Qimera CUBE Options Dialog
How to Start
- CUBE sub-menu of the Dynamic Surface menu option in the Main Menu bar
What it Does
This dialog provides editing of key CUBE processing parameters.
|Distance Scale||Scale on predicted or estimated depth for how far out to accept data. (unitless; typically 5% for hydrography but can be greater for geological mapping in flat areas with sparse data)|
|Distance Min.||Only accept data with this radius.|
When running the CUBE algorithm, sometimes multiple hypotheses are generated. The algorithm must make a best guess on which hypothesis is correct using a Hypothesis Resolution Algorithm. The following algorithms are supported:
|Estimate Offset||Threshold for significant offset from current estimate to warrant an intervention.|
|Horizontal Error Scale||This parameter is used to control the exponential growth of a soundings vertical uncertainty as a function of distance from the node.|
|Distance Exponent||Exponent on distance for variance scale.|
|Queue Length||Length of median pre-filter sort queue.|
|Quotient Limit||Outlier quotient upper allowable limit.|
|Discount Factor||Discount factor for evolution noise variance.|
|Bayes Factor Threshold||Bayes factor threshold for either a single estimate, or the worst-case recent sequence to warrant an intervention.|
|Run Length Threshold||Run-length threshold for worst-case recent sequence to indicate a drift failure and hence to warrant an intervention.|
CUBE Capture Distance specifies how close a sounding must be in x/y distance to where the seafloor is being estimated. When building a dynamic surface the estimation point is the center of each cell in the surface. Thus you should never choose a distance which is smaller than the diagonal length of a cell or the surface might not get a value contribution from all samples in the incoming data. Generally speaking a diameter that is 1.25 * the cell size is a good option. The Distance Scale option adjusts the capture radius based on depth. For example if you choose 5% and the water depth was 25 meters for a particular incoming sounding then it would have a capture radius of 1.25m. This means it would contribute a value to any cells whose center was no more then 1.25 meters away from the measurement. The Distance Minimum is exactly that - every sounding is assigned exactly the same capture diameter as that which is given.
Internally, the CUBE algorithm has no concept of cells. A sounding may contribute to many different hypotheses depending on how far away the sounding is away from the hypothesis center in the XY plane. The Capture Distance option controls how far the sounding can be to contribute to a hypothesis and the algorithm assumes that deeper soundings will be less accurate. If the distance from the hypothesis center to the sounding is less than the sounding height multiplied by the Capture Distance percentage, the sounding will be included in the hypothesis. Smaller Capture Distance values result in less soundings contributing to a hypothesis and larger values result in more soundings contributing to a hypothesis. If the Capture Distance is too small, holes may appear in the data. In some cases, this Capture Distance does not make sense so to turn the algorithm off, enter 100 as the Capture Distance value.
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