Our GPS Audio Technology
One engine, three genuinely different jobs. What changes between them is not the content — it is the geometry: how fast the listener is moving, how tightly the trigger zones have to sit, and how early the guide has to start talking. All three are web pages: no app store, no download, no install, nothing to update. Designed, built and operated by Antratel Pty Ltd, Sydney — content authored by a licensed Sydney guide since 2006.
What the engine actually does
The same core runs under all three technologies. Only the point database, the trigger geometry and the audio change.
🧭 Orientation — it knows which way you face
Path projection and bearing detection let the guide say "look on your right" or "look on your left" instead of a vague "attraction ahead". The map can rotate to Heading-Up, so left on the screen is your actual left — no mental flipping at intersections.
🎧 It never goes silent
A continuous Australia podcast plays in the gaps between points. When a landmark comes into range the podcast steps aside, the landmark story plays with its direction cue, then the podcast resumes from the exact second it left off — across sessions, days and separate trips.
⏮ A player built for a moving listener
There is no scrubber to aim at on a bumpy road. ⏮ and ⏭ jump whole paragraphs, not fifteen seconds: every file ships with a map of its own sentence boundaries, so a skip always lands at the start of a thought. Skip back from the beginning of one podcast episode and you continue into the last paragraph of the previous one — eighteen episodes behave like a single continuous file. Speed 1× / 1.5× / 2× / 3×, volume and day-night sit one tap away, and every menu opens downwards so it never covers the map.
☰ Interest groups — the visitor picks the tour
One tick-box panel filters the whole route: Historical, Nature & Beach, Shopping, Wildlife, Photo Sights, Bicycle trails. The list re-sorts and re-numbers itself, so two people on the same street can be running two different tours.
🕑 Speed-adaptive triggers
Trigger zones are computed from your real movement speed: tight and directional for walkers, wide and early for a car or a tram. The same point database serves 4 km/h and 60 km/h without a separate build.
📱 Nothing to install
It is a web page. Scan a QR code or open a link and the tour starts. No App Store, no account, no updates, no 200 MB download on hotel Wi-Fi — and no app review process standing between you and a content change.
💬 Written by a guide, voiced by AI
Every word is written by a Sydney guide with 20 years on the road and voiced with an AI model of his own voice — which is how one guide can cover 150+ points and still sound consistent from the first stop to the last.
Sydney Light Rail — a free audio guide that rides with the tram
A QR poster at the stop, a phone, headphones — and the tram becomes a guided tour. The guide tracks the vehicle along the line, announces each stop, and tells the story of what is passing the window right now. Between stops the podcast keeps talking, so a 30-minute ride is never dead time.
Stops and stories in a single list. Tram stops carry their own marker style and sit inline with the numbered attractions, so a passenger can see at a glance which stop the next story belongs to and where to get off. One button re-sorts everything: by distance — what is nearest right now, re-ordering itself as the vehicle moves — or by number, the line in its proper running order. The GPS strip at the top reports accuracy, bearing and speed, which matters in the CBD: tall buildings degrade the fix, and the engine widens its zones to compensate rather than firing a story in the wrong block. And nobody has to guess what is currently talking: the card of the attraction being narrated lights up — an amber ring and a slight lift — the nearest few carry a brightness gradient behind it, and anything already heard fades back.
Between stops the podcast plays, and the player is what regular riders end up using most. ⏮ and ⏭ step through the episode paragraph by paragraph instead of a blind fifteen seconds, volume and playback speed are one tap away, and nothing has to be found again: the position is remembered, so a passenger who gets off at Central and boards again next Tuesday hears the podcast resume at the exact second it stopped.
The map tracks the vehicle live and holds either orientation — North Up, or Heading Up, where the map turns automatically with the direction of travel, so left on the screen is always the left-hand window.
Events — audio that unlocks when you walk into the artwork
Built for festivals, light walks, sculpture trails and precinct events. Each installation gets a trigger zone on the map; walk inside it and the commentary starts by itself — who made it, what it means, what to look for. Visitors keep their eyes on the artwork instead of reading a plaque with a torch.
The same geometry works as a property guide. Give the zones to buildings instead of artworks and the city becomes a self-guided tour of what is for sale or for lease: the listing speaks for itself as the buyer arrives at the address — what the building is, when it was built, what the precinct is like, what is being offered and at what price. It does not matter whether they walk or drive: at walking pace the commentary starts at the doorway, at road speed it starts early enough to be heard while passing. An agent sends one link to a shortlist of addresses and the client tours them alone, at their own hour, without an appointment and without an app.
- Trigger zones drawn per installation — a wide circle for a building-scale projection, a tight one for a small sculpture.
- Navigate button routes the visitor to the next piece; the list re-sorts by distance as they move.
- Night-mode interface by default — readable on a phone in the dark without wrecking night vision.
- Content can be swapped between festival editions in hours, not through an app release cycle.
The whole festival mapped as geofences. Each pink circle is an audio trigger zone, sized to its installation — wide for a building-scale projection you can see from three streets away, tight for a sculpture you have to walk up to. The radii are drawn on the map deliberately: the visitor can see where the audio is going to start and step closer, instead of wondering whether the guide is working. Because the zones do the work, the numbering is a suggestion rather than a queue — wander in any order. The card of the installation currently playing lights up in the list while the closest few glow behind it, so in a dark, crowded precinct you can find your place on the screen in a glance instead of reading it.
Nobody has to wait for a trigger either. Listen plays any piece from wherever you are standing, which matters when a queue is long or a lane is closed, and Navigate hands that installation to Google Maps for turn-by-turn walking directions.
The list keeps ordering itself around the visitor: whatever is nearest rises to the top, and anything already heard sinks to the bottom, so what remains up top is what is still ahead of you. The map can stay locked to North or switch to Heading Up and rotate with your direction of travel — in a dark, crowded precinct that is the difference between “it is on your left” and half a minute of turning on the spot. And the guide keeps your place in the audio: stop the podcast mid-sentence, wander off for a coffee or come back the following night, and it resumes from the exact second it was stopped.
One guide, three speeds — on foot, on two wheels or at the wheel
Same page, same point database, completely different geometry underneath. The engine measures your real average speed and rebuilds the trigger zones around it. Below 10 km/h it works out which way you are facing and splits the distance between two nearby markers, so a story fires at the right doorway instead of a block early. At road speed it does the opposite — wide, early, decided once — because a driver gets exactly one chance to look.
🚶 On foot and on two wheels
On a bicycle the same route runs with wider, earlier zones, and the group filter carries dedicated bicycle trails so the route follows cycleways rather than footpaths.
What the walker gets — and the player behind it
- Listen on demand for anything in the list, or leave Guide Mode on and let GPS do it.
- Navigate hands the point to the phone’s map app for turn-by-turn walking directions.
- Download Route exports the whole walk for offline planning.
- The card of whatever is being narrated lights up — amber ring, slight lift — the nearest few glow behind it, and anything already heard fades back.
- The podcast fills every gap between points — and resumes at the exact second on the next outing.
The player itself is the part visitors notice last and miss first. It carries no seek bar — dragging a thin line is hopeless while walking — so ⏮ and ⏭ move by paragraph, using a sentence map generated for every audio file. A skip lands on a full thought, back-skip from the top of an episode rolls into the last paragraph of the one before, and playback speed (1× to 3×), volume and the day-night switch are each a single tap, with menus opening downward so the map is never hidden. Interrupt an attraction halfway and the guide remembers where you were; walk away mid-podcast and it is still there tomorrow.
🚗 At the wheel
The hardest case, and the one the platform was born for. At road speed the guide has to decide early, speak once, and say which window to look through — all without asking the driver to touch anything. It runs on the phone and plays through the car speakers over Bluetooth, so the driver’s hands and eyes stay where the law and common sense want them.
Operator side: console, analytics and a simulator
A guide product is only half the system. The other half is what the operator sees — who used it, where they started, where they gave up, and whether a new trigger actually fires before you send anyone out to test it.
Session console
Every tour is logged: start and end time, duration, start and end GPS coordinates, device fingerprint, IP, browser, and how the visitor got in (free trial, demo link, paid token). Headline numbers sit on top — total sessions, completed, abandoned, average duration, unique devices — and the whole table exports to CSV.
Access links are generated from the same screen: pick a duration, pick the language edition, press Generate and hand over the link. Tokens bind to the device, so one link does not quietly become a hundred.
Design mode & GPX simulator
Design mode draws the invisible layer on the map: every trigger circle, every directional crossing pair, every bearing vector. You can see at a glance where two zones overlap or where a radius is too generous.
The GPX simulator then replays a recorded route at up to 5× speed straight from the desk. A whole tram line or a full driving loop can be regression-tested in minutes — before anyone gets in a car.
One database, many tours
Points carry group tags, so the same content set can be published as a heritage walk, a family wildlife route, a shopping loop or a cycling trail. The visitor ticks what they want and the route re-numbers itself; the operator maintains one database instead of six apps.
📢 Not only an information system — an advertising channel
Everything the engine already knows in order to tell a story — where the listener is, which way they face, how fast they are moving and what time it is — is exactly what makes an advertising slot valuable. The same trigger that plays a landmark can play a sponsored message, and it can play it at the only moment that matters: while the business is passing the window.
Geofenced audio spots
A restaurant precinct, a shopping centre, a winery on the highway: the insert fires as the vehicle enters the zone and nowhere else. Radius, direction of travel and speed are all conditions you can set.
Sponsored points in the list
A branded card with its own Listen and Navigate buttons sits in the visitor’s route list — a one-tap path from an audio mention to the front door.
Route-level sponsorship
An operator, council or brand can present an entire line or trail: opening credit, closing credit, and a matching QR poster campaign at the stops.
Measured, not estimated
The console counts real sessions, real durations and real positions — so an advertiser is quoted delivered plays inside a zone, not printed circulation.
Editorial discipline: sponsored audio is frequency-capped, kept clearly separate from the guide narration, and never fires while a landmark story is playing. A tour that starts nagging is a tour that gets switched off — which would cost more than the slot is worth.
🗺 The map: no licence, no per-view fee, labels that stay upright
Most audio guides rent their map. The basemap is licensed from a tile vendor, the licence is priced per map view, and the meter runs faster the better the product does. For a route licensed to an operator that is a recurring cost with someone else’s hand on the tap.
Our own basemap
The basemap runs on vector tiles built from OpenStreetMap data, served from our own object storage as a single file, with no third-party API key in the page — in production on all four live guides since August 2026. There is no per-view fee, no request quota and no vendor who can reprice or revoke access in the middle of a contract. The data is open under the Open Database Licence, so the only obligation is the visible “© OpenStreetMap” credit on the map — which is on it.
Why it matters when the map turns
A rented basemap arrives as finished pictures with the street names painted into them, so when the map rotates to face the direction of travel the names rotate too and end up upside down. With vector tiles the names are drawn by the browser, so the map turns while the type stays level at every angle — and in heading-up mode the view tilts towards the horizon like a car navigator, with two-finger rotate, tilt and zoom gestures live on the visitor’s phone.
What it means for a licence
Nothing in the map layer has to be re-licensed to hand the platform over: the tiles are a file the customer can hold, and the escrow deposit can include it. One less external dependency in a tender, and one less line item that grows with success.
📦 What the engine has actually shipped
Before the licensing terms, the full list of what has been built and run in public on this engine. Every one of them is the same core with a different tour configuration — no separate codebase, no separate app.
Sydney Light Rail — live, free
Eighteen city landmarks narrated automatically as the tram passes, with the stop announced before it arrives and continuous audio covering the run in between. Free to the passenger, distributed by a QR poster on the platform, no payment and no signup. This is the transit engine in daily public service. Open it.
Sydney city guide — live, paid
150+ points and roughly five hours of audio — about three hours of attraction narration plus a two-hour podcast that fills the gaps — in English and Russian from one content set. One guide adapts to walking, cycling and driving speed. This is the commercial product that pays for the platform. Prices.
Festival night walk — built, seasonal
A free guide for a winter light festival: no route at all, a dense field of geofences sized per installation, night interface, visited in any order. It runs during the festival and is out of season the rest of the year, so it is listed here as a delivered example rather than something on sale today. This is the pattern a council, marathon or open day would license.
📄 How licensing actually works
Two different things can be bought here, and confusing them wastes everyone’s time. Either you resell the Sydney guide that already exists — a finished product, nothing to build — or you license the engine for your own line, city or event, which means a route gets built. The second one is what a transport operator, a council or a festival needs, so here is exactly how it runs.
Step 1 · Pilot on your own route
Two to three weeks, no procurement required to start. We take a short section of your actual line or route, build a handful of real trigger points on it, and give you an unlisted link. Your team rides it with their own phones and hears what a passenger would hear. Nothing is installed, nothing is announced, and if it does not convince you on the ground it stops there.
Step 2 · The route build
This is the unglamorous part that decides whether the product feels magic or broken. The route is driven or walked and recorded as a GPS trace at real operating speed. Every point gets its own geometry — radius, approach direction, entry and exit vectors — because a trigger tuned for a pedestrian fires far too late at 40 km/h. Then the words: written for that spot, voiced, and cut into paragraph maps so the player can skip by paragraph rather than by fifteen seconds. Priced per point, quoted once the route length and stop count are known.
Step 3 · Acceptance on the ground
We ride the whole route with you and tune until it passes written criteria: every point fires within an agreed distance at line speed, in both directions, with no double-firing and no silence longer than the agreed gap. This step is where the complaints that would have arrived in month three get eliminated instead.
Step 4 · The licence itself
Three deployment choices: hosted by us (you publish a link or an iframe and touch no infrastructure), self-hosted (a container into your own Azure, AWS or on-premises server, with Australian data residency where required), or white label (your brand, your domain, our engine underneath). Term, service levels, escrow and territory exclusivity are settled here — one operator per line or city in a category, so what you pay for cannot be sold to the operator next door.
Step 5 · Handover and console
Your staff get the operator console: sessions, listens per point, where people drop off, and a GPX simulator that replays a whole journey at a desk so changes can be tested without going outside. Training takes an hour, not a course, because there is no app to administer and no devices to manage.
Step 6 · Ongoing
An annual licence covers the platform, updates and support. Content changes as the city does — new stops, closures, seasonal events — and are quoted as they arise or bundled. Where the advertising layer is switched on, sponsorship revenue is split on agreed terms and reported from real session data rather than estimates.
Who owns what
Stays ours
The engine, the platform and the operator console remain our intellectual property and are licensed to you, not sold — which is precisely why the escrow below exists. Aggregated, anonymised usage statistics may inform how the product develops.
Becomes yours
Your route data, your branding, your sponsor content and your passenger statistics are yours. Scripts and recordings written for your route are licensed to you for the term, and can be bought out permanently if you would rather own them outright.
What we need from you
Four things, and nothing technical: the route or permission to trace it, either a content source or sign-off on ours, a decision on branding and domain, and one named person who can accept the result. Everything else is on our side.
Buying through government procurement
Antratel Pty Ltd (ABN 24 122 328 492) is a registered NSW Government supplier — an SME, NSW-based, registered for faster payments. NSW agencies buy ICT through the ICT Services Scheme (SCM0020), so engagement runs through that route rather than as an ad-hoc purchase. For the documents a tender asks for — capability statement, accessibility position against AS EN 301 549, data residency, escrow terms, insurance — ask and they come back the same week, not the same quarter.
🔒 A risk-free proposition: full technology escrow
Buying a platform from a specialist team raises one fair question: what happens to our service if that team disappears? The answer is a real, extended technology escrow: under contract we lodge a complete working package with an independent escrow agent, sufficient for any third-party IT team to redeploy the platform from scratch.
1. Technical base
- Platform source code.
- A list of every external service, API and software dependency.
- Full deployment documentation — step-by-step instructions for standing the system up from zero.
2. Content and data
- The points database: all GPS coordinates, trigger radii, direction vectors and text descriptions.
- Studio-quality master audio files, from which the streaming audio can be regenerated.
3. Infrastructure and access
- A mechanism for transferring domain rights, DNS records and SSL certificates — so tourists never have to find a new address or download anything new.
Release conditions (triggers)
The buyer has no access to these materials in normal operation — they sit in the escrow agent’s safe. The package is opened and handed over only on a critical event:
- Our company declares bankruptcy or liquidation.
- The service is unavailable — servers down, for example — for more than 30 consecutive days.
- A critical breach of the SLA occurs and is not remedied.
Implementation: .NET, JavaScript and scaling up to 500.000 users
A procurement question we get early: what happens when it works too well? A festival opening night, a cruise ship arrival, a stadium crowd — all reaching for the same link in the same ten minutes.
🖥 Server: ASP.NET Core on .NET 10
The pages, the access-token layer, the session logging and the audio streaming handler run on ASP.NET Core, targeting .NET 10 — the current Long Term Support release, supported by Microsoft until November 2028. Audio is delivered with proper HTTP range support (206 responses), which is what makes seeking, resuming and paragraph skipping work on mobile networks instead of forcing a full re-download every time somebody moves the playhead.
💻 Client: plain JavaScript
The whole guide — GPS loop, trigger geometry, bearing maths, map, player, interest filtering — runs in the visitor’s browser in vanilla JavaScript. No framework to go out of support, no app binary to rebuild and resubmit, and no client-side dependency that a government network is likely to block.
☁ Azure-ready autoscaling
The stack deploys to Microsoft Azure App Service without a rewrite, with autoscale rules on instance count and a CDN in front of the audio. Capacity becomes a configuration value: you raise the ceiling before opening night and lower it on Monday, and nobody touches the code.
📈 Why it scales at all
Because the guide holds no per-listener state on the server. Position, progress and playback all live in the visitor’s own browser; the server hands out static audio and records sessions. That is the architectural reason a crowd of half a million streaming simultaneously is an infrastructure setting rather than an engineering limit — there is no shared bottleneck for concurrency to collide with.
Want it running on your line, your festival or your fleet?
All three technologies above are live in Sydney today — open any of them on your phone right now and walk outside. If you operate transport, run an event, rent cars or manage a destination, the same engine can carry your route, your voice and your sponsors.
📄 Download capability statement (PDF) Email [email protected]Antratel Pty Ltd (ABN 24 122 328 492) — tourism technology, Sydney. Content authored by a licensed Sydney guide since 2006.