Livinus,
There is also an online course at http://coursemeasurement.org.uk/lessons/index.htm
After several pages explaining basic things it has a test to see if you can cope with the necessary calculations.
If you pass the test you will be invited to do a ten lesson theory course, designed for UK measurers, but it could be used by trainees anywhere.
After doing the theory you need to do a practical test to check your riding skill and measure a real course alongside an experienced measurer. If you had a number of people who had done the theory and wanted to become measurers recognised by the IAAF you could get an IAAF course measurement administrator to organise a practical seminar in Nigeria, or if you ever visit England, I would be happy to ride with you to check your practical skills.