Maplore® GoencheगोंयचेCarbon, khazan and coast How Goenche measures Goa
Nothing here is forecast or modelled from scratch. Every number is measured from open maps, cut to the boundary of each panchayat and municipality.
In short
- 200 places
- 186 village panchayats and 14 municipal bodies, covering 3,580 km² of Goa.
- 79% trees
- Of that land, by satellite at 10 m. Crops are 3%, built-up land 2%.ESA WorldCover 2021
- 13.9 Mt C
- Carbon in Goa's trees and shrubs above ground, an estimate from biomass. The top 30 cm of soil holds more: about 20.5 million tonnes.
- 13,027 ha
- Of khazan, the tidal fields behind Goa's bunds, and 566 km of bunds, from the state's draft coastal plan.
The boundaries
Each place on the map is a local body: a village panchayat, a municipality or the Corporation of the City of Panaji. The boundaries are ICAR-NBSS's, as assembled by amche.in, the community atlas of Goa, and matched to the government's Local Government Directory codes.
| Step | What we did |
|---|---|
| Read | 207 shapes from amche.in. |
| Repaired | 5 shapes whose outlines crossed themselves. |
| Joined | 7 pieces that belonged to a body already on the list. |
| Overlaps | 6.0 km² claimed by two neighbours, given to one, so no hectare is counted twice. |
| Missing | 5 of the 205 bodies in the directory have no boundary of their own: Rumdamol-Davorlim, Harvalem, Morlem, Shristhal, Quelossim. Their land is counted inside their neighbours. |
The layers
Five satellite maps, read only over Goa, straight from their publishers:
| Layer | From | What we take |
|---|---|---|
| Land cover | ESA WorldCover 2021, 10 m pixels. CC BY 4.0. | Share of each class (trees, crops, built-up, mangroves and others) in each local body |
| Tree loss | Hansen / UMD Global Forest Change v1.12, 30 m pixels. CC BY 4.0. | Hectares of tree cover lost each year, 2001–2024 |
| Biomass | ESA CCI Biomass v7.0, 2022 and 2010, 100 m pixels. Open, with credit. | Above-ground biomass, with its uncertainty; the change since 2010 |
| Soil carbon | SoilGrids 2.0 (ISRIC), 250 m pixels. CC BY 4.0. | Organic carbon in the top 30 cm |
| Surface water | JRC Global Surface Water 1984–2021, 30 m pixels. Open, with credit. | Water at least half the time (permanent) or ever (seasonal) |
And 10 mapped records, measured in metres on the ground (UTM zone 43N), never in degrees. Where plots overlap, the overlap is counted once. A layer we haven't been able to fetch shows as missing, never as zero.
Sharing a pixel
A panchayat boundary cuts straight through pixels. Goenche counts each pixel by how much of it lies inside: a 10 m square that is 30% inside Aldona adds 30% of its area to Aldona and the rest to its neighbour. This matters most for the coarse layers. A soil pixel is 250 m across, and a small panchayat may hold only a few dozen of them.
Hectares always come from the boundary's true area, measured on the ground. The satellite gives the share of each class; the share times the area gives the hectares.
A worked example: Bhati
Bhati, in Sanguem, holds more tree carbon than any other local body in Goa. Here is how its number is made.
| Step | Working | Result |
|---|---|---|
| Area | The boundary, measured on the ground | 13,064 ha |
| Biomass | Average above-ground biomass over its pixels, each weighted by how much lies inside | 142.3 t a hectare |
| Total biomass | 142.3 × 13,064 ha | 18,59,036 t |
| Carbon | × 0.47, the IPCC's default share of carbon in dry wood | 8,73,747 t C |
| As CO₂ | × 44 ⁄ 12 | 32,03,738 t |
| Uncertainty | The biomass map's own error, ± 78.7 t a hectare on average here | 3,90,515 to 13,56,978 t C |
The biomass map's error is given pixel by pixel; averaged over a whole panchayat the true total is likely closer than this range, but the map doesn't let us say how much closer, so the wide range is the one shown. Since 2010 the biomass here has changed by +20.5%.
Where sources disagree
Two sources measuring the same thing rarely agree, and Goenche shows both rather than picking the convenient one.
- Mangroves. WorldCover maps 40 km²; the Forest Survey of India counts 26 km² (ISFR 2023). They classify from different images with different rules, and the map shows both.
- Trees. WorldCover maps 2,841 km² under trees. The Forest Survey counts 2,219 km² of forest and 334 km² of trees outside it, 2,553 km² in all. The satellite counts any tree canopy it sees; the survey applies its own thresholds of canopy density and patch size.
- Tree loss. The Global Forest Change map's own picture of 2000 shows almost no trees over a fifth of the Mollem and Bhagwan Mahavir block, which WorldCover maps as 93% trees; its satellite images from 2000 were monsoon-clouded. So Goenche takes loss from that map on every pixel, not only where it thought trees stood in 2000, and takes tree cover from WorldCover. Loss since 2001 across Goa: 1,756 ha.
- Hazard lines. The coastal plan's hazard layer mixes three lines: hazard, low tide and high tide. Only the hazard line is measured; the tide lines trace every creek and would swamp it.
What it can't tell you
- Who owns land, or what may be built on it. The coastal zones and eco-sensitive area are shown as published; the notification, not the map, is the law. The eco-sensitive area is still a draft.
- Carbon for sale. The carbon figures are estimates from global maps, good for comparing panchayats, not for a carbon credit.
- Change since the maps were made. WorldCover is 2021, biomass 2022, soil a long-term average.
Built on amche.in by Public Map and its contributors, which gathered Goa's boundaries, khazan, wetlands and private forests in the open. The code that measures all of this is in Maplore's goa-profile pipeline; the numbers are stored with the run that produced them.