Design rule purpose

The purpose of this design rule is to ensure that options generated by Optioneer avoid areas of high (risky) slopes. This is relevant for both onshore and offshore assets - steeper slopes mean more difficult construction, higher risk to the asset as a result of potential subsidence or long-term soil processes. A good, intuitive option for a linear asset follows mild slopes and only crosses high-slope areas if absolutely necessary.

How to configure

This design rule is fairly simple and is based on configuration of ranges of slope values and defining preference of crossing through these ranges.

In the example below, we demonstrate a simplified version of the model where only two slope ranges are present.

Slope values are derived from elevation or bathymetry dataset. Most systems in ArcGIS or QGIS would use logic similar to described in GDAL documentation here.

These slope values can be segmented into ranges. In this example, we consider two ranges - high slope (to be avoided) and low slope (below three degrees). The map, if segmented into separate datasets, would look as presented below.

In reality, Optioneer keeps the original dataset as-provided by users and samples values of the data along the centerline. The values are then divided into ranges and penalties are calculated appropriately. That allows the user to only provide a single dataset and make the configuration fully Optioneer-based and very flexible.

Important notes

  • The dataset provides a single value for slope and there is no data about the direction of slope. In general, side slopes are often more challenging than 'head on' slopes. There is no distinction between upwards or downwards slope.

  • Users don't have to use all ranges. Ranges can be simply set to be bound between 0 and 0 and will effectively be ignored by Optioneer.

  • There is a final threshold beyond which slope is simply considered infeasible and has to be treated as a no-go zone.

Input / output summary

Input parameters

This design rule requires a dedicated 'slope' dataset which has to be uploaded by the user as a raster file.

Name

Default value

Unit

'Preferable' slope range
minimum

maximum

penalty value

0,

3,

1

degrees,

degrees,

penalty points

'Moderate' slope range
minimum

maximum

penalty value

3,

5,

2

degrees,

degrees,

penalty points

'Acceptable' slope range
minimum

maximum

penalty value

5,

10,

4

degrees,

degrees,

penalty points

'Difficult' slope range
minimum

maximum

penalty value

10,

15,

8

degrees,

degrees,

penalty points

'Very difficult' slope range
minimum

maximum

penalty value

15,

25,

15

degrees,

degrees,

penalty points

Threshold to consider slope infeasible

25

degrees

Output parameters

Name

Example value

Unit

Total length through

'Preferable' slope range

1000

meters

Total length through

'Moderate' slope range

800

meters

Total length through

'Acceptable' slope range

400

meters

Total length through

'Difficult' slope range

1000

meters

Total length through

'Very difficult' slope range

100

meters

Total slope penalty

17800

points

This design rule can also provide visualisation of results along the centerline.

The plot can be accessed via Vertical Profile Chart > Composition > Penalty. The penalty will be mixed with other sources of penalty points, giving a quick insight into main risks related to the option being studied.

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