`serde_esri`

Esri JSON parsing library.

This crate provides representations of Esri JSON objects with serde::Deserialize and serde::Serialize trait implementations.

serde_esri has two additional features geo and geoarrow.

geo implements From for the Esri JSON objects.
geoarrow provides compatibility with arrow and geoarrow by implementing geoarrow geometry traits as well as providing a utility function featureset_to_arrow() which converts a FeatureSet to an arrow RecordBatch.

Supported Esri JSON objects:

Geometry

Esri Geometries Objects are encoded by the following structs:

EsriPoint
EsriMultiPoint<N>
EsriPolyline<N>
EsriPolygon<N>

They are encapsulated by the EsriGeometry enum:

enum EsriGeometry<const N: usize> {
    Point(EsriPoint),
    MultiPoint(EsriMultiPoint<N>),
    Polygon(EsriPolygon<N>),
    Polyline(EsriPolyline<N>),
}

The parameter N is used to specify the dimension of the geometries. Use <2> for 2 dimensional data, <3> for Z values and <4> when M and Z are present.

FeatureSets

An Esri JSON FeatureSet is what is most commonly returned from a Feature Service. It is comprised of a number of optional fields and most importantly, a vector of Features.

Features are a struct with a geometry and an attributes field. The geometry must be one of the possible geometry types and attributes can be an key-value pair.

struct Feature<const N: usize> {
    geometry: Option<EsriGeometry<N>>,
    attributes: Option<Map<String, Value>>,
}

FeatureSets are defined as

pub struct FeatureSet<const N: usize> {
    // ... other optional fields 
    features: Vec<Feature<N>>,
    geometryType: Option<String>,
    spatialReference: SpatialReference,
}

Spatial References

Esri Spatial Reference Objects are represented by the SpatialReference struct. Note that while all fields are optional, one should always be provided.

struct SpatialReference {
    wkid: Option<u32>,
    latest_wkid: Option<u32>,
    vcs_wkid: Option<u32>,
    latest_vcs_wkid: Option<u32>,
    wkt: Option<String>,
}

Example usage:

This example reads a single feature from a feature service and returns a FeatureSet struct.

use serde_esri::features::FeatureSet;
use reqwest::Error;
use std::io::Read;

fn main() -> Result<(), Error> {
    let flayer_url = "https://services.arcgis.com/P3ePLMYs2RVChkJx/ArcGIS/rest/services/USA_Counties_Generalized_Boundaries/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&resultRecordCount=1&f=json";
    let mut res = reqwest::blocking::get(flayer_url)?;
    let mut body = String::new();
    res.read_to_string(&mut body).unwrap();

    let fset: FeatureSet<2> = serde_json::from_str(&body).unwrap(); 
    println!("{:#?}", fset);
    Ok(())
}

You might also like...

JSON parser which picks up values directly without performing tokenization in Rust

Comments

Use separated Coords

Per recommendation separated x &y coordinates should be used when creating a geoarrow array as it will improve conversion to R types.

Comment: https://github.com/geoarrow/geoarrow-c/issues/78

Example affected lines: https://github.com/JosiahParry/serde_esri/blob/1f7f70e086463079bc2d99b925580e052b7382be/src/arrow_compat.rs#L209

@kylebarron

opened by JosiahParry 3