Decoding Process

This guide explains how to convert encoded PFPX navdata files into readable text format.

Overview

PFPX navdata files use XOR encryption with a custom character mapping. The decoding process reverses this encryption to reveal the original navigation data.

Manual Decoding Method

Requirements

• Notepad++ with Converter plugin
• PFPX navdata file (.nav)
• Time and patience (for large files)

Step-by-Step Process

1. Open the file in Notepad

   File → Open → navdata.nav

   You'll see the plaintext header followed by encoded content.

2. Switch to Notepad++

   • Open the same file in Notepad++
   • You'll see the same header + encoded sections

3. Select the encoded content

   • Start from line 9 (skip the plaintext header)
   • Select the content you want to decode
   • Important: Don't select more than 3,000-4,000 lines at once

4. Convert to hexadecimal

   Menu → Plugins → Converter → ASCII-to-HEX

5. Apply character mapping

   • Use the encoding table to convert hex codes
   • Each pair of hex characters represents one original character

Important Notes

File Handling

• Never modify the original file directly
• Always work on a copy
• Use ANSI encoding when saving new files
• Process in small chunks to avoid errors

Automated Decoding Method

Our Python decoder automates this entire process:

Basic Usage

# Decode a navdata file
python nav_decoder.py decode navdata.nav output.txt

# Encode a text file back to navdata format  
python nav_decoder.py encode input.txt navdata.nav

Auto-processing Mode

# Automatically process files with standard names
python nav_decoder.py auto

This looks for:

• wait2decode.nav → creates already_decode.txt
• wait2encode.txt → creates already_encode.nav

Understanding the Output

Once decoded, you'll see readable navigation data:

PFPX NAVDATA
NG2509
2025/09/04
2025/10/01
NAVIGRAPH

RWY 00AN03   04517060030ASP+59088889-156463889
RWY 00AN21   04517060210ASP+59098056-156447778
......
RWY ZYYJ09   08530148092ASP+42881175+129435625
RWY ZYYJ27   08530148272ASP+42884531+129467125

WPT ENOE QAT0ENOEA1P 1CA1TROLL AIRFIELD                003733     -71956667+002453333+0412509843ENOR    18000
WPT NZFX    0NZFXA1P 1PA1PHOENIX                       011402     -77957092+166745389+0003710006NZZO    18000
......
WPT ZYTX SHE0ZYTXZYP 1CZYTAOXIAN                       016367     +41641667+123485000+0019810499ZYSH    
WPT ZYYJ YNJ0ZYYJZYP 1CZYCHAOYANGCHUAN                 016368     +42881667+129450000+0062208530ZYSH    9490

WPT AARON   6AARONA1E0 A1AARON                         016368     -79384500-110927167+0000000000NZZO         
WPT ANGIE   6ANGIEA1E0 A1ANGIE                         016369     -89754667-176959167+0000000000NZZO       
......
WPT LJ      5LJZYP   0 ZYSANJIAZI QIQIHAR              27493901770+47195903+123944392+0000000000ZYSH         
WPT JA      5JAZYP   0 ZYDEXIN YANJI                   27494003320+42871356+129341022+0000000000ZYSH            

AWY A1    SA32690940745071+33447742+135794494+33364503+13544151408000UNLTD0
AWY A1    SA30745070749101+33364503+135441514+33248769+13499722208000UNLTD0
......
AWY Z999  SO30223222639891+47559389+010305583+47745775+01034983309500FL6601
AWY Z999  SA22639890222801+47745775+010349833+47929603+01074995606500FL2451

SID 0ID211   000001099539FLNGJYOYYU1      +44255928-1134392501
SID 0ID211   000002034960YOYYUYOYYU1      +43948250-1133553641
......
SID ZYYJ27   164665263457YJ401WQG19D      +43242778+1297413891
SID ZYYJ27   164666271707WQG  WQG19D      +43293333+1297850001

STR 06FAALL  164667050581BISKSCLMNT2BISKS +27981592-0796214061
STR 06FAALL  164668051894HEMSICLMNT2BISKS +27640356-0797136671
......
STR ZYYJ27   330409263457YJ401WQG19A      +43242778+1297413891
STR ZYYJ27   330410263468YJ604WQG19A      +43017778+1296950001

Validation

After decoding, verify your results:

1. Check the header - Should be identical to original
2. Verify record formats - Each line should follow expected patterns
3. Count records - Compare with expected quantities
4. Test encoding - Re-encode and compare with original

Troubleshooting

Common Issues

Problem	Cause	Solution
Converter plugin missing	Notepad++ installation	Install Converter plugin
"Error" message	Processing too many lines	Reduce selection size
Garbled output	Wrong encoding	Use ANSI encoding
Missing characters	Incomplete selection	Include full line ranges

Performance Tips

• Chunk processing: Process 3,000-4,000 lines at a time
• Progress tracking: Use automated tools for large files
• Memory management: Close other applications for large operations
• Backup strategy: Always keep original files safe

Integration Options

Scripting

from nav_codec import NavCodec

codec = NavCodec()
codec.decode_file("navdata.nav", "output.txt")

Batch Processing

# Process multiple files
for file in *.nav; do
    python nav_decoder.py decode "$file" "${file%.nav}.txt"
done

Next Steps

• Explore data sections - Learn about specific data formats
• Use Python tools - Automate the process
• See examples - Practical usage scenarios