The Challenges of measuring distances between places

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

21 July 2024

What is the distance from Kenya to Tanzania? Would you be able to answer that question? Perhaps you would ask from where in Kenya to where in Tanzania. The challenge is that the two countries are neighbours sharing a common land boundary. So, their distance apart is zero!

I asked Google Maps this question and it gave a very exact answer of 1,051km. Looking closer, I found that the system picked points near the centres of the two countries. The same can be asked about the distance between two towns: which points are the start and end of measurement?

Depending on who you ask, the distance from Nairobi to Thika is 45km or 40km or 38km, etc. In Kenya, it is assumed that inter-town distances are measure from the main post offices. Indeed, there is a monument near the General Post Office in Nairobi indicating distances to various destinations around the country. It is called the Nairobi Milliary Stone and was erected in 1939. I am not sure what came first: the post office or the stone!

Nevertheless, the distance from here to the post office in Thika town centre is 43km. However, one might also argue that the relevant distance between towns is the length of the main road linking them. In that case, we would take the measurement from the Pangani to the Thika flyovers – it is 37km.

The lesson here is that, when stating the distance between two places, it is very important to clarify the exact points between which the measurements are taken. In some instances, even knowing the exact points isn’t enough; we need to say the size of the “measuring stick” to be used.

Take the simple question of the length of Kenya’s coastline. The straight-line distance from Vanga Beach in the South to the Border Control Point at Sona in the North is 425km. If we connect the five major towns of Ukunda, Mombasa, Kilifi, Malindi and Lamu with straight line segments, the length increases to 429km. If we include some of the prominent creeks along the coast it goes up further to 463km.

One can continue this process with shorter and shorter line segments and each time the total distance measured gets bigger. The limit of how small the “measuring stick” can be is the size of an atom! In that case, the coastline is unfathomably long!