Frame the decision
What is to be built, to what tolerance, and what would make the site the wrong one. A platform for containers and a site for gravity irrigation fail for entirely different reasons.
Ghana terrain and site intelligence / Capability 02
TerraGhana™
Make the site reveal its constraints before design begins.
Terrain, drainage, soil and climate signals combined into a defensible site-suitability and earthworks decision layer.
DecisionBuild · re-grade · re-site
ControlGround proven before design
CoverageAll 16 Ghana regions
Terrain, drainage and suitability layer / Ghana Live
Slope · water · bearing
Resolvable gradient / peak flow / outfall capacity / suitability
Operating model
Most sites fail
before the first drawing.
Ghanaian projects rarely fail because the structure was wrong. They fail because the platform was set from a global elevation model that could not see a 1% fall, because an expansive clay was never tested, or because the drain the design discharged into had never been surveyed. TerraGhana™ settles all three before the design starts.
Establish the ground model
A terrain model whose accuracy is stated, on Ghana National Grid with a declared transformation. Free global DEMs screen a site; they cannot set out a platform.
Investigate the ground
Boreholes and trial pits to below the depth of influence, with SPT, CBR and swell testing where the clays demand it. A published soil range is a hypothesis, not a bearing.
Model the water
Catchment, flow path, concentration time, pre- and post-development peaks, and the delivered capacity of the drain that actually receives the discharge.
Test the statutory position
Riparian buffers, wetland and Ramsar screening, EPA registration under LI 1652, planning permission and the affected persons the earthworks would reach.
Return a decision, not a map
Suitability, the earthworks burden, the constraints that block the use as drawn, and the register of what must be resolved before design proceeds.
Accuracy decides what you may conclude
A contour you cannot see
is not a contour.
Copernicus GLO-30 DEM
Better edited than SRTM and the best free option for a Ghanaian screening study; still a canopy-influenced surface.
Resolves gradients to 36.96% · contours to 15.68 m
TanDEM-X 12 m (licensed)
Licensed radar DEM. Good regional relief, still not bare earth under closed forest.
Resolves gradients to 46.20% · contours to 7.84 m
Satellite stereo photogrammetry (0.5 m imagery)
Useful where no flight is possible; fails under canopy and in deep shadow.
Resolves gradients to 138.59% · contours to 3.92 m
UAV photogrammetry with surveyed ground control
Bare-earth only where the ground is visible — vegetation must be cleared or the model is a canopy surface.
Resolves gradients to 166.31% · contours to 0.24 m
Airborne LiDAR
The only aerial method that returns true bare earth under vegetation in Ghanaian conditions.
Resolves gradients to 66.52% · contours to 0.47 m
Ground survey — GNSS RTK / total station grid
Highest point accuracy, lowest density. Interpolation between points is the real uncertainty, not the point itself.
Resolves gradients to 0.55% · contours to 0.08 m
Why Ghanaian ground is its own problem
The Accra plains carry expansive Akuse clays that move through the seasons and crack slabs founded on them. The savanna sits on ironpan that bears magnificently and infiltrates nothing, so a cleared site behaves hydrologically as if it were already paved. The forest zone hides deep, variable saprolite under canopy that no radar DEM can see through. And everywhere, a single wet-season storm at 90 mm/h will find the one drainage assumption nobody surveyed.
Service boundary
TerraGhana™ establishes the ground model, the hydrology and the suitability position, and states the accuracy behind each. Geotechnical design and foundation certification remain with the geotechnical engineer; structural and civil design remain with the designer; environmental permitting remains with the EPA under LI 1652; planning permission remains with the Assembly; and boundary certification remains with a licensed surveyor.
TerraGhana™ terrain and site desk / Ghana
Make the ground
declare itself first.
Site suitability55/ 100 · Constrained
Drainage exposure35%
Earthworks index100/100
Resolvable gradient36.96%
Evidence confidence0%
01 / The site
Where the ground is, what is to be built on it, and what it is made of
Accra plains — Densu and Sakumono catchments: Shallow gradients over Akuse/Accraian clays. Drainage is long and flat, so a small blockage backs water a long way upstream.
Lateritic gravel over weathered rock: The best common founding and subgrade material in Ghana. Competent when compacted, but the weathered profile beneath it can be deep and variable. Hydrologic group B, shrink–swell low.
Housing estate or residential layout: Plot-by-plot grading, gravity sewerage and internal roads; the layout absorbs slope better than a single platform but drainage falls must still work.
02 / The terrain model
What the ground model can actually resolve
Copernicus GLO-30 DEM: Better edited than SRTM and the best free option for a Ghanaian screening study; still a canopy-influenced surface.
At 30 m grid and ±4 m vertical accuracy, this model resolves gradients no finer than 36.96% and supports a contour interval of 15.68 m at 95% confidence. The platform is designed to 1.5% — the model cannot see it, so grading from it would be guesswork.
Relief across the site works out at 8.66 m over a 346.4 m span, against a model relief uncertainty of ±11.09 m. That relief is inside the noise of the model — it cannot be relied on.
03 / Water
What the storm does, and where it is meant to go
04 / Controls
What has actually been done before design
Saved to your workspace with every input, every method and every gap that remains.
Siting gate
Hold — resolve the ground before design
55/100 suitability (Constrained) · evidence confidence 0% · control coverage 0%.
Evidence basis
Working from the figures typed on this desk only. Upload terrain, ground investigation and drainage evidence to the Ghana data studio and the desk will read it instead.
- Topographic survey or LiDAR — without it the gradient is read from a global model that cannot resolve a platform fall
- Borehole or trial-pit log — bearing and settlement cannot be taken from a published soil range
- Soil, CBR or swell test — decides whether the cut can be reused as engineered fill
- Drainage or outfall section survey — the developed peak has nothing to be tested against
- Rainfall or IDF record — the design storm should come from a Ghanaian gauge, not a default
- Observed flood record — a recorded high-water mark outranks any model for the same site
- EPA or wetland screening — the buffer and permit position must be evidenced before earthworks
- Land record for the site — ties the platform to a parcel interest rather than an area on a plan
Site section · 346.4 m span, 8.66 m relief
The section is drawn from the stated mean gradient over the square-root span of the site, not from a surveyed profile. The amber bar is what the terrain model cannot see: any feature smaller than ±11.09 m is noise until a survey-grade model replaces it.
Storm against capacity · 10-year event at 90 mm/h
Pre-development peak0.751 m³/s
Developed peak1.824 m³/s
Surveyed outfall capacityNot surveyed
Rational method, runoff coefficient 0.25 before and 0.61 after development, concentration time 15.8 minutes by Kirpich. Runoff rises 143% on development. The receiving drain has not been surveyed, so no surcharge ratio is computable.
Earthworks to a 1.5% platform
Cut51,958 m³
Fill51,958 m³
Unsuitable material2,598 m³
To import7,794 m³
Balanced-platform estimate over 12 ha with 8.66 m of relief, a shrinkage factor of 0.9 for lateritic gravel over weathered rock, and 5% of the cut treated as unusable as engineered fill. No import rate stated, so the earthworks are not costed. A mass-haul from a survey-grade model replaces this estimate.
Suitability, criterion by criterion
- Gradient against the intended use85/100 · weight 16% · asserted
2.5% mean gradient against a workable 12% for housing estate or residential layout. Read from Copernicus GLO-30 DEM, which cannot resolve a gradient finer than 36.96%.
- Terrain model fit for the decision20/100 · weight 12% · asserted
Copernicus GLO-30 DEM resolves gradients only to 36.96%, coarser than the 1.5% platform fall. Grading set out from it would be guesswork.
- Ground bearing for the intended loads100/100 · weight 14% · asserted
No measured bearing on file. Lateritic gravel over weathered rock typically offers 200–400 kPa against 100 kPa required — a published range, not this site.
- Outfall capacity against the design storm0/100 · weight 15% · asserted
No outfall capacity on file, so the developed peak has nothing to be tested against. Survey the receiving drain.
- Flood and waterlogging exposure65/100 · weight 14% · asserted
Not yet asked. Water table at 3 m, accra plains — densu and sakumono catchments, hydrologic group B.
- Earthworks burden0/100 · weight 11% · asserted
103,916 m³ of cut and fill to reach a 1.5% platform, 8,660 m³ per hectare, with 7,794 m³ to import.
- Erosion and slope stability75/100 · weight 8% · asserted
Slope-length factor 0.99 on lateritic gravel over weathered rock at 90 mm/h. Exposed faces and stockpiles need protection before the first major storm.
- Riparian, wetland and statutory setbacks100/100 · weight 10% · asserted
120 m to the nearest watercourse against a 30 m required buffer for a 6 m channel.
Constraints
- The terrain model cannot resolve the platform fall this use needs (36.96% against 1.5%). Commission a survey-grade model before grading.
- The receiving drain has not been surveyed, so the developed peak has nothing to be tested against.
- 6 of 6 investigation positions still to be sunk for a 12 ha site.
- Flood history has not been asked of the community or NADMO — the cheapest evidence available on this site.
- No EPA screening or permit recorded for the intended use.
Evidence pack for the design and the permit
- Topographic survey or LiDAR on national control
- Ground investigation report with bearing and CBR
- Drainage catchment and outfall capacity survey
- Design storm and rainfall basis stated
- Flood history from the community and NADMO
- Riparian buffer set out and wetlands screened
- EPA screening or permit for the intended use
- Earthworks mass-haul and borrow/spoil plan
- Erosion and sediment control plan for the wet season
- Affected-persons and access screening
05 / Action register
What has to happen before this ground is designed on
Before detailed design
Commission a survey-grade terrain model
Copernicus GLO-30 DEM resolves 36.96%; the platform is designed to 1.5%. UAV photogrammetry on surveyed control, or LiDAR where the site carries canopy, both resolve it. Tie it to Ghana National Grid with a stated transformation.
Before any earthworks
Survey the receiving drain and prove a legal outfall
Section, invert and condition survey of the drain 350 m away, then confirm with the Assembly and the downstream owner that a discharge of about 1.824 m³/s is accepted.
Before detailed design
Ask the community and NADMO about flooding
Walk the site with long-standing occupiers, record high-water marks on standing structures and level them. One afternoon of this outranks any global model for the same site.
Before detailed design
Plan for unsuitable material
About 2,598 m³ of the cut is unlikely to be reusable as engineered fill on lateritic gravel over weathered rock. Identify a permitted spoil destination and a borrow source of equivalent volume.
Before detailed design
Register the undertaking with the EPA
Screening under LI 1652 for the intended use, obtained before earthworks. A stop notice after the platform is cut costs far more than the screening did.
Before detailed design
Screen affected persons and access
Farms, tenancies, shrines, graves, footpaths and abutting occupiers identified and recorded, with the access route agreed before plant is mobilised.
Acquire stage / the chain
Nothing here
stands alone.
TerraGhana™ answers “Will the ground carry this use?”. It produces the terrain model, drainage regime and siting gate — and that record is exactly what the next desk refuses to work without.
Feeds in
LandIntel™The verified parcel boundary the terrain study is cut toHydroGhana™Observed flood record that upgrades the siting assessment02 / now
TerraGhana™
Terrain, drainage, soil and climate signals combined into a defensible site-suitability and earthworks decision layer.
TerrainDrainageClimate risk
Feeds on
Subsurface Ghana™Ground conditions that decide what detection kit can seeHydroGhana™Terrain accuracy, catchment and outfall levelsBuildGhana™Design platform levels and earthworks baselineMineGhana™Terrain surfaces and ground conditions behind the pit and dump volumesInfraGhana™Earthworks baseline and drainage design the works are measured againstConnected intelligence
Evidence, research
and access.
The public evidence library and licensing catalogue stay connected to this capability. New published material appears here automatically.
From analysis to site
Brief one decision.
We resolve the ground.
Send the operating question, geography and timing. The team returns a scoped pilot with inputs, outputs and evidence standard defined.