rtk (1)

1"x1" Centimeter-Level Accuracy RTK Module

updated September 5, 2015

25mm x 25mm S2525F8-BD-RTK single-frequency cm-level accuracy RTK module is nearly ready.

Below is a test board that allows receiving base-station RTCM 3.0 data from Bluetooth 4.0 over smartphone's 3G/4G network running ntrip, the rover module receives global positioning satellite signal, performs on-board RTK processing to generated cm-level accuracy position data by itself, and output the result over Bluetooth 4.0 to other applications. 

Alternatively another carrier phase raw measurement module can be used in place of the base station for high-accuracy relatively positioning applications such as precision farming, grass cutting, or UAV multi-rotor precise landing.

A new evaluation board is being prepared with interface options of Bluetooth 4.0 or USB 2.0 or pin-header for both input and output. The UART pin-headers can be used to connect to other wireless interface modules when needed.

Dynamic Testing

Antenna: Harxon HX-CSX601A
Baseline: 1.7Km
Max Speed: 81.2Km/hr (due to speed limit of the road, not capability of the receiver)
Blue point: single solution
Yellow point: float solution
Green point: fixed solution

The dynamic test on the road, being able to maintain fixed solution at speed over 80Km/hr, shows promising result for precision navigation guidance beyond low speed agricultural and data collection applications.

We are setting up fixed IP for our base-station, to allow more robust RTCM 3.0 transmission over the Internet for longer baseline faster speed dynamic testing.

Aug 27, 2015

Below is test result we got earlier showing performance of our single frequency RTK receiver in terms of baseline distance. 

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The rain is pouring heavily today. Not knowing how single frequency RTK would perform under such condition, our engineer went out and did some testing.

Rover Antenna: HX-CSX601A
Test Environment: Road with open sky view

Static Testing with 4.5Km Baseline: It took slightly more than 4 minutes to get fixed solution; which is much longer time than earlier results on a sunny day.  

Dynamic Testing with 4.5Km Baseline: On section A the car drove on adjacent 3 lanes separated roughly 2 meters apart, on section B the car drove on the same lane on each pass. The result shows mostly float solution with small number of fixed solution. What's remarkable is that the 3 tracks on section A are distinctively on separate lanes roughly 2 meters apart running in parallel, and the 3 tracks on section B roughly overlap; a result similar to getting all fixed solution while actually it's float solution most of the time. It's operation under such non-ideal conditions that typical users will encounter and pushing to get good performance out of single-frequency RTK that we have been spending time optimizing.

Sep 5, 2015

We received a compact active helix antenna sample for high precision application. Incredibly when mounted on roof top for preliminary testing, it does receive signal very well and can get RTK fixed solution. This antenna + S2525F8-BD-RTK module + Bluetooth + battery configuration, receiving RTK correction data via NTRIP over smartphone's Internet connection and make the NMEA output position data available to other smartphone App, might be able to serve as a portable RTK receiver for anyone seeking 100X better position accuracy than what their smartphone offers (from meters to centimeters), or for data collection usage as mentioned in this interesting "democratization accuracy" article by Brent Jones.

More testing will be done later with this interesting antenna. Below is how it might fit with SMA connector device:

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