Open-Imo-Registration-Number-Validator 🔍✔

What is this?

An unofficial open source validator for the International Maritime Organisation (IMO)'s registration numbers. Ships and shipping companies have IMO Registration numbers, made up of "IMO" followed by seven numerical digits. The digits are validated using a checksum. This application implements validation for both companies and ships in C#.

Getting Started

The library can be installed via Nuget

dotnet add package EtiveMor.OpenImoRegistrationNumberValidator --version 1.0.0

Available methods

Validate arbitrary strings

Once installed, run ImoNumberValidator.ValidateImoNumber(imoNumber);, where imoNumber is your 10 character IMO number. The method will return an Enum of type EtiveMor.OpenImoRegistrationNumberValidator.ImoNumberType:

public enum ImoNumberType
{
    Invalid = -1,
    Ship = 1,
    Company = 2
}

Ship IMO number validation 🚢

  bool shipResult = ImoNumberValidator.IsValidShipRegistrationNumber(companyImoNumber);

The method validates a Ship's registration number. Returns either true if the number is a valid ship IMO number. Returns false in any other scenario - the method does not return details of the validation failure.

Ship IMO number validation (with descriptive exceptions)

try{
  // success condition
  bool shipResult = ImoNumberValidator.ValidateShipRegistrationNumber(companyImoNumber);
} catch (ImoNumberValidationException ex) {
  // fail condition
  // ...
}

The method validates a Ship's registration number. Returns either true if the number is a valid ship. Throws an ImoNumberValidationException in any other scenario. The ImoNumberValidationException's Message property includes details of the failure.

Company IMO number validation 💼

  bool companyResult = ImoNumberValidator.IsValidCompanyRegistrationNumber(companyImoNumber);

The method validates a Company's registration number. Returns either true if the number is a valid company. Returns false in any other scenario - the method does not return details of the validation failure.

Company IMO number validation (with descriptive exceptions)

  try{
    // success condition
    bool companyResult = ImoNumberValidator.ValidateShippingCompanyRegistrationNumber(companyImoNumber);
  } catch (ImoNumberValidationException ex) {
    // fail condition
    // ...
  }

The method validates a Company's registration number. Returns either true if the number is a valid company. Throws an ImoNumberValidationException in any other scenario. The ImoNumberValidationException's Message property includes details of the failure.

IMO Number Validation Algorithm

All IMO numbers must be 10 characters in length. The first three characters are uppercase "IMO". The next 6 characters are a set of numbers (unique to each ship). The final (7th) character is a check-digit. Ships and Companies have two different algorithms to calculate the check-digit integrity, outlined below:

Validating a ship's IMO check-digit

Weights: [7, 6, 5, 4, 3, 2]

• Take each of the first six numerical digits in the input-string (ignore the "IMO" characters)
• Multiply each by its corresponding weight, so
  • Digit 1 is multiplied by 7
  • Digit 2 is multiplied by 6
  • Digit 3 is multiplied by 5
  • Digit 4 is multiplied by 4
  • Digit 5 is multiplied by 3
  • Digit 6 is multiplied by 2
• Sum the results of the multiplication step
• Take the last character from the sum
  • Check against the last character for the input-string

Example: The ship Nordic Sola's IMO number "IMO9375989"

• Multiply each numerical char by its weight:
  • $(9 \times 7) + (3 \times 6) + (7 \times 5) + (5 \times 4) + (9 \times 3) + (8 \times 2) = 179$
• Take the last digit of 179 (9)
• Take the last digit of IMO9375989 (9)
• Compare the two:
  • If they are the same (9 in this case) then the number is a valid Ship IMO Registration number
  • If they are different, the IMO number is not a valid Ship IMO Registration number

Validating a company's IMO check-digit

Weights: [8, 6, 4, 2, 9, 7]

• Take each of the first six numerical digits in the input-string (ignore the "IMO" characters)
• Multiply each by its corresponding weight, so
  • Digit 1 is multiplied by 8
  • Digit 2 is multiplied by 6
  • Digit 3 is multiplied by 4
  • Digit 4 is multiplied by 2
  • Digit 5 is multiplied by 9
  • Digit 6 is multiplied by 7
• Sum the results of the multiplication step
• With the result, apply the mod11 algorithm
• Subtract the results of the mod11 step from 11
• With the result, apply the mod10 algorithm
• Take the last character from the input-string and compare to the mod10 result

Example: The company EVERGREEN MARINE CORP's IMO number "IMO0344771"

• Multiply each numerical char by its weight:
  • $(8 \times 0) + (6 \times 3) + (4 \times 4) + (2 \times 4) + (9 \times 7) + (7 \times 7) = 154$
• Apply mod11 to 154
  • $(154) \mod{11} = 0$
• Subtract 0 from 11
  • $11 - 0 = 11$
• Apply mod10 to 11
  • $11 \mod{10} = 1$
• Take the last digit of IMO0344771: 1
• Compare the two:
  • If they are the same (1 in this case) then the number is a valid Company IMO Registration number
  • If they are different, the IMO number is not a valid Company IMO Registration number

References & datasets

• IMO Number Wiki page: https://en.wikipedia.org/wiki/IMO_number
• All ship and company IMO numbers: https://gisis.imo.org/Public/Default.aspx
• IMO Ship Identification Number Schemes: https://www.imo.org/en/OurWork/MSAS/Pages/IMO-identification-number-scheme.aspx