Despite being in use for more than 150 years, the error accumulation in precise levelling has not yet been completely clarified. It is believed that the error accumulation in this method is proportional to the square root of the levelling length. The first goal of this article is to demonstrate that this belief is not always scientifically proven. The second aim is to show that it is likely that a better adjustment decision will be missed if inverse distance weighting with a power parameter equal to one is automatically applied. Using linear regression analysis the measuring data of the Second Levelling of Finland is analysed. An inadequacy of the relationship between the absolute values of the differences between both measurements of the elevations in the levelling lines and their length is shown, which is due to heteroscedasticity. In order to obtain a homoscedastic model, the other two models are constructed. Based on the regression analysis results, the network is adjusted using three types of weights. The adjustment with traditional weights has produced significantly greater mean errors of the nodal benchmarks than both variants based on weights, which are functions of the absolute values of the line elevations.

On December 5, 2012, American contemporary music lost one of its most important personalities-pianist and composer Dave Brubeck, who died one day before his 92nd birthday. His death marks the passing of one of the most creative and versatile musicians in American history. Widely known as an innovative jazz musician, Brubeck's skills in writing and arranging music for classical ensembles went far beyond jazz traditions, making him a subject of interest and investigation for contemporary music researchers. He became an emblematic figure for those, who, like me, received a classical music upbringing and became fascinated by his ability to fuse jazz and classical sources into the specific style that eventually became his trademark.Despite having received a classical education, I have always been attracted by the jazz sound, so that discovering and demonstrating the plenitude of Brubeck's legacy became a natural research goal in my graduate studies. In planning this personal tribute to the late Dave Brubeck, I came to the conclusion that, perhaps, the most eloquent examples of his unique compositional style could be demonstrated around the story of a little tetrachord. Throughout a period of 17 years (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003), it inspired Brubeck to create five important compositions and came to be known, by those who love Brubeck's music, as the "Jazzanians tetrachord." The compositions varied in form, covering the full spectrum of jazz, classical, and fusion styles. I call these compositions "realizations."Trying to trace Brubeck's realizations chronologically through that 17-year period, I first examined published scores but discovered that there were mysterious gaps. I found Internet performances and obtained recordings that were not related to any of the published scores. For example, watching a DVD of Brubeck's second tour in Russia, I heard a short excerpt of orchestral background music which included the "Jazzanians" theme. I realized this was yet another version of the "Chorale" that I had studied as a published score.

<p>The North American Vertical Datum of 1988 (NAVD88) was established by the minimum-constrain adjustment of geodetic levelling observations in Canada, USA, and Mexico. It held fixed the height of the primary tidal benchmark at Rimouski, Quebec, Canada. The NAVD88 datum was never officially adapted in Canada due its large east-west tilt of 1.5 m from the Atlantic to Pacific coast (Hayden <em>et al.</em><em>,</em> 2012). Also, a large systematic difference (ranging from -20 cm to +130 cm) was found between NAVD88 and the pure geoid gravimetric models. Using Factor Analysis it was discovered that one of the factors, which can explain the tilt of the NAVD88, is the terrain, i.e. small in the flat states but large in the mountainous areas such as in the Rockies and the Appalachians (Li, 2012). A possible reason for the tilt of the NAVD88 might be the weights used into adjustment of the network. In this study the data of two precise national levelling networks are used, e.g. the Second Levelling of Finland and the Third Levelling of Bulgaria, in order to support the above hypothesis. An iterative procedure based on the Inverse Absolute Height Weighting (IAHW) is applied. The core of this procedure is to find this value of the power parameter (p) of the weights w=H<sup>p</sup>, where H is the absolute elevation difference of the terminals in the levelling lines, that minimize the mean of the mean squared errors (MSE) of the nodal bench marks (NBM) in both networks. It has been found that p=1 and p=4.3 for the Bulgarian and the Finnish networks, respectively. Also, a similar iterative procedure based on the Inverse Distance Weighting (IDW) is performed and the best decisions for the Finnish and the Bulgarian networks are obtained. It has been found that the weights w=L<sup>-5.9</sup> and w=L<sup>-1.6</sup>, where L is the length of the levelling line, lead to the minimal MSE of the NBM for the Finnish and the Bulgarian networks, respectively. The results of both the IDW and the IAHW procedures are compared. It has been revealed that the IAHW based adjustments lead to significantly less MSE of the NBM than all variants of the IDW. It has also been shown that concerning the Bulgarian and the Finnish analyzed here data, the IAHD approach leads to physically lower adjusted heights than the IDW. In some cases these differences are more than 1.5-2 times greater than the MSE of the corresponding bench marks.</p>