# GISela

> A GIS in your browser: layers, attribute tables, styling, analysis and print layouts. GISela opens GeoJSON, KML/KMZ, GPX, CSV, TopoJSON and zipped shapefiles as map layers, converts between coordinate systems such as UTM, Swiss LV95 or the British National Grid, and lets you style them by category, by class or as a heatmap. Edit attributes with a field calculator, run buffers, overlays, dissolves, Voronoi polygons or spatial joins, measure true areas and lengths on the ellipsoid, and print a map with legend, scale bar and north arrow. Everything runs in your browser.

GISela (Browser GIS) is an app of usefulweb.app (https://usefulweb.app/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows.

## Use it
- Landing page: https://gisela.usefulweb.app/
- Workspace (browser app): https://gisela.usefulweb.app/app - open a project with https://gisela.usefulweb.app/app#project=<base64url-encoded project JSON> or a template with https://gisela.usefulweb.app/app#template=<id>
- Project file format (JSON Schema): https://gisela.usefulweb.app/project.schema.json
- Tutorials: https://gisela.usefulweb.app/tutorials
- JSON API: POST https://gisela.usefulweb.app/api/v1/tools/<toolId>/calculate (catalog: https://gisela.usefulweb.app/api/v1/tools)
- OpenAPI: https://gisela.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://gisela.usefulweb.app/mcp

## Engine tools
- [GISela Coordinate Reprojection](https://giselareproject.usefulweb.app/): Convert GeoJSON, KML, GPX, CSV or shapefiles between WGS 84, UTM, LV95, British Grid and more. Part of [GISela](https://gisela.usefulweb.app/) (ownerApp: gisela). API: POST https://gisela.usefulweb.app/api/v1/tools/gisela-reproject/calculate · MCP tool `gisela_reproject`
- [GISela Buffer](https://giselabuffer.usefulweb.app/): Buffer zones around points, lines or polygons at a distance in metres, merged or one per feature. Part of [GISela](https://gisela.usefulweb.app/) (ownerApp: gisela). API: POST https://gisela.usefulweb.app/api/v1/tools/gisela-buffer/calculate · MCP tool `gisela_buffer`
- [GISela Shapefile to GeoJSON](https://giselashapefiletogeojson.usefulweb.app/): Turn a zipped shapefile (.shp, .dbf, .prj) into GeoJSON in WGS 84 or another coordinate system. Part of [GISela](https://gisela.usefulweb.app/) (ownerApp: gisela). API: POST https://gisela.usefulweb.app/api/v1/tools/gisela-shapefile-to-geojson/calculate · MCP tool `gisela_shapefile_to_geojson`
- [GISela Area & Length](https://giselaarealength.usefulweb.app/): True area, perimeter and length of polygons and lines on the WGS 84 ellipsoid, per feature. Part of [GISela](https://gisela.usefulweb.app/) (ownerApp: gisela). API: POST https://gisela.usefulweb.app/api/v1/tools/gisela-area-length/calculate · MCP tool `gisela_area_length`

## Formats
- Import: GISela project (.gisela.json), GeoJSON (.geojson, .json; also the old “crs” member), TopoJSON, KML and KMZ, GPX (waypoints, routes, tracks), CSV with lat/lon or x/y columns or a WKT column, WKT (one geometry per line), Zipped shapefile (.shp, .dbf, .prj, .cpg), Share link (#project=)
- Export: GISela project (.gisela.json), GeoJSON, KML, GPX, CSV (x/y or WKT), WKT, Zipped shapefile with .prj, Print layout as PDF, SVG or PNG, Map view as SVG or PNG, Attribute table as CSV

## Limits
- No street or satellite basemap: the built-in background is a world map of country outlines.
- Raster data (GeoTIFF, images) and 3-D data are not supported; Z and M values are dropped.
- Overlays work on longitude/latitude like a desktop GIS on an EPSG:4326 layer; buffers and distances use a local metric plane.
- Datum shifts use Helmert parameters (about 1–5 m), not national grid files such as OSTN15 or BeTA2007.
- Coordinate systems outside the built-in list cannot be read or written.
- Large datasets (more than 50,000 features per layer) are not supported, and drawing slows down above a few thousand complex features.
- No geocoding (address search); place data comes from your files.