diff --git a/frontend/src/components/korea/FleetClusterLayer.tsx b/frontend/src/components/korea/FleetClusterLayer.tsx
index 76f3b10..f73cf35 100644
--- a/frontend/src/components/korea/FleetClusterLayer.tsx
+++ b/frontend/src/components/korea/FleetClusterLayer.tsx
@@ -6,6 +6,7 @@ import type { Ship, VesselAnalysisDto } from '../../types';
 import { fetchFleetCompanies } from '../../services/vesselAnalysis';
 import type { FleetCompany } from '../../services/vesselAnalysis';
 import { classifyFishingZone } from '../../utils/fishingAnalysis';
+import { convexHull, padPolygon, clusterColor } from '../../utils/geometry';
 
 export interface SelectedGearGroupData {
   parent: Ship | null;
@@ -29,59 +30,6 @@ interface Props {
   onSelectedFleetChange?: (data: SelectedFleetData | null) => void;
 }
 
-// 두 벡터의 외적 (2D) — Graham scan에서 왼쪽 회전 여부 판별
-function cross(o: [number, number], a: [number, number], b: [number, number]): number {
-  return (a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0]);
-}
-
-// Graham scan 기반 볼록 껍질 (반시계 방향)
-function convexHull(points: [number, number][]): [number, number][] {
-  const n = points.length;
-  if (n < 2) return points.slice();
-  const sorted = points.slice().sort((a, b) => a[0] - b[0] || a[1] - b[1]);
-  const lower: [number, number][] = [];
-  for (const p of sorted) {
-    while (lower.length >= 2 && cross(lower[lower.length - 2], lower[lower.length - 1], p) <= 0) {
-      lower.pop();
-    }
-    lower.push(p);
-  }
-  const upper: [number, number][] = [];
-  for (let i = sorted.length - 1; i >= 0; i--) {
-    const p = sorted[i];
-    while (upper.length >= 2 && cross(upper[upper.length - 2], upper[upper.length - 1], p) <= 0) {
-      upper.pop();
-    }
-    upper.push(p);
-  }
-  // lower + upper (첫/끝 중복 제거)
-  lower.pop();
-  upper.pop();
-  return lower.concat(upper);
-}
-
-// 중심에서 각 꼭짓점 방향으로 padding 확장
-function padPolygon(hull: [number, number][], padding: number): [number, number][] {
-  if (hull.length === 0) return hull;
-  const cx = hull.reduce((s, p) => s + p[0], 0) / hull.length;
-  const cy = hull.reduce((s, p) => s + p[1], 0) / hull.length;
-  return hull.map(([x, y]) => {
-    const dx = x - cx;
-    const dy = y - cy;
-    const len = Math.sqrt(dx * dx + dy * dy);
-    if (len === 0) return [x + padding, y + padding] as [number, number];
-    const scale = (len + padding) / len;
-    return [cx + dx * scale, cy + dy * scale] as [number, number];
-  });
-}
-
-// cluster_id 해시 → HSL 색상
-function clusterColor(id: number): string {
-  const h = (id * 137) % 360;
-  return `hsl(${h}, 80%, 55%)`;
-}
-
-// HSL 문자열 → hex 근사 (MapLibre는 hsl() 지원하므로 직접 사용 가능)
 // GeoJSON feature에 color 속성으로 주입
 interface ClusterPolygonFeature {
   type: 'Feature';
diff --git a/frontend/src/components/korea/KoreaDashboard.tsx b/frontend/src/components/korea/KoreaDashboard.tsx
index 7d4c14a..d0a8e28 100644
--- a/frontend/src/components/korea/KoreaDashboard.tsx
+++ b/frontend/src/components/korea/KoreaDashboard.tsx
@@ -1,6 +1,7 @@
 import { useState, useCallback } from 'react';
 import { createPortal } from 'react-dom';
 import { useTranslation } from 'react-i18next';
+import { useLocalStorage, useLocalStorageSet } from '../../hooks/useLocalStorage';
 import { KoreaMap } from './KoreaMap';
 import { FieldAnalysisModal } from './FieldAnalysisModal';
 import { LayerPanel } from '../common/LayerPanel';
@@ -82,7 +83,7 @@ export const KoreaDashboard = ({
   const { hiddenAcCategories, hiddenShipCategories, toggleAcCategory, toggleShipCategory } =
     useSharedFilters();
 
-  const [koreaLayers, setKoreaLayers] = useState<Record<string, boolean>>({
+  const [koreaLayers, setKoreaLayers] = useLocalStorage<Record<string, boolean>>('koreaLayers', {
     ships: true,
     aircraft: true,
     satellites: true,
@@ -122,25 +123,25 @@ export const KoreaDashboard = ({
 
   const toggleKoreaLayer = useCallback((key: string) => {
     setKoreaLayers(prev => ({ ...prev, [key]: !prev[key] }));
-  }, []);
+  }, [setKoreaLayers]);
 
-  const [hiddenNationalities, setHiddenNationalities] = useState<Set<string>>(new Set());
+  const [hiddenNationalities, setHiddenNationalities] = useLocalStorageSet('hiddenNationalities', new Set());
   const toggleNationality = useCallback((nat: string) => {
     setHiddenNationalities(prev => {
       const next = new Set(prev);
       if (next.has(nat)) { next.delete(nat); } else { next.add(nat); }
       return next;
     });
-  }, []);
+  }, [setHiddenNationalities]);
 
-  const [hiddenFishingNats, setHiddenFishingNats] = useState<Set<string>>(new Set());
+  const [hiddenFishingNats, setHiddenFishingNats] = useLocalStorageSet('hiddenFishingNats', new Set());
   const toggleFishingNat = useCallback((nat: string) => {
     setHiddenFishingNats(prev => {
       const next = new Set(prev);
       if (next.has(nat)) { next.delete(nat); } else { next.add(nat); }
       return next;
     });
-  }, []);
+  }, [setHiddenFishingNats]);
 
   const koreaData = useKoreaData({
     currentTime,
@@ -158,6 +159,7 @@ export const KoreaDashboard = ({
     koreaData.visibleShips,
     currentTime,
     vesselAnalysis.analysisMap,
+    koreaLayers.cnFishing,
   );
 
   const handleTabChange = useCallback((_tab: DashboardTab) => {