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brentperteet
291
analyze_rtcm_correct.py
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291
analyze_rtcm_correct.py
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#!/usr/bin/env python3
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"""
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Correct RTCM3 message analyzer with proper bit-level parsing.
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Also detects non-RTCM data (ASCII, NMEA) in the stream.
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"""
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import sys
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import argparse
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from pathlib import Path
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def parse_rtcm_stream(data: bytes) -> list[dict]:
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"""Parse RTCM3 stream, identifying both RTCM messages and non-RTCM data."""
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items = []
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i = 0
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while i < len(data):
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# Check for RTCM3 message (0xD3 header)
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if data[i] == 0xD3 and i + 2 < len(data):
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# Parse header: 0xD3 + 2 bytes (6 bits reserved + 10 bits length)
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reserved = (data[i+1] >> 2) & 0x3F
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length = ((data[i+1] & 0x03) << 8) | data[i+2]
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msg_total_len = 3 + length + 3 # header + payload + CRC
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if i + msg_total_len <= len(data) and length >= 3:
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payload = data[i+3:i+3+length]
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# Extract message type - CORRECTLY from 12 bits
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# Bits 0-11 of payload contain message type
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msg_type = (payload[0] << 4) | (payload[1] >> 4)
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# Extract station ID (typically bits 12-23, next 12 bits)
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station_id = ((payload[1] & 0x0F) << 8) | payload[2]
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# CRC
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crc = data[i+3+length:i+3+length+3] if i+3+length+3 <= len(data) else None
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items.append({
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'type': 'rtcm',
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'offset': i,
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'message_type': msg_type,
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'station_id': station_id,
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'reserved': reserved,
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'length': length,
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'total_length': msg_total_len,
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'payload': payload,
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'crc': crc,
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})
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i += msg_total_len
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continue
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# Check for ASCII data (NMEA, text, etc.)
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# Look for printable ASCII or common NMEA starters
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if data[i] == ord('$') or (32 <= data[i] < 127):
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# Find end of ASCII block
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start = i
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while i < len(data) and (32 <= data[i] < 127 or data[i] in [9, 10, 13]):
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i += 1
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if i > start:
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text = data[start:i].decode('ascii', errors='ignore')
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items.append({
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'type': 'ascii',
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'offset': start,
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'length': i - start,
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'text': text,
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})
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continue
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# Unknown/binary data
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i += 1
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return items
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def get_message_description(msg_type: int) -> str:
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"""Get human-readable description for RTCM message type."""
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descriptions = {
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1001: "GPS L1 RTK Observables",
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1002: "GPS L1 RTK Observables (Extended)",
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1003: "GPS L1/L2 RTK Observables",
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1004: "GPS L1/L2 RTK Observables (Extended)",
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1005: "Stationary RTK Reference Station ARP",
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1006: "Stationary RTK Reference Station ARP + Antenna Height",
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1007: "Antenna Descriptor",
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1008: "Antenna Descriptor & Serial Number",
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1009: "GLONASS L1 RTK Observables",
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1010: "GLONASS L1 RTK Observables (Extended)",
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1011: "GLONASS L1/L2 RTK Observables",
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1012: "GLONASS L1/L2 RTK Observables (Extended)",
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1013: "System Parameters",
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1019: "GPS Ephemerides",
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1020: "GLONASS Ephemerides",
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1033: "Receiver and Antenna Descriptors",
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1071: "GPS MSM1",
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1072: "GPS MSM2",
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1073: "GPS MSM3",
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1074: "GPS MSM4",
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1075: "GPS MSM5",
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1076: "GPS MSM6",
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1077: "GPS MSM7",
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1081: "GLONASS MSM1",
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1082: "GLONASS MSM2",
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1083: "GLONASS MSM3",
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1084: "GLONASS MSM4",
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1085: "GLONASS MSM5",
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1086: "GLONASS MSM6",
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1087: "GLONASS MSM7",
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1091: "Galileo MSM1",
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1092: "Galileo MSM2",
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1093: "Galileo MSM3",
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1094: "Galileo MSM4",
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1095: "Galileo MSM5",
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1096: "Galileo MSM6",
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1097: "Galileo MSM7",
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1121: "BeiDou MSM1",
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1122: "BeiDou MSM2",
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1123: "BeiDou MSM3",
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1124: "BeiDou MSM4",
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1125: "BeiDou MSM5",
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1126: "BeiDou MSM6",
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1127: "BeiDou MSM7",
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1230: "GLONASS Code-Phase Biases",
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}
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return descriptions.get(msg_type, f"Unknown/Proprietary Type {msg_type}")
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def hex_dump(data: bytes, offset: int = 0, max_bytes: int = 64) -> str:
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"""Create a hex dump of data."""
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lines = []
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data = data[:max_bytes]
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for i in range(0, len(data), 16):
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chunk = data[i:i+16]
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hex_part = " ".join(f"{b:02X}" for b in chunk)
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ascii_part = "".join(chr(b) if 32 <= b < 127 else "." for b in chunk)
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lines.append(f"{offset + i:08X} {hex_part:<48} {ascii_part}")
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return "\n".join(lines)
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def analyze_file(filename: str, show_hex: bool = False, filter_type: int = None,
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max_items: int = 50, show_ascii: bool = True):
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"""Analyze binary file with correct RTCM parsing."""
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path = Path(filename)
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if not path.exists():
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print(f"ERROR: File not found: {filename}")
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return
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print(f"Analyzing: {filename}")
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print(f"File size: {path.stat().st_size:,} bytes")
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print(f"{'=' * 80}\n")
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# Read and parse
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data = path.read_bytes()
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items = parse_rtcm_stream(data)
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# Statistics
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rtcm_count = sum(1 for item in items if item['type'] == 'rtcm')
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ascii_count = sum(1 for item in items if item['type'] == 'ascii')
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print(f"STREAM SUMMARY:")
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print(f"{'─' * 80}")
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print(f"Total RTCM messages: {rtcm_count}")
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print(f"Total ASCII blocks: {ascii_count}")
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print()
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# Message type distribution
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if rtcm_count > 0:
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type_counts = {}
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station_ids = set()
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for item in items:
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if item['type'] == 'rtcm':
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msg_type = item['message_type']
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type_counts[msg_type] = type_counts.get(msg_type, 0) + 1
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station_ids.add(item['station_id'])
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print(f"RTCM MESSAGE TYPES:")
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print(f"{'─' * 80}")
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for msg_type in sorted(type_counts.keys()):
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desc = get_message_description(msg_type)
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count = type_counts[msg_type]
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print(f" Type {msg_type:4d}: {count:5d} messages - {desc}")
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print()
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print(f"Station IDs found: {sorted(station_ids)}")
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print()
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# Show individual items
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print(f"STREAM CONTENT (first {max_items} items):")
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print(f"{'=' * 80}\n")
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shown = 0
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for i, item in enumerate(items):
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if shown >= max_items:
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remaining = len(items) - i
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print(f"\n... and {remaining} more items (use --max-items to show more)")
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break
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# Filter if requested
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if filter_type is not None and (item['type'] != 'rtcm' or item.get('message_type') != filter_type):
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continue
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shown += 1
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if item['type'] == 'rtcm':
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msg_type = item['message_type']
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desc = get_message_description(msg_type)
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print(f"[{i+1}] RTCM Message {msg_type:4d} - {desc}")
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print(f" Offset: 0x{item['offset']:08X} ({item['offset']})")
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print(f" Station ID: {item['station_id']}")
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print(f" Length: {item['length']} bytes payload, {item['total_length']} bytes total")
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if show_hex:
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print(f" Payload (first 64 bytes):")
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hex_lines = hex_dump(item['payload'], item['offset'] + 3, max_bytes=64)
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for line in hex_lines.split('\n'):
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print(f" {line}")
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# Check for ASCII in payload
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payload = item['payload']
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printable_count = sum(1 for b in payload if 32 <= b < 127)
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printable_percent = (printable_count / len(payload) * 100) if len(payload) > 0 else 0
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if printable_percent > 30:
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print(f" Contains {printable_percent:.0f}% ASCII text:")
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try:
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text = payload.decode('ascii', errors='ignore')
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text_display = text.replace('\r', '\\r').replace('\n', '\\n').replace('\t', '\\t')
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if len(text_display) > 150:
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text_display = text_display[:150] + "..."
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print(f" {text_display}")
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except:
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pass
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print()
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elif item['type'] == 'ascii' and show_ascii:
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text = item['text'].replace('\r', '\\r').replace('\n', '\\n').replace('\t', '\\t')
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if len(text) > 150:
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text = text[:150] + "..."
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print(f"[{i+1}] ASCII DATA")
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print(f" Offset: 0x{item['offset']:08X} ({item['offset']})")
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print(f" Length: {item['length']} bytes")
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print(f" Text: {text}")
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print()
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def main():
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parser = argparse.ArgumentParser(
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description="Analyze RTCM3 binary file with correct message type parsing",
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formatter_class=argparse.RawDescriptionHelpFormatter,
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epilog="""
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Examples:
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# Basic analysis
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python analyze_rtcm_correct.py ntrip_raw_20250605_120000.bin
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# Show hex dumps
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python analyze_rtcm_correct.py ntrip_raw_20250605_120000.bin --hex
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# Only show specific message type
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python analyze_rtcm_correct.py ntrip_raw_20250605_120000.bin --type 1005
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# Show more items
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python analyze_rtcm_correct.py ntrip_raw_20250605_120000.bin --max-items 100
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"""
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)
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parser.add_argument('filename', help='Binary file to analyze')
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parser.add_argument('--hex', action='store_true', help='Show hex dumps of message payloads')
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parser.add_argument('--type', type=int, help='Filter to show only specific message type')
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parser.add_argument('--max-items', type=int, default=50, help='Maximum number of items to display')
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parser.add_argument('--no-ascii', action='store_true', help='Hide ASCII blocks in output')
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args = parser.parse_args()
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analyze_file(
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args.filename,
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show_hex=args.hex,
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filter_type=args.type,
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max_items=args.max_items,
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show_ascii=not args.no_ascii
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)
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if __name__ == "__main__":
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main()
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