Soft ground map (Source: WesternGeco)
A soft ground map is created on a project/basin scale. A soft ground map is a raster file that highlights areas that are not suitable for vehicles/operations or present a risk for vehicles/operations. Soft ground mapping derived from EO data provides the user a first look at the surface and its suitability for oil field operations. EO derived data are good at identifying areas of sabkha (wet and dry), peat/marsh/bog areas and potential high water table areas.
Soft ground mapping is a product of topography (soft ground typically occurs in topographic lows), terrain information such as vegetation cover and the surface lithology.
The soft ground map is a supervised classification of multispectral optical satellite data combined with topographic data to produce a clear risk map that identifies locations of soft or wet ground. Soft ground tends to be found in coastal areas, but inland topographic lows are also possible risks.
Seasonal variations are important to appreciate and account for. Review of multi-temporal imagery can be beneficial to identify seasonal variations in soft ground.
A radar dataset would not typically provide an input to this product, but may be applicable to geographies where there is a lack of cloud-free optical data e.g. tropics.
DEM data (optically or radar derived) can provide detail of soft ground at different resolutions. Elevation mapping helps identify topographic lows and areas where the water table maybe high.
Known restrictions / limitations
Cloud cover would be a limitation on the optical data, most commonly in tropical areas, however archive imagery should provide mitigation against this.
Seasonality will have an impact so it is important for the user to understand when the image was acquired and the preceding weather conditions.
In dense vegetation where bare earth models are needed (for example in Seismic Planning) EO derived products cannot provide a solution.
Soft ground mapping from DEM data is limited by the availability of DEM data. DEM data derived from stereo pairs can have a lead time of 3 weeks, but have a higher degree of accuracy than freely available lower resolution DEM’s. Commercial radar derived DEM data are available off-the-shelf, with affected in steep mountainous regions and densely vegetated regions.
Lifecycle stage and demand
Geographic coverage and demand
Global coverage (with a few restrictions see below). Demand in remote regions is high with exposed non vegetated surfaces best suited.
Input data sources
Optical: VHR1, VHR2, HR1, HR2, MR1
Spatial resolution and coverage
Spatial resolution: 1 m – 90 m pixel size
Minimum Mapping Unit (MMU)
Variable, depending on source data resolution MMU as small as 0.5 ha is possible.
Accuracy / constraints
Thematic accuracy: 80-90%
Spatial accuracy: The goal would be one pixel, but depends on reference data
Accuracies for selected off-the-shelf elevation products:
Accuracy assessment approach & quality control measures
Stratified random points sampling approach utilizing in-situ measurements and any available published data or reports. Statistical confusion matrix with user’s, producer’s accuracy and kappa statistics for hydrological network and catchment area mapping.
Frequency / timeliness
Observation frequency: Archive data can be used although new acquisition may be a requirement in some situations. The frequency is constrained by client needs, satellite revisit and acquisition timeframes, but also processing requirements. Depending on the requirements of the customer the best suitable satellite sensor has to be chosen regarding spatial / spectral resolution as well as revisit frequency.
Timeliness of delivery: Delivery in time with project planning requirements. Archive data can be used to good effect if the prevailing conditions are known and the time of year is accounted for.
Freely available or commercially acquired depending on the selected sensor and methodology used.
Availability if DEM data:
1km, 90m (most common) and 30m DEM are freely available from SRTM version 3 and Aster GDEM2 for higher resolution this is a paid for data set. These data sets for example are Elevation 30 (SPOT DEM 30m), WorldDEM (TanDEM-X 12m), Elevation 8 (SPOT DEM 8m), Elevation 4 & 1 (Pleiades DEM 4m & 1m), WorldView Elevation Suite (1m).
Delivery / output format
|Peer Reviewer:||Hatfield Consultants|
# of Pages:
Internal – Project consortium and science partners
External – ESA
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