GNSS position errors, GNSS data from satellites are compared against the precisely documented locations of each land-based monitor. Any discrepancy is determined to be an error. Corrections to the errors are sent to geostationary satellites and broadcast throughout the region. These SBAS corrections – called deviation corrections – allow GNSS receivers to more accurately and reliably determine their position.

GNSS is normally accurate to around five meters. Using SBAS, users can achieve an accuracy of two meters or better. Some receivers can apply SBAS corrections with additional techniques to achieve sub-meter or better accuracy.

What regions have SBAS coverage?

WAAS United States, Canada, Mexico:?Wide Area Augmentation System, or WAAS, is operated by the United States Federal Aviation Administration. Development for WAAS began in 1994.

EGNOS European Union:?European Geostationary Navigation Overlay Service, or EGNOS, was developed by the European Space Agency.

MSAS Japan:?The Multi-Functional Satellite Augmentation System, or MSAS, is operated by the Japan Civil Aviation Bureau, a division of the Ministry of Land, Infrastructure, and Transport.

GAGAN India:?GPS-Aided GEO Augmented Navigation, or GAGAN, was developed by the Indian Space Research Organization and Airport Authority of India.

The Test:

9 random points with various levels of tall buildings around on a sunny clear day.

Point #1

S700A:

Satellites Locked 30 Satellites View 38

H 22.3cm V 29.0cm

S580:

Satellites Locked 27 Satellites View 36

H 23.0cm V 29.0cm

Virtually no difference other than S700A locked in faster.

Point 2:

S700A:

Satellites Locked 28 Satellites Viewed 36

H 30.4cm V 37.0cm

S580:

Satellites Locked 24 Satellites Viewed 29

H 39.6cm V 49.7

Wide open in the middle of the street they were virtually the same right underneath a tree was a different story.

Point 3:

S700A:

Satellites Locked 29 Satellites Viewed 36

H 26.2cm V 35.0cm

S580:

Satellites Locked 27 Satellites Viewed 32

H 36.3cm V 47.3cm

Replace Tree Canpoy with building canpoy & you get the same result

Point 4:

S700A:

Satellites Locked 35 Satellites Viewed 41

H 15.7cm V 21.5cm

S580:

Satellites Locked 22 Satellites Viewed 27

H 33.0cm V 40.0cm

Not sure how to explain this one. Both were in less canpoy than than the last 2.

Point 5:

S700A:

Satellites Locked 35 Satellites Viewed 41

H 16.7cm V 22.6cm

S580:

Satellites Locked 30 Satellites Viewed 36

H 20.0cm V 26.0cm

Wide open shot, bigger difference than point 1 but not enough to matter in the real world.

Point 6:

S700A:

Satellites Locked 31 Satellites Viewed 35

H 19.1cm V 22.6cm

S580:

Satellites Locked 29 Satellites Viewed 35

H 20.2cm V 22.8cm

Great results from both.

Point 7:

S700A:

Satellites Locked 31 Satellites Viewed 35

H 18.6cm V 25.5cm

S580:

Satellites Locked 29 Satellites Viewed 34

H 19.4cm V 24.0cm

Less channels actually preforms better in this situation in the V. V isn't as important as the H but still something to note.

Point 8:

S700A:

Satellites Locked 34 Satellites Viewed 39

H 25.0cm V 36.0cm

S580:

Satellites Locked 31 Satellites Viewed 35

H 18.6cm V 23.0cm

Wide open shot & the S580 shines for it even with less Satellites.

Point 9:

S700A:

Satellites Locked 34 Satellites Viewed 39

H 18.1cm V 26.0cm

S580:

Satellites Locked 31 Satellites Viewed 35

H 17.2cm V23.0cm

Virtually the same yet again but this time the S580 is coming out ahead.

Recap:

So to conclude part 1 as you can see in the data the more channels/satellites usually the better results you are going to get on average.

See you all for Part 2 to see if being rtk corrected will make a change!