[vonmoltke]

A radar returns a vector of measurements along the line of sight of the beam. These are in-range measurements from a particular position and time. SAR stitches together a series of these in-range measurements taken at different positions and times to create a single 2D image of the static elements of a scene.

[vonmoltke]

Anna, I'm replying to myself since your posts are coming up [dead] and I can't vouch for your reply to me like I did for your top-level comment.

Yes, that is basically how it works. The system takes measurements at a series of slant ranges (called range bins) for each beam position. The returns from those range bins can be mapped to a physical location as long as the location of the receiver is known. Record enough beam positions in a line and you can map a 2D image.

[annacollins]

That means the second axis is generated by measuring the distance (slant range) from the antenna to each point. right ?

[function_seven]

Right. If the radar is held stationary, it can produce a one-dimensional "image" of what is in its line-of-sight. Move it sideways and you generate the 2nd axis.

It's a little more complex than that, because the field of view is not a perfectly narrow beam, but same idea.