[Gdal-dev] Any hints on increasing performance?

[Rick Niles]

I've written a program to show line-of-sight coverage of various radars 
and aircraft navigation aids such as DME and VOR.  It should also work 
for com links as well.  I used the GDal library for reading in the 
terrain data (DTED Level 1, USGS DEM, or GTOPO30).  The problem is 
performance.  To do all of 48-US states it takes about an hour, which 
may seem quick, but I wanted to make it a web based application that has 
a faster turn-around.

I'm calling GDALRasterIO for one point at a time.  I know that's what 
everyone is going to say that is the bottleneck, but I tried reading all 
the data into arrays and it took 100x longer, because I don't use a 
large chunk of the data and reading it all in was quite time consuming, 
not to mention it used a huge amout of memory.   Also, with the caching 
that GDAL does, it works quite well.  BTW, I coverted the DEM and 
GTOPO30 data in GeoTiff format which helped a whole bunch too.

Anyway, the obvious answer is to just not evaluate as many locations, 
but I just thought I'd ask if someone had a better solution, since that 
effects the accuracy of the results.

I'm working on convincing my employeer to let me release it as 
open-source.   We'll see how that goes.

    Thanks,
    Rick Niles.