Link Search Menu Expand Document

Tutorial 1 & 2

Getting access

  • Create (or verify) an email account associated with Google. e.g. abcdef\@gmail.com.

  • Register for a GEE account at https://earthengine.google.com/signup/.

The GEE Interface (Code Editor)

../../../../Desktop/Screen%20Shot%202018-01-23%20at%2011.36.0

Figure 1. Image of Code Editor highlighting components of layout.

Programming in JavaScript

  • Every command line ends with a semi-colon (;)

  • " and ' can be used interchangeably

  • Use comments to make your code readable

    Comments start with // and any text in a line after the // is a comment

    Multi-line comments can start with /* and end with */

    or use Control and /

  • Use the keyword var to create a variable e.g.
    var my_grade = 100;
    
  • Parentheses are used to pass parameters to functions. e.g.
    print("This string will print in the Console tab.");
    
  • String objects (i.e. text) start and end with a single quote e.g.
    var opinion = "GEE is awesome";
    
  • Square brackets are used to specify items in a list.
    var my_list = ["eggplant", "apple", "wheat"];
    
  • The zero index is the first item in the list e.g.
    print(my_list[0]);
    
  • Square brackets can be used to access dictionary items by key e.g.
    print(my_dict["color"]);
    
  • Or you can use the dot notation to get the same result.
    print(my_dict.color);
    
  • Curly brackets (or braces) are used to define dictionaries (key:value pairs).
    var my_dict = {"food":"bread", "color":"red", "number":42};
    
  • For mathematical operations, you can use the built-in mathematical functions or you can use the mathematical symbols directly:
    //build in function
    print(3.subtract(2)); 
        
    //mathematical symbols
    print(3-2);
        
    //making it more readable
    print("Subtracting two from three equals",3-2);
    
  • Functions that combine commonly reused steps improve efficiency and make code easier to read. The my_hello_function below takes input from the user, adds some text and prints the result to the Console tab. The add_function takes an input value, adds 3, and then returns the results with an appropriate text description.

    var my_hello_function = function(string) { return "Hello " + string + "!"; }
    print(my_hello_function("world"));  //would print Hello world! in the Console tab
        
    var add_function = function(a) { return a+3; }; 
    var a = 1;
    print(a + " plus 3 is " + add_function(a));  //would print 1 plus 3 is 4 in the Console tab