diff --git a/logic/tracks.js b/logic/tracks.js
index 3211758..18e20f9 100644
--- a/logic/tracks.js
+++ b/logic/tracks.js
@@ -1,4 +1,5 @@
 const csvParse = require('csv-parse/lib/sync');
+const csvStringify = require('csv-stringify/lib/sync');
 
 function _parseFloat(token) {
   if (typeof token !== 'string') {
@@ -29,7 +30,8 @@ function _parseFloat(token) {
 }
 
 function _parseInt(token) {
-  const asFloat = parseFloat(token);
+  const asFloat = _parseFloat(token);
+
   if (asFloat !== null) {
     return Math.floor(asFloat);
   } else {
@@ -274,6 +276,28 @@ function normalizeUserAgent(userAgent) {
   return null;
 }
 
+function buildObsver1(points) {
+  return csvStringify(points, {
+    columns: [
+      { key: 'date', header: 'Date' },
+      { key: 'time', header: 'Time' },
+      { key: 'latitude', header: 'Latitude' },
+      { key: 'longitude', header: 'Longitude' },
+      { key: 'course', header: 'Course' },
+      { key: 'speed', header: 'Speed' },
+      { key: 'd1', header: 'Right' },
+      { key: 'd2', header: 'Left' },
+      { key: 'flag', header: 'Confirmed' },
+      { key: 'private', header: 'insidePrivacyArea' },
+    ],
+    cast: {
+      boolean: (v) => (v ? '1' : '0'),
+    },
+    delimiter: ';',
+    header: true,
+  });
+}
+
 module.exports = {
   detectFormat,
   normalizeUserAgent,
@@ -281,4 +305,5 @@ module.exports = {
   parseObsver2,
   parseTrackPoints,
   replaceDollarNewlinesHack,
+  buildObsver1,
 };
diff --git a/logic/tracks.test.js b/logic/tracks.test.js
index b84a50b..d2d933c 100644
--- a/logic/tracks.test.js
+++ b/logic/tracks.test.js
@@ -1,4 +1,5 @@
 const {
+  buildObsver1,
   detectFormat,
   normalizeUserAgent,
   parseObsver1,
@@ -140,3 +141,31 @@ describe('normalizeUserAgent', () => {
     }
   });
 });
+
+describe('buildObsver1', () => {
+  it('is a function', () => {
+    expect(typeof normalizeUserAgent).toBe('function');
+  });
+
+  it('transforms properly back and forth', () => {
+    const inputString = replaceDollarNewlinesHack(test1);
+
+    const points1 = Array.from(parseObsver1(inputString));
+    const builtString = buildObsver1(points1);
+    const points2 = Array.from(parseObsver1(builtString));
+
+    expect(points2).toEqual(points1);
+  });
+
+  it('produces a header', () => {
+    const builtString = buildObsver1([]);
+    expect(builtString).toBe('Date;Time;Latitude;Longitude;Course;Speed;Right;Left;Confirmed;insidePrivacyArea\n');
+  });
+
+  it('produces empty rows', () => {
+    const builtString = buildObsver1([{}]);
+    expect(builtString).toBe(
+      'Date;Time;Latitude;Longitude;Course;Speed;Right;Left;Confirmed;insidePrivacyArea\n;;;;;;;;;\n',
+    );
+  });
+});
diff --git a/package-lock.json b/package-lock.json
index 677cdf9..52eac42 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2163,6 +2163,11 @@
       "resolved": "https://registry.npmjs.org/csv-parse/-/csv-parse-4.14.1.tgz",
       "integrity": "sha512-4wmcO7QbWtDAncGFaBwlWFPhEN4Akr64IbM4zvDwEOFekI8blLc04Nw7XjQjtSNy+3AUAgBgtUa9nWo5Cq89Xg=="
     },
+    "csv-stringify": {
+      "version": "5.5.3",
+      "resolved": "https://registry.npmjs.org/csv-stringify/-/csv-stringify-5.5.3.tgz",
+      "integrity": "sha512-JKG8vIHpWPzdilp2SAmvjmAiIhD+XGKGdhZBGi8QIECgJAsFr7k5CmJIW2QkSxBBsctvmojM25s+UINzQ5NLTg=="
+    },
     "dashdash": {
       "version": "1.14.1",
       "resolved": "https://registry.npmjs.org/dashdash/-/dashdash-1.14.1.tgz",
diff --git a/package.json b/package.json
index b1fe17d..751718f 100644
--- a/package.json
+++ b/package.json
@@ -22,6 +22,7 @@
     "connect-busboy": "0.0.2",
     "cors": "2.8.5",
     "csv-parse": "^4.14.1",
+    "csv-stringify": "^5.5.3",
     "ejs": "^3.1.5",
     "errorhandler": "1.5.1",
     "express": "4.17.1",