TracePoint

Locate the origin point of a photograph using geometric ray intersection.

TracePoint is a browser-based geolocation tool built for OSINT investigators, journalists, and researchers who already know how to geolocate images, and want a dedicated instrument to do it faster and more precisely. No uploads. No server. Everything runs locally in your browser.

Try it live → kluter.github.io/TracePoint

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The Method

Draw a vertical line across a photograph and it passes through objects at different depths: foreground, midground, horizon. Each of those objects can be found on a map, and together they define a geographic bearing: a ray.

Repeat for a second line and you get a second ray. Where the rays cross is where the photographer was standing.

The more lines you add, the more rays are generated and the more robustly the intersection is averaged. This is a photographic application of the surveying technique known as Resection by Intersection, the same principle used to triangulate a position from known landmarks. TracePoint turns that manual, tab-switching workflow into a single focused tool.

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Features

• Split-panel interface: photo left, satellite map right
• Drop any image to load it, or click Browse
• Multi-image session manager: all sessions visible on the map simultaneously, each with its own intersection result
• Bearing display: each line shows its outward bearing once an intersection is found
• Confidence ellipse: with 3 or more lines (up to 5 per image), a dashed ellipse around the intersection visualises the spread of ray crossings. A tighter ellipse means higher confidence. Computed via Eigendecomposition
• Session export and import: save and restore lines, geo points, bearings, and map view as JSON
• EXIF metadata viewer: camera, lens, capture settings, GPS, altitude, and camera direction read from the image. GPS can be placed on the map as a reference marker
• Built-in Potsdam demo with step-by-step guide
• Horizon correction for tilted images
• Map layer switcher: Esri Satellite, Sentinel-2 2024, OpenStreetMap, Esri Dark Gray, Esri Topo, Esri Streets
• Custom map layers: add any XYZ tile source by URL (same format as QGIS), saved in your browser
• Full keyboard shortcut support
• Fully client-side: no server, no uploads, no tracking

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How to Use

Start with the ☰ menu on the image panel and select Demo — Potsdam for a guided walkthrough. If the photo is tilted, use the Level button first to compensate before adding lines.

1. Load a photo: Drop an image onto the left panel, or click Browse. To work on multiple images at once, open the ☰ image menu and click + Add image.
2. Add a line: Click + New Line (or press E) and drag it over a recognisable object you can also find on the map: a building corner, tower, road junction.
3. Mark points: Switch to Add Point mode (or press Tab) and click on the line twice to place exactly two reference points.
4. Place points on the map: Click the 🌐 P1 pill next to each point (or press F to jump straight to the next unmapped point), then click its real-world location on the map.
5. Read the result: Once two lines each have two geo points, rays appear and the intersection is calculated. The pulsing yellow marker shows the estimated camera origin. With 3 or more lines, a confidence ellipse appears around the intersection: the tighter the ellipse, the more consistent your bearings.
6. Add more images: Use the ☰ image menu to add further sessions. Each session shows its own rays and intersection on the map simultaneously.
7. Save your work: Click the ↓ button on any session row to export it as JSON, or use ↓ Export all sessions to save everything at once. To restore, click ↑ Import session and reload the image when prompted.

Tips: Use objects spread across different depths for a more accurate bearing. Press Esc to deselect or cancel at any time. Press X to toggle the help card from anywhere on the page.

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Controls

Mouse & UI

Action	How
Zoom image	Scroll wheel
Pan image	Space + drag, or middle-click drag
Level image	Level button, then click two points on a horizontal reference
Reset level	Click Level button again when correction is active
Add a line	+ New Line button
Drag a line	Click and drag the line
Deselect / cancel	Click blank canvas, or Esc
Add a point	Add Point mode, click on the line
Place point on map	Click the map pill, then click the map
Delete a line or point	× button in the line bar
Switch map layer	☰ button, top-right of map panel
Add custom map layer	☰ map menu → + Add custom layer…
Edit / remove custom layer	✎ / × next to the layer in the ☰ map menu
Manage image sessions	☰ button, right of line bar
Browse for image	Click the drop zone
Export session	↓ button on session row in ☰ menu
Export all sessions	↓ Export all sessions in ☰ menu
Import session	↑ Import session in ☰ menu
Open help guide	? button, top-right of map panel
View image metadata	</> button, left of line bar
Place EXIF GPS on map	Show on map inside the metadata card

Keyboard shortcuts

Key	Action
W	Toggle level tool / reset rotation
E	New line
R	Delete active line
F	Map next unmapped point of active line
X	Toggle help card
Tab	Toggle Drag Line / Add Point mode
1 – 5	Jump to line 1–5
Esc	Cancel / deselect

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Custom Map Layers

Besides the built-in layers you can add any tile server that uses the standard XYZ URL format, the same format QGIS uses for its "XYZ Tiles" connections. Open the ☰ map menu, click + Add custom layer…, give it a name and paste the URL template. The template must start with https:// and contain {x}, {y} and {z}:

https://example.com/tiles/{z}/{x}/{y}.png

You can add as many layers as you like and switch between them like the built-in ones. They are saved in your browser's localStorage only. They are not shared between browsers or devices, and they are not included in exported session files.

Useful tile URLs

Copy a URL into the Tile URL field as-is. Every server has its own terms of use. Which servers you add, and whether you are allowed to use them, is up to you.

Google (at your own risk)

Google does not permit direct tile access outside its official APIs. These URLs are widely used in QGIS tutorials, but using them may break Google's terms and can stop working at any time:

Layer	URL
Google Satellite	https://mt1.google.com/vt/lyrs=s&x={x}&y={y}&z={z}
Google Hybrid	https://mt1.google.com/vt/lyrs=y&x={x}&y={y}&z={z}
Google Roadmap	https://mt1.google.com/vt/lyrs=m&x={x}&y={y}&z={z}
Google Terrain	https://mt1.google.com/vt/lyrs=p&x={x}&y={y}&z={z}

Imagery

Layer	URL	Notes
Esri Clarity	https://clarity.maptiles.arcgis.com/arcgis/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}	Esri's sharper imagery set. Sometimes shows a different capture than the built-in Esri Satellite
Esri Wayback	https://wayback.maptiles.arcgis.com/arcgis/rest/services/World_Imagery/WMTS/1.0.0/default028mm/MapServer/tile/RELEASE/{z}/{y}/{x}	Historical Esri imagery. Replace RELEASE with a release number from the table below

Esri Wayback releases

Esri has published the World Imagery basemap as a dated snapshot roughly every few weeks since 2014. Each snapshot has a release number, and that number goes into the URL in place of RELEASE. The numbers are IDs, not dates, so they do not run in order. Add several releases as separate layers to flip between dates and see when a building appeared or a road changed.

Snapshot	Release	Snapshot	Release
2014-02-20	10	2021-01-13	1049
2015-01-21	20222	2022-01-12	42663
2016-01-13	3515	2023-01-11	11475
2017-01-11	577	2024-01-18	41468
2018-01-08	13161	2025-01-30	36557
2019-01-09	6036	2026-01-29	22252
2020-01-08	23001	2026-10-29	43291

All ~200 releases are listed in Esri's Wayback config: search for a date, and the number after tile/ in that entry's itemURL is the release. To find which releases actually changed the imagery at a given place, use Esri's Wayback app. A snapshot date is when Esri published the release, not when the imagery was captured. Where nothing changed between releases, they show the same imagery.

Providers whose tiles use a different numbering scheme, such as Bing (quadkeys), cannot be added this way.

A custom layer's tiles are requested from the server in its URL. See Security & Privacy for what that means.

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Reading the Confidence Ellipse

When three or more lines are used, a dashed ellipse appears around the estimated camera position. Its size and shape tell you how much to trust the result.

Ellipse shape	Meaning	Confidence
Small and round	Rays converge tightly from all directions	High
Small and elongated	Good estimate, but uncertain along one axis. Two lines may be nearly parallel	Moderate
Large and round	General spread in all directions, recheck geo points or add more lines	Low
Large and elongated	One bearing is likely off, or two lines run too close to parallel	Low

The ideal result is a small, round ellipse. If you see a large or elongated one, adding a line at a different angle usually improves it significantly.

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Technical Notes

Rays are computed from the bearing between two geo-referenced points. Each ray extends 50 km in both directions, long enough to contain any realistic intersection while keeping the map readable.

Intersection uses flat-plane geometry on lat/lon coordinates. For most photography this is accurate to within a few metres. The assumption holds well as long as the distance between the camera and the furthest reference landmark stays under roughly 10 km, which covers virtually all real-world OSINT photography. Accuracy degrades in the following cases:

• Very steep mountainous terrain. When reference landmarks sit at dramatically different elevations than the camera, the apparent bearing in the image no longer matches the flat map bearing.
• Aerial photography. Shooting downward at an angle from a plane or drone introduces the same kind of vertical distortion as steep terrain.
• Very long rays. Reference points placed more than 20 to 30 km apart on the map, where the curvature of the Earth starts to affect flat-plane calculations.
• Heavily distorted lenses. Fisheye or extreme wide-angle lenses warp straight lines, so bearing lines drawn on the image no longer correspond accurately to real-world directions.

When three or more lines are used, every pair of rays produces a crossing point. Those crossings form a small cloud around the estimated origin. The confidence ellipse is fitted to that cloud using Eigendecomposition. The ellipse stretches in the direction the crossings are most scattered and stays narrow where they agree. A tight ellipse means the lines converge cleanly; a wide one means at least one bearing is off.

No data leaves your machine. Map imagery is served by public tile servers (Esri, OpenStreetMap, EOX). Dependencies are Leaflet for maps and exifr by MikeKovarik for metadata parsing. Everything else is vanilla HTML, CSS, and JavaScript.

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Running Locally

npx serve .
# or
python3 -m http.server

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Changelog

Version	Changes
v1.7.0	Custom XYZ map layers (add, edit, remove, saved in browser). Sentinel-2 2024 layer. Esri Dark Gray replaces CARTO Dark Matter.
v1.6.2	Fixed map panning to intersection on every geo point placement.
v1.6.1	EXIF GPS popup restyled. Copy button added to GPS. EXIF ray fixed after session import.

Older releases

Version	Changes
v1.6.0	EXIF direction ray: ray from GPS position and camera bearing. Copy coordinates button.
v1.5.0	Keyboard shortcuts, confidence ellipse for 3+ lines, 5-line maximum per image.
v1.4.3	Line bar redesign: lines and points move to a dedicated bar below the toolbar.
v1.4.2	UX bug fixes: orphaned map rays, map-point mode not clearing, auto-zoom false trigger.
v1.4.1	Security hardening, JSON import validation, toast notification system.
v1.4.0	EXIF metadata viewer with GPS map marker.
v1.3.0	Session export / import, browse button, bearing display.
v1.2.1	Session naming, colour and map view fixes.
v1.2.0	Multi-image session manager.
v1.1.0	Horizon correction tool.
v1.0.0	Initial release.

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Recognition

Curated Lists

List	Section	Stars
jivoi/awesome-osint	Image Analysis	25k+
Astrosp/Awesome-OSINT-List	GEO	3.3k
The-Osint-Toolbox/Geolocation-OSINT	Geolocation	313

Press

Publication	Publisher
TracePoint: A Browser-Based Tool for Image Geolocation by Ray Intersection	Earth Observation Research Cluster, University of Würzburg

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Security & Privacy

A polished interface is not the same as a safe one. This section explains exactly what TracePoint does and does not do with your data, so investigators can make an informed decision before using it on sensitive material.

Images never leave your machine

Photos are loaded directly into an HTML5 <canvas> element and processed entirely in memory. No upload, no base64 POST, no fetch call carries image data anywhere. You can verify this yourself:

1. Open DevTools → Network tab (F12)
2. Load an image into TracePoint
3. Filter by Fetch/XHR → no requests involving your image will appear

The only outbound requests are map tile fetches from public CDN servers (Esri, OpenStreetMap, EOX), plus the servers of any custom map layer you add yourself. These are standard HTTP requests for map imagery. They contain no session data, no coordinates from your work, and no image content.

// The full extent of network activity in TracePoint:
// GET https://server.arcgisonline.com/ArcGIS/rest/services/.../tile/z/y/x
// GET https://tile.openstreetmap.org/z/x/y.png
// GET https://tiles.maps.eox.at/wmts/1.0.0/s2cloudless-2024_3857/default/g/z/y/x.jpg
// GET <your custom layer URL>   ← only if you add one and select it
// No other requests.

No persistent storage

TracePoint writes only your chosen map layer, and any custom layers you added, to localStorage so they persist between sessions. Nothing else is stored — no image data, no session content, no coordinates. IndexedDB, sessionStorage, and cookies are unused. Closing the tab leaves no investigation trace in the browser.

// Verify in DevTools → Application → Storage
// localStorage:   { "tp-tileset": "esri-sat" }  ← your map layer choice
//                 { "tp-custom-layers": [...] } ← name + URL of custom layers, if you added any
// sessionStorage: empty
// IndexedDB:      empty
// Cookies:        none set by TracePoint

Session files are plain JSON

Exported sessions are standard .json files saved to your local disk. No cloud sync, no server involved. You control where they go and who can access them.

JSON import is validated and sanitised

Importing a session does not execute any code. Every field is type-checked and validated on the way in. Unknown or unexpected keys are discarded. String values are sanitised before display. There is no eval(), no raw HTML injection, and no way for a crafted session file to run code or exfiltrate data.

// Example of how imported values are handled:
function escHtml(str) {
    return String(str)
        .replace(/&/g, '&')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
        .replace(/"/g, '&quot;');
}

A manipulated session file cannot execute code, redirect the page, or exfiltrate data. The worst a malformed file can do is fail to import.

The code is fully auditable

TracePoint is vanilla HTML, CSS, and JavaScript with no build step and no obfuscation. Its own logic lives in js/script.js, unminified. What you read in the repo is what runs in your browser. The third-party libraries, Leaflet and exifr, are their standard minified builds (Leaflet from CDN, exifr bundled in the repo).

This tool was developed with AI assistance. That is disclosed here precisely because the risks of opaque, AI-generated OSINT tools are real. The answer is not to hide the involvement. It is to make the code readable so anyone can verify what it does.

Dependencies

TracePoint has two runtime dependencies:

Library	Purpose	Loaded from	Touches your data?
Leaflet	Map rendering	CDN (unpkg)	No. Renders tiles only
exifr	EXIF metadata parsing	bundled in js/	Locally only. No network calls

Only Leaflet is loaded from unpkg.com, a public CDN; exifr is bundled in the repo (js/exifr.min.js). The CDN is a trust assumption: if unpkg were compromised, a malicious Leaflet could be served. Investigators who require full control can clone the repository, replace the Leaflet CDN link with a local copy, and run entirely offline:

<!-- Replace in index.html: -->
<link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" />
<script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"></script>

<!-- With local copies: -->
<link rel="stylesheet" href="js/leaflet.css" />
<script src="js/leaflet.js"></script>

Then serve locally with npx serve . or python3 -m http.server. No outbound requests except map tiles.

Security caveats

• Map tiles reveal your target location. Tile requests follow the format tile/z/x/y. The coordinates directly encode the area of the map you are viewing. A tile server operator can infer what location you are investigating. Use a VPN or TOR if that is a concern.
• Custom layers add another party. A custom layer's server sees the same tile coordinates. If its URL carries an API key or token, that key is also tied to every request, and it is stored in plain text in your browser.
• Browser and OS trust. If your browser or operating system is compromised, no web application can protect you. TracePoint is only as secure as the environment it runs in.
• Session files on disk. Exported JSON files are unencrypted plaintext. Treat them with the same care as any other sensitive investigation material.
• CDN dependency. Only Leaflet is loaded from unpkg (exifr is already bundled locally). Self-hosting Leaflet too eliminates the assumption entirely.

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Related

ShadowFinder Web - Geolocate a photo by the length of a shadow.

SiliconAperture - Measure the real-world size of an object from a single photograph.