GeoDesk 1.0.0-pre.8

GeoDesk for .NET

GeoDesk is a fast and storage-efficient geospatial database for OpenStreetMap data. This package is a C# port of the GeoDesk Java library, bringing the same query model to .NET. (GeoDesk is also available for Java, for C++ and for Python.)

You query a GOL (Geographic Object Library) file — a compact, pre-indexed snapshot of OSM data — and get back Node, Way and Relation features with their tags and geometry.

GOL files are read, not built, by this library. Build a .gol from an .osm.pbf extract with GOL Tool 2.0, then open it here. This package targets the GOL 2.0 format.

Why GeoDesk?

• Small storage footprint — GOL files are only 20% to 50% larger than the original OSM data in PBF format — less than a tenth of what a traditional SQL-based database consumes.

• Fast queries — typically 50 times faster than SQL.

• Intuitive API — no object-relational mapping; queries return INode, IWay and IRelation objects. Discover tags, way-nodes and relation members; get a feature's geometry; measure its length or area.

• Proper handling of relations — traditional geospatial databases deal in geometric shapes and need workarounds for this unique and powerful aspect of OSM data.

• Seamless integration with NetTopologySuite (NTS) — the .NET port of JTS — for advanced geometric operations: buffer, union, simplify, convex and concave hulls, Voronoi diagrams, and more.

• Modest hardware requirements — runs anywhere .NET runs: Windows, Linux and macOS.

Status: this is a faithful in-progress port. The full read + query path is implemented and validated against real GOL data. Writing/building GOLs is handled by the external GOL Tool, not this library.

Get Started

Install from NuGet:

dotnet add package GeoDesk

…or add a PackageReference to your project (the package targets .NET 10):

<PackageReference Include="GeoDesk" Version="1.0.0" />

To build the latest version from source instead:

git clone https://github.com/alethic/geodesk-net.git
cd geodesk-net
dotnet build

Example Application

using GeoDesk.Feature;
using GeoDesk.Geom;

using FeatureLibrary library = FeatureLibrary.Open("switzerland.gol");   // 1

foreach (IFeature pub in library                                         // 2
    .Select("na[amenity=pub]")                                           // 3
    .In(Box.OfWSEN(8.53, 47.36, 8.55, 47.38)))                           // 4
{
    Console.WriteLine(pub.StringValue("name"));                          // 5
}                                                                        // 6

What's going on here?

1. We open a feature library (switzerland.gol). FeatureLibrary is IDisposable, so using closes it for us.
2. We iterate through all the features ...
3. ... that are pubs (GeoDesk query language — similar to MapCSS).
4. ... in downtown Zurich (a bounding box with West/South/East/North coordinates, in degrees).
5. We print the name of each pub.
6. The using block disposes the library when we're done.

That's it — your first GeoDesk application!

More Examples

Find all movie theaters within 500 meters of a given point:

IFeatures movieTheaters = library
    .Select("na[amenity=cinema]")
    .MaxMetersFromLonLat(500, myLon, myLat);

Remember, OSM uses British English for its terminology.

Discover the bus routes that traverse a given street:

foreach (IFeature route in street.Parents("[route=bus]"))
{
    Console.WriteLine($"- {route.StringValue("ref")} " +
        $"from {route.StringValue("from")} to {route.StringValue("to")}");
}

Count the number of entrances of a building:

long numberOfEntrances = building.Nodes("[entrance]").Count();

Differences from the Java edition

The API mirrors the Java library closely; the main adaptations are idiomatic .NET:

The GeoDesk query language (GOQL) is identical.

Documentation

The Java API is mirrored closely, so the official GeoDesk documentation applies (translate method names to PascalCase):

• GeoDesk Developer's Guide
• GeoDesk Query Language (GOQL)

Related Repositories

• geodesk-gol — command-line tool for building and querying GOL files
• geodesk — GeoDesk for Java (the upstream this port mirrors)
• libgeodesk — GeoDesk for C++
• geodesk-py — GeoDesk for Python

License

Licensed under the Apache License 2.0. GeoDesk is a project of Clarisma; this .NET port is maintained separately.