Geoida Help

Geoida very slow loading geoid file

Question: My job covers a very large area (thousands of square kilometres); when Geoida is loading the geoid file or is re-sizing it because of new points, it becomes very slow and takes some time for the progress bar to get to 100%.

Answer: The size of a sub-set of geoid data windowed from the primary geoid file increases according to the area of the job covered, ie if the dimensions of the area covered double in both east-west and north-south directions then the area will be 4 times larger. The number of nodes contained depends on the grid interval, so if the grid interval is 1 minute, an area 1 degree in longitude by 1 degree in latitude will contain 60 x 60 nodes = 3600 and the windowed file size will be approximately 100800 kb in size; however an area 10 degrees by 10 degrees will contain 600 x 600 = 360000 nodes and file size will be 10080000 kb or about 10 mb and performance will be adversely affected.

To aid performance where geoid interpolations are required:

1. Limit the extent of larger jobs as much as possible
   
   
2. Use as small a primary geoid file as possible. In Australia geoid files are available that cover whole states and even all of Australia, but it may be more efficient to select as the primary file one of the smaller series that match the 1:250,000 map sheets. Sometimes when one of these small primary geoid files is used, it may not even be necessary for Geoida to create a windowed file, either because it may not be significantly smaller than the original geoid file anyway, or because it may not be significantly more efficient than using the original file

If geoid interpolation is not needed, turn off Apply Geoid in Job Configuration.