Change some PHP script with drop downs instead of text field

Okay, here is what I need. I got a website with an form and when I input some coordinates and click submit it prints the coordinates on a image.. but well that code already exists. What I want now is that I got buttons with predefined coordinates and when I click one of the buttons it automatically goes on with these coordinates. That means i skip the input and the submit button. The input field and submit button should still remain for special cases. I attached a draft how it should look like :)