Hello, I have designed a new RTK GPS unit I call TGM100 (100 x 100 mm ground plane), based on a uBlox NEO-M8P receiver. As the image shows, the ground plane is equipped with 24 LEDs, which will show the relative position of received satellites. I'm looking for some assistance in testing and validating the RTK mode (Robustness, Degradation performance etc.).
TGM100A1 - top side with LEDs 3.jpg
TGM100A1 - bottom with processor board.jpg
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System has been flown on a Logo helicopter as well as several Tarot 680 drones. Even without external correction, it performs great, much better than the M8N receiver.
However, the RTK mode is not solid so more work is needed on that front. Recent testing in a partially obstructed environment resulted in intermittent RTK Fixed mode and some jumps in velocity when the system entered and exited RTK Fixed mode. Next, we may add some shielding to the uBlox receiver and investigate methods for further improvements.
Summary: In spite of the challenges related to the RTK mode, my experience is that the NEO-M8P receiver out-performs the other 8-series receivers from uBlox. The extra cost of the receiver is well worth the improved performance in flight.
The LED feature is a quick and easy indication of how many satellites the system has locked on to. The "ON" time is proportional to the SNR (<35dB is a solid ON). The LED feature certainly does not improve signal reception, nor does it impact it, negatively.
Most of the weight of the GPS board comes from the Taoglas antenna. It is relatively heavy, but it improves receiver performance significantly. The combination of the uBlox NEO-M8P, 100 mm ground plane and the 35 mm Taoglas antenna delivers impressive performance, even without RTK Lock.
For testing, maybe it's useful, but I prefer to check both SNR and SkyPlot. As an antenna on Drone, I don't think it helps, but increases the weight.
Chris, the LED feature is 80% cool and 20% useful (depending on who you ask :) ). It only adds a few dollars to the overall cost and it provides instant information about the number and "spread" of the received satellites. The "outer ring" shows satellites with an elevation below 55 degrees. SNR > 35 result in a solid ON, while lower SNR result in shorter ON-time. On the GCS I typically use, I only receive a single number for average SNR, so this provides more information about the quality of the lock and whether or not some satellites are "shaded" by buildings or other structures. FYI, the unit also features a Honeywell HMC6343 compass, which is used for navigation and orienting the LED display, properly.
Aside from looking cool, what's the utility of knowing where the sats are?