Hey Timmy, welcome to the Zone.
I don’t have a lot of experience with pics -> Gcode (read none) but I will put in my $.02 worth. From what I have read there are two version of conversion. #1 will carver deeper with a dark color and less with a light color. This is the standard jpeg to Gcode converter that is included with Mach3 and others. You have to select your pictures carefully. Not sure the examples you have will produce what I think you want. #2 is PhotoCarve (from the Vcarve guys). It will carve thicker small lines for dark colors and thinner small lines for light colors. You do not end up with 3D but a 2D representation; kind of like a newspaper, but the result is quite unique. They usually rub stain into the end product to enhance the effect.
If you really want a 3D topographic result, you will have to find 3D wire models of the area you want to carve and then use a true 3D modeler (like MeshCam) to carve the model.
Don’t worry about copying someone else’s posts when you post. It might help explain what you are trying to accomplish.
This is an interesting project to me. My eldest son graduated with a degree in Cartography although he ended up selling advertising space for beer commercials. Funny how life goes. I’ll try to ask him about a source of 3D models of land space, but don’t count on it.