I am wondering what area is covered by a dataset which is one arc second wide.
At sea level at the equator:
One degree of longitude is about 111km
One minute of longitude is one sixtieth of that: about 1.85km
One second of longitude is one sixtieth of that amount: about 31 meters or 100 feet.
Arc-seconds of latitude remain nearly constant, while arc-seconds of longitude decrease in a trigonometric cosine-based fashion as one moves toward the earth's poles.
Arc seconds aren't really a great way to measure distance. Is there no possibility of using a ruler tool in your GIS or any kind of distance function?
1 nautical mile is one minute of arc. At equatorial sea level, this is equivalent to 1852m/60 = 30.86666667m (the equatorial arc-second).
As noted above, this distance will become smaller as one moves towards the poles.
At 33.6º latitude South, cos 33º = 0.83292, cos 33.6 * 30.866666667m = 25.709m for arc-second of longitude at this latitude (33.6º, approximately)