Coverage area of optical transport networks (OTNs) are used in several estimations such as the average link length. However, estimating the coverage area may become complex in some cases without appropriate computing tools. In this work, we present the geometrical properties of the OTNs such as the convex area and establish their correlation with the circumferential ellipse (CE) of the networks. We provide the estimation and application of the CEs for the OTNs by evaluating the parameters of 40 real OTNs. We show that the average link length of the OTN can be estimated from the CE and thus several other link-related parameters as well. We estimated their eccentricities, and finally present their correlations with the OTN parameters. By comparing the results obtained from the estimations using CEs with the previous outcomes using the convex areas, we show that the methods based on the CEs are as effective as the methods based on the convex areas.