diff --git a/src/App.tsx b/src/App.tsx
index b2b1331..a6f5749 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -41,6 +41,7 @@ import Back from './components/buttons/Back';
 import Forward from './components/buttons/Forward';
 import CurrentLocation from './components/map/CurrentLocation';
 import GpxImport from './components/dialogs/GpxImport';
+import Gpxes from './components/map/Gpxes';
 // import { initDb } from './db';
 // import PouchDB from 'pouchdb';
 // import PouchDBFind from 'pouchdb-find';
@@ -96,7 +97,7 @@ export const setCenterAtom = atom(null, (get, set, center: geoPoint) => {
 // initDb(db);
 
 dispatch({ action: 'initDb' });
-
+//dispatch({ action: 'getGpxesForViewport', params: { type: 'tech' } });
 /**
  *
  * @returns The root app component
@@ -113,7 +114,10 @@ const App: React.FC = () => {
             scope={scope}
             setScope={debounce(setScope, 1000)}
             numberOfTiledLayers={5}
-            slippyGraphics={[<CurrentLocation key='currentLocation' />]}
+            slippyGraphics={[
+              <CurrentLocation key='currentLocation' />,
+              <Gpxes key='gpxes' />,
+            ]}
           />
         </IonApp>
       </IonContent>
diff --git a/src/components/map/Gpxes.tsx b/src/components/map/Gpxes.tsx
new file mode 100644
index 0000000..15883f3
--- /dev/null
+++ b/src/components/map/Gpxes.tsx
@@ -0,0 +1,36 @@
+import react, { useEffect, useState } from 'react';
+import dispatch from '../../workers/dispatcher-main';
+import { TileKeyObject, Rectangle } from './types';
+
+export interface GpxesProperties {
+  keyObject?: TileKeyObject;
+  zoom?: number;
+  viewPort?: Rectangle;
+}
+
+export const Gpxes: react.FC<GpxesProperties> = (props: GpxesProperties) => {
+  const [visibleGpxes, setVisibleGpxes] = useState<any>([]);
+  useEffect(() => {
+    const getVisibleGpxes = async () => {
+      const gpxes = await dispatch({
+        action: 'getGpxesForViewport',
+        params: {
+          viewport: props.viewPort,
+          zoomLevel: props.keyObject?.zoomLevel,
+        },
+      });
+      console.log(`Gpxes, visibles: ${JSON.stringify(gpxes)}`);
+      setVisibleGpxes(gpxes);
+    };
+    getVisibleGpxes();
+  }, [
+    props.viewPort?.bottomRight.x,
+    props.viewPort?.bottomRight.y,
+    props.viewPort?.topLeft.x,
+    props.viewPort?.topLeft.y,
+    props.keyObject?.zoomLevel,
+  ]);
+  return <></>;
+};
+
+export default Gpxes;
diff --git a/src/db/gpx.ts b/src/db/gpx.ts
index 92d8611..e581d3f 100644
--- a/src/db/gpx.ts
+++ b/src/db/gpx.ts
@@ -1,8 +1,8 @@
 import { PureComponent } from 'react';
-import { Point } from '../components/map/types';
-import { lat2tile, lon2tile } from '../lib/geo';
+import { Point, Rectangle } from '../components/map/types';
+import { lat2tile, lon2tile, rectanglesIntersect } from '../lib/geo';
 import getUri, { intToGpxId } from '../lib/ids';
-import { get, put, putAll } from './lib';
+import { get, getDocsByType, put, putAll } from './lib';
 
 const emptyGpx: Gpx = {
   $: {
@@ -166,3 +166,24 @@ export const pruneAndSaveImportedGpx = async (params: any) => {
     console.error(`error: ${err}`);
   }
 };
+
+export const getGpxesForViewport = async (params: any) => {
+  const { viewport, zoomLevel } = params;
+  const zoomedViewport: Rectangle = {
+    topLeft: {
+      x: viewport.topLeft.x / 2 ** zoomLevel,
+      y: viewport.topLeft.y / 2 ** zoomLevel,
+    },
+    bottomRight: {
+      x: (viewport.bottomRight.x + 1) / 2 ** zoomLevel,
+      y: (viewport.bottomRight.y + 1) / 2 ** zoomLevel,
+    },
+  };
+  const techs = await getDocsByType('tech');
+  console.log(`getGpxesForViewport, techs: ${JSON.stringify(techs)}`);
+  return techs
+    .filter((tech: any) => {
+      return rectanglesIntersect(zoomedViewport, tech.doc.viewport);
+    })
+    .map((tech: any) => getUri('tech', tech._id));
+};
diff --git a/src/db/index.ts b/src/db/index.ts
index 5a6c935..49536bf 100644
--- a/src/db/index.ts
+++ b/src/db/index.ts
@@ -53,7 +53,7 @@ export const initDb = async (params: any) => {
   // WARNING: defs must use the canonical form and be identical to what will be returned by db.getIndexes
   const requiredIndexes: any = [
     {
-      name: 'type-subtype',
+      name: 'type',
       def: {
         fields: [{ type: 'asc' }],
       },
diff --git a/src/db/lib.test.ts b/src/db/lib.test.ts
index fb68891..2d8d58f 100644
--- a/src/db/lib.test.ts
+++ b/src/db/lib.test.ts
@@ -1,6 +1,6 @@
 import { initDb } from '.';
 import uri from '../lib/ids';
-import { getFamily } from './lib';
+import { getDocsByType, getFamily } from './lib';
 import { putNewRte } from './rte';
 import { putNewRtept } from './rtept';
 import { putNewTrk } from './trk';
@@ -269,3 +269,31 @@ Object {
 `);
   });
 });
+
+describe('getDocsByType', () => {
+  beforeEach(async () => {
+    await initDb({});
+    globalThis.Date.now = () => 0;
+  });
+  afterEach(async () => {
+    await db.destroy();
+    db = undefined;
+    globalThis.Date.now = originalDateNow;
+  });
+  test('gets the rte amongst other docs', async () => {
+    await putNewRtept();
+    const rtes = await getDocsByType('rte');
+    expect(rtes).toMatchInlineSnapshot(`
+Array [
+  Object {
+    "_id": "gpx/4320000000000000/2rte/000000",
+    "_rev": "1-2ca14f512a9c83f5a239389e580befce",
+    "doc": Object {
+      "number": 0,
+    },
+    "type": "rte",
+  },
+]
+`);
+  });
+});
diff --git a/src/db/lib.ts b/src/db/lib.ts
index 3309276..0b98445 100644
--- a/src/db/lib.ts
+++ b/src/db/lib.ts
@@ -46,3 +46,7 @@ export const get = async (id: string) => {
 export const putAll = async (docs: any[]) => {
   return await db.bulkDocs(docs);
 };
+
+export const getDocsByType = async (type: string) => {
+  return (await db.find({ selector: { type: type } })).docs;
+};
diff --git a/src/lib/geo.ts b/src/lib/geo.ts
index 01116a2..f4b920b 100644
--- a/src/lib/geo.ts
+++ b/src/lib/geo.ts
@@ -1,4 +1,4 @@
-
+import { Rectangle } from '../components/map/types';
 
 // cf https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#ECMAScript_(JavaScript/ActionScript,_etc.)
 export const lon2tile = (lon: number, zoom: number) => {
@@ -25,3 +25,11 @@ export function tile2lat(y: number, z: number) {
   var n = Math.PI - (2 * Math.PI * y) / Math.pow(2, z);
   return (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n)));
 }
+
+export const rectanglesIntersect = (r1: Rectangle, r2: Rectangle) =>
+  !(
+    r2.topLeft.x > r1.bottomRight.x ||
+    r2.bottomRight.x < r1.topLeft.x ||
+    r2.topLeft.y > r1.bottomRight.y ||
+    r2.bottomRight.y < r1.topLeft.y
+  );
diff --git a/src/workers/dispatcher-worker.ts b/src/workers/dispatcher-worker.ts
index 71b335d..979ddd2 100644
--- a/src/workers/dispatcher-worker.ts
+++ b/src/workers/dispatcher-worker.ts
@@ -1,10 +1,22 @@
 import { initDb } from '../db';
-import { putNewGpx, existsGpx, pruneAndSaveImportedGpx } from '../db/gpx';
+import {
+  putNewGpx,
+  existsGpx,
+  pruneAndSaveImportedGpx,
+  getGpxesForViewport,
+} from '../db/gpx';
 import { putNewTrk } from '../db/trk';
 
 const self = globalThis as unknown as SharedWorkerGlobalScope;
 
-const actions = { initDb, putNewGpx, putNewTrk, existsGpx, pruneAndSaveImportedGpx };
+const actions = {
+  initDb,
+  putNewGpx,
+  putNewTrk,
+  existsGpx,
+  pruneAndSaveImportedGpx,
+  getGpxesForViewport,
+};
 
 self.onconnect = function (e) {
   var port = e.ports[0];