Azimuthal map projection

I am an amateur radio operator who would like to do azimuthal map projections from my home location. While we tend to think of England, for example, as being “east” of the US, it’s more NNE than we think. Ideally, I’d like to overlay the projection from my home on a world map and show the correct heading to rotate a beam antenna. I’d like to use a TFT color display for the world map and project a “wedge” starting at my location and, fanning out in a small arc to the edges of the map, showing the general path of the radio waves with a beam antenna. Ideally, the operator would enter their longitude/latitude (or Maidenhead coordinates) once and, from then on, read those base coordinates from EEPROM at startup and be able project the “wedge” for any country in the world. I would store coordinates for world capitals and use that for the endpoint. My guess is that someone has already done this, but I sure can’t find it.

That sounds like a project more suited to a PC or maybe a RaspberryPI rather than an Arduino. An Arduino does not have the speed or memory to deal with images.

...R

If you wish to point the antenna along the great circle route (minimum path length) toward the station of interest, as represented by its lat/long, this site has the relevant equations for the bearing.

It takes a few tricks to get a really accurate answer from Arduino, as single precision floats don't have the accuracy required to use those formulas. But maybe that is not required.

Hi Robin: I have a Teensy 3.6 which scoots along pretty fast. I also have an STM32F7 series which also does pretty well, but both can be programmed in the Arduino IDE. I already have the code controlling the rotator for the beam. This is just a little sizzle I'd like to add. Because my video display has a builtin SD card, I could construct the image once after the user enters their coordinates, read that in, and they do an overlay for the "wedge". It should be reasonably fast.

jremington: ...single precision floats don't have the accuracy required to use those formulas. But maybe that is not required.

Very true, but accuracy here is not all that critical. If I can just show a general heading, that would be good enough. I also would really like to have the person's location as the center point for the map, too. I'll check out the link you gave...thanks!

econjack: Hi Robin: I have a Teensy 3.6 which scoots along pretty fast. I also have an STM32F7 series which also does pretty well,

Then I apologise. I am out of my depth.

...R