Image Processing and Geo-Referencing - Environmental Modeling - page 310

use. ginput stores the position in the current coordinate system in the variables x0
and y0 . The input parameter 1 in the command tells that a single point is read. Note
that the command waits for user input, i.e. the execution of the M-file does not
continue before the user has not finished the task.
The following plot command places a black ' + ' at the location on the display
where the mouse click occurred (see Fig. 17.2 ). inputdlg is the MATLAB ®

command for an input dialog, which here asks the user to input the coordinates of
the marked location in the real coordinate system. The dialog box is shown in
Fig. 17.2 , with the values '900' and '1,000', which have been entered by the user.
The input parameters of the command are easy to relate: 'horizontal' and 'vertical'
are text strings associated with the input fields; 'Field position' is the header text.
Both input fields are located in a single line, and default values for the two variables
are '0'.
After the input dialog is closed, the coordinate values, chosen by the user, are
stored in the coords variable, containing two strings. As for further processing the
values (not the strings) are required, the strings have to be transformed into
numbers. The two str2double commands transform the strings to double precision
values. After the reference point 1 is read, the following delete command deletes

Fig. 17.2 Illustration of work with the geo-referencing example