Flutter Filter for nearest Place by latitude/longitude

Question

I'm trying to code an app and I'm loading an Eventplace object from my server with the class. I want to use Isar as my offline database, but I don't know how to filter for the nearest eventplace by lat and lng. Unfortantely I couldn't add LatLng as an embedded Object bc of their is not default constructor. I am just needing a possiblity to filter through the objects by the db and check the distance with Geolocator.distanceBetween(lat, lng, lat2, lng2) or should i just query through all and filter the list by myself.

final database = isar!.eventplaces;

import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:isar/isar.dart';

part 'eventplace.g.dart';

@collection
class Eventplace {

  Id? id;
  int? city_id;
  String? city_name;
  float? city_lat;
  float? city_lng;
  String? name;
  String? adress;
  String? url;
  float? latitude;
  float? longitude;

  Eventplace({
    this.id,
    this.city_id,
    this.city_name,
    this.city_lat,
    this.city_lng,
    this.name,
    this.adress,
    this.url,
    this.latitude,
    this.longitude,
  });

  LatLng createCityLatLng(){
    return LatLng(this.city_lat ?? 0.0, this.city_lng ?? 0.0);
  }

  LatLng createLatLng(){
    return LatLng(this.latitude ?? 0.0, this.longitude ?? 0.0);
  }

  static toJSON(Eventplace ev){
    return {};
  }

  factory Eventplace.fromJSON(Map<String, dynamic> json){
    return Eventplace(
      id: json['id'] as int,
      city_id: json['city_id'] as int,
      city_name: json['city_name'] as String?,
      city_lat: json['city_lat'] as float?,
      city_lng: json['city_lng'] as float?,
      name: json['name'] as String?,
      adress: json['adress'] as String?,
      url: json['url'] as String?,
      latitude: json['latitude'] as float?,
      longitude: json['longitude'] as float?,
    );
  }
}