[GRASSLIST:4713] Re: vector point dataset

[Radim Blazek]

It is normal.
Spatial index is important also for points, I think. Otherwise 
v.distance for example
must always go through all points. Say that you have another vector with 
4,000,000
and you want to find the nearst in the first one. Withou spatial index it
must do 4,000,000 x 4,000,000 checks.
Spatial index is stored as tree of boxes, 6x8 bytes each, so 430 M is 
possible.

Any advice appreciated....


Brent Wood wrote:

>I have a vector point dataset (ascii XYZ, the basis of a DEM).
>
>I'm importing into GRASS5.7 with
>
>cat <file> | v.in.ascii -Z output=nzxyz xcol=1 ycol=2 zcol=2 catcol=0
>
>There are about 4,000,000 XYZ points.
>
>The vector coor file is 150Mb. GRASS is now building the topology & index.
>The topo file is almost 200Mb and the sidx is at 430Mb and growing.
>
>Is this normal? It seems very excessive for a point dataset. A spatial
>index & topology make more sense for line/polygon data, with over 4x the
>actual data volume to store this extra info doesn't look right somehow...
>
>The system is a SuSE Linux 9.1 23 bit OS on A64 3500 with 1Gb memory.
>Swapped out 1.4Gb & still using 800Mb main memory.
>
>
>Any advice appreciated....
>
>
>  Brent Wood
>  
>