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DEM-Terrain

Global terrain data (elevation, slope, aspect) pre-computed on H3 hexagonal grids, stored as Parquet files for fast spatial queries. https://walkthru.earth/indices?section=terrain

Product Details

Visibility: Public
Owner: walkthru.earth
Created: 1 Mar 2026
Last Updated: 11 Mar 2026

Product Contents

root

README

Global DEM Terrain Derivatives

H3-indexed terrain data from GEDTM-30m in Apache Parquet format. Ten H3 resolutions (1–10), one file per resolution, sorted by h3_index. Available in two versions: v2 (recommended) with BIGINT h3_index and no geometry columns, and v1 (legacy) with VARCHAR h3_index and native Parquet 2.11+ GEOMETRY.


Source	GEDTM-30m (OpenGeoHub), 30m resolution, global land coverage
Format	Apache Parquet — v2: BIGINT h3_index, no geometry; v1: VARCHAR h3_index, native GEOMETRY (DuckDB 1.5)
CRS	EPSG:4326 (WGS 84)
License	CC BY 4.0 by walkthru.earth
Code	walkthru-earth/dem-terrain

Quick Start

v2 (recommended)

For deck.gl H3HexagonLayer (needs hex string):

v1 (legacy — requires `INSTALL spatial`)

Files

v2 (recommended)

v1 (legacy)

Same cell counts and resolutions as v2.

Total: 10,450,894,746 cells (~10.5 billion) in ~287 GB. Compression: ZSTD level 3. Row groups: 1,000,000 rows.

Schema

v2 (recommended)

Column	Type	Unit	Description
`h3_index`	BIGINT	—	H3 cell ID (int64). Sorted for delta encoding compression and range-based queries.
`elev`	FLOAT	meters	Elevation above sea level
`slope`	FLOAT	degrees	Terrain slope (0 = flat, 90 = cliff)
`aspect`	FLOAT	degrees	Slope direction (0/360 = N, 90 = E, 180 = S, 270 = W)
`tri`	FLOAT	meters	Terrain Ruggedness Index — mean abs. elevation diff to 8 neighbors
`tpi`	FLOAT	meters	Topographic Position Index — elevation minus mean of 8 neighbors (+ridge, -valley)

geometry, lat, and lon columns are removed in v2 — derive them via the DuckDB h3 extension: h3_cell_to_lat(h3_index), h3_cell_to_lng(h3_index), h3_cell_to_boundary_wkt(h3_index).

v1 (legacy)

Column	Type	Unit	Description
`h3_index`	VARCHAR	—	H3 cell ID (hex string)
`geometry`	GEOMETRY	—	Cell center point (native Parquet 2.11+ GEOMETRY, EPSG:4326)
`lat`	FLOAT	degrees	Cell center latitude
`lon`	FLOAT	degrees	Cell center longitude
`elev`	FLOAT	meters	Elevation above sea level
`slope`	FLOAT	degrees	Terrain slope (0 = flat, 90 = cliff)
`aspect`	FLOAT	degrees	Slope direction (0/360 = N, 90 = E, 180 = S, 270 = W)
`tri`	FLOAT

Sample values (res 5, Everest region):

h3_index	elev	slope	aspect	tri	tpi
853c0317fffffff	6,879 m	40.8°	134°	327 m	52 m
853c03bbfffffff	6,568 m	23.0°	221°	223 m	31 m

How It Works

Terrain derivatives are computed from the GEDTM-30m elevation raster:

Derivative	Method	Reference
Slope	`arctan(√(dz/dx² + dz/dy²))` via central differences, pixel sizes converted to meters using latitude-dependent scale	Horn (1981)
Aspect	`atan2(-dz/dx, dz/dy)`, converted to 0–360° compass bearing	Horn (1981)
TRI	Mean absolute elevation difference across 3×3 neighborhood	Riley et al. (1999)
TPI	Center pixel minus mean of 3×3 neighborhood	Weiss (2001)

Values at H3 cell centers are obtained by bilinear interpolation from the raster grid (scipy RegularGridInterpolator).

DEM is read at different resolutions depending on H3 level:

H3 Res	DEM Sampling	Rationale
1–5	~500 m	Cells are 8–418 km; coarse DEM sufficient
6–7	~110 m	Cells are 1.2–3.2 km; finer detail needed
8–10	~30 m (native)	Cells are 66–461 m; full resolution

More Examples

v2 queries

v1 legacy queries (requires `INSTALL spatial`)

Geometry Format

v2 drops the geometry column entirely. Coordinates are derivable from the BIGINT h3_index via the DuckDB h3 extension (h3_cell_to_lat, h3_cell_to_lng, h3_cell_to_boundary_wkt). This eliminates the need for INSTALL spatial and reduces file size.

v1 retains the geometry column, written with GEOPARQUET_VERSION 'BOTH', providing dual compatibility:

Native Parquet 2.11+ GEOMETRY logical type — per-row-group bounding box statistics for spatial filter pushdown. Supported by DuckDB 1.5+, Apache Arrow (Rust), Apache Iceberg, GDAL 3.12+.
GeoParquet 1.0 geo file-level metadata — backwards compatibility with older tools (QGIS, pyarrow, GeoPandas).

Source

GEDTM-30m — Global Ensemble Digital Terrain Model at 30m resolution. Cloud Optimized GeoTIFF, 1,440,010 × 600,010 px, Int32 (decimeters, scale 0.1), EPSG:4326, global land coverage 65°S–85°N.

Ho, Y., Grohmann, C. H., Lindsay, J., Reuter, H. I., Parente, L., Witjes, M., & Hengl, T. (2025). GEDTM30: global ensemble digital terrain model at 30 m and derived multiscale terrain variables. PeerJ, 13, e19673. doi:10.7717/peerj.19673

Dataset: doi:10.5281/zenodo.14900181

License

This dataset is licensed under CC BY 4.0 by walkthru.earth. The source GEDTM-30m is licensed under CC BY 4.0 by OpenGeoHub.

README

Global DEM Terrain Derivatives


Source	GEDTM-30m (OpenGeoHub), 30m resolution, global land coverage
Format	Apache Parquet — v2: BIGINT h3_index, no geometry; v1: VARCHAR h3_index, native GEOMETRY (DuckDB 1.5)
CRS	EPSG:4326 (WGS 84)
License	CC BY 4.0 by walkthru.earth
Code	walkthru-earth/dem-terrain

Quick Start

v2 (recommended)

For deck.gl H3HexagonLayer (needs hex string):

v1 (legacy — requires `INSTALL spatial`)

Files

v2 (recommended)

v1 (legacy)

Same cell counts and resolutions as v2.

Total: 10,450,894,746 cells (~10.5 billion) in ~287 GB. Compression: ZSTD level 3. Row groups: 1,000,000 rows.

Schema

v2 (recommended)

Column	Type	Unit	Description
`h3_index`	BIGINT	—	H3 cell ID (int64). Sorted for delta encoding compression and range-based queries.
`elev`	FLOAT	meters	Elevation above sea level
`slope`	FLOAT	degrees	Terrain slope (0 = flat, 90 = cliff)
`aspect`	FLOAT	degrees	Slope direction (0/360 = N, 90 = E, 180 = S, 270 = W)
`tri`	FLOAT	meters	Terrain Ruggedness Index — mean abs. elevation diff to 8 neighbors
`tpi`	FLOAT	meters	Topographic Position Index — elevation minus mean of 8 neighbors (+ridge, -valley)

geometry, lat, and lon columns are removed in v2 — derive them via the DuckDB h3 extension: h3_cell_to_lat(h3_index), h3_cell_to_lng(h3_index), h3_cell_to_boundary_wkt(h3_index).

v1 (legacy)

Column	Type	Unit	Description
`h3_index`	VARCHAR	—	H3 cell ID (hex string)
`geometry`	GEOMETRY	—	Cell center point (native Parquet 2.11+ GEOMETRY, EPSG:4326)
`lat`	FLOAT	degrees	Cell center latitude
`lon`	FLOAT	degrees	Cell center longitude
`elev`	FLOAT	meters	Elevation above sea level
`slope`	FLOAT	degrees	Terrain slope (0 = flat, 90 = cliff)
`aspect`	FLOAT	degrees	Slope direction (0/360 = N, 90 = E, 180 = S, 270 = W)
`tri`	FLOAT

Sample values (res 5, Everest region):

h3_index	elev	slope	aspect	tri	tpi
853c0317fffffff	6,879 m	40.8°	134°	327 m	52 m
853c03bbfffffff	6,568 m	23.0°	221°	223 m	31 m

How It Works

Terrain derivatives are computed from the GEDTM-30m elevation raster:

Derivative	Method	Reference
Slope	`arctan(√(dz/dx² + dz/dy²))` via central differences, pixel sizes converted to meters using latitude-dependent scale	Horn (1981)
Aspect	`atan2(-dz/dx, dz/dy)`, converted to 0–360° compass bearing	Horn (1981)
TRI	Mean absolute elevation difference across 3×3 neighborhood	Riley et al. (1999)
TPI	Center pixel minus mean of 3×3 neighborhood	Weiss (2001)

Values at H3 cell centers are obtained by bilinear interpolation from the raster grid (scipy RegularGridInterpolator).

DEM is read at different resolutions depending on H3 level:

H3 Res	DEM Sampling	Rationale
1–5	~500 m	Cells are 8–418 km; coarse DEM sufficient
6–7	~110 m	Cells are 1.2–3.2 km; finer detail needed
8–10	~30 m (native)	Cells are 66–461 m; full resolution

More Examples

v2 queries

v1 legacy queries (requires `INSTALL spatial`)

Geometry Format

v1 retains the geometry column, written with GEOPARQUET_VERSION 'BOTH', providing dual compatibility:

Native Parquet 2.11+ GEOMETRY logical type — per-row-group bounding box statistics for spatial filter pushdown. Supported by DuckDB 1.5+, Apache Arrow (Rust), Apache Iceberg, GDAL 3.12+.
GeoParquet 1.0 geo file-level metadata — backwards compatibility with older tools (QGIS, pyarrow, GeoPandas).

Source

GEDTM-30m — Global Ensemble Digital Terrain Model at 30m resolution. Cloud Optimized GeoTIFF, 1,440,010 × 600,010 px, Int32 (decimeters, scale 0.1), EPSG:4326, global land coverage 65°S–85°N.

Ho, Y., Grohmann, C. H., Lindsay, J., Reuter, H. I., Parente, L., Witjes, M., & Hengl, T. (2025). GEDTM30: global ensemble digital terrain model at 30 m and derived multiscale terrain variables. PeerJ, 13, e19673. doi:10.7717/peerj.19673

Dataset: doi:10.5281/zenodo.14900181

License

This dataset is licensed under CC BY 4.0 by walkthru.earth. The source GEDTM-30m is licensed under CC BY 4.0 by OpenGeoHub.

1walkthru-earth/dem-terrain/
2  v2/h3/
3    h3_res=1/data.parquet       12 KB           223 cells
4    h3_res=2/data.parquet       57 KB         1,546 cells
5    h3_res=3/data.parquet      373 KB        10,851 cells
6    h3_res=4/data.parquet      2.5 MB        76,135 cells
7    h3_res=5/data.parquet       17 MB       533,062 cells
8    h3_res=6/data.parquet      115 MB     3,730,922 cells
9    h3_res=7/data.parquet      783 MB    26,115,785 cells
10    h3_res=8/data.parquet      5.3 GB   182,814,924 cells
11    h3_res=9/data.parquet     36.1 GB 1,279,700,961 cells
12    h3_res=10/data.parquet   244.7 GB 8,957,910,337 cells

1walkthru-earth/dem-terrain/
2  v2/h3/
3    h3_res=1/data.parquet       12 KB           223 cells
4    h3_res=2/data.parquet       57 KB         1,546 cells
5    h3_res=3/data.parquet      373 KB        10,851 cells
6    h3_res=4/data.parquet      2.5 MB        76,135 cells
7    h3_res=5/data.parquet       17 MB       533,062 cells
8    h3_res=6/data.parquet      115 MB     3,730,922 cells
9    h3_res=7/data.parquet      783 MB    26,115,785 cells
10    h3_res=8/data.parquet      5.3 GB   182,814,924 cells
11    h3_res=9/data.parquet     36.1 GB 1,279,700,961 cells
12    h3_res=10/data.parquet   244.7 GB 8,957,910,337 cells

1walkthru-earth/dem-terrain/
2  v1/h3/
3    h3_res=1/data.parquet  ...  h3_res=10/data.parquet

1walkthru-earth/dem-terrain/
2  v1/h3/
3    h3_res=1/data.parquet  ...  h3_res=10/data.parquet

1-- DuckDB — no spatial extension needed for v2
2INSTALL h3 FROM community; LOAD h3;
3INSTALL httpfs; LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index,
7       h3_cell_to_lat(h3_index) AS lat,
8       h3_cell_to_lng(h3_index) AS lng,
9       elev, slope, aspect
10FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet')
11WHERE h3_index BETWEEN ? AND ?  -- row group statistics prune efficiently
12ORDER BY elev DESC
13LIMIT 20;

1-- DuckDB — no spatial extension needed for v2
2INSTALL h3 FROM community; LOAD h3;
3INSTALL httpfs; LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index,
7       h3_cell_to_lat(h3_index) AS lat,
8       h3_cell_to_lng(h3_index) AS lng,
9       elev, slope, aspect
10FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet')
11WHERE h3_index BETWEEN ? AND ?  -- row group statistics prune efficiently
12ORDER BY elev DESC
13LIMIT 20;

1SELECT h3_h3_to_string(h3_index) AS h3_hex, elev
2FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet')

1SELECT h3_h3_to_string(h3_index) AS h3_hex, elev
2FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet')

1-- DuckDB
2INSTALL spatial; LOAD spatial;
3INSTALL httpfs;  LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index, elev, slope, aspect, tri, tpi
7FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=5/data.parquet')
8WHERE lat BETWEEN 35 AND 45
9  AND lon BETWEEN -10 AND 5
10ORDER BY elev DESC
11LIMIT 20;

1-- DuckDB
2INSTALL spatial; LOAD spatial;
3INSTALL httpfs;  LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index, elev, slope, aspect, tri, tpi
7FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=5/data.parquet')
8WHERE lat BETWEEN 35 AND 45
9  AND lon BETWEEN -10 AND 5
10ORDER BY elev DESC
11LIMIT 20;

1-- Range query on sorted BIGINT h3_index — row group min/max statistics prune efficiently
2INSTALL h3 FROM community; LOAD h3;
3INSTALL httpfs; LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index,
7       h3_cell_to_lat(h3_index) AS lat,
8       h3_cell_to_lng(h3_index) AS lng,
9       elev, slope
10FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=7/data.parquet')
11WHERE h3_index BETWEEN ? AND ?
12ORDER BY elev DESC
13LIMIT 100;
14
15-- Query across all resolutions (Hive partitioning)
16SELECT h3_res, h3_index, elev
17FROM read_parquet(
18    's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=*/data.parquet',
19    hive_partitioning = true
20)
21WHERE h3_res = 5
22ORDER BY elev DESC
23LIMIT 20;
24
25-- DuckDB-WASM (browser) — use HTTPS URL
26SELECT h3_index,
27       h3_cell_to_lat(h3_index) AS lat,
28       h3_cell_to_lng(h3_index) AS lng,
29       elev, slope
30FROM read_parquet(
31    'https://data.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet'
32)
33ORDER BY elev DESC
34LIMIT 100;

1-- Range query on sorted BIGINT h3_index — row group min/max statistics prune efficiently
2INSTALL h3 FROM community; LOAD h3;
3INSTALL httpfs; LOAD httpfs;
4SET s3_region = 'us-west-2';
5
6SELECT h3_index,
7       h3_cell_to_lat(h3_index) AS lat,
8       h3_cell_to_lng(h3_index) AS lng,
9       elev, slope
10FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=7/data.parquet')
11WHERE h3_index BETWEEN ? AND ?
12ORDER BY elev DESC
13LIMIT 100;
14
15-- Query across all resolutions (Hive partitioning)
16SELECT h3_res, h3_index, elev
17FROM read_parquet(
18    's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=*/data.parquet',
19    hive_partitioning = true
20)
21WHERE h3_res = 5
22ORDER BY elev DESC
23LIMIT 20;
24
25-- DuckDB-WASM (browser) — use HTTPS URL
26SELECT h3_index,
27       h3_cell_to_lat(h3_index) AS lat,
28       h3_cell_to_lng(h3_index) AS lng,
29       elev, slope
30FROM read_parquet(
31    'https://data.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet'
32)
33ORDER BY elev DESC
34LIMIT 100;

1-- Spatial pushdown using native geometry bbox stats (no lat/lon filter needed)
2SELECT h3_index, elev, slope
3FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=7/data.parquet')
4WHERE geometry && ST_MakeEnvelope(86.5, 27.5, 87.5, 28.5);
5
6-- lat/lon filtering (v1 only — these columns exist in v1)
7SELECT *
8FROM read_parquet(
9    's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=*/data.parquet',
10    hive_partitioning = true
11)
12WHERE h3_res = 5
13  AND lat BETWEEN 27 AND 29 AND lon BETWEEN 86 AND 88;

1-- Spatial pushdown using native geometry bbox stats (no lat/lon filter needed)
2SELECT h3_index, elev, slope
3FROM read_parquet('s3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=7/data.parquet')
4WHERE geometry && ST_MakeEnvelope(86.5, 27.5, 87.5, 28.5);
5
6-- lat/lon filtering (v1 only — these columns exist in v1)
7SELECT *
8FROM read_parquet(
9    's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v1/h3/h3_res=*/data.parquet',
10    hive_partitioning = true
11)
12WHERE h3_res = 5
13  AND lat BETWEEN 27 AND 29 AND lon BETWEEN 86 AND 88;

1# Python (v2)
2import duckdb
3
4con = duckdb.connect()
5con.install_extension("h3", repository="community"); con.load_extension("h3")
6for ext in ("httpfs",):
7    con.install_extension(ext); con.load_extension(ext)
8con.sql("SET s3_region = 'us-west-2'")
9
10df = con.sql("""
11    SELECT h3_index,
12           h3_cell_to_lat(h3_index) AS lat,
13           h3_cell_to_lng(h3_index) AS lng,
14           elev, slope, aspect, tri, tpi
15    FROM read_parquet(
16        's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet'
17    )
18    ORDER BY elev DESC
19    LIMIT 100
20""").fetchdf()

1# Python (v2)
2import duckdb
3
4con = duckdb.connect()
5con.install_extension("h3", repository="community"); con.load_extension("h3")
6for ext in ("httpfs",):
7    con.install_extension(ext); con.load_extension(ext)
8con.sql("SET s3_region = 'us-west-2'")
9
10df = con.sql("""
11    SELECT h3_index,
12           h3_cell_to_lat(h3_index) AS lat,
13           h3_cell_to_lng(h3_index) AS lng,
14           elev, slope, aspect, tri, tpi
15    FROM read_parquet(
16        's3://us-west-2.opendata.source.coop/walkthru-earth/dem-terrain/v2/h3/h3_res=5/data.parquet'
17    )
18    ORDER BY elev DESC
19    LIMIT 100
20""").fetchdf()

Featured Products

DEM-Terrain

DEM-Terrain

Global DEM Terrain Derivatives

Quick Start

v2 (recommended)

v1 (legacy — requires INSTALL spatial)

Files

v2 (recommended)

v1 (legacy)

Schema

v2 (recommended)

v1 (legacy)

How It Works

More Examples

v2 queries

v1 legacy queries (requires INSTALL spatial)

Geometry Format

Source

License

Global DEM Terrain Derivatives

Quick Start

v2 (recommended)

v1 (legacy — requires INSTALL spatial)

Files

v2 (recommended)

v1 (legacy)

Schema

v2 (recommended)

v1 (legacy)

How It Works

More Examples

v2 queries

v1 legacy queries (requires INSTALL spatial)

Geometry Format

Source

License

v1 (legacy — requires `INSTALL spatial`)

v1 legacy queries (requires `INSTALL spatial`)

v1 (legacy — requires `INSTALL spatial`)

v1 legacy queries (requires `INSTALL spatial`)