I am trying to rescue a world map that has way too many nodes. Which is the best command to reduce these without changing the overall contours too much?
Just be picky about the factor you use. A lot of those extra nodes will be so close as to not be really doing anything, though a world map can sometimes look better without all that filigree stuff around the edge ;)
For me simplify has some unexpected results. It removes draws and ridgelines, shortens and straighten streams and roads, and markedly changes contours. But that is perhaps because I am trying to duplicate the complexity of a topographic map and I may be too nit-picky about following the real lines. But, it's a wargame and terrain is important.
SIMPLIFY does remove nodes, so yes, it will always change the map. The trick is to use a simplify distance that is so small that it doesn't remove visible features, while at the same time large enough to actually do remove a portion of the nodes.
I have used it, with factor of 0.2. This worked perfectly (I tried 10, the 1, then 0.5, then 0.1 first). I guess it depends on the size of the map. This one was world sized and massively overfractalised by my client to the stage he could only just open it but do nothing with it. it didn't help that the client has also multipolied the whole thing. Still, all fixed now, and a very satisfied customer. Thanks for your pointers, folks.
SIMPLIFY with a 0.0 value will do things like merge completely straight end-to-end segments, but without otherwise affecting shapes. For those who would like to contemplate the exact inner workings of SIMPLIFY, the article Ramer–Douglas–Peucker algorithm - Wikipedia is a good starting point.
Well, I didn't know about the 0.0 thing. A good thing to remember. Thanks Joe