缓解时间的流逝

In the 17th century, vessels were not built from plans or drawings but from “rule of thumb”, based on a shipwright’s instincts and his sea experience. The builder of the warship Vasa poorly estimated its proportions. The underwater section of the vessel was far too small for the visible part above the waterline, making the ship completely unstable. On the day of its maiden voyage in 1628, the Vasa was loaded to full capacity. 64 bronze cannons were proudly displayed with all gun port windows open. As the Vasa left the harbour and its sails filled with wind, the boat rolled dangerously to one side and was swiftly filled with water coming in from all the open gun port windows.

Although the ship sat in less than 40 metres (131 feet) 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（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在不少于29个棱镜点上。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，以确定变形发生的速度。

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.

由于最近15年的监视，将开发一个新的VASA支持系统。超过600万瑞典krona（690,000美元 / 650,000欧元）已用于研究用途，并将研究木材质量和船舶结构如何随着时间的流逝而发生变化。研究将持续到2016年，此后将建立设计新的工作结构的基础，并且可以开始进行船舶存储块的实际结构。

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