function submit_add(form) {
		return true;
	}
		
	function submit_delete(form) {
		if (form.antenna_count.value == 1) {
			window.alert("It's not possible to delete the last antenna.");
			return false;
		}
		return true;
	}
		
	function submit_update_antenna(form) {
		if (!verify_antenna_count(form)) { return false }
		if (!verify_antennas(form)) { return false }
		return true;
	}
		
	function set_full_sky(form) {
		form.display_center_al.value = 90;
		form.display_center_az.value = 0;
		form.display_width.value = 180;
		form.submit();
	}
		
	function enable_ground(form) {
		if (form.enable_ground_computation.checked) {
			window.alert("Don't forget to set *all* the antenna UD parameters to a non-zero value.");
		}
	}
		
	function submit_calculate(form) {
		if (!verify_display(form)) { return false }
		if (!verify_antenna_count(form)) { return false }
		if (!verify_antennas(form)) { return false }
		if (form.enable_object_path.checked) {
			if (!verify_object(form)) { return false }
		}
		if (check_for_trivial_case(form)) { return false }
		return true;
	}
		
	function verify_display(form) {
		if (form.display_center_al.value == '') {
			window.alert("The Altitude Display Center value is missing.");
			form.display_center_al.focus();
			return false;
		}
		
		if (form.display_center_al.value < 0) {
			window.alert("The Altitude Display Center field must be greater than or equal to 0 degrees.");
			form.display_center_al.focus();
			return false;
		}
		
		if (form.display_center_al.value > 90) {
			window.alert("The Altitude Display Center field must be less than or equal to 90 degrees.");
			form.display_center_al.focus();
			return false;
		}
		
		if (form.display_center_az.value == '') {
			window.alert("The Azimuth Display Center value is missing.");
			form.display_center_az.focus();
			return false;
		}
		
		if (form.display_center_az.value < 0) {
			window.alert("The Azimuth Display Center field must be greater than or equal to 0 degrees.");
			form.display_center_az.focus();
			return false;
		}
		
		if (form.display_center_az.value > 360) {
			window.alert("The Azimuth Display Center field must be less than or equal to 360 degrees.");
			form.display_center_az.focus();
			return false;
		}
		
		if (form.display_width.value == '') {
			window.alert("The Display Width value is missing.");
			form.display_width.focus();
			return false;
		}
		
		if (form.display_width.value < 5) {
			window.alert("The Display Width field must be greater than or equal to 5 degrees.");
			form.display_width.focus();
			return false;
		}
		
		if (form.display_width.value > 180) {
			window.alert("The Display Width field must be less than or equal to 180 degrees.");
			form.display_width.focus();
			return false;
		}
		
		return true;
	}
		
	function verify_object(form) {
		if (form.enable_object_path.value != '' && !form.enable_object_path.value.match(/on/i)) {
			window.alert("The Enable Object Path value is missing.");
			form.enable_object_path.focus();
			return false;
		}
		if (form.object_declination.value == '') {
			window.alert("The Object Declination value is missing.");
			form.object_declination.focus();
			return false;
		}
		if (form.object_declination.value <= -90) {
			window.alert("The Object Declination value must be greater than or equal to -90 degrees.");
			form.object_declination.focus();
			return false;
		}
		if (form.object_declination.value >= +90) {
			window.alert("The Object Declination value must be less than or equal to +90 degrees.");
			form.object_declination.focus();
			return false;
		}
		
		if (form.observing_latitude.value == '') {
			window.alert("The Observing Latitude value is missing.");
			form.observing_latitude.focus();
			return false;
		}
		if (form.observing_latitude.value <= -90) {
			window.alert("The Observing Latitude value must be greater than or equal to -90 degrees.");
			form.observing_latitude.focus();
			return false;
		}
		if (form.observing_latitude.value >= +90) {
			window.alert("The Observing Latitude value must be less than or equal to +90 degrees.");
			form.observing_latitude.focus();
			return false;
		}
		
		if (form.display_HA_step.value == '') {
			window.alert("The Display Hour Angle Step value is missing.");
			form.display_HA_step.focus();
			return false;
		}
		if (form.display_HA_step.value <= 0) {
			window.alert("The Display Hour Angle Step value must be greater than zero.");
			form.display_HA_step.focus();
			return false;
		}
		if (form.display_HA_step.value >= 24) {
			window.alert("The Display Hour Angle Step value must be less than 24 hourss.");
			form.display_HA_step.focus();
			return false;
		}
		
		return true;
	}
		
	function verify_ground(form) {
		
		return true;
	}
		
	function verify_antenna_count(form) {
		if (form.antenna_count.value < 1) {
			window.alert("There must be at least one antenna.");
			return false;
		}
		return true;
	}
		
	function check_for_trivial_case(form) {
		if (form.antenna_count.value == 1 && form.antenna_1_pattern[0].checked && 
					!form.enable_ground_computation.checked && !form.enable_object_path.checked) {
			window.alert("It's really boring to look at one isotropic antenna in free space with no object path.\nPlease change one or more the following parameters and resubmit.\n - # of Antennas\n - Antenna #1 Gain Pattern\n - Enable Object Path Simulation\n - Enable Ground Simulation");
			return true;
		}
		return false;
	}
		
	function verify_antennas(form) {
//		// create an array of objects to contain the antenna information
//		var antenna_element = new Array();
//		for (var antenna_number = 1; antenna_number <= form.antenna_count.value; antenna_number++) { 
//			antenna_element[antenna_number] = new Object();
//		}
//		
//		// scan the form elements for all antenna elements 
//		for (var item = 0; item < form.elements.length; item++) { 
//			antenna = form.elements[item].name.match(/^antenna_(\d+)_(.+)$/);
//			// if an antenna is found store its elements in a two-dimensional associatiative array
//			if (antenna) {
//				if (antenna[2] == "pattern") {
//					if (form.elements[item].checked) { antenna_element[antenna[1]]["pattern"] = form.elements[item].value; }
//				} else {
//					antenna_element[antenna[1]][antenna[2]] = form.elements[item].value;
//				}
//			}
//		}
		
		for (var item = 0; item < form.elements.length; item++) { 
			antenna = form.elements[item].name.match(/^antenna_(\d+)_NS$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The NS position of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_EW$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The EW position of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_UD$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The UD position of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
				if (form.enable_ground_computation.checked && form.elements[item].value == 0) {
					window.alert("The UD position of antenna #" + antenna[1] + " is zero - this is not allowed when ground simulation is enabled.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_phase$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The Relative Phase of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_gain$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The Relative Gain of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_al$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The Altitude Pointing of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
				if (form.elements[item].value < 0) {
					window.alert("The Altitude Pointing of antenna #" + antenna[1] + " must be greater than or equal to 0 degrees.");
					form.elements[item].focus();
					return false;
				}
				if (form.elements[item].value > 90) {
					window.alert("The Altitude Pointing of antenna #" + antenna[1] + " must be less than or equal to 90 degrees.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_az$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The Azimuth Pointing of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
				if (form.elements[item].value < 0) {
					window.alert("The Azimuth Pointing of antenna #" + antenna[1] + " must be greater than or equal to 0 degrees.");
					form.elements[item].focus();
					return false;
				}
				if (form.elements[item].value >= 360) {
					window.alert("The Azimuth Pointing of antenna #" + antenna[1] + " must be less than 360 degrees.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_03_width$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The -3 dBc Width of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_06_width$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The -6 dBc Width of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			antenna = form.elements[item].name.match(/^antenna_(\d+)_10_width$/);
			if (antenna) {
				if (form.elements[item].value == '') {
					window.alert("The -10 dBc Width of antenna #" + antenna[1] + " is missing.");
					form.elements[item].focus();
					return false;
				}
			}
			
		}
		return true;
	}

	function start_time() {
	    var d = new Date();
		return d.toLocaleString();
	}