ConceptStation - level of accuracy between USGS low, medium and high level terrain data from Geocoordination services

Hello,

I am looking to verify the accuracy of the various resolution options (low, medium and high) for the terrain data that ConceptStation can import from it's geocoordination services (within the US).

From what I understand, the data is pulled from from USGS. Does geocoordination services filter terrain data between each resolution option (low, medium, and high) at a set percentage and if so what is that value used? If not, what is the quantifiable differentiating factor between each resolution status?

Also, is there information available on the overall level of accuracy of the terrain imported from USGS and any specifics on how that data was collected?

Thank you,

Marc