GT SignApp Privacy Policy
How the GT SignApp research app handles the information it collects from you.
In short. GT SignApp is a research tool, not a consumer product. You get an account from the research team; there is no public sign-up. While you drive a route, the app records road video and your precise location. It records no sound. When you choose to upload, that video and location file go to Georgia Tech's research servers, which run in an Amazon Web Services (AWS) cloud account that Georgia Tech controls, in the United States. Members of the research team — at Georgia Tech and at our partner organizations, Pima County and the University of Arizona — watch the video to identify and check road signs.
We do not sell your data, show you ads, or use it for marketing. Please read the section on deleting your data carefully — it explains exactly what we can and cannot undo.
What GT SignApp collects
Your account details
To sign in, you enter the email address and password that the research team issued to you. These are sent to our server over an encrypted connection. Your password is stored on our server only as a salted one-way hash, and it is never saved on your phone.
After you sign in, your phone stores your name, email address, organization, and a sign-in token so you do not have to sign in again. That token stays valid for one year unless you sign out.
Video
The app records video through your phone's camera, pointed at the road ahead. The app does not record audio. It never asks for microphone permission. On Android, the permission needed to capture sound is not part of the app; on iPhone, the app declares no microphone use. Neither operating system will give it microphone access. The video files contain no sound track at all.
Precise location
While you are recording, the app writes your location to a data file saved next to the video. It asks your phone's operating system for a new position at most about once per second, and it records every position it is given, whether or not the vehicle is moving. Each entry contains:
- latitude and longitude
- altitude
- direction of travel and speed
- the accuracy figure your phone reports
- two timestamps
Together these form a continuous trace of the route you drove for the whole recording. Positions normally come from your phone's GPS receiver. If GPS is switched off or unavailable when a recording starts, Android supplies a position worked out from nearby Wi-Fi networks and cell towers instead, and the app records that in exactly the same way. On most Android phones, that network-based position is calculated by Google Play services. On iPhone, positions come from Apple's Location Services, which combine GPS with Wi-Fi and cell information in the same way.
The location coordinates are not written into the video file itself. But the video and the location file belong to the same recording, are uploaded together, and are deliberately matched up by time during analysis. You should assume that any video we hold can be linked to the precise route on which it was recorded.
What the app does not collect
- No audio, ever, as described above.
- No device identifiers. The app does not read your phone's IMEI, serial number, advertising ID, or any similar identifier. (If you look inside an uploaded file you will see a folder named
IMEINotAvailable. That is a fixed piece of text kept for compatibility with older processing tools. No IMEI is read or stored.) - No access to your photos, media, or files. Everything the app writes goes into its own folder on the phone, and your recordings never appear in your photo gallery. On iPhone that folder is private to the app and no other app can read it. On Android the folder sits in external storage, at
Android/data/edu.gatech.ce.sci.signapp/files: it is deleted when you uninstall the app, but on Android 9 and earlier another app holding storage permission can read it, and on any Android version it can be browsed with a file manager or over a USB cable. - No contacts, no messages, no browsing history, no health data, no financial data.
- No advertising and no analytics. The app contains no advertising software and no analytics or crash-reporting service.
Technical information our servers record
When your phone connects to our server — to sign in or to upload — the server automatically records your IP address, the time, the web address requested and the type of app making the request, as web servers normally do. Georgia Tech's standard network and security monitoring on the cloud account also records connection details, including IP addresses. These records are used only to run and protect the systems. We do not use them to work out where you are, and they are not added to your recordings or to the research data. They are kept only as long as needed for those operational and security purposes.
Permissions the app asks you for
- Camera — to record the road video that is the subject of the study.
- Location (precise) — to log where each part of the video was recorded.
On iPhone, these are the only two permission prompts you will see. The location prompt is for use only while the app is open; the app never asks for Always location, Photos, Microphone, Bluetooth, or local network access. On Android 13 and later you will also be asked whether GT SignApp may show notifications. The app uses notifications only to show the progress of an upload you started; if you say no, the app still works and you simply will not see that progress notification. On Android, the system's app info screen may additionally list network, Wi-Fi state, and file-storage permissions for GT SignApp. They are declared by software libraries the app is built from: one of them checks whether your phone is online and whether it is on Wi-Fi or mobile data, so the app knows when it can start or resume an upload. That check happens on your phone. The app never asks you to grant these permissions, does not use them to read anything of yours, and does not store or send your network details.
When location is recorded
Location logging starts when you tap Record, and it normally stops when you tap Stop.
We want to be straightforward about a limitation in the current version. If the camera fails while a recording is starting, or if you sign out while a recording is running, location logging can keep going for as long as the app stays open on your screen, even though the app is no longer showing a recording in progress. Closing the app always stops it.
GT SignApp does not have Android's background-location permission, and that permission is not present in the app at all. On iPhone, the app requests location only while it is in use and declares no background location mode. When the app leaves your screen — for example when you switch to another app, go to the home screen or lock the phone — it stops any recording in progress, and the location logging with it. On iPhone, and on Android 10 and later, the operating system also stops giving the app your location at that point. The app has no feature that collects anything while it is closed, and it cannot track you then.
If you leave the app while an upload is in progress, Android may show a notification. That is the app finishing the upload of a recording you already made. It does not record video or location.
Why we collect this
The study inventories and assesses the condition of roadway signs. The video is the raw material: automated software finds signs in the frames, and people review the results. The location trace is what places each detected sign on the map, which is the entire point of the exercise. Your account identity is what lets us tell whose recordings are whose, ask you about a specific drive, and honour a request about your own data.
Your data is used only for this research project and the purposes described in this policy and in the instructions the research team gave you. It is not used for advertising, marketing, profiling, or any commercial purpose, and it is not sold.
Where your data goes
Recordings stay on your phone until you choose to upload them. Nothing is uploaded automatically. When you tap Upload on a recording, it travels in two steps:
- Your phone to Georgia Tech's research server. The app packages the recording folder — the video and the location file — into a single ZIP archive and sends it over an encrypted connection to
https://pima.sci.ce.gatech.edu/upload. This server is operated by the Georgia Tech research team. It is a virtual server (Amazon EC2) in an Amazon Web Services account that Georgia Tech controls, in Amazon's US East (Ohio) region. Uploads can use Wi-Fi or mobile data, and the app will resume an interrupted upload when your connection returns, which may use your mobile data allowance. - Processing and storage in that same Georgia Tech account. The server unpacks the archive, deletes the uploaded ZIP, and keeps a working copy of the recording on network file storage in the same account (Amazon Elastic File System). It copies the location file to Amazon S3 storage. A second Georgia Tech server in the same account, a GPU machine (also Amazon EC2), re-encodes the video and runs the sign-detection software, and the re-encoded video is stored in Amazon S3.
So your data stays in one place: an Amazon Web Services account controlled by Georgia Tech, in Amazon's US East (Ohio) region — on Georgia Tech's servers there and in the file storage attached to them. Amazon Web Services provides those servers and that storage as an infrastructure provider; it does not use your data for its own purposes. As with other Georgia Tech cloud accounts, Georgia Tech's Office of Information Technology runs standard security and logging tools on the account. They record network connections and may examine stored files, only to protect the systems.
Automated software then examines the video and records the type and map position of each sign it detects in a database on Georgia Tech's research server, together with a record of your recording, the date it was uploaded, and which account uploaded it.
When a member of the research team sends a recording for human review, the detected signs, the location trace and a reference to the video are passed to a second Georgia Tech system, the sign-annotation tool at qaqc.sci.ce.gatech.edu, which runs on the same Georgia Tech server. There, reviewers watch the video and correct the sign labels. That system keeps its own copy of the location trace and of the sign records.
All of these systems are operated by or for Georgia Tech and are located in the United States. When someone on the research team looks at recordings on a map in these web tools, their web browser loads map images from OpenStreetMap and, in the sign-annotation tool, satellite images from Esri. Those map requests reveal which area of the map is being viewed, but they do not contain your video, your location file, or your account details.
Who can see your data
- People who hold an account in the same organization as you on the Georgia Tech systems described above. Accounts are grouped by organization, and an account can see that organization's recordings, their location traces, and the name of the person who uploaded each one. Depending on how your organization is set up, that may include other participants in your group as well as the research team.
- Reviewers on the sign-annotation system, who watch the video frame by frame to check the detected signs.
- Amazon Web Services, as the provider of the servers and storage that hold the files.
- Georgia Tech administrators, information-security staff and the security tools they operate, and oversight offices, where they need access to protect or oversee the project.
This study is carried out in partnership with Pima County, Arizona, and the University of Arizona. Staff at those organizations who work on the study hold research-team accounts, and they can view recordings, location traces and uploader names in their organization, on the same terms and for the same research purpose as the Georgia Tech team. The project's results — an inventory of road signs, their locations and their condition — are also provided to Pima County.
We do not share your data with advertisers, data brokers, or any commercial third party, and we do not sell it. If the study's findings are published, they are reported in aggregate or as sign inventory data — not as identifiable recordings of individual participants.
Other people and vehicles in the video
Road video inevitably captures whatever is in front of the camera: other vehicles and their number plates, pedestrians, cyclists, buildings and addresses. The app and our processing pipeline do not blur faces or number plates, and no automatic redaction of any kind is performed. Those images are held under the access controls described above and are used only to find and assess road signs.
Please record only on public roadways as instructed by the research team, and do not point the camera at people, private property, or anything unrelated to the study.
Third-party software and services
GT SignApp contains no advertising software and no analytics or crash-reporting service. When you use the app, it communicates only with Georgia Tech's research server at pima.sci.ce.gatech.edu. The links described below open in your web browser, not inside the app.
The Android version is assembled from standard Android software libraries. One of them includes Google's location library from Google Play services, but GT SignApp never calls it: the app gets your position from Android's own location service, as described under Precise location. Google states that this library collects no end-user data. The iPhone version contains no Google components; it uses only Apple's system frameworks for the camera, location, and networking.
The Feedback button inside the app opens a Google Forms page in your browser. That page is hosted by Google, not by us, and it is optional to use. Anything you type there is handled under Google's terms as well as ours, and depending on the form's settings Google may also record the Google account you are signed in to. Please do not enter anything there that you would not want stored outside the systems described in this policy.
Separately from the app, Apple and Google may collect crash reports, diagnostic information and usage statistics about GT SignApp: from people who have chosen to share that information with app developers in their device settings, and from anyone testing a pre-release version through Apple's TestFlight. Apple and Google collect this under their own privacy policies and make it available to us. We use it only to find and fix technical problems in the app.
How long we keep your data
Nothing in our systems deletes data automatically after a set time. There is no scheduled clean-up and no expiry date. Uploaded recordings, location files, the detected sign records, and your account remain until someone removes them.
Older files may be moved into lower-cost long-term archival storage. That is a change in how the file is stored, not a deletion — the data still exists and can be brought back, though it takes time and a request to an administrator.
There is no fixed retention period, and we are not promising one. Because this project does not run under an approved IRB protocol, no protocol sets an end date for the data. In practice, uploaded recordings, location files, the derived sign records, and your account are kept for as long as the research team has a use for them, which may be years. They are removed when you ask us to remove them, or when the Principal Investigator decides the data is no longer needed.
On your phone, a recording stays there after it has been uploaded. It is removed only when you delete it in the app or uninstall the app.
Deleting your data — what we can and cannot do
This is the most important section in this policy, and we would rather be exact than reassuring.
On your phone
Deleting a recording in the app removes it from your phone. Uninstalling GT SignApp removes everything the app stored on your phone: any recordings you have not deleted, its bookkeeping files, and your saved sign-in. The app is configured so that this data is not included in Android's automatic cloud backup or in iCloud backup on iPhone. Neither action affects a copy that has already been uploaded.
On our systems
Write to gtsignapp@groups.gatech.edu and a member of the research team will delete an uploaded recording for you. Tell us the date and rough time of the drive so we can find it. You can also ask us to delete your account, and we will.
What that deletion actually does. It removes the working copy of the recording from the Georgia Tech server, its entry in our database along with the sign locations derived from it, and the current copies of the video and location files in Amazon cloud storage.
What we cannot promise, and why.
- Our cloud storage keeps a version history of files. Deleting a file removes the current copy but can leave earlier stored versions behind. Removing those requires separate manual work by an administrator, and it is not part of the automatic process.
- If the recording has already been passed to the sign-annotation review system, that system keeps its own record of it. Our deletion does not reach that copy; removing it is a separate manual step.
- If the working copy on the Georgia Tech server has already been cleared away, our deletion tool will not run at all, and removing the cloud copies then has to be done by hand by an administrator.
- We cannot recall data that has already been used in analysis, or that forms part of research results that have been shared or published.
So, plainly: we will remove your recording from the systems we work in day to day, and we will act on your request. We cannot honestly promise that every copy is irrecoverably destroyed at the moment you ask. If complete erasure matters to you, say so in your request and we will tell you what was removed by hand and confirm when it is done.
Withdrawing from the study
You can stop using GT SignApp at any time. Stopping means we collect nothing further from you. Data you have already uploaded stays in our systems unless you ask us to delete it; the paragraphs above describe exactly what we are technically able to remove.
What you can ask us for
- A copy of the information we hold that relates to you.
- Correction of your account details if they are wrong.
- Deletion of a specific recording, or of your account, as described above.
- An explanation of how a particular recording of yours was used.
Write to gtsignapp@groups.gatech.edu. If you would rather raise a concern with someone independent of the research team, contact the Georgia Tech Office of Research Integrity Assurance at IRB@gatech.edu or 404.894.6942.
How your data is protected
- Everything the app sends — your sign-in and your uploads — travels over an encrypted HTTPS connection.
- Uploads are authenticated with a token tied to your account. Your password is never stored on the phone and is held on the server only as a salted one-way hash.
- On your phone, recordings are kept in the app's own folder and are removed when you uninstall the app. On iPhone that folder is private to the app and other apps cannot read it. On Android it sits in external storage, so on Android 9 and earlier another app holding storage permission can read it, and it can be browsed with a file manager or over a USB cable.
- Georgia Tech's research server requires a signed-in account for every action on stored recordings, and an account sees only the recordings of its own organization.
- Cloud storage sits in an Amazon Web Services account controlled by Georgia Tech.
No system is perfectly secure, and we do not claim otherwise. If we discover a breach affecting participant data, we will notify affected participants and the responsible Georgia Tech offices in line with Georgia Tech policy and applicable law.
Children
GT SignApp is not directed to children. It is distributed only to adults enrolled in the study who hold an account issued by the research team, and there is no public sign-up. We do not knowingly collect data from anyone under 18. If you believe a minor has used an account, contact us and we will remove the data.
Changes to this policy
If we change how the app or our systems handle your data, we will update this page and change the effective date at the top. If a change materially affects data already collected from you, we will contact enrolled participants directly and ask for your agreement again where that is warranted.
Contact
Questions about this policy, about your data, or about the study:
Smart City Infrastructure Lab
School of Civil and Environmental Engineering
Georgia Institute of Technology
Principal Investigator: Dr. Yichang James Tsai
Email: gtsignapp@groups.gatech.edu
To raise a concern with someone independent of the research team, contact the Georgia Tech Office of Research Integrity Assurance at IRB@gatech.edu or 404.894.6942.