SatTemps

Android app (Kotlin / Jetpack Compose) that shows the exact time (hour, minute, second, millisecond) and the best orientation to pick up:

• GNSS satellites (GPS, Galileo, GLONASS, BeiDou),
• a geostationary satellite (dish: azimuth, elevation, LNB tilt),
• the strongest 5G NR / 4G LTE cell tower.

Features

"Time" tab

• Millisecond clock based on GNSS time from the satellite fix (first choice), otherwise an NTP server (time.google.com, pool.ntp.org, time.cloudflare.com), otherwise the phone clock.
• Shows the measured offset from the phone clock and the estimated uncertainty.
• Local time + UTC, GPS position (latitude, longitude, altitude, accuracy).

"GPS Sky" tab

• Polar sky view: each satellite is placed by its azimuth and elevation; color and size show signal quality (C/N0 in dB-Hz).
• The view rotates with the phone (compass corrected for magnetic declination: true north).
• Best direction = signal-weighted vector average of the azimuths, with the rotation angle to apply.

"Dish" tab

• From the GPS position, computes pointing toward a dozen common geostationary satellites (Astra 19.2E, Hotbird 13E, Eutelsat 5W/7W, Nilesat, Turksat...).
• Azimuth (true north), elevation, LNB tilt (skew), slant range, highest satellite.

"Network" tab

• Operator, technology (5G NR / LTE / UMTS / GSM), serving cell and neighbor cells: power (SS-RSRP / RSRP), quality (RSRQ), SINR, bands, identifiers (NCI, PCI, TAC).
• 360° directional scan: start the scan and slowly turn around; the app samples signal power per 15° sector and shows the direction of the best-received tower, along with the rotation to apply.

Build

Requirements: JDK 17 and the Android SDK (platform 34, build-tools 34).

# Set the SDK path
echo "sdk.dir=/path/to/Android/sdk" > local.properties

./gradlew assembleDebug
# APK: app/build/outputs/apk/debug/app-debug.apk

Install on a phone connected over USB (USB debugging enabled):

adb install -r app/build/outputs/apk/debug/app-debug.apk

Tests

The calculations (geostationary pointing, GNSS sky analysis, NTP encoding, time source priority, 360° directional scan, UI azimuths) are covered by JVM unit tests, no emulator needed:

./gradlew test
./gradlew lint

Field tests (several phones, several regions, different modems) still need to be done on real devices.

Languages

All displayed texts are in app/src/main/res/values/strings.xml (French, default language) and app/src/main/res/values-en/strings.xml (English). To add a language, copy the file into a values-xx folder.

Permissions

Permission	Usage
ACCESS_FINE_LOCATION	GPS position, satellite status, cell information
READ_PHONE_STATE	network technology and cell identifiers
INTERNET	NTP synchronization

Time accuracy

• GNSS: the GPS fix carries a UTC timestamp derived from the satellites' atomic clocks. It is compared with the phone's monotonic clock (elapsedRealtimeNanos) to remove the fix reporting latency; typical accuracy is a few tens of milliseconds.
• NTP: standard SNTP algorithm; the displayed uncertainty is half the round-trip time.
• Android does not expose the leap second; the displayed time follows the UTC scale.

Known limitations

• Neighbor cell information depends on the modem and manufacturer; some phones only report the serving cell.
• The cell tower direction is inferred from the power measured during rotation (the user's body blocks the signal on the opposite side): it is an estimate, not a triangulation.
• The list of geostationary satellites is static and covers Europe, Africa and part of the Americas.