RETROCHANGE DATASET METADATA - UC4 / RETROCANOPY
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Dataset title:
RETROCHANGE UC4 RETROCANOPY Havesova 1975 Image and Gap Correction

Use case:
Historical Canopy Gap Analysis in Old-Growth Beech Forests

Study area:
Havešová old-growth beech forest, Poloniny National Park, Slovakia

Reference year: 1975, as identified in the package documentation
Data provider: Technical University in Zvolen, Slovakia
Project: RETROCHANGE
Documentation edition: November 2026
Dataset version: No separate dataset version is recorded in the files.


DESCRIPTION
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The dataset contains a single-band historical panchromatic image
clipped to the Havešová study area, plus one hand-drawn gap polygon.
The image is an input to canopy-opening detection. It is not a
forest/non-forest classification or a complete gap inventory.

The correction polygon supplies an opening missed by the detector in
the worked example. It is specific to this image and study area.


RASTER - Havesova.tif
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Format: GeoTIFF
CRS: EPSG:5514 - S-JTSK / Krovak East North
Coordinate units: meters
Columns: 3,681
Rows: 3,079
Bands: 1 (grayscale / panchromatic imagery)
Stored sample type: Unsigned 8-bit integer (UInt8)
Compression: None
Pixel size: 0.5 x 0.5 m
Grid: North-up, no rotation; pixel is area
NoData value: 255

Outer pixel-edge bounds, EPSG:5514:
Minimum easting (X):   -183338.5 m
Maximum easting (X):   -181498.0 m
Minimum northing (Y): -1211303.5 m
Maximum northing (Y): -1209764.0 m

Rectangular raster footprint:
1,840.5 x 1,539.5 m; 283.344975 ha

Total pixels: 11,333,799
Valid pixels (value other than 255): 5,788,370
Valid image area: 144.70925 ha (approximately 144.7 ha)

The valid-pixel mask defines the study area. The rectangular raster
footprint also includes NoData outside that area; it is not the
analysis-area denominator. Preserve the NoData mask during reuse.

The dimensions, CRS code, georeferencing, sample type, and NoData
were inspected in the GeoTIFF header. Valid coverage was calculated
by counting image pixels other than 255, at 0.25 m2 per pixel.
The 0.5 m grid does not establish original sensor resolution or
independently measured positional accuracy.


VECTOR CORRECTION - add_gaps
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Format: ESRI Shapefile
Geometry type: Polygon
Feature count: 1
CRS: S-JTSK / Krovak East North, consistent with EPSG:5514
Attribute encoding: UTF-8 (declared in add_gaps.cpg)
Planar polygon area: Approximately 547.39 m2 (0.05474 ha)

Components:
add_gaps.shp - polygon geometry
add_gaps.shx - geometry record index
add_gaps.dbf - attribute table
add_gaps.prj - coordinate reference system
add_gaps.cpg - attribute encoding declaration
add_gaps.qix - spatial index

Keep the components together with the same base name. The .qix file
is an optional spatial index; the other supplied components should
accompany the geometry when transferring the dataset.

The geometry count, projected extent, and planar polygon area were
checked directly in the Shapefile. The polygon represents a manual
interpretation correction, not independent field validation. Its raw
area is not necessarily the increase in final mapped gap area, which
also depends on rasterization, overlap, clipping, and cleanup.


SOURCE AND PROCESSING PROVENANCE
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Source imagery: Declassified KH-9 HEXAGON, approximately 1975.
Source provider: U.S. Geological Survey (USGS), Earth Resources
Observation and Science (EROS) Center.

The package README describes the image as orthorectified and clipped
to the Havešová old-growth core. The raster contains a georeferenced
grid and a NoData-defined study area. An exact acquisition date,
mission/scene identifier, orthorectification report, and independent
positional accuracy assessment are not supplied in this package.

Data preparation and distribution: Technical University in Zvolen,
RETROCHANGE project. A separate processing date is not recorded
in the inspected data headers.


WORKFLOW AND INTERPRETATION
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The associated notebook is Poloniny_canopy_gaps_1975.ipynb.
The notebook and its supporting materials use the Poloniny canopy gaps
name within the UC4 / RETROCANOPY package.

The notebook uses Havesova.tif as SRC and add_gaps.shp as ADD_GAPS.
The default minimum mapped gap is 20 m2. It detects image-based
canopy-opening candidates under an explicit brightness/illumination
rule, applies optional manual corrections, and summarizes gap area,
size distribution, arrangement, and canopy distance to openings.

Detection depends on the chosen threshold, minimum area, image
quality, shadows, and interpretation. Reviewing detected polygons
alone does not measure omission error or establish map accuracy.
A single historical image provides a baseline, not a temporal change
measurement. The correction polygon must not be transferred to
another study area as a reusable reference layer.


LICENSE AND CITATION
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CC BY 4.0, to the extent of rights held by the Technical University
in Zvolen. See LICENSE.txt for scope and attribution requirements.
https://creativecommons.org/licenses/by/4.0/

Recommended citation:
Technical University in Zvolen (2026).
RETROCHANGE UC4 RETROCANOPY Havesova 1975 Image and Gap Correction.
RETROCHANGE project. https://gis.tuzvo.sk/retrochange

Historical imagery: KH-9 HEXAGON, courtesy of USGS EROS.


CONTACT AND PROJECT
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Technical University in Zvolen
T. G. Masaryka 24, 960 01 Zvolen, Slovakia

RETROCHANGE - Retrospective Analysis of Forest and Landscape
Changes from Historical Satellite Imagery
https://gis.tuzvo.sk/retrochange
