Could not process this DEM
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DEM Warnings
Processing Options
Use 1 when horizontal and vertical units already match.
Raster Size
pixels
Cell Size
calculation units
Mean Slope
Horn method
Max Slope
valid cells
Elevation Range
DEM band 1
South Facing
valid aspect cells
Slope Preview
Blue and green are gentle slopes; orange and red are steeper terrain.
Aspect Preview
Hue shows downhill direction. Flat and nodata cells are transparent.
DEM Slope and Aspect Workflow
The calculator reads the elevation grid from a DEM GeoTIFF, samples each 3 x 3 neighborhood, estimates east-west and north-south gradients, then creates slope and aspect previews without uploading the raster.
Horn 3 x 3 Elevation Window
Terrain Direction Output
What Is a DEM Slope & Aspect Calculator?
This DEM Slope & Aspect Calculator turns a local GeoTIFF elevation model into terrain slope and aspect previews. It is built for GIS analysts, environmental engineers, agronomists, drainage designers, survey teams, and flood modelling workflows that need a fast terrain check without opening desktop GIS software.
Slope measures how quickly elevation changes across the raster. Aspect measures the downhill direction of that change. Together they explain whether land is flat, gentle, steep, north-facing, south-facing, or likely to concentrate runoff. Those outputs are used in erosion studies, road design, solar exposure, irrigation planning, wildfire risk, habitat modelling, and watershed analysis.
The file is processed in your browser. The page reads the DEM band, applies a 3 x 3 terrain gradient calculation, renders preview images, and creates download links from local memory. Your raster is not uploaded to CalculatorsUniverse.
How Slope Is Calculated from a DEM
The calculator uses the Horn finite-difference method, a common GIS approach also used by terrain tools in desktop software. For each cell, the surrounding 3 x 3 elevation window estimates horizontal and vertical gradients. The combined gradient is converted to slope degrees and percent grade.
| Slope Degrees | Percent Grade | Typical Meaning |
|---|---|---|
| 0-2 | 0-3.5% | Flat to nearly flat terrain |
| 2-5 | 3.5-8.7% | Gentle slope |
| 5-15 | 8.7-26.8% | Moderate slope |
| 15-30 | 26.8-57.7% | Steep terrain |
| 30+ | 57.7%+ | Very steep terrain |
How Aspect Shows Terrain Direction
Aspect is the compass direction that a terrain surface faces. In GIS azimuth convention, north is 0 degrees, east is 90 degrees, south is 180 degrees, and west is 270 degrees. Flat cells do not have a meaningful downhill direction, so they are masked as flat.
| Aspect Range | Direction |
|---|---|
| 337.5-22.5 | North |
| 22.5-67.5 | Northeast |
| 67.5-112.5 | East |
| 112.5-157.5 | Southeast |
| 157.5-202.5 | South |
| 202.5-247.5 | Southwest |
| 247.5-292.5 | West |
| 292.5-337.5 | Northwest |
Why Projected CRS Matters for DEM Analysis
Slope depends on the ratio between vertical elevation units and horizontal cell size. A DEM in metres with a metre-based projected CRS is straightforward. A DEM in latitude and longitude degrees is not, because one degree is not a fixed ground distance and changes with latitude. For engineering-grade terrain analysis, reproject the DEM to a suitable projected CRS before calculating slope.
The z-factor option can adjust elevation units when the vertical units differ from horizontal units. For example, elevation in feet with horizontal metres needs a conversion factor. The tool shows CRS and cell-size warnings so the result is not mistaken for a survey-grade output when the source raster lacks usable georeferencing.
Common Uses in Engineering, Agriculture, and Flood Modelling
Civil engineering
Screen road corridors, embankments, cut slopes, drainage paths, and earthwork constraints before detailed design.
Agriculture
Find slope risk, runoff direction, machinery limits, erosion-prone fields, and aspect-driven sunlight differences.
Flood modelling
Inspect terrain controls, drainage direction, hillslope runoff, and DEM quality before hydrologic modelling.
DEM Slope Calculator FAQ
Can I calculate slope from a GeoTIFF DEM in the browser?
Yes. The calculator reads the selected GeoTIFF with browser APIs and processes the elevation grid locally. The raster is not uploaded to a server.
What is the difference between slope degrees and percent slope?
Slope degrees report the angle above horizontal. Percent slope reports rise divided by run multiplied by 100. A 45 degree slope equals 100 percent grade.
What does aspect mean in GIS?
Aspect is the compass direction that terrain faces or drains toward. It is commonly used for sunlight, vegetation, snowmelt, fire behavior, and drainage analysis.
Why does my DEM need a projected coordinate system?
A projected CRS gives cell size in linear units such as metres or feet. Latitude and longitude degrees are angular units, so slope values need reprojection or careful unit conversion.
Can I use this for flood modelling or agriculture?
Yes for screening, QA, and exploratory terrain analysis. For regulatory modelling or engineering deliverables, validate results in a full GIS workflow with documented CRS and vertical units.
Does the DEM file upload to the server?
No. The file is read from your device and processed in browser memory. Downloads are generated locally from canvas previews and a CSV summary.
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