Zen

Translation

畫地圖的第一步就是決定繪製區域。如同前一章「\ :doc:`making_first_map`\ 」所述，我們可以使用 *Google Map* 等工具決定區域。這裡我們考慮到高度的呈現效果，選擇經度從 -70.8 到 -66.56 (負值表示西經)，緯度從 -17.17 到 -14.42 (負值表示南緯。)
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Chinese (Traditional) English (United States) Actions
Z 值 (高度) 從 -10907 到 8170 公尺。為什麼最高的地方不是 8848 公尺 (聖母峰的高度)? 那是因為網格的解析度還是不夠高，1 弧分其實只相當於 1 至 2 公里才取一個點而已。
Z value (height) is from -10907 to 8170 meters. The reason why the highest point is not 8848 m (the elevation of Mt. Everest) is that the resolution of this grid file is not high enough. A 1-arc-minute spacing means we only take one height measurement every 1-2 km.
操作流程
Procedure
從本章開始，我們需要使用兩個以上的 GMT 指令製作地圖。在上一章介紹過的 ``coast`` 用來畫向量式資料 (河流、湖泊以及國界)，而在本章中新介紹的 ``grdimage`` 則用來畫地形起伏。因為上一章介紹的 ``-png`` 選項只適用於單一指令，所以在本章我們要用另一種更通用的方式指定輸出檔。具體做法是使用 ``gmt begin`` 和 ``gmt end`` 這兩個關鍵字串把其他所有繪圖指令包起來，像這樣：
Starting from this chapter, we will need more than one GMT command to make a map. ``coast`` (introduced in the previous chapter) is for plotting vector data (rivers, lakes, and country borders), and ``grdimage`` (introduced in this chapter) is for plotting topography. In the previous chapter, we introduced the ``-png`` option, but this way is only for single-command mapping. Thus, we will use a more general method to specify the output file in this chapter. It is the use of ``gmt begin`` and ``gmt end`` to wrap all the other plotting commands, like this:
$ gmt begin [輸出地圖主檔名，不用加附檔名] [格式] # 輸入後按下 enter
$ [繪圖指令1] # 輸入後按下 enter
$ [繪圖指令2] # 輸入後按下 enter
...
$ gmt end
$ gmt begin [map name without file extension] [format] # when the command is entered, press enter
$ [plotting command 1] # when the command is entered, press enter
$ [plotting command 2] # when the command is entered, press enter
...
$ gmt end
你可以一行一行的在命令列中打好指令再送出執行，不過為了修改方便，我們通常會選擇把所有的指令先寫在\ :ref:`腳本 <腳本>`\ 內，再執行此腳本以一次送出所有指令給電腦。在本章中，我們就要來介紹這種更爲便捷的方式。
You can enter these commands line by line and run them separately, but for the convenience of editing, we usually choose to write everything down in a text :ref:`Script`. When you run this script, you send all commands to the computer at once. We will introduce this way by showing how to write a script in this chapter.
畫地圖的第一步就是決定繪製區域。如同前一章「\ :doc:`making_first_map`\ 」所述，我們可以使用 *Google Map* 等工具決定區域。這裡我們考慮到高度的呈現效果，選擇經度從 -70.8 到 -66.56 (負值表示西經)，緯度從 -17.17 到 -14.42 (負值表示南緯。)
Once we get the global topography data, the next step would be deciding where on the Earth we want to plot (that is, map extent). Like we said in the previous chapter :doc:`making_first_map`, we can use tools like *Google Maps* to determine the region. Here we choose longitude from -70.8 to -66.56 (negative number means W) and latitude from -17.17 to -14.42 (negative number means S), based on the distribution of elevations.
本次作圖區域在 `Google Map` 上呈現的樣子。
The map extent viewed on `Google Maps`.
使用 ``grdimage`` 呈現地形數據，最少需要提供兩個參數，分別是 ``輸入檔`` 和 ``-J`` (投影方法和地圖大小)。在這裡我們也需要使用 ``-R`` 指定繪製區域，如果不加 ``-R`` 的話，GMT 會把全網格檔的資料話在地圖上 (因爲我們使用的是全球地形資料，所以輸出會是全球地圖)。就讓我們來畫一張跟\ `前一章 <making_first_map.html>`_\ 一樣寬度的地圖吧。請建立新文字檔，檔名可以為 ``titicaca.bash`` 或任何你喜歡、且符合作業系統格式慣例的名字。然後在檔案中輸入：
To use ``grdimage`` to plot topography, we need at least two arguments, which are ``input file`` and ``-J`` (projection and map size). We also need ``-R`` (map extent) here since GMT would plot all the gridded data on the map without an ``-R`` setting. (This would be a global map in our case because we are using a global topography dataset.) Let’s make a map with the same size from the map in the `previous chapter <making_first_map.html>`_. Please create a new text file, entitled ``titicaca.bash`` or whatever you like (it’s still better to fit your system format convention). Enter the following lines:
gmt begin titicaca png
gmt grdimage @earth_relief_01m -R-70.8/-17.17/-66.56/-14.42r -JM6i
gmt end
gmt begin titicaca png
gmt grdimage @earth_relief_01m -R-70.8/-17.17/-66.56/-14.42r -JM6i
gmt end
你會注意到我們在 ``gmt grdimage`` 前面多加了四個空格，這純粹只是製造縮排效果，讓閱讀腳本的人知道這行被包在 ``gmt begin`` 和 ``gmt end`` 之間，增加腳本的可讀性。縮排與否和空格數量不會影響腳本的執行。如需 ``-R`` 與 ``-J`` 選項的語法說明，請至「\ :doc:`making_first_map`\ 」中查閱。存檔後，在\ :ref:`終端機`\ 模式下前往 ``titicaca.bash`` 所在的資料夾，然後執行腳本 (以 Linux 系統爲例)：
You may notice that we added four spaces before the ``gmt grdimage`` command. This makes an indentation and lets the readers know that this line is between ``gmt begin`` and ``gmt end`` for readability. The indentation does not affect the script at all. For more information about ``-R`` and ``-J`` options, please go to :doc:`making_first_map`. Save you file, and in the :ref:`Terminal` mode, go to the folder where ``titicaca.bash`` is located and run the script. For example, type this in Linux:
$ bash titicaca.bash
$ bash titicaca.bash

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String updated in the repository

  1. GMT Tutorials
  2. coloring topography
  3. English (United States)
畫地圖的第一步就是決定繪製區域。如同前一章「\ :doc:`making_first_map`\ 」所述，我們可以使用 *Google Map* 等工具決定區域。這裡我們考慮到高度的呈現效果，選擇經度從 -70.8 到 -66.56 (負值表示西經)，緯度從 -17.17 到 -14.42 (負值表示南緯。)
Once we get the global topography data, the next step would be deciding where on the Earth we want to plot (that is, map extent). Like we said in the previous chapter :doc:`making_first_map`, we can use tools like *Google Maps* to determine the region. Here we choose longitude from -70.8 to -66.56 (negative number means W) and latitude from -17.17 to -14.42 (negative number means S), based on the distribution of elevations.
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Source string location
../../SOURCE_DOCS/coloring_topography.rst:102
String age
a year ago
Last updated
a year ago
Source string age
3 years ago
Translation file
docs/locale/en_US/LC_MESSAGES/main/coloring_topography.po, string 30