Navigation question (loosely related to 107 test)

[Skybuyer]

I'm brushing up on my weakness for the Part 107 test coming up. I realized that I didn't understand how to UTILIZE latitude and longitude in calculating position. Much less, I didn't understand how to calculate ETA based on Lat/Long over speed.

I recognize that one "minute"= 1.15 miles and speed is often measured in "knots". I have recognized that 100mph is the same as 87 knots, and that 87, or .87 miles (more precisely 0.8695652) is the inverse of 1.15.

IS THERE A CORRELATION BETWEEN KNOTS AND MINUTES in terms of navigating between two points establishing an ETA? If so, how can the correlation be utilized for navigation?

 

[Deleted member 103366]

I recognize that one "minute"= 1.15 miles

This is from the perspective of someone who has no knowledge of "part 107" and it maybe that the literature etc. for that defines certain things for the purposes of "part 107" but if there are no definitions and the meaning of words and terms is the same as their everyday/layman usage......

What are you referring to by "minute"?

If it is a minute of arc of longitude then the distance subtended by 1 minute of longitude is a maximum at the equator and diminishes as you move away from the equator, i.e it is not fixed. (It varies roughly in accordance with the cosine of the latitude (that's assuming a spherical earth which is not entirely accurate))
From How much distance does a degree, minute, and second cover on your maps?
"One-degree of longitude equals 288,200 feet (54.6 miles), one minute equals 4,800 feet (0.91 mile), and one second equals 80 feet. "

If it is a minute of latitude then I think that distance remains more or less constant from the equator to the poles at approximately 1.15 miles.

Given the above and if the "literature" contains no definitions then I see no 'simple' way to relate minutes of longitude to knots etc.etc

 

[Skybuyer]

I was wondering if there is a relationship between lat/long and knots that can be translated into mph and ETA. I'm not that good at math, but the knots>mph conversion numbers and the degrees/minutes/seconds are conspicuously similar as it relates to miles and miles per hour.

If a navigator is plotting a course, he would use the coordinates to plot the direction, and then calculate the distance. The pilot is managing air speed in knots. One would think there would be a direct coorelation, no?

 

[Meta4]

If it is a minute of latitude then I think that distance remains more or less constant from the equator to the poles at approximately 1.15 miles.

One minute of Latitude equals exactly one nautical mile, so you can use the markings on the east or west edges of the map as a distance scale.
One minute of Longitude varies with distance from the equator, so cannot be used for distance measurement.

I was wondering if there is a relationship between lat/long and knots that can be translated into mph and ETA. I'm not that good at math, but the knots>mph conversion numbers and the degrees/minutes/seconds are conspicuously similar as it relates to miles and miles per hour.
If a navigator is plotting a course, he would use the coordinates to plot the direction, and then calculate the distance. The pilot is managing air speed in knots. One would think there would be a direct coorelation, no?

It's hard to see how this has any application at all to drone flying (but that's nothing new for the 107 test).
But if you were flying a real plane, you use nautical miles for distance and knots for speed.
One knot is one nautical mile per hour, so calculations are easy.
Don't complicate things by using mph or the miles you are familiar with on the ground.

Remember you only need 70% to pass the 107 test.

 

[Skybuyer]

One minute of Latitude equals exactly one nautical mile, so you can use the markings on the east or west edges of the map as a distance scale.
One minute of Longitude varies with distance from the equator, so cannot be used for distance measurement.

It's hard to see how this has any application at all to drone flying (but that's nothing new for the 107 test).
But if you were flying a real plane, you use nautical miles for distance and knots for speed.
One knot is one nautical mile per hour, so calculations are easy.
Don't complicate things by using mph or the miles you are familiar with on the ground.

Remember you only need 70% to pass the 107 test.

Thank you. You gave me the specific information I needed. While not necessarily on the 107 test, I'm surprised that in all the courses I've seen they don't really talk at all about navigation in terms of course, distance and knots as a combined entity. As I studied the lat/long area, trying to understand it in terms of every day measurements , and knowing that "87" knots is going to appear as an answer in the maximum speed a drone is allowed to legally fly, the relationship of the numbers was such that the question begged to be asked. So thank you for the answer. I'm not just studying to pass the test, but to truly understand the information (could be a thing in actual schools one day too ).

 

[Gandalf00]

As someone who passed the test just a few weeks ago, I can tell you there will not be any navigation questions of the "what is the travel time between two lat/long points" type. The only lat/long questions you will see will be similar to "what airport is located near lat X, long Y". The only calculation you may see has to do with load factor in terms of aircraft mass and bank angle. Also, in terms of max speed, be aware that 87 knots is not the only correct answer. 100 mph is also correct. Be sure to carefully look at the answers as the test can include subtle differences that can mislead you if you don't read closely.

 

[Skybuyer]

As someone who passed the test just a few weeks ago, I can tell you there will not be any navigation questions of the "what is the travel time between two lat/long points" type. The only lat/long questions you will see will be similar to "what airport is located near lat X, long Y". The only calculation you may see has to do with load factor in terms of aircraft mass and bank angle. Also, in terms of max speed, be aware that 87 knots is not the only correct answer. 100 mph is also correct. Be sure to carefully look at the answers as the test can include subtle differences that can mislead you if you don't read closely.

I know most of that. Where I had difficulty is understanding how to find areas with the coordinates, particularly with questions like "Scuttlebutt Ranch is 4NM SW of 40°N by 67°W" making it a little hard for me to zero in on the area. But when using learning the coordinates it led me to wonder how to use them to actually navigate- even though the deeper information won't be tested. Understanding the information fully hopefully will help wade through the nuance and trick trap questions I know I'll encounter. I hope my nerves don't allow me to miss stupid and easy stuff.

 

[Cymruflyer]

As someone who passed the test just a few weeks ago, I can tell you there will not be any navigation questions of the "what is the travel time between two lat/long points" type. The only lat/long questions you will see will be similar to "what airport is located near lat X, long Y". The only calculation you may see has to do with load factor in terms of aircraft mass and bank angle. Also, in terms of max speed, be aware that 87 knots is not the only correct answer. 100 mph is also correct. Be sure to carefully look at the answers as the test can include subtle differences that can mislead you if you don't read closely.

FAA tests often do that, give you multiple choices for an answer, that sound similar, but are subtly different and only one is correct. If you find yourself pondering such a question with multiple choices for answers, discard immediately, what are obviously the wrong answers. Then study the wording in what will probably be the two remaining choices that may be confusing you.

Read them out loud maybe, and listen to how they sound and all being well, the correct answer will eventually stand out to you. Or maybe not, but, as Meta4 has stated, you only need to achieve 70% to pass. Remember, of all the doctors out there in practice, there are some who gradated bottom of their class, but they are still doctors!! Good luck with your exam.

 

[maelstrom]

If a navigator is plotting a course, he would use the coordinates to plot the direction, and then calculate the distance. The pilot is managing air speed in knots. One would think there would be a direct coorelation, no?

Yes and no! When making time calculations in navigation, you not only need to know the distance to your destination and the airspeed, you also need to know the wind velocity to enable you to calculate groundspeed. Most aircraft fly at a fixed airspeed in the cruise but that only represents the speed they're moving through the air. The airmass itself is probably also moving (wind) so your speed across the ground can be significantly different to your speed through the air - if your airspeed is 100 mph and you fly into a 20 mph headwind, your groundspeed will only be 80 mph and this is the speed you need to calculate timings.

 

[Cymruflyer]

Yes and no! When making time calculations in navigation, you not only need to know the distance to your destination and the airspeed, you also need to know the wind velocity to enable you to calculate groundspeed. Most aircraft fly at a fixed airspeed in the cruise but that only represents the speed they're moving through the air. The airmass itself is probably also moving (wind) so your speed across the ground can be significantly different to your speed through the air - if your airspeed is 100 mph and you fly into a 20 mph headwind, your groundspeed will only be 80 mph and this is the speed you need to calculate timings.

Furthermore, the wind speed changed in velocity and direction at different altitudes. The pilot needs to change the yaw position of the aircraft in order to fly a straight line across the ground, otherwise the pilot would drift off course and never arrive at the intended destination. Also the pilot would need to take into account the velocity and direction of the wind at different altitudes in order to keep a straight course over the ground. There is a lot to calculate while flying as a pilot/navigator. There is sooo much more to flying an aircraft that you sit in, than most non pilots ever thought of.

Those of us who do fly, know all this but I believe it would be too much info and too many variables to bring into the conversation for the OP, who just needed to understand the relation of Knots, Nautical miles, distance etc. in a mathematical way, which, has been very well explained to him by our valued members here.