Geoprocessing Toolbox: Clip, Dissolve, Merge Online
Load several layers and run clip, dissolve, intersect, buffer, grid and other operations one after another. Download the result as Shapefile, GeoJSON, KML or CSV in the coordinate system you need.
1 Layers
Loaded layers
2 Operation
Each result is added to the list as a new layer and can be used as input for the next operation.
Data and privacy
Your files are processed in your browser; their content is not sent to any server. The processing libraries are loaded from jsDelivr and cdnjs. Basemap tiles for the preview map are downloaded from Esri and OpenStreetMap servers, which only see the map area being displayed.
Related Tools
Geoprocessing in the browser
Most GIS projects rely on a handful of basic steps: cutting away data outside the study area, merging polygons that share an attribute, combining layers from different sources into one file, finding where two layers overlap or drawing a buffer zone around a route. This tool lets you run these operations on Shapefile, GeoJSON, KML, GPX and CSV files without installing desktop GIS software. Every result is added to the list as a new layer, so you can select it as the input of the next operation and chain the steps together.
How to use it
- Choose or drop your files. For a shapefile, choose the .zip archive or the .shp, .dbf and .prj files together. The coordinate system is read from the .prj file; if it is missing and the coordinates are not latitude and longitude, the tool asks you to pick the system.
- Choose an operation, set the input and second layer, and enter the parameters.
- Press Run. The result is drawn on the map, its attribute table opens and the step is written to the history.
- Use the Download button on the layer card to pick a format and target coordinate system.
Operations
| Operation | What it does |
|---|---|
| Clip, Erase | Cuts a layer at the boundary of a polygon layer and keeps the parts inside or outside. Works with points, lines and polygons. |
| Intersect, Union | Overlays two layers and writes the attributes of both to the shared parts. Union also keeps the parts found in only one layer. |
| Dissolve | Merges features with the same values in the chosen fields and computes sum, mean, minimum and maximum for numeric fields. |
| Merge | Combines several layers into one and lets you map field names. |
| Spatial join | Transfers attributes by intersection, containment, distance or nearest feature and writes the match count. |
| Buffer | Creates buffers in meters; a negative value shrinks polygons inward. |
| Centroid, inside point, convex hull, bounding box | Creates representative points, convex hulls, bounding boxes and minimum rotated rectangles. |
| Voronoi, grid | Creates Thiessen polygons from points and square or hexagonal grids in meters. |
| Simplify, explode, make valid | Reduces vertices, splits multipart geometries and repairs broken geometries. |
| Measure columns | Adds area (m², ha, km²), perimeter and length computed on the ellipsoid. |
Why measurements use the ellipsoid
Computing area directly from latitude and longitude gives a meaningless number in square degrees, and an area computed on the Web Mercator plane is about 1.7 times too large at the latitude of Türkiye and grows further toward the poles. This tool computes area, perimeter and length geodesically on the WGS84 ellipsoid. Operations that need meters, such as buffer, grid, minimum rectangle and centroid, run for each feature in a Transverse Mercator projection centered on that feature, where the scale error is very small, and the result is converted back to latitude and longitude. A 100 meter buffer is therefore 100 meters wherever the feature lies.
Cadastral and design drawings usually compute area on a projection plane. When adding measure columns you can also write the planar area of each feature in a projection of your choice and compare the two values side by side.
Invalid geometry
Self-intersecting rings, unclosed rings and overlapping parts can make clipping and dissolving fail or return wrong results. The tool checks every polygon layer on load, shows the number of problem features on the layer card and offers a one-click repair. The repair splits crossing rings into valid parts; a bow-tie polygon, for example, becomes two triangles.
Data and method
Clip, intersection, difference and union are computed with polygon-clipping 0.15.7 (MIT license); Voronoi and some spatial relationship tests use Turf.js 7.2.0 (MIT). Areas and distances on the ellipsoid come from GeographicLib geodesic 2.1.1 (MIT) and coordinate transformations from proj4js 2.9.0 (MIT). For ED50 in Türkiye the tool applies the seven-parameter transformation EPSG:1784 (ED50 to WGS 84 (30)), whose accuracy EPSG gives as about 2 meters. Files are read with shpjs 6.1.0 (MIT), JSZip 3.10.1 (MIT), PapaParse 5.4.1 (MIT) and @tmcw/togeojson 5.8.0 (BSD-2-Clause); the shapefile writer is this page's own code and writes attributes in UTF-8 with .cpg and .prj files. The map uses Leaflet 1.9.4 (BSD-2-Clause) and Leaflet.draw 1.0.4 (MIT), and icons come from Lucide (ISC). Large jobs run in a Web Worker.
Accuracy limits
- Clip and overlay operations work on the latitude-longitude plane, treating edges as straight lines between vertices. On edges kilometers long with few vertices this can differ slightly from the geodesic curve.
- Buffers and grids are accurate to the centimeter level up to a few hundred kilometers in the local projection; the tool warns you about much larger features.
- Z values are not kept after clip and overlay operations.
- Simplify handles each feature separately; to keep shared boundaries of neighboring polygons together, use the Geometry Simplifier.
Rodosto Teknoloji builds GIS data workflows and web mapping solutions for organizations. You can find more about our work on the Rodosto Teknoloji website or send us a message through the contact page.
Frequently Asked Questions
What is the difference between Clip and Intersect?
Clip cuts the input layer at the boundary of the clip layer and keeps only the attributes of the input layer; the clip layer acts as a cookie cutter. Intersect creates the overlapping parts of both layers and writes the attributes of both layers to each part. If a parcel falls into two zoning areas, Intersect returns two separate parts.
Why can the area differ slightly from ArcGIS or a CAD drawing?
The tool computes area on the WGS84 ellipsoid, which is the closest to the true size on the ground. Areas in cadastral and design drawings are usually computed on a projection plane such as Transverse Mercator and include the scale effect of that projection. To compare both, tick the planar area option when adding measure columns and choose the projection.
What happens when field names differ while merging shapefiles?
Merge lists the fields of each layer and lets you set the output name for every field. Names that differ only in letter case or accents (for example NAME, Name, name) are collected in the same column by default. A field whose name you clear is left out of the result.
Will the browser freeze with large files?
When the total vertex count is high, the operation runs in a background thread (Web Worker) and the page stays responsive. The limit is the memory of your browser; with hundreds of thousands of features the run time grows. You can reduce the vertex count first with Simplify.
Is my file uploaded to a server?
No. Reading, processing and writing files all happen in your browser. Only the library files are loaded from a CDN, and basemap tiles for the preview map are downloaded from Esri and OpenStreetMap servers.