LAB #1 Solution

One of the goals of this lab is to make you familiar with C in a Linux (or Linux like) environment. If you are on a Windows machine you should install Cygwin, which is available at http://cygwin.com. Cygwin is a free environment that simulates Linux on a Windows machine. When installing it you must install the following packages that are development packages and aren't installed by default:




gcc-g++




and




make




If you have a Mac, make sure that you have the Xcode command line tools installed. Open a terminal and try to type




make -v




and




gcc -v




(-v asks for the version of the product - we don't care about the version, it's just to check that make and gcc are understood).




If they are not installed, issue the following command:




xcode-select --install




it should install what you'll need for this course.




Try to refrain from using an Integrated Development Environment (IDE) for the first labs at least. IDEs are extremely convenient, but sometimes you have none installed, or there is an IDE you aren't familiar with. It's good to also know how to use the basic commands that an IDE runs in the background.




You are asked for this lab to write a simple program that, as you will see, may not be as simple to write in C as it looks if you want to write robust programs. It will allow you to learn about basic input/output.




This program must prompt the user for the name of a first city, then its latitude and longitude, then for the name of a second city with its latitude and longitude, then compute the flying distance between the two and display




The distance between and is km




Here is the formula for computing the distance.




Formula (adapted from mathforum.org, provided by Doctor Rob)




Assume the Earth is a perfect sphere. Let all angles be measured in signed degrees (negative latitude means South, negative longitude means West)




Let phi = 90 - latitude. The North Pole has phi = 0, the South Pole has phi = 180, and 0 <= phi <= 180.




Let theta = longitude. Greenwich, England, has theta = 0, and -180 <= theta <= 180.
Let the angles for the two points be (phi1, theta1) and (phi2, theta2). Then compute c = sin(phi1)*sin(phi2)cos(theta1-theta2) + cos(phi1)cos(phi2).




Then the shortest great circle distance between the two points is d = R*Arccos(c)Pi/180,*




where R is the radius of the earth in kilometers, and the arccosine is taken between 0 and 180 degrees, inclusive. Earth radius: 6,371 km




Some cities for testing:




Shenzhen: 22.55, 114.1




Beijing : 39.9139, 116.3917




New York, USA : 40.7127, -74.0059




San Francisco, USA : 37.7833, -122.4167




London, UK : 51.5072, -0.1275




Paris, France : 48.8567, 2.3508




Kolkata, India : 22.567, 88.367




Moscow, Russia : 55.7500, 37.6167




Rio de Janeiro, Brazil : -22.9083, -43.1964




Sydney, Australia: -33.865, 151.209444




For checking out if your results are roughly correct:




http://www.worldatlas.com/travelaids/flight_distance.htm