Geoid and Lot Deviation Date 17.2.2009

Geoid: The geoid is defined by an area with constant gravity potential, which best corresponds to the mean sea level and the conceived continuation in the continental area. The mean sea level is determined by level observations (e.g. Amsterdam, Trieste). Geoidundulations: The distance of the geoid surface to a reference ellipsoid is called geoidundulation N. For Austria, the geoidundulations N were calculated in relation to the international ellipsoid GRS80 (reference system ETRS89) and the Bessel ellipsoid (reference system MGI): NGRS80 and NBessel Austrian geoid map: The Austrian geoid map shows in isoline representation the geoidundulations on the Austrian territory in two different representations: (a) Austrian Geoid Map GRS80: The geoidundulations NGRS80 show the distances of the geoide above the international ellipsoid model GRS80 (reference system ETRS89) in a range between ~42 m in the northeast and ~53 m in the Ötztal Alps. (B) Austrian Geoid Card MGI: The geoidundulations NBessel show the distances of the geoide above the Bessel ellipsoid (reference system MGI). The range of values lies between ~-2 m in the western Innviertel and ~ + 3.5 m in the Ötztal Alps or in East Tyrol. Solder deviation: The solder deviation is the angle between a geometrically defined ellipsoid normal and the physically defined solder direction at a point. It describes the direction of the heavy vector, shown in a north/south and an east/west component. For the entire territory of Austria, solder deviations – more precisely, surface lottering deviations – can be calculated and released in relation to the Bessel ellipsoid in the reference system MGI. Reference date = creation date: The data for this day are the most up-to-date database of the BEV. This is not identical with the recording or survey date.大地水准面（geoid）： 大地水准面由重力势能恒定的区域所定义，其与平均海平面及大陆区域内的假想延续体最为契合。平均海平面通过水准观测确定（例如阿姆斯特丹、的里雅斯特观测站）。 大地水准面起伏（geoidundulations）： 大地水准面相对于参考椭球体的距离被称为大地水准面起伏值N。针对奥地利地区，已分别以国际椭球体GRS80（参考系统ETRS89）与贝塞尔椭球体（参考系统MGI）为基准计算得到大地水准面起伏值N，分别记为N_GRS80与N_Bessel。 奥地利大地水准面图集： 本图集以等值线形式呈现奥地利境内两种不同基准下的大地水准面起伏值： (a) GRS80版奥地利大地水准面图集： 大地水准面起伏值N_GRS80表示大地水准面相对于国际椭球体模型GRS80（参考系统ETRS89）的高度差，数值范围为东北部约42米，奥茨塔尔阿尔卑斯山区约53米。 (b) MGI版奥地利大地水准面图集： 大地水准面起伏值N_Bessel表示大地水准面相对于贝塞尔椭球体（参考系统MGI）的高度差，数值范围为因河谷西部地区约-2米，奥茨塔尔阿尔卑斯山区或东蒂罗尔地区约+3.5米。 垂线偏差（plumb line deviation，原文疑似笔误为solder deviation）： 垂线偏差指某点上几何定义的椭球法线与物理定义的铅垂线方向之间的夹角，其描述了重力矢量的方向，可分解为南北向与东西向两个分量。 针对奥地利全境，可基于参考系统MGI下的贝塞尔椭球体计算并发布垂线偏差——更确切地说，为地表垂线偏差分量（原文疑似笔误为surface lottering deviations）。 参考日期=生成日期： 当日对应的数据集为BEV的最新数据库，该日期与数据的记录或勘测日期并不一致。