Research for GEOCODE (Geospatial Entity Object Code) to represent a geographic point of interest (POI) and methods to evaluate or choose codes for an appropriate purpose 地理的座標を表現するコードシステムと、目的に応じたコードの評価お よび選択手法の研究 Naoki Ueda and Venkatesh Raghavan Graduate School for Creative Cities, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan ABSTRACT: A time-expression format such as “10:15” is common and everyone uses it naturally in daily life. In contrast, a location-expression format, such as “latitude and longitude,” are not used in daily life. This is because it is not convenient for people to remember and use. Today, a GPS device is built-into most mobile phones and many location-based services (LBS) are gaining popularity. However, we still use a descriptive explanation to show location and spend much time and cost to communicate a location to others. Therefore, in attempts to handle location as easily as time, various GEOCODEs (geospatial entity object code) have been invented around the world. All, however, are not yet in popular use. In this report, an overview of GEOCODE is introduced and some perspectives given to evaluate and choose an appropriate GEOCODE for a specific purpose. The author of this report is a GEOCODE researcher and an inventor of several GEOCODEs. KEY WORDS: GIS, LBS, Coordinates, GEOCODE, geospatial entity object code 概要：時刻を表す『10:15』のようなフォーマットは、ごく自然に日常生活の中で使われています。 これに対して、場所を表すフォーマット、例えば『緯度・経度』は日常生活で自然に使用できるよう な便利なフォーマットではなく、あまり利用されていません。 今日、ほとんどの携帯電話には GPS 機能が内蔵され、位置ベースサービス(LBS)が普及してきました。 しかし、我々は場所を表すには住所や説明的な文章を使うことが多く、他社に場所を伝えるときに大 変な労力を使っています。 まだ一般的ではありませんが、時刻と同じように簡単に場所を扱えるように、これまでたくさんのジ オコード（地理空間物を特定するコード）が世界中で発明されてきました。 本レポートの筆者はいくつかのジオコードの発明者でもあり、ジオコードの研究者でもあります。本 レポートでは、ジオコードの概要を紹介し、目的に応じたジオコードを評価・選択する上でポイント となる幾つかの「視点」を紹介します。 キーワード：GIS、LBS、座標、ジオコード 1. INTRODUCTION Focusing on time, we usually use “time” in our daily life. For example, “Where?” Asking place is a very fundamental question in daily life. However, the answer to this “What time is the meeting?” question is not always as simple as the answer “10:15.” to the question, “When?” To clarify the main theme of this research, it is useful to compare At the beginning, however, it wasn’t that simple. the generic characteristics of time and location in According to Alvin Toffler, the concept of “time” our lives. was drastically changed in the era of industrialization. Before that era, people used the sun, the moon, stars, or other natural mobile devices enables to lookup location for phenomenon to know “When” (2006, Toffler). LBS usage. For example: We will soon be demanding a new concept of “location,” and we will be able to handle it as we “Let’s meet when the sun comes up to do for “time.” the top.” Currently, most people do not have a common “It will begin two days after the day and popular way to express geographic location. when Sirius rises just before sunrise.” Latitude and longitude is not as easy to say or remember as “10:15.” In addition, for people, time was a kind of Therefore, we also cannot teach children how to rounding, as a season, and sometimes it flowed read location in a manner as easy as how to slowly and sometimes flowed quickly. read a clock. Therefore, telling another person “exactly when,” Society will soon need an easy and common needed considerable effort or cost. method or format to express location, as easy time format. I define codes to point exact In the industrialization era, the commoditization geographic location as “GEOCODE” of watches and clocks enabled people to first (Geographic Entity Object Coding System) in begin to know an exact time. capital alphabet in this report. Secondly, industrialization needed a concept of According to George Miller, it is hard to obtain “industrialized-time” that was straight, linear, and more than seven chunks of information at once that moved at a constant speed to enabled in a human brain's short memory capacity (1956, factory efficiency, as we know today. A new Miller). The traditional coordinate system, latitude school system taught people how to read a clock, and longitude is usually written as like following, and how to work or study along with a planned schedule. +34.592121, +135.505140. In addition, it should be mentioned that the In the example above, each description of analog and digital format was also a key part of latitude and longitude has more than seven digits. the commoditization of “time.” It is because of Thus, the latitude and longitude system is not a this change that we can now write down candidate for an “easy” code for location, even “13:15” instead of “13 hours and 15 minutes.” though it is widely used in some industries. When talking about location, like time, we use Recently various GEOCODEs have been location information as often as time information invented and introduced to point to exact in our daily life. However, regarding location, we locations. All have taken a different approach, are in a situation similar to the people of the 19th but they all have a common goal – to make century. “where” as simple and easy as “when.” Most people do not have a geometric concept of In this report, an overview of GEOCODEs is location. People use a descriptive explanation for explained. In addition, perspectives or insight to location, such as a postal address, landmark, or evaluate GEOCODEs will be introduced. The direction and spend much effort or cost to tell author of this report is an inventor of several another person “Exactly where.” GEOCODEs and also a GEOCODE researcher. This report is written to giving a general idea of For example: GEOCODEs and shows how you can choose an “Let us meet in front of the statue.” appropriate code that meets your purpose. “My home is, from the station, go west and turn to the right at the second Note: Proper names of GEOCODEs are shown corner, then….” in italic and bold (ex. “LocaPoint”). “My office is 3-3-138, Sugimotocho, Sumuyoshi-ku, Osaka, ZIP 558-8585.” As we needed a new concept for “time” in the industrialization era, today we are entering into a new era regarding “location.” In the history of mankind, this is the first time that most people can individually know an exact location.The commoditization of GPS-equipped with only 10 numbers. This is suitable for car 2. Basic theories behind GEOCODE navigation purposes. 2.1. The limitation of length compression Another approach is called “length compression.” Generally speaking, making something short is To express 49.507 bits of information, 50 digits considered “compressing.” Thus, “data are needed in a binary expression. Fifteen digits compression” technology was the first to be are needed as decimal. In theory, if you use a considered to make latitude/longitude shorter. notation system where the base radix is higher However, the data which is the target of than 10, it should be shorter than latitude and compression is only a set of latitude and longitude, because they are in decimal (Figure 1). longitude, and it is very difficult to apply the usual A decimal-based GEOCODE, including latitude data compression methods, such as Hoffman- and longitude coordinates, needs 15 numbers to compression, ZIP, etc. express about a 1 by 1 meter precision. Fifteen For example, assume that both the Earth’s numbers is almost the same length as a credit meridian and equator are 40,000,000 meters. To card number (16 numbers) and thus it is hard identify a location with 1 meter by 1 meter for a person to remember without some sort of precision, tool. A hexadecimal-based GEOCDE realizes 13 digits, but it usually becomes something like 20,000,000 * 40,000,000 "28a6f6b021cf3," and it is still difficult for a = 8 * 10^14 combinations. person to handle. If you use 10,000 different characters like a Chinese character set, only 4 Thus, letters can express a location. However, it is also difficult to recognize or remember 10,000 log 2 (8 * 10^14) different kanji characters. = 49.507 bit of information amount As the Figure 1 shows, increasing the radix base For this, there are two approaches to make it number does not have a linear effect for its shorter. length. If a radix base is more than 36 or 60, the effectiveness of raising the radix base number The first approach is by reducing the amount of won’t decrease code length effectively. information, by limiting covered area, or reducing precision. Some GEOCODEs, such as LocaPoint, LP- Address and Maidenhead Locator System, For example, MapCode reduces the amount of use a complex-radix notation. In short, they use information needed by limiting the coverage a different radix-base for different digits in their area to only the land area in Japan, and format. However, they are all still following the decreases the precision to 30 meters. By doing same rule. this, MapCode can locate any location in Japan Figure 1: Radix base and minimum length for 8*10^14 value. Each type has a strength and weakness (Figure. 2.2. Trade-offs among parameters 3). This basic categorization is helpful in If a GEOCODE is shorter then it should be easier evaluating a new GEOCODE. and simpler to use and remember. But if your GEOCODE covers global location, the length 3.1 Mesh-code type of GEOCODE needs to be longer than a regional code. This type of GEOCODE divides a coverage area If you want your code to show a more precise into multiple areas with a mesh and then uses a location, the length must be longer. Therefore, mesh ID as a code. Many GEOCODEs take this there are the following trade-offs in length, ease, approach precision, and coverage.