It is known that determination of TV white space (TVWS) availability, in absence of geo-location databases, can be based on sensing and applying a detection threshold. In this paper we assess the availability of TVWS spectrum, using on site measurements in urban environment in Kosovo, obtained with NARDA SRM 3006 spectrum analyzer in the UHF and VHF bands. The measurement locations are chosen such as to represent various types of environments within the city of Prishtina. Results show that using a fixed low threshold setting for detection of TV signal presence, i.e., -95 dBm or lower, may heavily underestimate the TVWS spectrum potential. On the other hand, setting the threshold too high may result in misdetection of TV broadcasting, and potentially lead to harmful interference to the primary user. Thus, we propose an adjustable threshold-sensing algorithm to be implemented during data processing for spectrum availability determination. To improve the accuracy and have a more reliable picture of spectrum occupancy, we apply different sensing thresholds for different channels and use a double adaptive thresholding technique to enhance the performance of the detection mechanism.