> For the complete documentation index, see [llms.txt](https://help.horizon.globalnaturewatch.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.horizon.globalnaturewatch.org/resources/quickstarts/how-to-prepare-your-data-for-upload.md). # How to prepare your data for upload {% hint style="info" %} [Goal: Get your own polygon into GNW Horizon on the first try - and know exactly how to fix it if it's rejected.](#user-content-fn-1)[^1] {% endhint %} ## What you need * A .geojson file of your area of interest * A text editor (or QGIS) to inspect and, if needed, fix the file ## Steps: what GNW Horizon checks Work through this list before you upload - it covers everything Horizon's upload dialog validates.
1. **File extension is exactly .geojson.** Not .json, even if the contents are identical. Horizon shows “Only .geojson files are supported” and won't offer the file otherwise. 2. **File is under 1 MB.** Large files (very high coordinate precision, dozens of features) can push past this - simplify or split the file if needed. 3. **Geometry type is “Polygon”, not “MultiPolygon.”** This is the single most common cause of rejection, especially for files exported from QGIS or ArcGIS, which default to MultiPolygon even for a single shape with no holes. Horizon shows “No valid Polygon features found” and will not accept the file until the geometry type is converted. (A geometry that's neither - a Point or LineString, for example - shows a related message, “No valid Polygon or MultiPolygon features found”). If your area is made of more than one separate piece rather than one shape, in QGIS Multipart to Singleparts will split it into multiple features. Export and upload each piece as its own file, since Horizon takes one polygon per file. 1. ***Fix in QGIS:** re-export via Export > Save Features As… and leave the geometry type on its default (don't force “Multi”), or use Vector > Geometry Tools > Multipart to Singleparts first.* 4. **One polygon feature per file.** A file with multiple Polygon features will only create one area in Horizon - keep each area of interest in its own file to avoid surprises. 5. **The ring is a real, closed shape.** GeoJSON expects the first and last coordinate pair in each ring to match, and the ring shouldn't cross itself (a “bowtie”). Horizon's upload check doesn't always catch a self-intersecting shape explicitly, but it can produce a wrong or misleadingly small area - so it's worth fixing at the source rather than relying on the upload to catch it. 1. ***Fix in QGIS:** Vector > Geometry Tools > Fix Geometries.* 6. **Area is at least 0.10 km² (10 hectares).** Anything smaller is rejected with “Area is too small (X km²). Minimum area is 0.10 km².” If your real area is genuinely smaller than that, you'll need to buffer it slightly or combine it with a neighboring plot. 7. **Coordinates are in \[longitude, latitude] order**, and longitude/latitude aren't accidentally swapped. This is a common mistake when building a file from a spreadsheet of lat/lon columns. Horizon doesn't always flag this with a clear error - a swapped file can silently upload with the shape placed somewhere else on the globe entirely, or it can coincidentally trip the minimum-area check depending on where it lands. Always confirm the uploaded shape appears where you expect on the map before trusting it. 8. **A “crs” block and ring winding direction don't need to be fixed.** Horizon accepts both a top-level “crs” member and either clockwise or counter-clockwise ring winding, even though a legacy “crs” member is technically deprecated in current GeoJSON. If your GIS software adds one automatically, you don't need to strip it out. If you see this error… | Messages | What it means | Fix | | ----------------------------------------------------- | --------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ | | “Only .geojson files are supported” | Wrong file extension | Rename to .geojson | | “No valid Polygon features found” | Geometry type is MultiPolygon (or similar) instead of Polygon | Convert to single-part Polygon (see step 3) | | “No valid Polygon or MultiPolygon features found” | File contains no polygon geometry at all (e.g. Points or lines) | Re-draw or re-export as an actual polygon boundary | | “Area is too small (X km²). Minimum area is 0.10 km²” | Polygon's real-world area is below the 10 ha minimum | Buffer or combine with a neighboring area - or check for swapped coordinates, which can shrink apparent area | {% hint style="info" %} **Try this prompt** “Give me a summary of land cover change in \[your area name] over the last five years.” {% endhint %} ## What to do next * Ready to explore the area you just uploaded → [Run your first analysis](/global-nature-watch-horizon-terms-of-use.md) [^1]: