北上南下

There is another problem with longitude, other than methods to calculate it, namely that a zero needs to be set arbitrarily. At first, as is to be expected, several different places were chosen as the zero such as Paris, Cadiz, Naples, Pulkova, Stockholm and London. International agreement was needed to set cartographic standards and the International Meridian Conference held in Washington D.C. USA in 1884 had delegates from 26 countries. They standardised the Greenwich Meridian as the zero for longitude and, after some delay, all countries adopted this and the equator as the basic reference lines.

There is, of course, another decision to be taken in order to standardise maps, namely how the map is oriented. It is fairly logical to have either north or south at the top, but which is chosen is a completely arbitrary decision. Early Christian maps had north at the top while early Arabic/Muslim maps had south at the top. Without any international agreement, it has become standard practice to have north at the top of a map. Other collaborative international projects have been less successful. In 1891 there was an International Geographical Congress in Bern which established the International Map of the World. Standards were set and a symbol convention was chosen. The scale was to be 1:1000000 and several nations agreed to cooperate to produce a world map to this standard. Some, but not all, of the proposed maps have been produced but the project has never been completed.

有趣的是河童也有這樣的嘗試，把地圖倒過來看。所有的視覺習慣收到挑戰的時候，有趣就產生了。找到一条規則，打破，重建。聽上去像是地震。

在練習河童的房間俯視圖後，還可嘗試把自己的房間倒過來畫。