gps

學習編輯是繪製地圖的重要部份 – 那就是如何增加資訊到實際的地圖上。其他的工作則是收集資訊本身 – 沒錯，就是外出與探勘一塊區域。在這個手冊裡我們將學習幾種不同的實地探勘方式。

在這個章節中我們將瞭解 GPS 能作些什麼與如何工作。你將學到如何操作 GPS ，與如何用它建立地圖。

這裡我們將解釋如何使用 Garmin 的 eTrex Vista HCx ，一個常見的、可以用來繪製地圖的 GPS。有許多其他型號的 GPS 可以作到相同的事情，所以不要擔心你使用不同的 GPS，原理是一樣的

什麼是 GPS?

GPS 就像隻手機，不同的是，它不是從電信業者接收無線信號，而是從正繞著地球的衛星上接收信號。透過來自衛星的信號，GPS 能計算出你在地球上的具體位置。它是一個在座標系統裡的兩個數字。第一個數字是告訴你離東或西有多遠 – 它被稱作經度（longitude）。第二個數字則是表示你離北或南有多遠 – 它被叫做緯度（latitude）。在地球上的每個地方都有唯一的地理座標。

例如：南緯 -8.639298, 東經 116.311607 是印尼的龍目(Lombok)

打開 GPS

在你打開GPS之前，請先確認你是在戶外可以看到清楚的天空處。因為GPS是經由接受衛星的訊號來決定你的所在位置。所以它在室內開啟是無法運作的。

持續按住位於GPS右邊的電源鈕，GPS 將會啟動，並顯示衛星頁。你應該可以看到一些類似下面圖片的畫面。你的GPS正尋找衛星信號直到連接到3顆或更多的衛星後，就可以得到你的位置。

一旦你的位置被計算出來，這個衛星畫面將會消失，接著你會看到主要的功能頁面。

操作 GPS

  • 這個 GPS 有許多不同的畫面與功能讓你能去處理不同的工作。按下位於裝置右邊電源鍵的上方的「X」按鈕就可以切換畫面。這個按鈕也代表返回，假如你按錯想取消，或是想返回就按「X」鈕吧。

  • 按下「X」鈕，你應該就能在不同畫面之間切換，就像這樣：

  • 如果你回到衛星頁，你會發現你已經連結到三顆以上的衛星。在左上方是你所在的座標，包含經度與緯度。

路徑（Track）與航點（Waypoint）

如果你已經把OSM加入你的GPS，這時翻到 地圖（map）頁，你可以看到地圖上你在哪，也許可以看到道路與地點等，或是看起來非常乾淨。縮放地圖可以透過位於裝置左邊的上下鈕。

如果你的GPS沒有從001開始計算，而你想要清除之前的航點，可以前往主選單的「Find」圖示。 點擊「waypoints」，接著右邊的子選單按鈕會顯示航點的子選單。往下卷，看到「Delete」以後，點擊「all symbols」與「Yes」。

當你存了一個點，你可以在紙上寫下數字，以及記下這個點是什麼，以及任何你會想要知道的屬性與指標。在你的 GPS 上，存好的地點稱為航點（waypoint）。

第二，你的 GPS 還能儲存稱為路徑（track）的東西。航點只存一個單一的地點，一個路徑會存下一系列你移動的地點。舉例來說，路徑會每秒記錄一次你的地點，或每移動一公尺就記錄一個點，結果就是可以顯示你移動路徑的一系列點。路徑在繪製線或是面的時候很好用，如路的走向，或是一塊區域的形狀。

Save Your Location

  • To save your current location as a waypoint, click the “X” button

    until your reach the Main Menu. Using the joystick, move it so that

    “Mark” is highlighted on the screen. Push the joystick button down

    to open the “Save Waypoint” page.

  • You can see on this page some information about the waypoint that

    you are saving. First is the name. If this is your first waypoint,

    it probably reads “001”. This is the number you should record on

    paper along with the information you want to collect with this

    object. Next you will see the time and date when the point is

    recorded. Below that are the coordinates, followed by the altitude.

  • Use the joystick to move to the “OK” button at the bottom of the

    screen. Press the joystick button down to save this point. Be sure

    to write down the number of the point, along with what the place is

    and any other information you want to record about the place in your

    notebook.

  • Press the “X” button to go to the map page. You should now see your

    point on the map.

Turn on the Track Log

  • Now that we have learned how to save points, let’s learn how to turn

    the track log on and off. When the track log is turned on, it will

    automatically record your path. It’s good practice to turn on the

    log when you begin mapping, and turn it off when you are finished.

    You will then be able to look at the track on a computer and see the

    path that you mapped. If you would like to map the course of a road,

    it is a good idea to save a waypoint at the beginning and end of the

    road, writing in your notebook the name and type of the road, and

    any other important information about the road.

  • To turn on the track log, click the “X” button until your reach the

    page that says Track Log.

  • If you would like to empty the track log to delete earlier

    recordings, use the joystick to select “Clear”, and press the

    joystick down. The bar at the top should read “0%”.

  • To turn on the log, move the joystick to highlight “On”, and press

    the joystick down. The track log is now recording your path.

  • Under the “Set up” option, you also can set time or distance intervals

    to track. Time intervals instruct your GPS to record your location at

    given intervals. If you have a memory card in your GPS, it is good

    practice to set this to 1 second, meaning that every second your location

    will be added to the track log. This may be useful when detailed surveys

    are needed.

  • Press the “X” button to go to the map page. As you move you will see

    your track shown as a series of dots.

Copy Waypoints and Tracks to the Computer

When you are finished mapping with the GPS you will want to copy the points and tracks to your computer so that you can open them in JOSM.

One way to copy the waypoints and tracks is to you use the free software that Garmin provides, called BaseCamp. It can be downloaded here. However, in this section we will use a program called GPSBabel, which offers a few additional features.

Attach GPS to the Computer

  • First, turn off the track log on your GPS, by going to the

    track page and selecting “Off”.

  • Attach the GPS to your computer with the cable. One end should plug

    into your computer’s USB port, and the other goes into the back of

    the GPS, beneath the rubber flap at the top. The GPS should be

    turned on to copy the points and tracks.

Install GPS Drivers

  • You may need to install GPS drivers on your computer. You can download

    the drivers at the Garmin Website.

  • Click “Download” to get the installation file. Locate it on your

    computer, and double-click to install.

  • If you are unable to download from the Garmin site, you may also

    download the drivers here.

Linux systems (at least Fedora) do not need special drivers to communicate with a Garmin device (at least the eTrex Vista HCx). Just make sure that your Garmin is powered and plug it into your compure with a USB cable. You can use GPSBabel (as instructed below) or GpsPrune to grab the saved data from your device.

Get the GPSBabel Setup Program

  • GPSBabel is a program that allows us to copy data from the GPS. If you

    have a copy of GPSBabel on a CD or usb flash drive, you can skip to

    the next section.

  • If you don’t have GPSbabel already, open your web browser

    and go to www.gpsbabel.org

  • Click “Downloads” at the top of the page.

  • Scroll down the page. If your computer uses Windows, you want to

    download the installation file for Windows. Click “GPSBabel-1.5.2-Setup.exe”.

    The file will be downloaded to your computer.

Install GPSBabel

  • Locate the GPSBabel setup file on your computer. Double-click it to install.

  • Click “Next”.

  • Click “I accept” and “Next”.

  • Continue clicking “Next” until the program installs.

  • When the program has finished installing, click “Finish” to start GPSBabel.

Copy Tracks and Waypoints

  • Click in the circle next to the word “Device” at the top of the

    window.

  • In the dropdown menu labelled “Format”, select “Garmin serial/USB

    protocol”

  • Go down to the middle of the window, under Output. In the dropdown

    menu labelled “Format”, select “GPX XML”:

  • Click “File Name” and type a name for your saved file. It should be

    something that describes the data, such as the date and the

    location. For example, jakarta-07-07-2011

  • Make sure your GPS is connected to the computer and turned on.

  • Click “Apply” in the bottom right corner of the window.

  • If all goes well you should see a bar move across the screen,

    indicating that the data is being retrieved from the GPS. When it is

    finished, your points and track will be saved in the file that you

    selected.

Open in JOSM

  • Now open JOSM. On the top menu, click “File” and then click “Open…”

  • Find and select the file that you created with GPSBabel. Click “Open”.

  • You should now see your points and tracks loaded into JOSM.

Summary

Congratulations! You should now have an understanding of how to use the GPS. If you haven’t already, practice saving points of some important locations.

In this section we learned how to collect points and tracks and open them in JOSM. Later, we will use this information to add new places to OpenStreetMap.

The next chapter is about a different survey method, known as Field Papers. These allow you to make maps without the need for a GPS!

Moving Forward

Click on the link for further reading on:

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