G'day davedingler,
...you certainly don't need to download every single one of them, Dave (if I may be so bold)! A lot will depend upon the area you need to cover and this will always determine the total number that the viewer offers for your selection. The four large files (labelled as "n30w95", for example), in your case, are the full 1 degree x 1 degree (lat/long) DEM tiles that most of us tend to use. From the four that you have, you should choose the one (or more as appropriate) that is/are suitable for your purpose (they are subtly different, depending upon how the data has been modified, which is explained in the descriptions provided). I usually choose the 1/3 arcsec, "Hydrologically Enforced" dataset but ultimately, the choice is yours. The other 145 files are 'smaller' chunks from each of these larger sets, known as "Quads". There are four of these "Quads" in each full sized tile and these cover an area of 7.5 minutes (square), each, hence their name. Sometimes, it is advantageous to grab these smaller ones as is required but I usually just get the big ones and reduce their size in TransDEM (using the provided tools) once I see how much needs to be kept/rejected to surround the map tiles that I have already imported...
Jerker {:)}
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