Hi, Sorry if this is slightly of topic. This is a typical dump from a file without Huffman encoding. (RGN Section 5) TRE - Section 7 dump 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C -------------------------------------------------------------------------------------- Sec 2 | Sec 3 | Sec 4 | |Columns related to RGN Section 6 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 0B 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 17 00 00 00 00 00 00 00 06 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 24 00 00 00 12 00 00 00 0C 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 32 00 00 00 26 00 00 00 12 00 00 00 01 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 41 00 00 00 3D 00 00 00 18 00 00 00 00 06 00 00 00 13 00 00 00 15 00 00 00 1B 00 00 00 All rows except the last row is related to it's sublevel, Row 2 to sublevel 2 and so on. Explanation to last row 41 00 00 00 = RGN Section 2 Length 3D 00 00 00 = RGN Section 3 Length 18 00 00 00 = RGN Section 4 Length 01 = Flag (Not allways first sublevel per zoom-level) 06 00 00 00 = End of first part RGN Section 6 13 00 00 00 = End of second part in RGN Section 6 15 00 00 00 = End of third part in RGN Section 6 1B 00 00 00 = Total Length of RGN Section 6 RGN Section 6 dump 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ----------------------------------------------- 0B 11 72 2C E5 36 19 11 04 4C 91 D7 FC 4B 11 BE CC 8F 1E E0 00 0B 11 72 2C E5 36 0B 11 72 2C E5 36 : 0B >> 1 gives following byte length of 5 19 11 04 4C 91 D7 FC 4B 11 BE CC 8F 1E : 19 >> 1 gives byte length of 12 decimal E0 00 : Seen E0 00 in other files 0B 11 72 2C E5 36 : 0B >> 1 gives following byte length of 5 Shifting the first byte to give following byte length seems to be valid if the value is odd. This is also valid within a byte array (amount of bytes in a sublevel) stated in TRE Section 7. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ----------------------------------------------- 15 11 70 7C 76 6F ED 1A 3E 2F 34 15 11 E0 AF F7 12 A7 CB CD 17 34 0D 11 8C 5A F9 2F 01 0D 11 E0 CF 70 D9 3A 0F 12 68 7C CC E6 F0 00 0D 12 E0 1E 80 79 1F 11 11 D4 0B 3E 19 00 17 0C 0D 01 78 B2 41 DB 11 0D 11 F4 D0 F3 D8 01 0D 11 24 7F 30 D7 15 11 70 7C 76 6F ED 1A 3E 2F 34 15 11 E0 AF F7 12 A7 CB CD 17 34 0D 11 8C 5A F9 2F 01 0D 11 E0 CF 70 D9 3A 0F 12 68 7C CC E6 F0 00 0D 12 E0 1E 80 79 1F 11 11 D4 0B 3E 19 00 17 0C 0D 01 78 B2 41 DB 11 0D 11 F4 D0 F3 D8 01 In a Huffman encoded file looks RGN Section 6 much more "random". 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ----------------------------------------------- F9 9F 7F F8 3E 80 98 7D FC 09 45 F0 7C E6 E4 00 83 FF 7C 0A C8 E5 1F 40 40 FF 41 E4 80 CF FF C6 FF 7E C0 C9 40 F4 21 F2 FE 02 FF 33 F8 20 40 FF FC FF E1 21 1F 7E 06 FF FD 00 FC FF A1 8F 29 FB According to this file TRE Section 7 it should be splitted as F9 9F 7F F8 3E 80 98 7D FC 09 45 F0 7C E6 E4 00 The question is: Do anyone know what it might be in RGN Section 6. Even a bit more than what I found so far is of interest. Any hint in this topic is much appreciated. Best Regards /Thomas