Read a file and write to new file with some condition

Hi....

I have a data file, which I want to split and write to new file...it looks like this...

Column1    column2    Column 3
1                 28.25          36.42  -----Read 
5                 28.26          36.42
10               28.23          36.43
15               28.22          36.43   --------- write to new file
5                 28.94          34.97   --------- Again read
10               28.95          34.98
15               28.96          34.99
20               28.95          34.99
25               28.96          34.99
30               28.96          34.99  ----------Write to another new file
2                 28.19          36.43  ---------Again read
3                 28.18          36.43
4                 28.18          36.43
5                 28.18          36.44
6                 28.19          36.45

------write to new file..

Depends on the change in value of 1st column, script has to write data to new file...

new file should contain data like this..
1st file

Column1    column2    Column 3
1                 28.25          36.42  
5                 28.26          36.42
10               28.23          36.43
15               28.22          36.43

2nd file

Column1    column2    Column 3
5                 28.94          34.97  
10               28.95          34.98
15               28.96          34.99
20               28.95          34.99
25               28.96          34.99
30               28.96          34.99  

Here I have attached one sample data file please have look...

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