An open-method geostory
How terrain turns a fixed distance into a question we can inspect, map and challenge.
A line beside water can look final on a map. In practice, it is the end of a chain of choices: which water objects count, what width to test, and where the land is steep enough to change the result.
I wanted to make that chain visible. This story follows one real test area from a one-metre elevation model and 52 mapped water features to a reproducible screening result.
The map does not establish a legal boundary. It shows a transparent protocol: the inputs, assumptions and outputs stay available for inspection and download.
A spatial rule becomes useful for public discussion when its assumptions can be seen—not hidden behind the final polygon.
The landscape, layer by layer
Scene 1 / 6
01
Begin with terrain
Across this compact test area, elevation changes from 128 to 216 metres. The one-metre DEM lets the method examine those changes close to the shoreline.
Scroll over the map to zoom; drag to pan after zooming. Select a coloured zone for details.
02
Map the evidence
The source contains 42 polygonal and 10 linear water features. Their geometry becomes the common reference from which distance and terrain are measured.
03
Expose the parameter
The source attributes do not legally classify each water object. I therefore use 50 metres as an explicit test setting, not as a claim about the correct statutory width for every feature.
04
Read the slope
At the 50 m ring, the method compares terrain height with the nearest shoreline. Shoreline pixels linked to a slope above 3° extend the analytical band toward 100 metres.
05
See the difference
The rust-coloured areas are not a second uniform buffer. They appear only where the terrain condition is met, adding 0.411 km² to the screening picture.
06
Keep the protocol open
The archive, individual inputs, derived layers, QGIS model, theory note, metadata, checksums and reproducibility script are published together. The map is an entry point, not a sealed conclusion.
Open the GitHub source →
From rule to repeatable operations
Align the DEM, water geometry and analysis extent in a projected CRS.
Create the 50 m test ring and associate terrain cells with the nearest shoreline.
Compare elevation change and distance to identify slopes above 3°.
Export the standard zone, extensions, metadata and reproducibility materials.
What the map adds
A transparent workflow lets someone else distinguish data from assumptions, rerun the analysis with another parameter, and argue about the method with the same evidence in view.
Area comparison; the extension value is 54% of the standard-zone area. These classes overlap conceptually as parts of one screening result and should not be read as legal land parcels.
Continue with the evidence
Version 1.0.0 keeps source data, results, documentation and checksums together. Choose the complete package or go to the resource record for individual files.
Analytical screening only. This result is not an official or legally established boundary and does not replace land-management documentation or a competent authority’s decision.