Calculates current heading

[Krithik1]

Description

• Resolves Publish desired heading sailbot_workspace#283
• Gets current waypoint from GPS subscriber and finds the waypoint in self.local_path.waypoints
• If found, calculates the heading based on formula linked in resources
• GPS data not being sent, so running into error. If mock GPS data then works fine

Verification

• Used mock GPS data for the current waypoint. Used the first value in the waypoints list.

Resources

• Link to formula

[jamenkaye]

Good start! I left a few comments 👍

[jamenkaye]

Would it be possible to add some tests for this function?

[Krithik1]

For the tests, should I create a new test_node_navigate.py file and manually set the value of self.gps to calculate the desired heading?

[jamenkaye]

I think this would be the best way to test this:

1. Create a helper function to get_desired_heading() that accepts "simple" arguments like waypoints or lists of waypoints, rather than "complicated" arguments like self (which is a whole sailbot object). get_desired_heading() will basically just call the helper function.
2. Create test_node_navigate.py like you suggested, and just test the helper function. I'd suggest using simple tests like when the desired heading is $0 \degree$ or $90 \degree$, and maybe some more complicated tests where the "actual" value is computed with geodesic.inv() as well.

[jamenkaye]

Hi Krithik, I left a few comments! We might need to add some more complexity here depending on if we need to determine which local waypoint we're going towards. Jay might be working on this tho so we can talk to him tomorrow.

[jamenkaye]

I believe self.gps.lat_lon is the current GPS position of the boat, which is generally not one of the waypoints. I think Jay might be working on code to determine the next local waypoint, but we can sync up with him tomorrow

[jamenkaye]

This is about line 175:

The function description says we should return something that violates the heading convention in the case of an error, but the heading convention allows $-180 \degree < \text{heading} \leq 180 \degree$.

Can you please change the return value on line 175 to something outside those bounds? I'd suggest 404 since that's a common error number for websites haha

[jamenkaye]

I think GEODESIC.inv() has multiple returns (documentation), and I think you only want the forward azimuth (image at bottom)

I believe Patrick is a fan of this kind of syntax for this situation: _, value, _ = myfunc(), where myfunc() returns a touple:

def myfunc():
	return (1, 2, 3)

In this example, print(value) outputs 2.

[jamenkaye]

I think this would be the best way to test this:

1. Create a helper function to get_desired_heading() that accepts "simple" arguments like waypoints or lists of waypoints, rather than "complicated" arguments like self (which is a whole sailbot object). get_desired_heading() will basically just call the helper function.
2. Create test_node_navigate.py like you suggested, and just test the helper function. I'd suggest using simple tests like when the desired heading is $0 \degree$ or $90 \degree$, and maybe some more complicated tests where the "actual" value is computed with geodesic.inv() as well.