Concepts
The COMET cost model
How each raster cell gets a relative crossing cost.
CO2GIS assigns every raster cell a relative crossing cost using the COMET formula. A cheap cell is easy and acceptable to cross; an expensive cell should be avoided.
The factors
Flu— land use. How acceptable the surface is to cross (unpopulated, cultivated, forest, urban, water…).Fs— slope. Steeper terrain is harder and costlier.Fci— crossing. The cost of crossing a road or railway.Fc— existing corridor. Routing alongside an existing corridor is cheaper (and encouraged).N— the number of road/rail features intersecting the cell.
Reading the formula
The bracket is a weighted average between land-use cost and crossing cost. With N = 0 (no infrastructure) the cell costs Flu; each crossing feature adds 10% weight toward the crossing cost Fci. N is capped at 10 so that (1 − 0.1·N) never goes negative — keeping the result mathematically and economically consistent.
Fc and Fs then scale the whole thing: an existing corridor on easy terrain pulls the cost down; a steep slope pushes it up.
All factors are pure multipliers. A value of 1.0 is the neutral baseline — 0.9 means 10% cheaper, 1.8 means 80% more expensive, 2.0 means double the cost. C_cell itself is dimensionless: it’s a relative cost multiplier applied to the base cost Bc, the diameter D, and the per-cell length L_cell when pricing the route — see Segment investment.
The full reference values are in Cost-factor tables.
Same factors, twice
These factors do double duty:
- building the cost surface that the routing minimises;
- pricing the CAPEX of the resulting route.
Because both use the same factors, the least-cost route is, by construction, also the cheapest to build. (At the routing stage the per-cell length L_cell is left out — constant scaling doesn’t change the optimal path — and reintroduced for the cost estimate.)
A generic tool — COMET is the default, not the tool
CO2GIS is not tied to COMET, nor to Portugal. COMET is the default cost model and supplies the formula above, but every factor value is editable — plug in your own region’s cost factors and the same machinery works. The COMET reference values (and the Portuguese COSc mapping) are provided as a convenient starting point: one approach, not the tool itself.
References
The cost-model formula and its reference factor values come from the COMET project and its paper:
van den Broek, M., Mesquita, P., Carneiro, J., Silva, J. R., Berghout, N., Ramírez, A., et al. (2013). Region Specific Challenges of a CO₂ Pipeline Infrastructure in the West Mediterranean Area: Model Results Versus Stakeholder Views. Energy Procedia, 37, 3137–3146. doi:10.1016/j.egypro.2013.06.200 — open access (Creative Commons).
COMET — Integrated Infrastructure for CO₂ Transport and Storage in the West Mediterranean (EU FP7 project 241400). CORDIS project page.