I don't think I will seek a solution for this, but thought I'd post what happened. Before I retired in 1997, I bought a Garmin GPS 38, a bit over $100 as I remember it, at Wal-mart. I have used it a lot over the years.
Last week, I was trying to write a program in YABasic to take the US Geological Survey coordinates of an earthquake, and produce bearing and distance. Distance works okay, but for some reason I can't get bearing to work at all. Obviously something I am doing wrong.
However, that is a side story. I decided to make up some coordinate numbers and see what happened. I ran them on a URL I found.
Then, I plugged them into my GPS. I set waypoint U at 18 N and -97W, and waypoint V at 16 N and -98 W. I mean like 16 00.00 etc.
I got distance and bearing of 180 degrees, straight south, which is wrong, and also 111 km, which is also wrong. In fact, flat wrong. Obviously, there is a major software bug in the original software. The correct answer is 246.5 km, and 205 degrees, 42' 10". My program said 246.8 km, but -115 degrees, which I think is wrong, but have not figured out how to convert -115 degrees to 0 to 360 degree system. My attempt to use modulo doesn't produce anything that seems correct.
If I take a fictional set of coordinates just a bit off 16.0000 and -97.0000, it starts working okay.
The GPS 38 is obsolete. Therefore I will not be bothering to attempt to obtain cable and update firmware, suspect it is not even available. For my simple needs, there is a good machine from Amazon for around $85.
But, I thought I'd share this strange technical issue.
Last week, I was trying to write a program in YABasic to take the US Geological Survey coordinates of an earthquake, and produce bearing and distance. Distance works okay, but for some reason I can't get bearing to work at all. Obviously something I am doing wrong.
However, that is a side story. I decided to make up some coordinate numbers and see what happened. I ran them on a URL I found.
Then, I plugged them into my GPS. I set waypoint U at 18 N and -97W, and waypoint V at 16 N and -98 W. I mean like 16 00.00 etc.
I got distance and bearing of 180 degrees, straight south, which is wrong, and also 111 km, which is also wrong. In fact, flat wrong. Obviously, there is a major software bug in the original software. The correct answer is 246.5 km, and 205 degrees, 42' 10". My program said 246.8 km, but -115 degrees, which I think is wrong, but have not figured out how to convert -115 degrees to 0 to 360 degree system. My attempt to use modulo doesn't produce anything that seems correct.
If I take a fictional set of coordinates just a bit off 16.0000 and -97.0000, it starts working okay.
The GPS 38 is obsolete. Therefore I will not be bothering to attempt to obtain cable and update firmware, suspect it is not even available. For my simple needs, there is a good machine from Amazon for around $85.
But, I thought I'd share this strange technical issue.
