Esri Geometry Objects • arcgislayers

Feature objects are different than geometry objects.
- geometry objects do not have attributes
- feature objects do have attributes

Features consist of 2 properties both of which are optional
- attributes
  - field values can be: string number, or boolean
    - cannot be arrays
- geometry
  - a geometry object
  - https://developers.arcgis.com/documentation/common-data-types/geometry-objects.htm
while both are optional, they both need to be included in the json the following are valid


{
  "geometry": {
    },
  "attributes": {
    }
}

{
  "geometry": {
    "x": -81.49822900952586,
    "y": 36.43139560823739
  },
  "attributes": {
  }
}

{
  "geometry": {
    "x": -81.49822900952586,
    "y": 36.43139560823739
  },
  "attributes": {
    "date": "2023-01-04"
  }
}

featureSet is created from feature objects
- tables do not return geometry
spatial references:
- should be set at the top level
- if not set at the top level then it takes the spatial reference of the first feature’s geometry object
  - note that geometry objects don’t have to have spatial reference
- if neither are set it takes on UnknownCoordinateSystem
  - by default, sf and sfc object should set a top level spatial reference
3 optional fields:
- objectIdFieldName
- globalIdFieldName
- displayFieldName

can either be a wkid or wkt
wkid is the well-known ID e.g. 4326
wkt is the well-known text format
st_crs() will always return the wkt, that should be used.
esriGeometry can also support Vertical Coordinate Systems (VCS) these should be supported, but later

adding a crs uses a lot of text so it should be done only once when possible. so its important to consider when this is done.

Development priority?