Added logic for handling stale GPS CAN

[hhenry01]

Description

• Resolves Handle sensors breaking tasks#7
• Add checks so that if the GPS AIS and GPS CAN data differs, and the GPS CAN data has not changed for 20 minutes, then we consider the GPS CAN data stale and publish GPS AIS latitude and longitude to the GPS CAN latitude longitude ROS topic.
• Note, we only get latitude and longitude from the GPS AIS so the other fields will still be the stale GPS CAN fields

Verification

• Not done
• Need to inject purposefully stale CAN data with good AIS data.

[patrick-5546]

Note

• This issue was originally created to ensure that we are always receiving signal from the GPS CAN field. If we don't, the averaging that we do when filtering could break. But this case would never happen right, if GPS CAN stopped working we would just publish the last published data.

Couple questions

• What happens when AIS data isn't changing as well? We could just be dead in the water with no wind
• Should we check occassionally to see if GPS CAN is changing? Or should we just discard it for the future?
• Should we check is CAN GPS is vastly different from AIS?

[hhenry01]

Note

• This issue was originally created to ensure that we are always receiving signal from the GPS CAN field. If we don't, the averaging that we do when filtering could break. But this case would never happen right, if GPS CAN stopped working we would just publish the last published data.

Couple questions

• What happens when AIS data isn't changing as well? We could just be dead in the water with no wind
• Should we check occassionally to see if GPS CAN is changing? Or should we just discard it for the future?
• Should we check is CAN GPS is vastly different from AIS?

1. I have a check such that if both the GPS and AIS data is the same, we do not consider it stale.
2. We do check if the GPS CAN is changing. We consider it no longer stale again if it matches the GPS AIS at some point.
3. The thing is, before this commit I'm trying to merge, the GPS AIS rostopic was just receiving GPS CAN data. I did not notice this before. Needs testing :/

[patrick-5546]

We consider it no longer stale again if it matches the GPS AIS at some point.

I see in the code that for it to match the latlon has to be the same to at least 4 decimal points. How many decimal points to be get from the GPS's again?