GDAL-VECTOR-SIMPLIFY(1)

📦
version 3.13.3 · 4 versions
, in alpine 3.24, arch rolling, ubuntu stonking

🦋 GDAL-VECTOR-SIMPLIFY(1) — the GDAL manual, bestie edition 💅

okay so you opened the gdal-vector-simplify page from the GDAL manual set, and honestly? you're about to have a great time. let's get into it 🫶

✨ NAME ✨

gdal-vector-simplify — Simplify geometries of a vector dataset

🌸 Added in version 3.12.

🎀 SYNOPSIS 🎀

Usage: gdal vector simplify [OPTIONS] <INPUT> <OUTPUT> <TOLERANCE>

Simplify geometries of a vector dataset.

Positional arguments:
  -i, --input <INPUT>                                  Input vector datasets [required] [not available in pipelines]
  -o, --output <OUTPUT>                                Output vector dataset [required] [not available in pipelines]
  --tolerance <TOLERANCE>                              Distance tolerance for simplification. [required]

Common Options:
  -h, --help                                           Display help message and exit
  --json-usage                                         Display usage as JSON document and exit
  --config <KEY>=<VALUE>                               Configuration option [may be repeated]
  -q, --quiet                                          Quiet mode (no progress bar or warning message) [not available in pipelines]

Options:
  -l, --layer, --input-layer <INPUT-LAYER>             Input layer name(s) [may be repeated] [not available in pipelines]
  -f, --of, --format, --output-format <OUTPUT-FORMAT>  Output format ("GDALG" allowed) [not available in pipelines]
  --co, --creation-option <KEY>=<VALUE>                Creation option [may be repeated] [not available in pipelines]
  --lco, --layer-creation-option <KEY>=<VALUE>         Layer creation option [may be repeated] [not available in pipelines]
  --overwrite                                          Whether overwriting existing output dataset is allowed [not available in pipelines]
  --update                                             Whether to open existing dataset in update mode [not available in pipelines]
  --overwrite-layer                                    Whether overwriting existing output layer is allowed [not available in pipelines]
  --append                                             Whether appending to existing layer is allowed [not available in pipelines]
                                                       Mutually exclusive with --upsert
  --output-layer <OUTPUT-LAYER>                        Output layer name [not available in pipelines]
  --skip-errors                                        Skip errors when writing features [not available in pipelines]
  --active-layer <ACTIVE-LAYER>                        Set active layer (if not specified, all)
  --active-geometry <ACTIVE-GEOMETRY>                  Geometry field name to which to restrict the processing (if not specified, all)

Advanced Options:
  --if, --input-format <INPUT-FORMAT>                  Input formats [may be repeated] [not available in pipelines]
  --oo, --open-option <KEY>=<VALUE>                    Open options [may be repeated] [not available in pipelines]
  --output-oo, --output-open-option <KEY>=<VALUE>      Output open options [may be repeated] [not available in pipelines]
  --upsert                                             Upsert features (implies 'append') [not available in pipelines]
                                                       Mutually exclusive with --append

like. look at that. so organized. ⭐

💖 DESCRIPTION 💖

gdal vector simplify simplifies geometries, and the glow-up rules are strict, bestie: the result is guaranteed to be a valid geometry that has the same dimension and the same number of components as the input. no shrinking, no shape-shifting into something else, no drama. 👑

The simplification uses a maximum distance difference algorithm, similar to the one used in the Douglas-Peucker algorithm. yes, that one. iconic behavior.

Under the hood this is done by the OGRGeometry::SimplifyPreserveTopology() method, which preserves the topology per feature — but not for a whole layer. 😭 so what does that mean for you? it means gaps or overlaps between geometries that were initially contiguous may happen. the vibes between neighbors are not guaranteed. if you need simplification that preserves shared boundaries between geometries, go look at gdal vector simplify-coverage instead, that's the one for that job.

This command can also be used as a step of gdal vector pipeline. 🔥

[image] Line dataset before (left) and after (right) simplification
with gdal vector simplify.
⚠️ NOTE: This command requires a GDAL build against the GEOS library. no GEOS, no simplify, that's just the situation. 💀

🌈 GDALG OUTPUT (ON-THE-FLY / STREAMED DATASET) 🌈

This program supports serializing the command line as a JSON file using the GDALG output format. ✨

The resulting file can then be opened as a vector dataset using the GDALG: GDAL Streamed Algorithm driver, and it will apply the specified pipeline in an on-the-fly / streamed way. so you write the recipe once and it just… cooks, on demand. obsessed. 🍓

🧚 PROGRAM-SPECIFIC OPTIONS 🧚

  • --tolerance <TOLERANCE> — The specified value of this option is the tolerance used to merge consecutive points of the output geometry, using the OGRGeometry::SimplifyPreserveTopology() method. The unit of the distance is in georeferenced units of the source layer. so like, mind your projection, bestie. also: this one is required, no skipping. 🙈

💅 STANDARD OPTIONS 💅

  • --active-geometry <ACTIVE-GEOMETRY> — Set the active geometry field from its name. When it is specified, only the specified geometry field will be subject to the processing. Other geometry fields will be not modified. If this option is not specified, all geometry fields will be subject to the processing. This option can be combined together with --active-layer. 🎯
  • --active-layer <ACTIVE-LAYER> — Set the active layer. When it is specified, only the layer specified by its name will be subject to the processing. Other layers will be not modified. If this option is not specified, all layers will be subject to the processing. 👑
  • --append — Whether appending features to existing layer(s) is allowed. This also creates the output dataset if it does not exist yet. so if the target's not there, it just shows up. main character energy. 🌸
  • --co, --creation-option <NAME>=<VALUE> — Many formats have one or more optional dataset creation options that can be used to control particulars about the file created. For instance, the GeoPackage driver supports creation options to control the version.

May be repeated.

The dataset creation options available vary by format driver, and some simple formats have no creation options at all. A list of options supported for a format can be listed with the --formats command line option, but the documentation for the format is the definitive source of information on driver creation options. See Vector drivers format specific documentation for legal creation options for each format.

🚨 Note that dataset creation options are different from layer creation options. do not mix them up, i am begging. 😭
  • --if, --input-format <format> — Format/driver name to be attempted to open the input file(s). It is generally not necessary to specify it, but it can be used to skip automatic driver detection, when it fails to select the appropriate driver. This option can be repeated several times to specify several candidate drivers. Note that it does not force those drivers to open the dataset. In particular, some drivers have requirements on file extensions. 👀

May be repeated.

  • --input-layer <INPUT-LAYER> — Specifies the name of one or more layers to process. By default, all layers will be processed. To read and write all layers but only process a subset, use --active-layer. 🫶
  • --lco, --layer-creation-option <NAME>=<VALUE> — Many formats have one or more optional layer creation options that can be used to control particulars about the layer created. For instance, the GeoPackage driver supports layer creation options to control the feature identifier or geometry column name, setting the identifier or description, etc.

May be repeated.

The layer creation options available vary by format driver, and some simple formats have no layer creation options at all. A list of options supported for a format can be listed with the --formats command line option, but the documentation for the format is the definitive source of information on driver creation options. See Vector drivers format specific documentation for legal creation options for each format.

🚨 Note that layer creation options are different from dataset creation options. same warning, other direction. 💀
  • --oo, --open-option <NAME>=<VALUE> — Dataset open option (format specific).

May be repeated.

  • -f, --of, --format, --output-format <OUTPUT-FORMAT> — Which output vector format to use. Allowed values may be given by gdal --formats | grep vector | grep rw | sort 👑
  • --output-layer <NAME> — Specifies the name of the layer to which features will be written. If not specified, output layer names will be the same as input layer names. 🎀
  • --output-open-option, --output-oo <NAME>=<VALUE> — Added in version 3.12. Dataset open option for output dataset (format specific).

May be repeated.

  • --overwrite — Allow program to overwrite existing target file or dataset. Otherwise, by default, gdal errors out if the target file or dataset already exists. no sneaky deletes without permission, bestie. ✋
  • --overwrite-layer — Whether overwriting the existing output vector layer is allowed. 🔥
  • --skip-errors — Added in version 3.12. Whether failures to write feature(s) should be ignored. Note that this option sets the size of the transaction unit to one feature at a time, which may cause severe slowdown when inserting into databases. so it's forgiving but it is not fast. 😭
  • --update — Whether to open an existing output dataset in update mode. 🦋
  • --upsert — Added in version 3.12. Variant of --append where the OGRLayer::UpsertFeature() operation is used to insert or update features, instead of appending with OGRLayer::CreateFeature().

This is currently implemented only in a few drivers: GPKG — GeoPackage vector, Elasticsearch: Geographically Encoded Objects for Elasticsearch and MongoDBv3 (drivers that implement upsert expose the GDAL_DCAP_UPSERT capability). 😮‍💨

The upsert operation uses the FID of the input feature, when it is set (and the FID column name is not the empty string), as the key to update existing features. It is crucial to make sure that the FID in the source and target layers are consistent. fr fr, check your FIDs.

For the GPKG driver, it is also possible to upsert features whose FID is unset or non-significant (the --unset-fid option of gdal vector edit can be used to ignore the FID from the source feature), when there is a UNIQUE column that is not the integer primary key. 💅

⭐ RETURN STATUS CODE ⭐

The program returns status code 0 in case of success, and non-zero in case of error (non-blocking errors emitted as warnings are considered as a successful execution). so if it grumbles but finishes, that's still a 0. slay. 🫶

✨ EXAMPLES ✨

🌸 Example 1: Simplify geometries using a tolerance of one km (assuming the CRS is in meters)

$ gdal vector simplify --tolerance=1000 in.gpkg out.gpkg --overwrite

okay bestie so what's happening here 💖 you're feeding it in.gpkg, telling it <italic>tolerance</italic> is 1000 (which is one whole kilometer 🦋 but only because the CRS units are meters — if your CRS is in degrees this number means something completely different, so do a lil vibe check on your projection first fr fr), and dumping the glow-up into out.gpkg with --overwrite so it doesn't clutch its pearls and refuse because the file already exists. slay. 👑

👑 AUTHOR 👑

Even Rouault <even.rouault@spatialys.com> — the icon, the moment, the main character of this whole operation 💜

1998-2026 🫶 no cap, that's a long and legendary run.

okay that's literally the whole page, you made it to the end, so proud of you 🌈✨ this was GDAL-VECTOR-SIMPLIFY(1), dated Aug 18, 2026 — go simplify some geometries and be iconic about it 💅💖

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