Friday, October 07, 2005

 

Google Earth and large data files

As people discover the power of Google Earth, they are producing larger and larger collections of placemarks.

Some fairly large collections include:
However, these are all eclipsed by two collections (presumably produced from the same raw data) of about 36500 cities in France: Collection 1, Collection 2.

Beware though - Google Earth shows why it it still in beta - it's extremely unstable, and when given sizable files is very prone to crash. Note that a crash will lose any placemarks you have accumulated since you last started Google Earth - even if they are in the "permanent" section of the placemarks (ie. not just in the Temporary Places section).

So Google Earth team, please get your act in order, and do two things:
I find that the safe limit on the number of placemarks in a file is somewhere in the low hundreds - I've not had a problem with my countries file (and noone else has reported problems with it to me), but stepping up beyond 500+ placemarks more often than not causes a crash.

Comments:
We have been experimenting with converting VMAP data into KML and a dataset with about 15,000 points seems to be OK. However, I have found that if you set the LookAt values so when you open the data you're already zoomed in and don't display the entire dataset at once - or set visibility off for the detailed themes then you'll be more successful.
Mark Stoakes
Safe Software - makers of FME
 
I was drawing a long path (Google Earth plus) and found that after about 3773 points, adding another point caused the entire path to become invisible. I Subtracted the added point and all was well. But at least the program didn't crash or act up after doing this.
 
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