Originally Posted by caleroific
I don't understand! My sensor is sending a reading approximately every 10 seconds. The reading contains no time stamp just a temperature and pressure. The plot on the the timeline looks good. It's the background graphics which are confused.
Surely the coordinates and associated graphics are generated by OpenCPN according to the clock even if no data is received. Is this the PC clock or the GPS
clock? Either way it is independent of the data being collected and in my opinion a display issue.
Please don't be mad at anyone. We are just trying to help. Most dashboard instruments get updated from 1 to 10 times per second. So getting an update once very 10 seconds may be the issue.
The data is plotted as a line drawn as a series of equal length segments. I believe there are 3,000 sensor readings on the graph. I have to check the source code to be sure. So if the sensor sends 1 reading every 10 seconds and it takes 3,000 readings to complete the graph it means 30,000 seconds of data or about 8 hours. If no pressure data is received the chart does not get updated.
The chart object tries to draw a vertical bar every 5 or 15 minutes of the CPU clock. Again, I have to check the source code to be sure about that because it is hard coded. So it's trying to draw lots of vertical bars and they overlap and get mangled. Sometimes they look right and sometimes they look stupid.
I think you could ask via the feature tracker at opencpn.org if the history
plot could be made user selectable for the time between vertical bars. For you it should probably be something like 2 hours not 15 minutes.
An alternative would be to make the barometer history
plot a fixed number of samples (say 1,000) between the vertical time bars. That might be more in tune with what the majority of users expect.