geojson-validation

GeoJSON-Validation

A GeoJSON Validation Library
Check JSON objects to see whether or not they are valid GeoJSON. Validation is based off of the GeoJSON Format Specification revision 1.0

• Installation
• Usage
• Cli usage
• Api
• Testing
• Cavets

Installation

npm install geojson-validation

usage

const gjv = require("geojson-validation");

const validFeatureCollection = {
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
            "properties": {"prop0": "value0"}
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "LineString",
                "coordinates": [
                    [102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]
                ]
            },
            "properties": {
                "prop0": "value0",
                "prop1": 0.0
            }
        }
    ]
};

//simple test
if(gjv.valid(validFeatureCollection)){
    console.log("this is valid GeoJSON!");
}

const invalidFeature =  {
    "type": "feature",
    "geometry": {
        "type": "LineString",
        "coordinates": [
            [102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]
        ]
    },
    "properties": {
        "prop0": "value0",
        "prop1": 0.0
    }
};

//test to see if `invalidFeature` is valid and return a "trace" which contains the error
const trace = gjv.isFeature(invalidFeature, true)
console.log(trace)

CLI usage

first install gobally
npm install geojson-validation -g
Then you can use gjv to validate file such as
gjv file1 file2..
Or you can stream files to it cat file | gjv
gjv will either return a list of error or a valid if the files are indeed valid.

API

All Function return a boolean and take a JSON object that will be evalatued to see if it is a GeoJSON object, with the exception of define.

Arguments

• geoJSON - a JSON object that is tested to see if it is a valid GeoJSON object
• trace - boolean is whether or not to return an array of validation errors for an invalid JSON object. If trace is false then the a Boolean will be returned depending on the validity of the object.

Define(type, function)

Define a Custom Validation for the give type. type can be "Feature", "FeatureCollection", "Point", "MultiPoint", "LineString", "MultiLineString", "Polygon", "MultiPolygon", "GeometryCollection", "Bbox", "Position", "GeoJSON" or "GeometryObject".

The function is passed the object being validated and should return a string or an array of strings representing errors. If there are no errors then the function should not return anything or an empty array. See the example for more.

Full Documention

---

Define Example

Thanks to @VitoLau for the code for this example.

const gjv = require("geojson-validation");

gjv.define("Position", (position) => {
    //the postion must be valid point on the earth, x between -180 and 180
    errors = [];
    if(position[0] < -180 || position[0] > 180){
        errors.push("the x must be between -180 and 180");
    }
    if(position[1] < -90 || position[1] > 90){
        errors.push("the y must be between -90 and 90");
    }
    return errors;

});

const gj = {type: "Point", coordinates: [-200,3]};
//returns false
gjv.isPoint(gj);

Testing

To run tests npm test
Test use mocha

Cavets

• Does not check ordering of Bouding Box coordinates
• Does not check Coordinate Reference System Objects
• Does not check order of rings for polygons with multiple rings