The final result of selecting operation depends on three types of source data:
sets of features which were chosen for taking part in the operation by one of the methods enumerated above;
sets of features which were selected by the moment of performing the operation;
the chosen variant of selecting operation.
All in all there are five variants of selecting operations. They are described in table 13-1. When using the selecting modes the choice of variant is determined by control keys which the user holds down while selecting features by means of a mouse. In other selecting methods the system provides the user with a choice in an explicit form.
Variant | Control keys | Cursor form | Description |
Setting | no key |
| Selection of one or several chosen features is performed, previous selection is reset |
Adding | Ctrl |
| Selection of chosen features is performed, previous selection remains |
Exclusion | Alt |
| Selection of chosen features is reset, but other previously selected features remain selected |
Adding with exclusion | <Ctrl+Alt> |
| For selected features selection state is switched to the reverse one (previous selection is reset, features not selected previously are selected). |
Intersection | Shift |
| Selection remains only for those features which were selected before and chosen to participate in the operation. For all other features selection is reset. |
Table 13-1. Variants of selecting operation
Different variants of selecting operation permit solving rather complex tasks of data analysis. For example, variant “Intersection” can be used to select only the parcels which are located in the specified rectangular map area and have common points with the specified transmission line at the same time.
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