The scale minimum value for soundings is calculated using a file named sdgparm.txt in ...\CARIS\HPD\<version>\system.
Scale minimum value for soundings is calculated using a sounding suppression radius and a scale factor. The sounding suppression radius determines what soundings in an area will have scale minimum values applied. The scale factor sets the scale minimum value for a selected sounding.
Scale minimum values are calculated using one of these formulas:
• Scale minimum = CSCALE × scale factor: This uses the CSCALE attribute of the M_CSCL meta feature. Soundings must be within this meta feature.
• Scale minimum = (compilation scale ÷ 2) × scale factor: This uses the compilation scale of the chart. Soundings are not inside an M_CSCL meta feature.
• Scale minimum = compilation scale × CSCLMultiplier × scale factor: This uses the CSCLMultiplier, which is a user-defined numeric value in sdgparm.txt. CSCLMultiplier can only be used with the compilation scale of a product, not with a meta feature scale. This method gives you greater control over scale minimum value calculation.
To use either of the last two formulas, you must define CSCLMultiplier in sdgparm.txt. To do this, add the following line, where N.N is a numeric value:
CSCLMultiplier = N.N
To use only the compilation scale and scale factor (the second formula), set CSCLMultiplier to 1.0.
The scale factor is calculated from an algorithm that uses sounding suppression values contained in a table in sdgparm.txt. This is an example of the table:
Table Number Minimum Depth Maximum Depth Radius (sounding suppression) (meters) (meters) (mm at map scale)
1 0 3 40 1 3 30 20 1 30 9999 30
2 0 3 30 2 3 30 12 2 30 9999 25
3 0 3 20 3 3 30 7 3 30 9999 18
|
This example has three depth ranges, identified by the Table Number. This is used to link to a second table, which defines the scale factor:
Table Number Scale Factor 1 4.0 2 3.0 3 2.0 default 2.0 |
For example, depth range 1 will be assigned a scale factor of 4.
The scale minimum value command is iterative; that is, soundings are passed through each section in sdgparm.txt in order. In the above example, the assignment of scale minimum value is done using three passes through the data, one for each depth range.
For each depth range, the shallowest sounding within the sounding suppression radius is assigned a scale minimum value. These soundings are excluded from the next pass.
Example
In this example, a sounding has a Z value of 25 metres and the chart has a compilation scale of 4000. The sounding will always fall into the second range in each group in section 1.
• First pass: Table 1. Suppression radius 20mm at map scale.
• If the sounding is the shallowest within the suppression radius, the scale factor of 4.0 is determined from section 2. Scale minimum value is calculated and assigned to the sounding:
8000 |
• If the sounding is not the shallowest, no scale minimum value is assigned. The sounding is passed.
• Second pass: Table 2. Suppression radius 12mm at map scale.
• If the sounding is the shallowest within the suppression radius, the scale factor of 3.0 is determined from section 2. Scale minimum value is calculated and assigned to the sounding:
6000 |
• If the sounding is not the shallowest, no scale minimum value is assigned. The sounding is passed.
• Third pass: Table 3. Suppression radius 7mm at map scale.
• If the sounding is the shallowest within the suppression radius, the scale factor of 2.0 is determined from section 2. Scale minimum value is calculated and assigned to the sounding:
4000 |
• If the sounding is not the shallowest, no scale minimum value is assigned. The sounding is passed.
Remaining soundings are given a default scale value of 2.0 and therefore a scale minimum value of 4000.