diff --git a/migrations/Version20260721135509.php b/migrations/Version20260721135509.php
new file mode 100644
index 000000000..d8c9cab0b
--- /dev/null
+++ b/migrations/Version20260721135509.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use App\Domain\Activity\Stream\StreamType;
+use App\Infrastructure\Serialization\Json;
+use App\Infrastructure\ValueObject\Geography\EncodedPolyline;
+use App\Infrastructure\ValueObject\Geography\Polyline;
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260721135509 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return '';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $results = $this->connection->fetchAllAssociative(
+            'SELECT Activity.activityId, Activity.polyline, ActivityStream.data AS latLngStream
+                FROM Activity
+                INNER JOIN ActivityStream ON ActivityStream.activityId = Activity.activityId
+                    AND ActivityStream.streamType = :streamType
+                WHERE Activity.polyline IS NOT NULL AND Activity.polyline != ""',
+            ['streamType' => StreamType::LAT_LNG->value]
+        );
+
+        foreach ($results as $result) {
+            if (count(EncodedPolyline::fromString($result['polyline'])->decodeAndPairLatLng()) >= 10) {
+                // Polyline was not collapsed, nothing to repair.
+                continue;
+            }
+
+            try {
+                $latLngStream = Json::uncompressAndDecode($result['latLngStream']);
+            } catch (\JsonException) {
+                continue;
+            }
+
+            /** @var array<int, array{float, float}> $coordinates */
+            $coordinates = array_values(array_filter(
+                is_array($latLngStream) ? $latLngStream : [],
+                is_array(...),
+            ));
+            if (count($coordinates) < 10) {
+                // The polyline is legitimately this small.
+                continue;
+            }
+
+            $this->addSql(
+                'UPDATE Activity SET polyline = :polyline WHERE activityId = :activityId',
+                [
+                    'polyline' => (string) Polyline::fromCoordinates($coordinates)->simplify()->encode(),
+                    'activityId' => $result['activityId'],
+                ]
+            );
+        }
+    }
+
+    public function down(Schema $schema): void
+    {
+    }
+}
diff --git a/src/Domain/Activity/Route/RouteGeographyAnalyzer.php b/src/Domain/Activity/Route/RouteGeographyAnalyzer.php
index 837257f37..3d180e439 100644
--- a/src/Domain/Activity/Route/RouteGeographyAnalyzer.php
+++ b/src/Domain/Activity/Route/RouteGeographyAnalyzer.php
@@ -6,6 +6,7 @@
 
 use App\Infrastructure\Serialization\Json;
 use App\Infrastructure\ValueObject\Geography\EncodedPolyline;
+use App\Infrastructure\ValueObject\Geography\Polyline;
 use Brick\Geo\Engine\GeosOpEngine;
 use Brick\Geo\Exception\InvalidGeometryException;
 use Brick\Geo\Geometry;
@@ -57,9 +58,14 @@ public function analyzeForPolyline(EncodedPolyline $polyline): array
     {
         $passedCountries = [];
         try {
+            $coordinates = $polyline->decodeAndPairLatLng();
+            $simplifiedPolyline = Polyline::fromCoordinates($coordinates)
+                ->simplify(0.005)
+                ->encode();
+
             $routeLineString = $this->reader->read(Json::encode([
                 'type' => 'LineString',
-                'coordinates' => $polyline->decodeAndPairLngLat(),
+                'coordinates' => $simplifiedPolyline->decodeAndPairLngLat(),
             ]));
         } catch (InvalidGeometryException) {
             // Given polyline is somehow not a valid LineString.
diff --git a/src/Infrastructure/ValueObject/Geography/EncodedPolyline.php b/src/Infrastructure/ValueObject/Geography/EncodedPolyline.php
index 64a4557e6..169f5dfc1 100644
--- a/src/Infrastructure/ValueObject/Geography/EncodedPolyline.php
+++ b/src/Infrastructure/ValueObject/Geography/EncodedPolyline.php
@@ -64,7 +64,7 @@ public function decode(): array
     }
 
     /**
-     * @return array<int, array<float, float>>
+     * @return array<int, array{float, float}>
      */
     public function decodeAndPairLngLat(): array
     {
@@ -75,7 +75,7 @@ public function decodeAndPairLngLat(): array
     }
 
     /**
-     * @return array<int, array<float, float>>
+     * @return array<int, array{float, float}>
      */
     public function decodeAndPairLatLng(): array
     {
diff --git a/src/Infrastructure/ValueObject/Geography/Polyline.php b/src/Infrastructure/ValueObject/Geography/Polyline.php
index c419d0e6a..c52c882cb 100644
--- a/src/Infrastructure/ValueObject/Geography/Polyline.php
+++ b/src/Infrastructure/ValueObject/Geography/Polyline.php
@@ -22,7 +22,11 @@ public static function fromCoordinates(array $coordinates): self
         return new self($coordinates);
     }
 
-    public function simplify(float $tolerance = 0.4): self
+    /**
+     * The tolerance is expressed in degrees, the same unit as the coordinates
+     * (0.0001° ≈ 11m on the ground).
+     */
+    public function simplify(float $tolerance = 0.0001): self
     {
         $points = $this->coordinates;
 
diff --git a/tests/Infrastructure/ValueObject/Geography/PolylineTest.php b/tests/Infrastructure/ValueObject/Geography/PolylineTest.php
index b1f1909ee..e2aba9168 100644
--- a/tests/Infrastructure/ValueObject/Geography/PolylineTest.php
+++ b/tests/Infrastructure/ValueObject/Geography/PolylineTest.php
@@ -25,15 +25,19 @@ public function testSimplifyRemovesPointsOnStraightLine(): void
     {
         $coordinates = [
             [0.0, 0.0],
-            [1.0, 1.0],
-            [2.0, 2.0],
-            [3.0, 3.0],
+            [0.5, 0.5],
+            [1.0, 1.02],
+            [1.5, 1.5],
+            [2.2, 2.2],
+            [2.95, 3.0],
+            [3.5, 3.5],
+            [4.0, 4.0],
         ];
 
         self::assertSame(
             (string) EncodedPolyline::fromCoordinates([
                 [0.0, 0.0],
-                [3.0, 3.0],
+                [4.0, 4.0],
             ]),
             (string) Polyline::fromCoordinates($coordinates)->simplify(0.1)->encode(),
         );
@@ -43,33 +47,49 @@ public function testSimplifyKeepsCorner(): void
     {
         $coordinates = [
             [0.0, 0.0],
+            [0.5, 0.0],
+            [1.0, 0.02],
             [1.0, 0.0],
+            [1.0, 0.5],
+            [1.02, 0.7],
             [1.0, 1.0],
+            [1.5, 1.0],
             [2.0, 1.0],
         ];
 
         self::assertSame(
-            (string) EncodedPolyline::fromCoordinates($coordinates),
+            (string) EncodedPolyline::fromCoordinates([
+                [0.0, 0.0],
+                [1.0, 0.0],
+                [1.0, 1.0],
+                [2.0, 1.0],
+            ]),
             (string) Polyline::fromCoordinates($coordinates)->simplify(0.1)->encode(),
         );
     }
 
-    public function testSimplifyWithLargeToleranceKeepsOnlyEndpoints(): void
+    public function testSimplifyWithDefaultToleranceKeepsGpsScaleRoute(): void
     {
-        $coordinates = [
-            [0.0, 0.0],
-            [1.0, 0.0],
-            [1.0, 1.0],
-            [2.0, 1.0],
-        ];
+        $centerLat = 51.2194;
+        $centerLng = 4.4025;
+        $radius = 0.03;
+        $numberOfPoints = 200;
 
-        self::assertSame(
-            (string) EncodedPolyline::fromCoordinates([
-                [0.0, 0.0],
-                [2.0, 1.0],
-            ]),
-            (string) Polyline::fromCoordinates($coordinates)->simplify(10)->encode(),
-        );
+        $coordinates = [];
+        for ($i = 0; $i < $numberOfPoints; ++$i) {
+            $angle = 2 * M_PI * $i / $numberOfPoints;
+            $coordinates[] = [
+                $centerLat + $radius * sin($angle),
+                $centerLng + $radius * cos($angle),
+            ];
+        }
+
+        $simplified = Polyline::fromCoordinates($coordinates)->simplify();
+
+        $decodedPoints = EncodedPolyline::fromString((string) $simplified->encode())->decodeAndPairLatLng();
+
+        self::assertGreaterThan(40, count($decodedPoints));
+        self::assertLessThan(150, count($decodedPoints));
     }
 
     public function testEncodeReturnsEncodedPolyline(): void