Acheng vs Songnim-ni
Tree cover and air quality for both, measured the same way: Sentinel-2 imagery at 10 m detail over a 2 km radius from each city centre, and the live US EPA air quality index. Same radius and same index, so the two numbers compare directly.
Songnim-ni has more tree cover — 55.1% against 38.5%.
Songnim-ni has cleaner air right now — AQI 38 against 45.
- Tree cover gap
- 16.6 points
- Songnim-ni is ahead.
- Air quality gap
- 7 AQI
- Songnim-ni is cleaner.
- Trees between them
- 52.4K
- Songnim-ni has more standing.
China
North Korea
Tree cover
Share of the 2 km radius under canopy.
38.5%
55.1%
Air quality index
US EPA index, live, with its band. Lower is better.
45 · Good
38 · Good
Trees standing
Estimated from the measured canopy area.
121K
173K
Trees still needed
To reach the same canopy target. Fewer is better.
0
0
CO₂ absorbed each year
By the trees already standing.
2.7M kg
3.8M kg
Air quality in detail
What each city is breathing
Concentrations in µg/m³, measured at the same moment as the index above. Lower is better in every row. Songnim-ni is read from nearby ground stations and Acheng is modelled — worth knowing, since the two are not quite like for like.
PM2.5
Fine particles, the pollutant that usually sets the index.
10.7 µg/m³
4.6 µg/m³
PM10
Coarser particles — dust, pollen, road grit.
11.8 µg/m³
5.4 µg/m³
Nitrogen dioxide
Mostly traffic and combustion.
9.5 µg/m³
1.1 µg/m³
Ozone
Forms in sunlight; peaks on hot, still afternoons.
88 µg/m³
101 µg/m³
The last week, day by day
A single reading can catch a city on a bad afternoon. The week says whether it was the weather or the place.
| Day | Acheng | Songnim-ni |
|---|---|---|
| 22 Sept | 71 | 59 |
| 23 Sept | 60 | 71 |
| 24 Sept | 56 | 69 |
| 25 Sept | 66 | 64 |
| 26 Sept | 80 | 63 |
| 27 Sept | 104 | 92 |
Reading these numbers
What is actually being measured
Tree cover
The share of ground under canopy inside a 2 km radius of each city centre, read from Sentinel-2 satellite imagery at 10 m detail. It is a measurement of that circle, not of the whole municipality — which is exactly what makes the two comparable, since city boundaries are drawn to wildly different rules around the world. Songnim-ni leads here at 55.1%.
Air quality index
The live US EPA index, computed from current pollutant concentrations — ground stations where a city has them nearby, and a model everywhere else. It moves hour to hour, so this is a snapshot rather than a verdict on either place: Acheng reads 45 (good) and Songnim-ni reads 38 (good) right now.
Frequently asked
Acheng and Songnim-ni, answered
Which has more trees, Acheng or Songnim-ni?
Songnim-ni, with roughly 173,102 trees inside its 2 km radius against 120,709. Tree cover tells a slightly different story from raw count: Songnim-ni has the denser canopy at 55.1%.
Which has better air quality, Acheng or Songnim-ni?
Songnim-ni right now, at AQI 38 against 45 — a gap of 7 points. This is a live reading rather than an annual average, so it can reverse within a day.
How many more trees does each city need?
Acheng needs about 0 more to reach its canopy target, and Songnim-ni about 0. The target is the same share of ground for both, so the figures are directly comparable.
Are these two measured the same way?
Yes — that is the point of the page. Identical radius, identical satellite source at 10 m detail, and the same US EPA index for air. Nothing here is adjusted for population, city limits or climate, so the numbers describe the same-sized circle of ground in each place.
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