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<H1>
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== GIS入門 ==
GIS入門
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<span id='label_intro'></span>
</H1>
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<P>
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地理情報システム (GIS){{Template:Cite|num=1|ref=mitchel05}}<ref>This chapter is by Tyler
地理情報システム (GIS)[#!mitchel05!#]<A NAME="tex2html1"
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Mitchell ({{Template:URL|http://www.oreillynet.com/pub/wlg/7053}}</ref>とは空間データを作成、
  HREF="footnode.html#foot16"><SUP><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]"
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SRC="/usr/share/latex2html/icons/footnote.png"></SUP></A>とは空間データを作成、
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表示、検索、解析するためのソフトウェアのことです。空間データはある要素の空間位置
 
表示、検索、解析するためのソフトウェアのことです。空間データはある要素の空間位置
 
に関する情報を持っています。これは緯度、経度のような空間座標を使用することを
 
に関する情報を持っています。これは緯度、経度のような空間座標を使用することを
 
意味します。空間データは同じ意味で別の言い方がいくつかあります。地理データ、
 
意味します。空間データは同じ意味で別の言い方がいくつかあります。地理データ、
GISデータ、地図データ、位置データ、座標データ、地理空間データなどです。  
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GISデータ、地図データ、位置データ、座標データ、地理空間データなどです。
  
<P>
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空間データを利用するアプリケーションには様々な機能があります。地図作成機能が
Applications using geospatial data perform a variety of functions. Map
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空間データ利用に最もわかりやすい仕事でしょう。地図プログラムは空間データに
production is the most easily understood function of geospatial
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アクセスしてそれを描画して可視化します。通常はコンピュータの画面や紙を利用して
applications. Mapping programs take geospatial data and render it in a form
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地図を表示します。
that is viewable, usually on a computer screen or printed page.
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アプリケーションでは静的な地図(単純なイメージ)かダイナミックに表示を変えられる
Applications can present static maps (a simple image) or dynamic maps that
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地図を表示します。ダイナミックな地図はデスクトッププログラムかWebページを使って
are customised by the person viewing the map through a desktop program or a
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地図のみかけを変えることができます。
web page.
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<P>
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多くの人たちは空間情報アプリケーションの機能は地図を作成するだけだと誤解
Many people mistakenly assume that geospatial applications just produce
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しています。しかし空間データ解析は空間情報アプリケーションの別の重要な
maps, but geospatial data analysis is another primary function of
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機能です。いくつかの典型的な解析処理はコンピュータの計算処理を含んでいます。
geospatial applications. Some typical types of analysis include computing:
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<P>
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<ol>
 +
<li>位置間の距離計算
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<li>ある領域内の面積集計 (たとえば平方メートル)
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<li>どの地物が他の地物と重なりあっているかの判定
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<li>地物間の重なり部分の集計
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<li>ある位置から指定した距離内にある地物の数
 +
<li>というように...
 +
</ol>
  
<OL>
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これらのことは単純なことのように見えるかもしれません。しかしこれらの機能は
<LI>distances between geographic locations
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いろいろな方法で多くの分野に適用できます。分析の結果を地図上に表示することは
</LI>
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経営の意思決定をサポートするレポートとして頻繁に使われます。
<LI>the amount of area (e.g., square meters) within a certain geographic
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region
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</LI>
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<LI>what geographic features overlap other features
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</LI>
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<LI>the amount of overlap between features
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</LI>
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<LI>the number of locations within a certain distance of another
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</LI>
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<LI>and so on...
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</LI>
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</OL>
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<P>
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最近の位置情報サービスでは多くの機能を紹介しています。それらの機能の
These may seem simplistic, but can be applied in all sorts of ways across
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多くは地図と解析処理の組み合わせで構成されています。たとえば携帯電話であなたの
many disciplines. The results of analysis may be shown on a map, but are
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位置を記録できます。あなたが適切なソフトウェアを持っていれば歩いていける距離に
often tabulated into a report to support management decisions.
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あるレストランを携帯電話で探せます。これは空間情報テクノロジーのを使った新しい
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アプリケーションです。この機能のためには空間データを解析して結果を一覧にする
 +
ことが必要です。
  
<P>
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=== どうして新しいのか? ===
The recent phenomena of location-based services promises to introduce all
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<span id='label_whynew'></span>
sorts of other features, but many will be based on a combination of maps
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and analysis. For example, you have a cell phone that tracks your
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geographic location. If you have the right software, your phone can tell
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you what kind of restaurants are within walking distance. While this is a
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novel application of geospatial technology, it is essentially doing
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geospatial data analysis and listing the results for you.
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<P>
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それはないですが。モバイル空間情報サービスを実現するための新しいハードウェア
<BR><HR>
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デバイスがたくさんあります。多くのオープンソース空間情報アプリケーションも
<H2>
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あります。しかし空間情報のためのハードウェアもソフトウェアも新しいものでは
Why is all this so new?
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ありません。 Global positioning system (GPS) receivers are
</H2>
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<P>
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Well, it's not. There are many new hardware devices that are enabling
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mobile geospatial services. Many open source geospatial applications are
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also available, but the existence of geospatially focused hardware and
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software is nothing new. Global positioning system (GPS) receivers are
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becoming commonplace, but have been used in various industries for more
 
becoming commonplace, but have been used in various industries for more
 
than a decade. Likewise, desktop mapping and analysis tools have also been
 
than a decade. Likewise, desktop mapping and analysis tools have also been
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resource management.
 
resource management.
  
<P>
 
 
What is new is how the latest hardware and software is being applied and
 
What is new is how the latest hardware and software is being applied and
 
who is applying it. Traditional users of mapping and analysis tools were
 
who is applying it. Traditional users of mapping and analysis tools were
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technology saturation has increased.
 
technology saturation has increased.
  
<P>
 
 
How is geospatial data stored? In a nutshell, there are two types of
 
How is geospatial data stored? In a nutshell, there are two types of
 
geospatial data in widespread use today. This is in addition to
 
geospatial data in widespread use today. This is in addition to
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applications.
 
applications.
  
<P>
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==== Raster Data ====
<BR><HR>
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<span id='label_rasterdata'></span>
<H3>
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Raster Data
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</H3>
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<P>
 
 
One type of geospatial data is called raster data or simply "a raster". The
 
One type of geospatial data is called raster data or simply "a raster". The
 
most easily recognised form of raster data is digital satellite imagery or
 
most easily recognised form of raster data is digital satellite imagery or
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represented as raster data, but there are limitations.
 
represented as raster data, but there are limitations.
  
<P>
 
 
A raster is a regular grid made up of cells, or in the case of imagery,
 
A raster is a regular grid made up of cells, or in the case of imagery,
 
pixels. They have a fixed number of rows and columns. Each cell has a
 
pixels. They have a fixed number of rows and columns. Each cell has a
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size).
 
size).
  
<P>
 
 
Multiple overlapping rasters are used to represent images using more than
 
Multiple overlapping rasters are used to represent images using more than
 
one colour value (i.e. one raster for each set of red, green and blue
 
one colour value (i.e. one raster for each set of red, green and blue
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for storage purposes and cell size for analytical or mapping purposes.
 
for storage purposes and cell size for analytical or mapping purposes.
  
<P>
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==== Vector Data ====
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<span id='label_vectordata'></span>
  
<H3>
 
Vector Data
 
</H3>
 
 
<P>
 
 
Vector data is also used in geospatial applications. If you stayed awake
 
Vector data is also used in geospatial applications. If you stayed awake
 
during trigonometry and coordinate geometry classes, you will already be
 
during trigonometry and coordinate geometry classes, you will already be
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values.
 
values.
  
<P>
 
 
This can be thought of in reference to a Cartesian plane - you know, the
 
This can be thought of in reference to a Cartesian plane - you know, the
 
diagrams from school that showed an x and y-axis. You might have used them
 
diagrams from school that showed an x and y-axis. You might have used them
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mapping.
 
mapping.
  
<P>
 
 
There are various ways of representing these geographic coordinates
 
There are various ways of representing these geographic coordinates
 
depending on your purpose. This is a whole area of study for another day -
 
depending on your purpose. This is a whole area of study for another day -
 
map projections.
 
map projections.
  
<P>
 
 
Vector data takes on three forms, each progressively more complex and
 
Vector data takes on three forms, each progressively more complex and
 
building on the former.   
 
building on the former.   
  
<P>
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<ol>
 
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<li>Points - A single coordinate (x y) represents a discrete geographic
<OL>
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<LI>Points - A single coordinate (x y) represents a discrete geographic
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location
 
location
</LI>
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<li>Lines - Multiple coordinates (x1 y1, x2 y2, x3 y4, ... xn yn) strung
<LI>Lines - Multiple coordinates (x1 y1, x2 y2, x3 y4, ... xn yn) strung
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together in a certain order, like drawing a line from Point (x1 y1) to
 
together in a certain order, like drawing a line from Point (x1 y1) to
 
Point (x2 y2) and so on. These parts between each point are considered line
 
Point (x2 y2) and so on. These parts between each point are considered line
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coordinates connected together, whereas a line string is multiple lines
 
coordinates connected together, whereas a line string is multiple lines
 
connected together.   
 
connected together.   
</LI>
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<li>Polygons - When lines are strung together by more
<LI>Polygons - When lines are strung together by more
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than two points, with the last point being at the same location as the
 
than two points, with the last point being at the same location as the
 
first, we call this a polygon. A triangle, circle, rectangle, etc. are all
 
first, we call this a polygon. A triangle, circle, rectangle, etc. are all
 
polygons. The key feature of polygons is that there is a fixed area within them.   
 
polygons. The key feature of polygons is that there is a fixed area within them.   
</LI>
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</ol>
</OL>
+
 
 +
 
 +
----
 +
<references />

2009年10月4日 (日) 14:17時点における最新版

GIS入門

地理情報システム (GIS)[1]<ref>This chapter is by Tyler Mitchell (http://www.oreillynet.com/pub/wlg/7053 </ref>とは空間データを作成、 表示、検索、解析するためのソフトウェアのことです。空間データはある要素の空間位置 に関する情報を持っています。これは緯度、経度のような空間座標を使用することを 意味します。空間データは同じ意味で別の言い方がいくつかあります。地理データ、 GISデータ、地図データ、位置データ、座標データ、地理空間データなどです。

空間データを利用するアプリケーションには様々な機能があります。地図作成機能が 空間データ利用に最もわかりやすい仕事でしょう。地図プログラムは空間データに アクセスしてそれを描画して可視化します。通常はコンピュータの画面や紙を利用して 地図を表示します。 アプリケーションでは静的な地図(単純なイメージ)かダイナミックに表示を変えられる 地図を表示します。ダイナミックな地図はデスクトッププログラムかWebページを使って 地図のみかけを変えることができます。

多くの人たちは空間情報アプリケーションの機能は地図を作成するだけだと誤解 しています。しかし空間データ解析は空間情報アプリケーションの別の重要な 機能です。いくつかの典型的な解析処理はコンピュータの計算処理を含んでいます。

  1. 位置間の距離計算
  2. ある領域内の面積集計 (たとえば平方メートル)
  3. どの地物が他の地物と重なりあっているかの判定
  4. 地物間の重なり部分の集計
  5. ある位置から指定した距離内にある地物の数
  6. というように...

これらのことは単純なことのように見えるかもしれません。しかしこれらの機能は いろいろな方法で多くの分野に適用できます。分析の結果を地図上に表示することは 経営の意思決定をサポートするレポートとして頻繁に使われます。

最近の位置情報サービスでは多くの機能を紹介しています。それらの機能の 多くは地図と解析処理の組み合わせで構成されています。たとえば携帯電話であなたの 位置を記録できます。あなたが適切なソフトウェアを持っていれば歩いていける距離に あるレストランを携帯電話で探せます。これは空間情報テクノロジーのを使った新しい アプリケーションです。この機能のためには空間データを解析して結果を一覧にする ことが必要です。

どうして新しいのか?

それはないですが。モバイル空間情報サービスを実現するための新しいハードウェア デバイスがたくさんあります。多くのオープンソース空間情報アプリケーションも あります。しかし空間情報のためのハードウェアもソフトウェアも新しいものでは ありません。 Global positioning system (GPS) receivers are becoming commonplace, but have been used in various industries for more than a decade. Likewise, desktop mapping and analysis tools have also been a major commercial market, primarily focused on industries such as natural resource management.

What is new is how the latest hardware and software is being applied and who is applying it. Traditional users of mapping and analysis tools were highly trained GIS Analysts or digital mapping technicians trained to use CAD-like tools. Now, the processing capabilities of home PCs and open source software (OSS) packages have enabled an army of hobbyists, professionals, web developers, etc. to interact with geospatial data. The learning curve has come down. The costs have come down. The amount of geospatial technology saturation has increased.

How is geospatial data stored? In a nutshell, there are two types of geospatial data in widespread use today. This is in addition to traditional tabular data that is also widely used by geospatial applications.

Raster Data

One type of geospatial data is called raster data or simply "a raster". The most easily recognised form of raster data is digital satellite imagery or air photos. Elevation shading or digital elevation models are also typically represented as raster data. Any type of map feature can be represented as raster data, but there are limitations.

A raster is a regular grid made up of cells, or in the case of imagery, pixels. They have a fixed number of rows and columns. Each cell has a numeric value and has a certain geographic size (e.g. 30x30 meters in size).

Multiple overlapping rasters are used to represent images using more than one colour value (i.e. one raster for each set of red, green and blue values is combined to create a colour image). Satellite imagery also represents data in multiple "bands". Each band is essentially a separate, spatially overlapping raster, where each band holds values of certain wavelengths of light. As you can imagine, a large raster takes up more file space. A raster with smaller cells can provide more detail, but takes up more file space. The trick is finding the right balance between cell size for storage purposes and cell size for analytical or mapping purposes.

Vector Data

Vector data is also used in geospatial applications. If you stayed awake during trigonometry and coordinate geometry classes, you will already be familiar with some of the qualities of vector data. In its simplest sense, vectors are a way of describing a location by using a set of coordinates. Each coordinate refers to a geographic location using a system of x and y values.

This can be thought of in reference to a Cartesian plane - you know, the diagrams from school that showed an x and y-axis. You might have used them to chart declining retirement savings or increasing compound mortgage interest, but the concepts are essential to geospatial data analysis and mapping.

There are various ways of representing these geographic coordinates depending on your purpose. This is a whole area of study for another day - map projections.

Vector data takes on three forms, each progressively more complex and building on the former.

  1. Points - A single coordinate (x y) represents a discrete geographic location
  2. Lines - Multiple coordinates (x1 y1, x2 y2, x3 y4, ... xn yn) strung together in a certain order, like drawing a line from Point (x1 y1) to Point (x2 y2) and so on. These parts between each point are considered line segments. They have a length and the line can be said to have a direction based on the order of the points. Technically, a line is a single pair of coordinates connected together, whereas a line string is multiple lines connected together.
  3. Polygons - When lines are strung together by more than two points, with the last point being at the same location as the first, we call this a polygon. A triangle, circle, rectangle, etc. are all polygons. The key feature of polygons is that there is a fixed area within them.



<references />