GIS Data Formats Guide: Master GeoJSON, KML, GPX, and WKT
Geographic Information Systems (GIS) rely on a variety of data formats to represent spatial information. Whether you are building a mapping application, analyzing urban growth, or tracking a hiking trail, understanding these formats is crucial.
In this guide, we will explore the most common geospatial formats, including GeoJSON, KML, GPX, and WKT, and the tools you need to work with them effectively.
1. The Web Standard: GeoJSON
GeoJSON is an open standard format designed for representing simple geographical features, along with their non-spatial attributes. It is based on JSON (JavaScript Object Notation), making it the preferred choice for web-based mapping libraries like Leaflet and Mapbox.
GeoJSON Validator and Editor
Because GeoJSON is human-readable, it is easy to edit. However, a single missing bracket can break your map. A GeoJSON validator checks your data against the RFC 7946 standard to ensure it is syntactically correct and geographically valid (e.g., longitude between -180 and 180).
Using a GeoJSON editor online allows you to visualize your points, lines, and polygons on a map while you edit the raw JSON code, providing instant feedback.
2. Google's Legacy: KML
KML (Keyhole Markup Language) is an XML-based format originally developed for Keyhole Earth Viewer (which later became Google Earth). It is widely used for displaying geographic data in 2D and 3D browsers.
KML to GeoJSON Converter
While KML is powerful for visualization, many modern web developers prefer GeoJSON for its simplicity and smaller file size. A KML to GeoJSON converter is a vital tool for migrating legacy data into modern web applications. This process involves stripping out XML tags and converting coordinates into the standard GeoJSON array format.
3. The Outdoorsman's Choice: GPX
GPX (GPS Exchange Format) is another XML-based format, but it is specifically designed for exchanging GPS data between applications and web services. It is the standard format for fitness trackers and handheld GPS units.
GPX Viewer Online and Conversion
If you have a trail log from your smartwatch, a GPX viewer online can render your path on a map and show elevation profiles. If you need to include that trail in a custom web map, a GPX to GeoJSON conversion is often the best path forward, as it allows for easier styling using CSS and JavaScript.
4. The Database Protocol: WKT
WKT (Well-Known Text) is a text markup language for representing vector geometry objects. It is the standard used by spatial databases like PostGIS and BigQuery.
Example WKT for a point: POINT (30 10)
Example WKT for a line: LINESTRING (30 10, 10 30, 40 40)
A WKT editor helps developers quickly generate these strings for use in SQL queries or to visualize database output on a map.
5. The Math Behind the Map: Coordinate Converter
One of the biggest challenges in GIS is the variety of coordinate systems. While most web formats use WGS 84 (decimal degrees), you may encounter data in UTM, MGRS, or DMS (Degrees, Minutes, Seconds) formats.
A coordinate converter is essential for ensuring your data aligns correctly. For example, converting 40° 44' 54" N, 73° 59' 10" W into 40.748333, -73.986111 is a common task when importing raw GPS data into a GeoJSON file.
6. Comparison Table: GIS Formats
| Format | Base | Best For | Complexity |
|---|---|---|---|
| GeoJSON | JSON | Web Apps, Leaflet, Mapbox | Low |
| KML | XML | Google Earth, 3D Visualization | Medium |
| GPX | XML | Fitness Tracking, GPS Devices | Medium |
| WKT | Text | Databases (PostGIS, SQL) | Low |
FAQ: Geospatial Data Questions
Q: Why is my GeoJSON not showing up on the map?
A: Check your coordinate order! GeoJSON uses [longitude, latitude] order, which is the opposite of many other formats. Use a GeoJSON validator to check for common errors.
Q: How do I open a .kml file if I don't have Google Earth?
A: You can use a KML to GeoJSON converter to transform it into a format that can be viewed in any browser-based GIS tool.
Q: Is GeoJSON or WKT better for performance?
A: For web display, GeoJSON is better because it is native to JavaScript. For database storage and spatial queries, WKT (or its binary version, WKB) is the standard.
Related Tools
Handle your geospatial data with ease:
- JSON Formatter - Perfect for prettifying your GeoJSON files.
- Unit Converter - Useful for converting distances (miles to kilometers, etc.).
- URL Encoder - Helpful when passing coordinates in API requests.
Note: Tool3M is currently building a specialized GeoJSON Validator and KML to GeoJSON Converter. Stay tuned!