# GPS Auto-Extraction from Filenames

## Feature Overview

The web interface now automatically detects and extracts GPS coordinates from filenames, eliminating the need for manual coordinate entry when filenames contain location data.

## Supported Filename Patterns

### 1. N/S/E/W Format (Primary)
**Pattern**: `LAT[NS]_LON[EW]`

**Examples**:
- `34.0478N_118.2348W_1637_raw_8.sub` → 34.0478, -118.2348
- `34.0478N_118.2349W_1351_raw_10.sub` → 34.0478, -118.2349
- `40.7128N_74.0060W_capture.sub` → 40.7128, -74.0060

**Notes**:
- Most common format from T-Embed RF captures
- N = positive latitude, S = negative latitude
- E = positive longitude, W = negative longitude

### 2. lat/lon Prefix Format
**Pattern**: `latLATlonLON`

**Examples**:
- `lat34.0478lon-118.2348_test.sub` → 34.0478, -118.2348
- `lat40.7128lon-74.0060_capture.sub` → 40.7128, -74.0060

**Notes**:
- Allows signed decimal notation
- Case-insensitive (LAT/LON also works)

### 3. Signed Decimal Format
**Pattern**: `LAT_LON` (with optional negative signs)

**Examples**:
- `-34.0478_118.2348_capture.sub` → -34.0478, 118.2348
- `40.7128_-74.0060_test.sub` → 40.7128, -74.0060

**Notes**:
- Simple signed decimal degrees
- Less common but supported

## How It Works

### 1. File Upload Detection
When user selects/drops .sub files:
```javascript
1. Files are added to upload queue
2. First file with GPS coordinates is automatically detected
3. GPS fields are auto-populated
4. User sees notification toast
```

### 2. UI Indicators
- **GPS Detection Notification**: Green toast shows which file provided coordinates
- **File List Badge**: Files with GPS show 📍 GPS badge
- **Coordinate Display**: Extracted coordinates appear next to filename

### 3. Validation
- Latitude range: -90 to 90
- Longitude range: -180 to 180
- Invalid coordinates are rejected
- Malformed patterns are skipped

## User Experience

### Upload Flow with GPS in Filename

1. **Drop/Select File**: User uploads `34.0478N_118.2348W_capture.sub`
2. **Auto-Detection**: System extracts GPS (34.0478, -118.2348)
3. **Notification**: Green toast appears:
   ```
   📍 GPS Auto-Detected!
   From: 34.0478N_118.2348W_capture.sub
   Coordinates: 34.047800, -118.234800
   ```
4. **Form Population**: Latitude and longitude fields auto-fill
5. **Upload**: User clicks "Upload Files" (no manual GPS entry needed)

### Upload Flow WITHOUT GPS in Filename

1. **Drop/Select File**: User uploads `raw_7.sub`
2. **No Detection**: No GPS found in filename
3. **Manual Entry**: User must manually enter GPS or use "Use Current Location"
4. **Validation**: System checks for valid coordinates before upload

## Implementation Details

### JavaScript GPS Extractor Class
Location: `static/js/upload.js`

```javascript
class GPSFilenameExtractor {
    extract(filename) {
        // Try each pattern in order
        return this.tryNSEW(filename) ||
               this.tryLatLon(filename) ||
               this.trySigned(filename);
    }
}
```

### Pattern Matching
- **PATTERN_NSEW**: `/(\d+\.?\d*)([NS])_(\d+\.?\d*)([EW])/i`
- **PATTERN_LATLON**: `/lat(-?\d+\.?\d+)lon(-?\d+\.?\d+)/i`
- **PATTERN_SIGNED**: `/(-?\d+\.?\d+)_(-?\d+\.?\d+)/`

### Auto-Population Logic
```javascript
function addFiles(files) {
    // Try to extract GPS from first file with coordinates
    if (!autoDetectedGPS) {
        for (const file of files) {
            const coords = gpsExtractor.extract(file.name);
            if (coords) {
                autoDetectedGPS = coords;
                document.getElementById('default-lat').value = coords.latitude.toFixed(6);
                document.getElementById('default-lon').value = coords.longitude.toFixed(6);
                showGPSDetectionNotification(file.name, coords);
                break;
            }
        }
    }
}
```

## Testing

### Test Suite
Location: `test_gps_extraction.html`

Open in browser to verify all patterns:
```bash
firefox test_gps_extraction.html
# or
chromium test_gps_extraction.html
```

### Test Coverage
- ✅ N/S/E/W format (3 test cases)
- ✅ lat/lon prefix format
- ✅ Signed decimal format
- ✅ Negative detection (files without GPS)

### Python Compatibility
The JavaScript implementation matches the Python `GPSFilenameExtractor` class:
- Same pattern support
- Same validation rules
- Same coordinate transformation logic

## T-Embed RF Compatibility

### Tested Files
From `signatures/t-embed-rf/`:
- ✅ `34.0478N_118.2348W_1637_raw_8.sub` → Auto-detected
- ✅ `34.0478N_118.2349W_1351_raw_10.sub` → Auto-detected
- ✅ `34.0478N_118.2349W_1650_test_raw.sub` → Auto-detected
- ⏭️ `raw_4.sub` → Manual entry required
- ⏭️ `raw_5.sub` → Manual entry required

**Success Rate**: 37.5% (3 of 8 files) auto-detected

## Error Messages

### GPS Required
If no GPS provided (manual or filename):
```
Please provide GPS coordinates (manually or via filename like: 34.0478N_118.2349W_filename.sub)
```

### GPS Detected but Not Populated
If GPS exists in filename but form is empty:
```
GPS detected in filename but not populated. Please refresh and try again.
```

### Out of Range
If coordinates exceed valid ranges:
```
GPS coordinates out of range
```

## Benefits

1. **Faster Uploads**: No manual GPS entry for T-Embed captures
2. **Fewer Errors**: Eliminates coordinate typos
3. **Better UX**: Clear feedback when GPS is detected
4. **Flexible**: Still allows manual entry for files without GPS
5. **Compatible**: Matches Python backend extraction logic

## Future Enhancements

### Additional Patterns
- DMS format: `34d02m52sN_118d14m05sW`
- Compact format: `N34.0478W118.2348`
- Plus codes: `8762+MXP_capture.sub`

### Multi-File GPS
Currently uses first file's GPS for all uploads. Future enhancement:
- Per-file GPS extraction
- Mixed batch uploads (some with GPS, some without)
- GPS override UI per file

### Companion JSON
Check for `.json` files alongside `.sub` files:
```json
{
    "capture.sub": {
        "latitude": 34.0478,
        "longitude": -118.2348,
        "accuracy": 5.0
    }
}
```

## Related Files

- `static/js/upload.js` - Frontend GPS extraction
- `src/parser/gps_extractor.py` - Backend GPS extraction
- `scripts/test_gps_extraction.py` - Python test suite
- `test_gps_extraction.html` - JavaScript test suite

## Summary

GPS auto-extraction is **LIVE** and working with the format `34.0478N_118.2349W_filename.sub`. Users can now simply drag and drop T-Embed captures without manually entering coordinates!