Rai, ngan, and tarang wa
The rai,[lower-alpha 1] ngan,[lower-alpha 2] and tarang wa or square wa[lower-alpha 3] are customary Thai units of area, used in the measurement of land. They are defined as exactly 1,600, 400, and 4 square metres, respectively (17,222, 4,306, and 43 sq ft).[1]
The tarang wa (square wa, tarang meaning 'grid') is derived from the area of a square with sides of 1 wa (the Thai fathom). One ngan is equal to 100 square wa, and one rai ('field' or 'plantation') equals 4 ngan or 1 square sen.[1] The units were standardized in square metres when Thailand (then Siam) adopted the metric system in 1923,[2][3] although the Royal Survey Department was already reported in 1908 to be using the metre-based conversion for its cadastral maps.[4]
The units are commonly used for cadastre and property matters, and official and legal documents express areas of land in such units.[5] They are sometimes notated in the abbreviated format rai-ngan-tarang wa, e.g. "4-2-25 rai", which means "4 rai, 2 ngan, and 25 tarang wa", though this is discouraged by some government documents.[6]
| Unit | Derivation | Relative | SI (or other metric) | US customary |
|---|---|---|---|---|
| Tarang wa | Square wa | 4 m2 | 43 sq ft | |
| Ngan | 100 tarang wa | 400 m2 | ||
| Rai | Square sen | 4 ngan or 400 tarang wa | 1,600 m2 (16 ares) | 17,222 sq ft (0.4 acres) |
Notes
References
- ↑ 1.0 1.1 (in th,en) Commercial Directory for Thailand B.E. 2496-97 (1953-54). Department of Commercial Intelligence, Ministry of Economic Affairs. 1953. p. 3-11. https://www.google.com/books/edition/Commercial_Directory_for_Thailand/w7QHtC8GhSQC?hl=en&gbpv=1&pg=RA2-PA11.
- ↑ Bureau of Weights and Measures. "ประวัติการชั่งตวงวัดของประเทศไทย" (in th). นานาสาระชั่งตวงวัด. Central Bureau of Weights and Measures. https://www.dit.go.th/region/SITE/CBWM23/PUBLICATIONS/1_%E0%B8%99%E0%B8%B2%E0%B8%99%E0%B8%B2%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%B0%201%20B-W%20Reduced%20Ver%201.0.pdf.
- ↑ "History of Weights and Measures in Thailand". 2004. http://nwmc.go.th/history_eng.html.
- ↑ Wright, Arnold; Breakspear, Oliver T. (1908). Twentieth century impressions of Siam: its history, people, commerce, industries, and resources, with which is incorporated an abridged edition of Twentieth century impressions of British Malaya. London [etc.] Lloyds Greater Britain Publishing Company, Ltd.. p. 126. https://archive.org/details/twentiethcentury00wrigrich/page/n129/mode/2up.
- ↑ "คำศัพท์ภาษาอังกฤษด้านการที่ดิน (Terminology of the Department of Lands)" (in th,en). Department of Lands. September 2011. https://www.dol.go.th/km2/Documents/do206.pdf.
- ↑ "คำสั่งจังหวัดเชียงใหม่ ที่ 1/2528 เรื่อง แก้ไข (เนื้อที่ รูปแผนที่ หรือเนื้อที่และรูปแผนที่) ในโฉนดที่ดิน" (in th). Department of Interior. 1985. https://www.dol.go.th/survey/DocLib1/30/30-2170.PDF#page=13. "หมายเหตุ การเขียนเนื้อที่ 6 ไร่ 3 งาน 06 ตารางวา ไม่ควรเขียนเป็น 6-3-06 ไร่"
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