How to obtain Checkbox values ( checked by user) using ng-model in AngularJS

While trying to implement Checkbox functionality,I am not able to obtain which checkboxes the user has selected. How is this done? Below is my HTML snippet:

<td>
                <table border="0"><th>Tier</th>
                <tr ng-repeat="item in tiertype">             
                    <td>
                    <label class="checkbox" for="{{item.id}}">
                    <input type="checkbox" ng-model="selection.ids[item.id]" name="tier_class" ng-checked="item.checked" id="{{item.id}}"/>{{item.name}}
                    </label>
                    </td></tr></table>
            </td>

And below is my javascript snippet:

$scope.tiertype = [ 
                       { id: 1, name: "All", checked: true}, 
                       { id: 2, name: "Standard", checked: false },
                       { id: 3, name: "Unreserved", checked: false },
                       { id: 3, name: "Reserved", checked: false },
                       { id: 4, name: "General", checked: false }
                       ];

Iam not getting proper values on using "check box value= {{selection.ids}}". Moreover, on checking any checbox, all are getting checked or the checbox with id:1 (default). Seems strange to me, not able to figure out. Where am I going wrong as I dont have much experience in AngularJS.