Scale Factor

The SCAMIN value for soundings is calculated using a file named sdgparm.txt located in

C:\Program Files\CARIS\<application>\<version>\modules\S‑57 Composer\support

Formula	Description
SCAMIN = (compilation scale ÷ 2) × scale factor	Uses the compilation scale of the chart. Soundings are not inside an M_CSCL meta feature
SCAMIN = CSCALE × scale factor	Uses the CSCALE attribute. Soundings are within an M_CSCL meta feature.
SCAMIN = compilation scale × CSCLMultiplier × scale factor	Uses the `CSCLMultiplier` which is a user-defined numeric value. This method gives greater control over SCAMIN calculation. For example, to use only the compilation scale and scale factor for calculating SCAMIN, set `CSCLMulitplier` to 1.0. `CSCLMultiplier` can only be used with the compilation scale of a product and not with a meta feature scale. `CSCLMultiplier` is not included in the `sdgparam` file so it must be inserted into the file and saved.To include the `CSCLMultiplier` in the `sdgpram` file, type the following line: CSCLMultiplier = N.N where `N.N` is a numeric value.

Formula

Description

SCAMIN = (compilation scale ÷ 2) × scale factor

Uses the compilation scale of the chart. Soundings are not inside an M_CSCL meta feature

SCAMIN = CSCALE × scale factor

Uses the CSCALE attribute. Soundings are within an M_CSCL meta feature.

SCAMIN = compilation scale × CSCLMultiplier × scale factor

Uses the CSCLMultiplier which is a user-defined numeric value. This method gives greater control over SCAMIN calculation. For example, to use only the compilation scale and scale factor for calculating SCAMIN, set CSCLMulitplier to 1.0. CSCLMultiplier can only be used with the compilation scale of a product and not with a meta feature scale.

CSCLMultiplier is not included in the sdgparam file so it must be inserted into the file and saved.To include the CSCLMultiplier in the sdgpram file, type the following line:

CSCLMultiplier = N.N

where N.N is a numeric value.

The scale factor algorithm uses sounding suppression values from the sdgparm file. This is an example:

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

Table Number defines the scale factor that is used. This is shown in the second part of the sdgparm file.

Table Number Scale Factor

1 4.0

2 3.0

3 2.0

default 2.0

The SCAMIN command is run iteratively. Soundings are passed through each section in the sdgparm file. In the above example, the assignment of SCAMIN is done over three passes.

For each depth range, the shallowest soundings within a sounding suppression radius are assigned a SCAMIN value. These soundings are excluded from the next pass.

In the following example, Assign SCAMIN is run on a sounding with a Z value of 25 metres. The chart has a compilation scale of 4000. Use the above tables to follow this example.

• On the first pass, if that sounding is the shallowest within a suppression radius of 20 mm at map scale, a SCAMIN value is calculated using Table Number to assign a scale factor of 4.0: (4000 ÷ 2) × 4.0

• If the sounding is not the shallowest, it is passed through the parameters in the sdgparam file.

• On the second pass, if the sounding is the shallowest within suppression radius of 12 mm at map scale, a SCAMIN value is calculated using Table Number to assign a scale factor of 3.0: (4000 ÷ 2) × 3.0

• On the third pass, if the sounding is the shallowest within suppression radius of 7 mm at map scale, a SCAMIN value is calculated using Table Number to assign a scale factor of 2.0: (4000 ÷ 2) × 2.0