Satellite Recon - John Dunn, Consultant, Ambertec, P.E., P.C.

Just how good are satellite reconnaissance photographs? Maybe this will give us a clue.

This is a satellite photograph of my home. Those two white dots are a pair of vents over my dining room's roof. Each vent is an aluminum square, approximately twelve inches on a side.

With this picture having been taken from shall we say two hundred miles up (1,056,000 feet), the one foot dimension would indicate an angular resolution of arcsin(1/1,056,000) which is 0.000054257 degrees or approximately 54.257 microdegrees.

Knowing that 1 arcsecond = (1/60)*(1/60) = 0.000277777778 degrees =  277.777778 microdegrees, we come to an angular resolution of approximately 0.195 arcseconds for the satellite that captured this image.

This angular resolution is actually pretty coarse by comparison to telescopes used for astronomy and nowhere near as good as spy satellite optics, but it's still pretty good resolution for looking down on someplace to see what's going on down there.

Comments

[Frank Walker]

Are you certain this is not a ariel photograph? The color profile and resolution is very much atypical of satellite images I have seen in the past.

[John Dunn]

Hi, Frank.

It's a satellite image via Google.