Create postgres postgis polygon from array of points

Question

I have array of locations and i want to insert them as a polygon column in a postgres table.

I have a column area with type geometry(Polygon,4326)

    const area = [
            { lat: 6.517784, lng: 3.368254 },
            { lat: 6.522207, lng: 3.376356 },
            { lat: 6.525885, lng: 3.376322 },
            { lat: 6.526396, lng: 3.379497 },
            { lat: 6.524009, lng 3.383188 },
            { lat: 6.523668, lng: 3.398294 },
            { lat: 6.517431, lng: 3.402618 },
            { lat: 6.514458, lng: 3.404732 },
            { lat: 6.510535, lng: 3.398294 },
            { lat: 6.501794, lng: 3.397425 },
            { lat: 6.496016, lng: 3.395054 },
            { lat: 6.488874, lng: 3.392029 },
            { lat: 6.491006, lng: 3.389969 },
            { lat: 6.492456, lng: 3.385677 },
            { lat: 6.494162, lng: 3.384990 },
            { lat: 6.492968, lng: 3.378467 },
            { lat: 6.498554, lng: 3.376289 }
]

I'm transforming the above data into a string

   const transform = area.map(position => return `${position.lat} ${position.lng}`}).join(', ')

then make an inset query using bookshelf and knex-posgis

const body = Object.assign({}, attrs, {
         area: st.geomFromText(`POLYGON((${transform}))`, 4326)
    });

    return Model.forge(body)
        .save()
        .then((result) => {
            return done(null, result)
        })
        .catch((error) => {
            return done(error, null)
        })

I'm getting an error saying geometry contains non-closed rings not sure what's causing the error. Any help will be appreciated.

Juan Carlos Oropeza · Accepted Answer · 2017-06-19 18:35:53Z

2

The polygon should end on the same point as the start. That is why say non-closed.

Check examples ST_MakePolygon

Just add the first point to the end.

const area = [
        { lat: 6.517784, lng: 3.368254 },
        { lat: 6.522207, lng: 3.376356 },
        { lat: 6.525885, lng: 3.376322 },
        { lat: 6.526396, lng: 3.379497 },
        { lat: 6.524009, lng 3.383188 },
        { lat: 6.523668, lng: 3.398294 },
        { lat: 6.517431, lng: 3.402618 },
        { lat: 6.514458, lng: 3.404732 },
        { lat: 6.510535, lng: 3.398294 },
        { lat: 6.501794, lng: 3.397425 },
        { lat: 6.496016, lng: 3.395054 },
        { lat: 6.488874, lng: 3.392029 },
        { lat: 6.491006, lng: 3.389969 },
        { lat: 6.492456, lng: 3.385677 },
        { lat: 6.494162, lng: 3.384990 },
        { lat: 6.492968, lng: 3.378467 },
        { lat: 6.498554, lng: 3.376289 },
        { lat: 6.517784, lng: 3.368254 }
]

edited Jun 19, 2017 at 18:35

answered Jun 19, 2017 at 18:29

Juan Carlos Oropeza

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