缓解时间的流逝

在17世纪，船只不是根据计划或图纸来建造的，而是基于船赖特的直觉和他的海洋经历的“经验法则”。军舰瓦萨的建造者估计其比例很差。该船的水下部分太小了，无法在水线上方的可见部分，使船完全不稳定。在1628年的首次航行之日，VASA被装满了。64座青铜大炮被自豪地展示，所有枪口窗户都打开了。当瓦萨（Vasa）离开港口及其帆充满风时，​​船危险地向一侧滚动，并迅速将所有开放式枪口窗户的水填满。

虽然这艘船坐在不到40米(131feet) of water, it remained to a large degree unscathed in Stockholm’s sheltered harbour until 1961. Now 333 years after sinking, the Vasa is an almost untouched piece of 17th century Swedish history that has returned to the surface. Before being moved to the museum where it now rests, the Vasa was stored in a harbour shipyard with little protection to elements. It was coated with PEG, a chemical compound that replaced the water in the wood, and helped to prevent shrinkage and cracking of the 300 year old timber. The first visible signs of change were seen in the 1990’s when white spots appeared on the surface of the wood caused by sulphur and iron used to build the ship.

这些可见的迹象最终导致研究人员专注于表面下方发生的变化，并于2000年开始对船舶进行第一次监测。当时，确定监视该船的最佳设备是Leica TDA5005。收集的数据证明，即使使用PEG处理，该船的结构也会因重力而严重改变。该船的300年历史的木结构已经损失了其机械强度的40％以上（在某些部位，甚至多达80％）。绝对有必要收集精确的数据，以决定如何停止变形并最好地保护这只历史悠久的船只。

The correct support for the structure
Today the Vasa sits on standard storage blocks in a museum that was specifically built for the ship. These common storage blocks date back to the 1960’s and do not provide proper support for the boat. Research shows a new storage system desperately needs to be built in order to properly support this fragile historic ship. However, in order for carpenters to build the correct support structure, huge amounts of accurate data need to be collected and analysed to determine exactly how the wood and the ship’s structure have chemically and mechanically changed over the course of time. A Leica Nova TS50 using Leica Smart-Worx Viva software was chosen to collect the data to make a prototype, which can be designed, tested and put to use.

监视
监视the Vasa takes place twice a year. Each surveying epoch takes roughly ten working days to accomplish, depending on the how many visitors are at the museum. Measurements are made by museum staff and the Department of Geodesy and Satellite Positioning at Kungliga Tekniska Högskolan.

为了绝对精确地从VASA收集数据，博物馆的静态墙壁附有不少于29个棱镜点。这些用作参考点，以获得Leica Nova TS50的确切位置。一旦计算出这些，操作员将测量已连接到船内部凸起的船体内部的33个棱镜，并在VASA外部的大约330个定制反射磁带，以收集有关船舶结构变形的信息。为了确保正确执行数据收集，从不同的设置位置进行了第二个测量过程。该过程一次又一次地完成，以确定变形的发生速度。

After each epoch, the data is processed and compared to earlier monitoring epochs done on the ship. The results prove that the ship has been tilted and pulled down by gravity over the course of time.

As a result of the last 15 years of monitoring, a new support system for Vasa will be developed. Over six million Swedish Krona (690,000 USD / 650,000 EUR) has been appropriated for research use and will include a study of how the quality of the wood and the structure of the ship have changed over the course of time. Research will last until 2016, after which a basis for designing a new working structure will be in place and the actual construction of the ship’s storage block can begin.

Aside from helping with the design of a new supporting storage block for Vasa, the measurement data collected using the Leica Nova TS50 will certainly help determine the extend and speed of the ravages of time on the Swedish vessel and will enable researchers to better predict future changes in the wood, which is of great importance to the future of the Vasa.

Written by Rikard Evertsson and Mattias Bornholm