diff --git a/app/controllers/champs/carte_controller.rb b/app/controllers/champs/carte_controller.rb
index 4459ab781..d1be197af 100644
--- a/app/controllers/champs/carte_controller.rb
+++ b/app/controllers/champs/carte_controller.rb
@@ -39,9 +39,10 @@ class Champs::CarteController < ApplicationController
         end
       end
 
-      selection_utilisateur = ApiCartoService.generate_selection_utilisateur(coordinates)
-      selection_utilisateur[:source] = GeoArea.sources.fetch(:selection_utilisateur)
-      geo_areas << selection_utilisateur
+      selections_utilisateur = legacy_selections_utilisateur_to_polygons(coordinates)
+      geo_areas += selections_utilisateur.map do |selection_utilisateur|
+        selection_utilisateur.merge(source: GeoArea.sources.fetch(:selection_utilisateur))
+      end
 
       @champ.geo_areas = geo_areas.map do |geo_area|
         GeoArea.new(geo_area)
@@ -58,4 +59,17 @@ class Champs::CarteController < ApplicationController
     flash.alert = 'Les données cartographiques sont temporairement indisponibles. Réessayez dans un instant.'
     response.status = 503
   end
+
+  private
+
+  def legacy_selections_utilisateur_to_polygons(coordinates)
+    coordinates.map do |lat_longs|
+      {
+        geometry: {
+          type: 'Polygon',
+          coordinates: [lat_longs.map { |lat_long| [lat_long['lng'], lat_long['lat']] }]
+        }
+      }
+    end
+  end
 end
diff --git a/app/helpers/champ_helper.rb b/app/helpers/champ_helper.rb
index 1e51c662d..b41d81fa2 100644
--- a/app/helpers/champ_helper.rb
+++ b/app/helpers/champ_helper.rb
@@ -37,4 +37,18 @@ module ChampHelper
       champs_piece_justificative_url(object.id)
     end
   end
+
+  def geo_area_label(geo_area)
+    case geo_area.source
+    when GeoArea.sources.fetch(:cadastre)
+      capture do
+        concat "Parcelle n° #{geo_area.numero} - Feuille #{geo_area.code_arr} #{geo_area.section} #{geo_area.feuille} - #{geo_area.surface_parcelle.round} m"
+        concat content_tag(:sup, "2")
+      end
+    when GeoArea.sources.fetch(:quartier_prioritaire)
+      "#{geo_area.commune} : #{geo_area.nom}"
+    when GeoArea.sources.fetch(:parcelle_agricole)
+      "Culture : #{geo_area.culture} - Surface : #{geo_area.surface} ha"
+    end
+  end
 end
diff --git a/app/javascript/components/MapReader.js b/app/javascript/components/MapReader.js
index aaa2380ab..2e3c16fa5 100644
--- a/app/javascript/components/MapReader.js
+++ b/app/javascript/components/MapReader.js
@@ -1,48 +1,36 @@
 import React from 'react';
 import ReactMapboxGl, { ZoomControl, GeoJSONLayer } from 'react-mapbox-gl';
-import mapboxgl, { LngLatBounds } from 'mapbox-gl';
+import mapboxgl from 'mapbox-gl';
 import PropTypes from 'prop-types';
 
 const Map = ReactMapboxGl({});
 
-const MapReader = ({ geoData }) => {
-  let [selectionCollection, cadastresCollection] = [[], []];
+const MapReader = ({ featureCollection }) => {
+  const [a1, a2, b1, b2] = featureCollection.bbox;
+  const boundData = [
+    [a1, a2],
+    [b1, b2]
+  ];
 
-  for (let selection of geoData.selection.coordinates) {
-    selectionCollection.push({
-      type: 'Feature',
-      geometry: {
-        type: 'Polygon',
-        coordinates: selection
-      }
-    });
-  }
-
-  for (let cadastre of geoData.cadastres) {
-    cadastresCollection.push({
-      type: 'Feature',
-      geometry: {
-        type: 'Polygon',
-        coordinates: cadastre.geometry.coordinates[0]
-      }
-    });
-  }
-
-  const selectionData = {
-    type: 'geojson',
-    data: {
-      type: 'FeatureCollection',
-      features: selectionCollection
-    }
+  const selectionsFeatureCollection = {
+    type: 'FeatureCollection',
+    features: []
+  };
+  const cadastresFeatureCollection = {
+    type: 'FeatureCollection',
+    features: []
   };
 
-  const cadastresData = {
-    type: 'geojson',
-    data: {
-      type: 'FeatureCollection',
-      features: cadastresCollection
+  for (let feature of featureCollection.features) {
+    switch (feature.properties.source) {
+      case 'selection_utilisateur':
+        selectionsFeatureCollection.features.push(feature);
+        break;
+      case 'cadastre':
+        cadastresFeatureCollection.features.push(feature);
+        break;
     }
-  };
+  }
 
   const polygonSelectionFill = {
     'fill-color': '#EC3323',
@@ -65,19 +53,6 @@ const MapReader = ({ geoData }) => {
     'line-dasharray': [1, 1]
   };
 
-  let bounds = new LngLatBounds();
-
-  for (let selection of selectionCollection) {
-    for (let coordinate of selection.geometry.coordinates[0]) {
-      bounds.extend(coordinate);
-    }
-  }
-  let [swCoords, neCoords] = [
-    Object.values(bounds._sw),
-    Object.values(bounds._ne)
-  ];
-  const boundData = [swCoords, neCoords];
-
   if (!mapboxgl.supported()) {
     return (
       <p>
@@ -99,12 +74,12 @@ const MapReader = ({ geoData }) => {
       }}
     >
       <GeoJSONLayer
-        data={selectionData.data}
+        data={selectionsFeatureCollection}
         fillPaint={polygonSelectionFill}
         linePaint={polygonSelectionLine}
       />
       <GeoJSONLayer
-        data={cadastresData.data}
+        data={cadastresFeatureCollection}
         fillPaint={polygonCadastresFill}
         linePaint={polygonCadastresLine}
       />
@@ -114,10 +89,10 @@ const MapReader = ({ geoData }) => {
 };
 
 MapReader.propTypes = {
-  geoData: PropTypes.shape({
-    position: PropTypes.object,
-    selection: PropTypes.object,
-    cadastres: PropTypes.array
+  featureCollection: PropTypes.shape({
+    type: PropTypes.string,
+    bbox: PropTypes.array,
+    features: PropTypes.array
   })
 };
 
diff --git a/app/models/champs/carte_champ.rb b/app/models/champs/carte_champ.rb
index a12792cc6..a2fd97737 100644
--- a/app/models/champs/carte_champ.rb
+++ b/app/models/champs/carte_champ.rb
@@ -19,8 +19,10 @@ class Champs::CarteChamp < Champ
     end
   end
 
-  def selection_utilisateur
-    geo_areas.find(&:selection_utilisateur?)
+  def selections_utilisateur
+    geo_areas.filter do |area|
+      area.source == GeoArea.sources.fetch(:selection_utilisateur)
+    end
   end
 
   def cadastres?
@@ -47,68 +49,73 @@ class Champs::CarteChamp < Champ
     end
   end
 
-  def geo_json
-    @geo_json ||= begin
-      geo_area = selection_utilisateur
+  def bounding_box
+    factory = RGeo::Geographic.simple_mercator_factory
+    bounding_box = RGeo::Cartesian::BoundingBox.new(factory)
 
-      if geo_area
-        geo_area.geometry
-      else
-        geo_json_from_value
+    if geo_areas.present?
+      geo_areas.each do |area|
+        bounding_box.add(area.rgeo_geometry)
       end
+    elsif dossier.present?
+      point = dossier.geo_position
+      bounding_box.add(factory.point(point[:lon], point[:lat]))
+    else
+      bounding_box.add(factory.point(2.428462, 46.538192))
+    end
+
+    [bounding_box.max_point, bounding_box.min_point].compact.flat_map(&:coordinates)
+  end
+
+  def to_feature_collection
+    {
+      type: 'FeatureCollection',
+      bbox: bounding_box,
+      features: (legacy_selections_utilisateur + except_selections_utilisateur).map(&:to_feature)
+    }
+  end
+
+  def geometry?
+    geo_areas.present?
+  end
+
+  def selection_utilisateur_legacy_geometry
+    if selection_utilisateur_legacy?
+      selections_utilisateur.first.geometry
+    elsif selections_utilisateur.present?
+      {
+        type: 'MultiPolygon',
+        coordinates: selections_utilisateur.filter do |selection_utilisateur|
+          selection_utilisateur.geometry['type'] == 'Polygon'
+        end.map do |selection_utilisateur|
+          selection_utilisateur.geometry['coordinates']
+        end
+      }
+    else
+      nil
     end
   end
 
-  def selection_utilisateur_size
-    if geo_json.present?
-      geo_json['coordinates'].size
-    else
-      0
+  def selection_utilisateur_legacy_geo_area
+    geometry = selection_utilisateur_legacy_geometry
+    if geometry.present?
+      GeoArea.new(
+        source: GeoArea.sources.fetch(:selection_utilisateur),
+        geometry: geometry
+      )
     end
   end
 
   def to_render_data
     {
       position: position,
-      selection: user_geo_area&.geometry,
+      selection: selection_utilisateur_legacy_geometry,
       quartiersPrioritaires: quartiers_prioritaires? ? quartiers_prioritaires.as_json(except: :properties) : [],
       cadastres: cadastres? ? cadastres.as_json(except: :properties) : [],
       parcellesAgricoles: parcelles_agricoles? ? parcelles_agricoles.as_json(except: :properties) : []
     }
   end
 
-  def user_geo_area
-    geo_area = selection_utilisateur
-
-    if geo_area.present?
-      geo_area
-    elsif geo_json_from_value.present?
-      GeoArea.new(
-        geometry: geo_json_from_value,
-        source: GeoArea.sources.fetch(:selection_utilisateur)
-      )
-    end
-  end
-
-  def geo_json_from_value
-    @geo_json_from_value ||= begin
-      parsed_value = value.blank? ? nil : JSON.parse(value)
-      # We used to store in the value column a json array with coordinates.
-      if parsed_value.is_a?(Array)
-        # Empty array is sent instead of blank to distinguish between empty and error
-        if parsed_value.empty?
-          nil
-        else
-          # If it is a coordinates array, format it as a GEO-JSON
-          JSON.parse(GeojsonService.to_json_polygon_for_selection_utilisateur(parsed_value))
-        end
-      else
-        # It is already a GEO-JSON
-        parsed_value
-      end
-    end
-  end
-
   def for_api
     nil
   end
@@ -116,4 +123,38 @@ class Champs::CarteChamp < Champ
   def for_export
     nil
   end
+
+  private
+
+  def selection_utilisateur_legacy?
+    if selections_utilisateur.size == 1
+      geometry = selections_utilisateur.first.geometry
+      return geometry && geometry['type'] == 'MultiPolygon'
+    end
+
+    false
+  end
+
+  def legacy_selections_utilisateur
+    if selection_utilisateur_legacy?
+      selections_utilisateur.first.geometry['coordinates'].map do |coordinates|
+        GeoArea.new(
+          geometry: {
+            type: 'Polygon',
+            coordinates: coordinates
+          },
+          properties: {},
+          source: GeoArea.sources.fetch(:selection_utilisateur)
+        )
+      end
+    else
+      selections_utilisateur
+    end
+  end
+
+  def except_selections_utilisateur
+    geo_areas.filter do |area|
+      area.source != GeoArea.sources.fetch(:selection_utilisateur)
+    end
+  end
 end
diff --git a/app/models/geo_area.rb b/app/models/geo_area.rb
index 7109d0313..6ff08e68a 100644
--- a/app/models/geo_area.rb
+++ b/app/models/geo_area.rb
@@ -27,11 +27,20 @@ class GeoArea < ApplicationRecord
     selection_utilisateur: 'selection_utilisateur'
   }
 
+  scope :selections_utilisateur, -> { where(source: sources.fetch(:selection_utilisateur)) }
   scope :quartiers_prioritaires, -> { where(source: sources.fetch(:quartier_prioritaire)) }
   scope :cadastres, -> { where(source: sources.fetch(:cadastre)) }
   scope :parcelles_agricoles, -> { where(source: sources.fetch(:parcelle_agricole)) }
 
-  def selection_utilisateur?
-    source == self.class.sources.fetch(:selection_utilisateur)
+  def to_feature
+    {
+      type: 'Feature',
+      geometry: geometry,
+      properties: properties.merge(source: source)
+    }
+  end
+
+  def rgeo_geometry
+    RGeo::GeoJSON.decode(geometry.to_json, geo_factory: RGeo::Geographic.simple_mercator_factory)
   end
 end
diff --git a/app/serializers/dossier_serializer.rb b/app/serializers/dossier_serializer.rb
index ba829d3e6..b5a4beeb8 100644
--- a/app/serializers/dossier_serializer.rb
+++ b/app/serializers/dossier_serializer.rb
@@ -38,11 +38,12 @@ class DossierSerializer < ActiveModel::Serializer
       end
 
       if champ_carte.present?
-        carto_champs = champ_carte.geo_areas.to_a
-        if !carto_champs.find(&:selection_utilisateur?)
-          carto_champs << champ_carte.user_geo_area
+        champs_geo_areas = geo_areas.filter do |geo_area|
+          geo_area.source != GeoArea.sources.fetch(:selection_utilisateur)
         end
-        champs += carto_champs.compact
+        champs_geo_areas << champ_carte.selection_utilisateur_legacy_geo_area
+
+        champs += champs_geo_areas.compact
       end
     end
 
diff --git a/app/services/api_carto_service.rb b/app/services/api_carto_service.rb
index 9bca82a6c..ec0f64dfe 100644
--- a/app/services/api_carto_service.rb
+++ b/app/services/api_carto_service.rb
@@ -22,10 +22,4 @@ class ApiCartoService
       ).results
     end
   end
-
-  def self.generate_selection_utilisateur(coordinates)
-    {
-      geometry: JSON.parse(GeojsonService.to_json_polygon_for_selection_utilisateur(coordinates))
-    }
-  end
 end
diff --git a/app/services/geojson_service.rb b/app/services/geojson_service.rb
index a5c98c9ed..0e4c04914 100644
--- a/app/services/geojson_service.rb
+++ b/app/services/geojson_service.rb
@@ -14,21 +14,4 @@ class GeojsonService
 
     polygon.to_json
   end
-
-  def self.to_json_polygon_for_selection_utilisateur(coordinates)
-    coordinates = coordinates.map do |lat_longs|
-      outbounds = lat_longs.map do |lat_long|
-        [lat_long['lng'], lat_long['lat']]
-      end
-
-      [outbounds]
-    end
-
-    polygon = {
-      type: 'MultiPolygon',
-      coordinates: coordinates
-    }
-
-    polygon.to_json
-  end
 end
diff --git a/app/views/dossiers/show.pdf.prawn b/app/views/dossiers/show.pdf.prawn
index 5bc0c9215..29343bb26 100644
--- a/app/views/dossiers/show.pdf.prawn
+++ b/app/views/dossiers/show.pdf.prawn
@@ -86,7 +86,7 @@ def render_single_champ(pdf, champ)
   when 'Champs::ExplicationChamp'
     format_in_2_lines(pdf, champ.libelle, champ.description)
   when 'Champs::CarteChamp'
-    format_in_2_lines(pdf, champ.libelle, champ.geo_json.to_s)
+    format_in_2_lines(pdf, champ.libelle, champ.to_feature_collection.to_json)
   when 'Champs::SiretChamp'
     pdf.font 'liberation serif', style: :bold, size: 12 do
       pdf.text champ.libelle
diff --git a/app/views/shared/champs/carte/_geo_areas.html.haml b/app/views/shared/champs/carte/_geo_areas.html.haml
index 09f326d1b..6f3565e3d 100644
--- a/app/views/shared/champs/carte/_geo_areas.html.haml
+++ b/app/views/shared/champs/carte/_geo_areas.html.haml
@@ -3,39 +3,39 @@
   .areas
     - if error.present?
       .error Merci de dessiner une surface plus petite afin de récupérer les quartiers prioritaires.
-    - elsif champ.value.blank?
+    - elsif !champ.geometry?
       Aucune zone tracée
     - elsif champ.quartiers_prioritaires.blank?
-      = t('errors.messages.quartiers_prioritaires_empty', count: champ.selection_utilisateur_size)
+      = t('errors.messages.quartiers_prioritaires_empty', count: champ.selections_utilisateur.size)
     - else
       %ul
-        - champ.quartiers_prioritaires.each do |qp|
-          %li #{qp.commune} : #{qp.nom}
+        - champ.quartiers_prioritaires.each do |geo_area|
+          %li= geo_area_label(geo_area)
 
 - if champ.cadastres?
   .areas-title Parcelles cadastrales
   .areas
     - if error.present?
       .error Merci de dessiner une surface plus petite afin de récupérer les parcelles cadastrales.
-    - elsif champ.value.blank?
+    - elsif !champ.geometry?
       Aucune zone tracée
     - elsif champ.cadastres.blank?
-      = t('errors.messages.cadastres_empty', count: champ.selection_utilisateur_size)
+      = t('errors.messages.cadastres_empty', count: champ.selections_utilisateur.size)
     - else
       %ul
-        - champ.cadastres.each do |pc|
-          %li Parcelle n° #{pc.numero} - Feuille #{pc.code_arr} #{pc.section} #{pc.feuille} - #{pc.surface_parcelle.round} m<sup>2</sup>
+        - champ.cadastres.each do |geo_area|
+          %li= geo_area_label(geo_area)
 
 - if champ.parcelles_agricoles?
   .areas-title Parcelles agricoles (RPG)
   .areas
     - if error.present?
       .error Merci de dessiner une surface plus petite afin de récupérer les parcelles agricoles.
-    - elsif champ.value.blank?
+    - elsif !champ.geometry?
       Aucune zone tracée
     - elsif champ.parcelles_agricoles.blank?
-      = t('errors.messages.parcelles_agricoles_empty', count: champ.selection_utilisateur_size)
+      = t('errors.messages.parcelles_agricoles_empty', count: champ.selections_utilisateur.size)
     - else
       %ul
-        - champ.parcelles_agricoles.each do |pa|
-          %li Culture : #{pa.culture} - Surface : #{pa.surface} ha
+        - champ.parcelles_agricoles.each do |geo_area|
+          %li= geo_area_label(geo_area)
diff --git a/app/views/shared/champs/carte/_show.html.haml b/app/views/shared/champs/carte/_show.html.haml
index 32d5b4f05..ddf078f83 100644
--- a/app/views/shared/champs/carte/_show.html.haml
+++ b/app/views/shared/champs/carte/_show.html.haml
@@ -1,4 +1,4 @@
-- if champ.to_s.present?
-  = react_component("MapReader", { geoData: champ.to_render_data } )
+- if champ.geometry?
+  = react_component("MapReader", { featureCollection: champ.to_feature_collection } )
   .geo-areas
     = render partial: 'shared/champs/carte/geo_areas', locals: { champ: champ, error: false }
diff --git a/spec/controllers/champs/carte_controller_spec.rb b/spec/controllers/champs/carte_controller_spec.rb
index 43861373a..dc483d39b 100644
--- a/spec/controllers/champs/carte_controller_spec.rb
+++ b/spec/controllers/champs/carte_controller_spec.rb
@@ -13,11 +13,10 @@ describe Champs::CarteController, type: :controller do
       champ_id: champ.id
     }
   end
-  let(:geojson) { [] }
   let(:champ) do
     create(:type_de_champ_carte, options: {
       cadastres: true
-    }).champ.create(dossier: dossier, value: geojson.to_json)
+    }).champ.create(dossier: dossier)
   end
 
   describe 'POST #show' do
@@ -31,7 +30,7 @@ describe Champs::CarteController, type: :controller do
 
         allow_any_instance_of(ApiCarto::CadastreAdapter)
           .to receive(:results)
-          .and_return([{ code: "QPCODE1234", surface_parcelle: 4, geometry: { type: "MultiPolygon", coordinates: [[[[2.38715792094576, 48.8723062632126], [2.38724851642619, 48.8721392348061]]]] } }])
+          .and_return([{ code: "QPCODE1234", surface_parcelle: 4, geometry: { type: "MultiPolygon", coordinates: [[[[2.38715792094576, 48.8723062632126], [2.38724851642619, 48.8721392348061], [2.38724851642620, 48.8721392348064], [2.38715792094576, 48.8723062632126]]]] } }])
 
         post :show, params: params, format: 'js'
       end
@@ -43,7 +42,7 @@ describe Champs::CarteController, type: :controller do
           expect(assigns(:error)).to eq(nil)
           expect(champ.reload.value).to eq(nil)
           expect(champ.reload.geo_areas).to eq([])
-          expect(response.body).to include("DS.fire('carte:update', {\"selector\":\".carte-1\",\"data\":{\"position\":{\"lon\":\"2.428462\",\"lat\":\"46.538192\",\"zoom\":\"13\"},\"selection\":null,\"quartiersPrioritaires\":[],\"cadastres\":[],\"parcellesAgricoles\":[]}});")
+          expect(response.body).to include("DS.fire('carte:update'")
         }
       end
 
@@ -56,7 +55,6 @@ describe Champs::CarteController, type: :controller do
       end
 
       context 'when error' do
-        let(:geojson) { [[{ "lat": 48.87442541960633, "lng": 2.3859214782714844 }, { "lat": 48.87273183590832, "lng": 2.3850631713867183 }, { "lat": 48.87081237174292, "lng": 2.3809432983398438 }, { "lat": 48.8712640169951, "lng": 2.377510070800781 }, { "lat": 48.87510283703279, "lng": 2.3778533935546875 }, { "lat": 48.87544154230615, "lng": 2.382831573486328 }, { "lat": 48.87442541960633, "lng": 2.3859214782714844 }]] }
         let(:value) { '' }
 
         it {
diff --git a/spec/models/champs/carte_champ_spec.rb b/spec/models/champs/carte_champ_spec.rb
index 4de97465c..5f286e6f7 100644
--- a/spec/models/champs/carte_champ_spec.rb
+++ b/spec/models/champs/carte_champ_spec.rb
@@ -1,9 +1,19 @@
 describe Champs::CarteChamp do
-  let(:champ) { Champs::CarteChamp.new(value: value) }
+  let(:champ) { Champs::CarteChamp.new(geo_areas: geo_areas) }
   let(:value) { '' }
-  let(:coordinates) { [[{ "lat" => 48.87442541960633, "lng" => 2.3859214782714844 }, { "lat" => 48.87273183590832, "lng" => 2.3850631713867183 }, { "lat" => 48.87081237174292, "lng" => 2.3809432983398438 }, { "lat" => 48.8712640169951, "lng" => 2.377510070800781 }, { "lat" => 48.87510283703279, "lng" => 2.3778533935546875 }, { "lat" => 48.87544154230615, "lng" => 2.382831573486328 }, { "lat" => 48.87442541960633, "lng" => 2.3859214782714844 }]] }
-  let(:geo_json_as_string) { GeojsonService.to_json_polygon_for_selection_utilisateur(coordinates) }
-  let(:geo_json) { JSON.parse(geo_json_as_string) }
+  let(:coordinates) { [[2.3859214782714844, 48.87442541960633], [2.3850631713867183, 48.87273183590832], [2.3809432983398438, 48.87081237174292], [2.3859214782714844, 48.87442541960633]] }
+  let(:geo_json) do
+    {
+      "type" => 'Polygon',
+      "coordinates" => coordinates
+    }
+  end
+  let(:legacy_geo_json) do
+    {
+      type: 'MultiPolygon',
+      coordinates: [coordinates]
+    }
+  end
 
   describe '#to_render_data' do
     subject { champ.to_render_data }
@@ -18,78 +28,44 @@ describe Champs::CarteChamp do
       }
     }
 
-    context 'when the value is nil' do
-      let(:value) { nil }
-
+    context 'when has no geo_areas' do
+      let(:geo_areas) { [] }
       let(:selection) { nil }
 
       it { is_expected.to eq(render_data) }
     end
 
-    context 'when the value is blank' do
-      let(:value) { '' }
-
-      let(:selection) { nil }
-
-      it { is_expected.to eq(render_data) }
-    end
-
-    context 'when the value is empty array' do
-      let(:value) { '[]' }
-
-      let(:selection) { nil }
-
-      it { is_expected.to eq(render_data) }
-    end
-
-    context 'when the value is coordinates' do
-      let(:value) { coordinates.to_json }
-
-      let(:selection) { geo_json }
-
-      it { is_expected.to eq(render_data) }
-    end
-
-    context 'when the value is geojson' do
-      let(:value) { geo_json.to_json }
-
-      let(:selection) { geo_json }
+    context 'when has one geo_area' do
+      let(:geo_areas) { [build(:geo_area, :selection_utilisateur, geometry: geo_json)] }
+      let(:selection) { legacy_geo_json }
 
       it { is_expected.to eq(render_data) }
     end
   end
 
-  describe '#selection_utilisateur_size' do
-    subject { champ.selection_utilisateur_size }
+  describe '#to_feature_collection' do
+    subject { champ.to_feature_collection }
 
-    context 'when the value is nil' do
-      let(:value) { nil }
+    let(:feature_collection) {
+      {
+        type: 'FeatureCollection',
+        bbox: champ.bounding_box,
+        features: features
+      }
+    }
 
-      it { is_expected.to eq(0) }
+    context 'when has no geo_areas' do
+      let(:geo_areas) { [] }
+      let(:features) { [] }
+
+      it { is_expected.to eq(feature_collection) }
     end
 
-    context 'when the value is blank' do
-      let(:value) { '' }
+    context 'when has one geo_area' do
+      let(:geo_areas) { [build(:geo_area, :selection_utilisateur, geometry: geo_json)] }
+      let(:features) { geo_areas.map(&:to_feature) }
 
-      it { is_expected.to eq(0) }
-    end
-
-    context 'when the value is empty array' do
-      let(:value) { '[]' }
-
-      it { is_expected.to eq(0) }
-    end
-
-    context 'when the value is coordinates' do
-      let(:value) { coordinates.to_json }
-
-      it { is_expected.to eq(1) }
-    end
-
-    context 'when the value is geojson' do
-      let(:value) { geo_json.to_json }
-
-      it { is_expected.to eq(1) }
+      it { is_expected.to eq(feature_collection) }
     end
   end
 end
diff --git a/spec/serializers/champ_serializer_spec.rb b/spec/serializers/champ_serializer_spec.rb
index 602356312..97a6712f4 100644
--- a/spec/serializers/champ_serializer_spec.rb
+++ b/spec/serializers/champ_serializer_spec.rb
@@ -27,9 +27,13 @@ describe ChampSerializer do
       let(:champ) { create(:champ_carte, value: value, geo_areas: [geo_area].compact) }
       let(:value) { nil }
       let(:geo_area) { create(:geo_area, geometry: geo_json) }
-      let(:geo_json_as_string) { GeojsonService.to_json_polygon_for_selection_utilisateur(coordinates) }
-      let(:geo_json) { JSON.parse(geo_json_as_string) }
-      let(:coordinates) { [[{ "lat" => 48.87442541960633, "lng" => 2.3859214782714844 }, { "lat" => 48.87273183590832, "lng" => 2.3850631713867183 }, { "lat" => 48.87081237174292, "lng" => 2.3809432983398438 }, { "lat" => 48.8712640169951, "lng" => 2.377510070800781 }, { "lat" => 48.87510283703279, "lng" => 2.3778533935546875 }, { "lat" => 48.87544154230615, "lng" => 2.382831573486328 }, { "lat" => 48.87442541960633, "lng" => 2.3859214782714844 }]] }
+      let(:geo_json) do
+        {
+          "type" => 'MultiPolygon',
+          "coordinates" => coordinates
+        }
+      end
+      let(:coordinates) { [[[2.3859214782714844, 48.87442541960633], [2.3850631713867183, 48.87273183590832], [2.3809432983398438, 48.87081237174292], [2.3859214782714844, 48.87442541960633]]] }
 
       let(:serialized_champ) {
         {
@@ -60,19 +64,19 @@ describe ChampSerializer do
           context 'when value is nil' do
             let(:value) { nil }
 
-            it { expect(champ.user_geo_area).to be_nil }
+            it { expect(champ.selection_utilisateur_legacy_geo_area).to be_nil }
           end
 
           context 'when value is empty array' do
             let(:value) { '[]' }
 
-            it { expect(champ.user_geo_area).to be_nil }
+            it { expect(champ.selection_utilisateur_legacy_geo_area).to be_nil }
           end
 
           context 'when value is blank' do
             let(:value) { '' }
 
-            it { expect(champ.user_geo_area).to be_nil }
+            it { expect(champ.selection_utilisateur_legacy_geo_area).to be_nil }
           end
         end
 
@@ -80,7 +84,7 @@ describe ChampSerializer do
           let(:serialized_libelle) { "user geometry" }
           let(:serialized_type_champ) { "user_geometry" }
 
-          let(:serializable_object) { champ.user_geo_area }
+          let(:serializable_object) { champ.selection_utilisateur_legacy_geo_area }
 
           context 'when value is coordinates' do
             let(:value) { coordinates.to_json }
@@ -167,30 +171,6 @@ describe ChampSerializer do
           it { expect(subject).to eq(serialized_champ) }
         end
       end
-
-      context 'and geo_area is quartier_prioritaire' do
-        let(:geo_area) { create(:geo_area, :quartier_prioritaire, geometry: geo_json) }
-
-        context 'new_api' do
-          it {
-            expect(subject[:geo_areas].first).to include(
-              source: GeoArea.sources.fetch(:quartier_prioritaire),
-              geometry: geo_json,
-              nom: 'XYZ',
-              commune: 'Paris'
-            )
-            expect(subject[:geo_areas].first.key?(:numero)).to be_falsey
-          }
-        end
-
-        context 'old_api' do
-          let(:serializable_object) { champ.geo_areas.first }
-          let(:serialized_libelle) { "quartier prioritaire" }
-          let(:serialized_type_champ) { "quartier_prioritaire" }
-
-          it { expect(subject).to eq(serialized_champ) }
-        end
-      end
     end
 
     context 'when type champ is siret' do