先舉例 First, an example:
台灣在地球上的正對面為巴拉圭 Taiwan is on the exact opposite side of the world from Paraguay:
(圖內黑區被反轉與倒置 In this map the black parts have been flipped and mirrored. (用的軟體 Software used.))
對蹠點（相對極）為地球上離你最遠的地方， 如台灣與巴拉圭， 或西班牙與紐西蘭等等 Your antipode is The farthest place in the world from you, e.g. Taiwan vs. Paraguay, NZ vs. Spain, Hawaii vs. Botswana, etc. Confluence project's antipodes.
圖 Image:世界各地之對蹠點 World antipodes, though centered on Taiwan, each point is overlayed on its antipode for the whole world. 雖以台灣為中心， 但全球各點均套繪於其對蹠點上。 (用的軟體 Software used.)
圖 Image:台灣套上巴拉圭、阿根廷國界 Taiwan/Paraguay, Argentina boundary overlay closeup : 台北人挖洞會挖到阿根廷， 而中、南部人則巴拉圭。 Dig straight down from Taipei and you'll hit Argentina (indeed, 竟然亦名為 Formosa 省 Province, same as Taiwan's old name.); if you go a little south first then start your digging, you'll hit 巴拉圭 Paraguay. (用的軟體 Software used.)
下次台灣高層去拜訪巴拉圭， 建議可手拿著ＧＰＳ衛星定位儀， 帶著媒體去找埔里台灣地理中心碑之對蹠點！ Next time high officials of Taiwan visit Paraguay, they could consider using a hand held GPS satellite navigation unit, and inviting the media along to track down the antipode of the Geographical Center of Taiwan monument (of Puli, Taiwan).
計算您對蹠點極為容易： 只不過是經度轉一八○度， 緯度的南北互換。 Computing your antipode is so simple. Just rotate your longitude 180 degrees and flip your latitude's north vs. south. Example:
Taiwan: 121 E, 24 N becomes 59 W, 24 S. For longitude one flips E and W, and can use the absolute value of (180 - current_longitude). For latitude one merely flips N and S.
Degree Confluence Project, BoundaryPoint, BoundaryPoint via Gmane, and the geocaching folks go through great lengths to find what they are after, but how about finding one's antipode -- quite easy with GPS -- and say, take a picture? I don't think anybody has done that yet. Most folks have mere boring sea antipodes, however there is still hope for those in S.E. Asia, S. America, Spain, New Zealand, etc.
半球及大圓（Hemispheres and great circles）
等距環（Equidistant small circles）以知各地距離 to get an idea of how far places are.
Let's assume you are in North America. You want to urge the students to understand antipodes. You rest the globe upon North America, the top now is the Indian Ocean. However in the Indian Ocean there are a few islands. OK, we are to find where their antipodes are: where lines drawn through the Earth's center connect them to North America... Do the students understand that just a spin and a flip is all that is needed to transform the coordinates... (as mentioned above)?
Then say we manage to get a topographic map of one of these islands. Now we can organize a field trip to the exact spot of say the antipode of the town hall of that island. Do the students realize that just reading the coordinates of any old topographic map has datum connotations? Sure we just follow our GPS to the exact antipode, however I bet that that map wasn't made with the WGS84 datum. If we don't get the datums straight, we could still be off by kilometers, after traveling so far!
Anyways last I checked, the antipode of one of those island was near San Francisco... not bad (because there are just a few islands, how lucky for an antipode to fall near a major population center)...
If you have no land antipode, you can still find the farthest piece of land from you. Just find the nearest point of land from your antipode.
Programs I used to make the images above. Displays antipodes with the center of the image at coordinates given by the user. Worked on GNU/Linux at least.
Find two cities that are antipodes: Maybe someone could overlay two GIS population layers in the fashion of my world map above, and find where the added values exceed that for one layer, thus finding two cities overlapping. thus antipodes. It seems they must be in South America and S.E. Asia.
How about elevation considerations. Perhaps of all the land/land antipodes, the pair with the most similar elevations could be considered more "perfect"? Wait, how about the pair with the highest combined elevations? Remember that we are talking about most distant pairs, and elevation increases distance. Of course polar flattening must then be considered.
請攝影 Please find and photograph confluences, 及逐對 and these pairs,
|台灣地理中心碑 Center of Taiwan Monument||巴拉圭 Paraguay|
|台灣總統府 Taiwan Presidential Palace||阿根廷 Formosa Province, Argentina|
Last modified: 2013-03-16 22:21:46 +0800