Assessing raw data
This guide describes how to assess raw data logs in Emlid Studio for further possible solution improvement.
Overview
To assess your raw data logs, you need to check the following parameters:
- Satellites signal, which indicates the clarity and usability of the satellite signals.
- Satellites distribution, which indicates the positions and trajectories of the satellites in the sky.
Workflow
To check the above parameters, drag and drop your observation logs (.**O) to the plot area in Emlid Studio.
To analyze your UBX log, first convert it to RINEX format using Emlid Studio's conversion tool.
Assessing the quality of satellite signals
To assess the satellite signals your receivers tracked while recording logs, check the SNR values and cycle slips on Emlid Studio’s Satellite Visibility or Skyplot screen.
The skyplot is only displayed if a navigation file (.**P) is in the same folder as the observation file (.**O).
Both screens display satellite systems and show the frequencies recorded for each satellite by default.
Checking SNR values
The signal-to-noise ratio is used to evaluate the signal reception from each tracked satellite for a specific frequency. You can view this information on Emlid Studio's Satellite Visibility and Skyplot screens. The Satellite Visibility screen opens by default.
To check the SNR value for a specific frequency, select the frequency from the list and check the color:
| Color | SNR value, dbHz |
|---|---|
| Green | 45+ |
| Orange | 40-45 |
| Pink | 35-40 |
| Blue | 30-35 |
| Red | 25-30 |
| Gray | 0-25 |
If the SNR value for most satellites is above 35 dBHz (Green, Orange, or Pink), it means that the signal from the satellites is clear and of good quality.
Checking cycle slips
Cycle slip is a discontinuity in a receiver's phase lock on a satellite's signal. Cycle slips occur when a GNSS signal experiences temporary delays or disruptions, and Reach loses track of the satellite. Electronic device interference, nearby power lines, obstructions such as trees or buildings, and other similar factors typically cause these slips. You can check the cycle slips on both Emlid Studio’s Satellite Visibility and Skyplot screens. They are displayed as vertical red ticks.
While it is normal to see some cycle slips in a log, the more you see, the worse the resulting output will be. Below are examples of cycle slips' acceptable (left) and unacceptable (right) numbers.
Assessing satellites distribution
Using the Skyplot screen, you can see the positions of the satellites and their trajectories in a projection view where the center of the projection is your Reach.
This screen shows the angle of elevation radiating out and decreasing from the center. If you look at the SNR of satellites found below 15 degrees, you will notice that these values are generally less than 35 dBHz, which means the signal is not good enough.
By fine-tuning the elevation mask, you can exclude these satellites from further processing. After analyzing your raw data logs, if you have identified areas for improvement, you can adjust some settings before post-processing. Read the Tuning post-processing solution guide to learn more about tuning options.