punchcard | Simple sinatra/active record app | Application Framework library

I have no experience with Unity or computer graphics, I'm approaching it purely from the navigation point of view.

Let's look at the real world. We want to travel either by walking/driving on the surface or flying at some altitude. When we do it, we move in the local coordinate system (North-South, East-West, Up-Down), we can't see any curvature. We assume the Earth is flat.

The problem arises when we try to do it on a computer, which is ruthlessly precise and knows the shape of the Earth. We can't assume the Earth is flat, we can't assume the Earth is a sphere. The Earth is a geoid. Fortunately for some purposes we can simplify things and assume the Earth is an ellipsoid. You chose WGS84. Good!

So how to move around an ellipsoid? Solving the problem analitically is a nightmare. We have to cheat ;) We should assume te Earth is flat for a moment, make a move in a chosen direction in the local coordinate system, write down the altitude of the new position, calculate the global geodetic coordinates (Lat, Long, Alt) of that new point and then replace the altitude with the one obtained while using the local coordinate system. In other words: each time we move forward along a perfectly straight line and diverge from the ellipsoid (just a tiny bit), we force the altitude not to change in relation to the ellipsoid.

Implementation. You need to be able to freely translate coordinates between geodetic (Lat, Long, Alt) and ECEF. Going from geodetic to ECEF is easy. Finding geodetic coordinates for a given ECEF position is much more complex, there are many different algorithms, I'm sure you should be able to find a ready to use implementation somewhere. What you also need is Local Tangent Plane, and to be precise, you are going to use NED. Let's assume your object is initially at some geodetic position. You write down the altitude (relative to the ellipsoid). Then you create a local NED coordinate system with its origin at that point. Then you move the object in that local coordinate system. You write down how much the altitude (or rather the Down coordinate) changed. Then you must calculate the ECEF coordinates of that new position and transform it to geodetic (Lat, Long, Alt). You have the old altitude, you have the altitude change in the NED coordinates, which means you know the new altitude. You then apply that altitude to your new geodetic coordinates (brutally replace the Alt in Lat/Long/Alt with a new value). Then you make another move in the NED coordinates defined for that new position. And so on...

I'm not sure if it is clear, the process is quite complicated. If you can't understand - shout :)

HDD and SSD's are not equivalent to ROM. There is a distinction between a program and a process. a process is a program in execution. Multiple programs are stored in HDD and SDD's. When a program is loaded into RAM it becomes a process. A loader which is part of OS does that. Multiple program can be loaded at the same time in RAM. Context switch is an OS function. Context switch requires not only movement of program or instructions but data as well. A lot of low level features are involved. It is not possible to list all of them. In sort, Yes it is mainly an OS thing.