Collineation measurement a method for constructing the imperial citadel of thang long in harmony with nature

RESEARCH ARTICLECollineation measurement: A method for constructing the imperial citadel of Thang Long in harmony with nature Theanh Dinh a,b,c, Xiaogeng Ren a,b,* aSchool of Architectur

RESEARCH ARTICLE

Collineation measurement: A method for

constructing the imperial citadel of Thang

Long in harmony with nature

Theanh Dinh a,b,c, Xiaogeng Ren a,b,*

aSchool of Architecture, Southeast University, Nanjing, China

bVNU School of Interdisciplinary Studies, Vietnam National University, Hanoi, Vietnam

cInstitute of Imperial Citadel Studies of the Vietnam Academy of Social Sciences, Hanoi, Vietnam

Received 16 February 2022; received in revised form 6 April 2022; accepted 27 April 2022

KEYWORDS

Human settlement;

Collineation

measurement;

Shan-shui structure;

Vietnamese ancient

capitals;

The imperial citadel

of Thang long

Abstract The Imperial Citadel of Thang Long is a crucial case in ancient Vietnam’s planning and design history Although historical materials indicate that the orientation of the Imperial Citadel of Thang Long has a dialectical unity relationship with the surrounding mountains, current research is only speculative generalization and lacks empirical analysis Based on existing findings, this paper identifies the collineation measurement as a general method in the Sinosphere countries for deter-mining spatial orientation Using a mixed-method of historical archives, fieldwork and simulation model, this paper summarizes historical clues and three design perspectives related to spatial orien-tation by statistical analysis Further, it analyzes the logic and application of collineation measure-ment in constructing the Imperial Citadel of Thang Long The results show that Vietnamese designers used Tản Vieˆn Mountain as a component of Thang Long city by collineating the two moun-tain peaks to the west Tản Vieˆn Mounmoun-tain and the highlands extending eastward from it are used as the key to establishing the position of the Imperial Citadel, setting the spatial structure of human settlements, and the development of city space The location, layout, and form of important build-ings in the Imperial Citadel are also closely related to the surrounding landscape within 50 km

ª2022 Higher Education Press Limited Company Publishing services by Elsevier B.V on behalf of KeAi Communications Co Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

1 Introduction

The ancient name for contemporary Hanoi is Thang Long

Vietnamese dynasties, such as Ly´ (1010e1225), Trần

(1225e1400), Leˆ (1428e1527), Mạc (1527e1592), and Leˆ Trung Hưng (1592e1789), had their regional political and cultural centres at Th
ang Long (Phan, 2010b) The Imperial Citadel of Thang Long’s core sector, which includes the citadel struc-tures and the remnants of the 18 Hoang Dieu ancient sites, was designated as a World Heritage Site on July 31, 2010, under the

* Corresponding author.

E- ma il a dd res se s : theanhdinh@vnu.edu.vn (T Dinh),

renxiaogeng@126.com (X Ren).

Peer review under responsibility of Southeast University.

Please cite this article as: T Dinh and X Ren, Collineation measurement: A method for constructing the imperial citadel of Thang Long in

https://doi.org/10.1016/j.foar.2022.04.010

2095-2635/ª 2022 Higher Education Press Limited Company Publishing services by Elsevier B.V on behalf of KeAi Communications Co Ltd This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).

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j o u r n a l h o m e p a g e : w w w k e a i p u b l i s h i n g c o m / f o a r

name Imperial Citadel of Thang Long.1Many Vietnamese and

non-Vietnamese academics have studied the Imperial

Cita-del’s structures and urban form (Kazuto, 2010;Bu`i and Tống,

2010;Phạm, 2013;Momoki, 2010;Vu and Vu, 2007)

As archaeological work progressed between 2002e2004

and 2008e2009, Vietnamese archaeologists have excavated

numerous building foundations dating back to the Ly Dynasty

on the site of the Imperial Citadel of Thang Long

Archaeo-logical investigations showed that the general structure of

the remains exhibited a phenomenon of uniform orientation

(Bu`i and Tống, 2010, pp 28, 34) The palaces, gates, and

ceremonial routes were all oriented along an azimuth of 185

(true north-based azimuths, with north being 0

) (Fig 1) (Bu`i and Tống, 2010, pp 28,33; Kazuto, 2010, p 42) Inoue

Kazuto (2010, pp 69e70) concluded that the Imperial

Citadel of Thang Long’s platform included the idea of an

orientation system According to Phạm Leˆ Huy (2018, p 82),

the citadel’s orientation was most likely decided during

design and construction by referencing the layout,

archi-tectural forms, and other characteristics of Bianjing (now

Kaifeng), the Northern Song Dynasty capital city

There are still two questions which have not been solved:

(1) Although the Imperial Citadel of Thang Long’s spatial

orientation system seems to be very apparent from the

excavated site, extant studies are primarily speculative and

deficient in the empirical examination;(2) Existing historical

materials indicate that the orientation of the Imperial Citadel

of Thang Long has a dialectical unity relationship with the

surrounding mountains, which is defined in this paper as the

issue of city-mountain relationship However, current

research has not yet provided a reasonable explanation for

this issue In other words, there has been very little research

that offers a thorough examination of the spatial orientation

and design process of the Imperial Citadel of Thang Long

This paper highlights that the approach of collineation

measurement is the key to a thorough understanding of the

spatial orientation design and its process of the Imperial

Citadel of Thang Long Three main historical clues serve as

the basis of this research: (1) The history of Sino-Vietnamese

exchanges in the 11th-century showcase that the theory and

methods of constructing capital cities in ancient Vietnam

were in line with those of the Tang-Song period Chinese

literature, such as Yu Hai (玉海) and Song Shi (宋史),

recorded in detail that the Vietnamese emperor in the 11th

century requested the Nine Classics from the Northern Song

court and was granted permission by the Northern Song

emperor.2The so-called Nine Classics is the collective name

for the nine Confucian classics, of which books such as Zhou

Li - Kaogong Ji (周礼$考工记) and Li Ji - Ming Tang Wei (礼记$

明堂位), and Yue Ling(月令) documented much about the

techniques used to build the royal cities and establish their

orientations (2) Vietnamese archaeologists unearthed a

Tang-style ’dougong’ (dated to the 11th century) on the ruins

of the Imperial Citadel of Thang Long (Bu`i, 2015, p 20)

Through the architectural analysis of excavated building

foundations, archaeology has identified the Northern Song

architectural ruler (a ruler of 0.299 m in length) as the key to the construction of the palace, courtyard, roads, and city walls of the Imperial Citadel (Kazuto, 2010, p 45) (3) Many scholars demonstrated that the collineation measurement approach effectively analyzes the orientation of ancient capital cities and resolves mountain-city relationships (see Sect 2.2 below for details) However, contemporary research mainly focused on Chinese capital cities, with an absence of studies on ancient Vietnamese capital cities Based on the cultural exchanges between China and Vietnam in the 11th century, it is necessary to examine the design method and process of the Imperial City of Thang Long to understand the city-mountain relationship fully in a more extensive perspective of East Asia This paper presents more expansive thinking on archaeology, architectural and planning histories of Thang Long, and a deeper understand-ing of the perception of its heritage value Additionally, it could compare historical capitals with East Asian nations and offer a solid foundation for urban morphology

2 Materials and methods

2.1 Materials This paper uses raw archives from the National Library of Vietnam, the Institute of Sino-Nom Studies, and the Chinese Text Project With the information of text, authorship, date, and provenance, the historical materials used were sub-jected to a thorough investigation by the imperial court of the period Therefore, their substance had some credibility Four categories of historical materials serve as the main sources: first are the royal chronicles, such as The concise summary of the Vietnamese historical records (越史略, hereafter, Concise summary) (the 1370s)3and The complete book of the historical records of Ðại Việt (大越史記全書, hereafter, Complete book) (1479).4 Second are the royal geographical historical materials, such as Atlas of Hongduc (洪 德版圖冊) (1490),5Descriptive Geography of Việt Kingdom (皇 越地輿誌) (1806),6Dai Nam Comprehensive Encyclopaedia (大 南一統志) (1882),7The Descriptive Geography of the Emperor

1 UNESCO., 2010 Central Sector of the Imperial Citadel of Thang

Long e Hanoi https://whc.unesco.org/en/list/1328

Volume 55; ’乙亥、交州來貢、賜黎龍廷九經及佛氏書’ in the Song

Shi[The History of Song] Volume 7.

3 The concise summary of the Vietnamese historical records [Việt

Sử Lược 越史略] is a historical text that was compiled during the Trần Dynasty The 3-vol book was finished around 1377 and covered the history of Vietnam from the reign of Triệu Ða` to the collapse of the Ly ´ Dynasty.

4 The complete book of the historical records of Ðại Việt [Ðại Việt

Sử Ky´ Toa`n Thư 大越史記全書] is the official national chronicle of the Vietnamese state, that was originally compiled by the royal historian Ngo ˆ S~ı Lie ˆn under the order of the Emperor Le ˆ Tha ´nh To ˆng and was finished in 1479 during the Le ˆ period.

5 Atlas of Hongduc [Hồng Ðức Bản Ðồ Sa´ch 洪德版圖冊], some-times called the Geography of Hồng Ðức, is a set of geographic maps of Dai Viet issued during the reign of Le ˆ Tha ´nh To ˆng, the 21st year of Hồng Ðức era (1490).

6 Descriptive Geography of Việt Kingdom [Hoa`ng Việt Ðịa Dư Chı´皇越地輿誌] is one of the earliest official geographical gazet-teers of the Nguyễn dynasty, written in the fifth year of the Gia Long era (1806).

7 Dai Nam Comprehensive Encyclopaedia [Ðại Nam Nh^aaˆ´t Thống Chı´大南一統志] is the official geographical record of Vietnam’s Nguyễn dynasty written in chữ Han compiled in the late nineteenth century It also contains historical records of military campaigns.

Dong Khanh (同慶地輿志) (1889),8and Complete Atlas of the

Ðại Việt Kingdom (大越地舆全编) (1900).9 Third comes

his-torical poetry, such as Selected Collections of Cao Ba´ Qua´’ s

Chinese Poetry (高伯适汉诗选) Fourth are the

contempora-neous materials from other Sinosphere countries that record

relevant techniques for determining the orientation of palace

cities, such as Ten Computational Canons (算经十书) (1084),10

Khanbaliq Capital Rhapsody (大都赋) (1298),11and The stele

of reconstruction of Qiyin Temple in Yangshan (重修仰山栖隐 寺碑记) (1459)

We also utilised information from archaeological exca-vations, topography, and geology The archaeological excavation data obtained from the field archaeological re-ports from the Institute of Imperial Citadel Studies and the Institute of Archaeology A 1:5000 scale topographic map of Hanoi for 2018 from the Hanoi Urban Planning Institute12

and 90 m DEM digital elevation data from the CGIAR-CSI online database make up the topographic data.13 The geological survey report of the Institute of Geophysics’ borehole provides the geological data (Bu`i and Nguyễn,

2015)

Fig 1 Map of the centre of Thang Long Imperial Citadel Archaeological Site Source: Institute of Imperial Citadel Studies (IICS)

8 The Descriptive Geography of the Emperor Ðồng Kha´nh [Ðồng

Kha ´nh Ðịa Dư Chı´ 同慶地輿志] is an important document of the

Nguyễn dynasty, and is regarded nowadays as the final work in the

bibliography of classical Vietnamese geography.

9 Complete Atlas of the Ðại Việt Kingdom [Ðại Việt Ðịa Dư Toa`n

Bie ˆn 大越地舆全编] introduces the history of Vietnam from the 10th

century B.C to the Nguyen dynasty, including administration

di-vision, mountains and rivers, and citadels.

10 The Ten Computational Canons [算经十书] was a collection of

ten Chinese mathematical works, compiled by early Tang dynasty

mathematician Li Chunfeng (602e670), as the official

mathemat-ical texts for imperial examinations in mathematics The

govern-ment of the Song dynasty actively promoted the study of

mathematics There were two government xylograph editions of

The Ten Computational Canons in 1084 and 1213.

11 Li Weisun’s Khanbaliq Capital Rhapsody [大都赋], introduces the information of the mountains around Beijing, showing the ge-ography of the capital from near to far as multiple perils protect it.

12 Hanoi City Committee Hanoi Urban Planning Institute, http:// vqh.hanoi.gov.vn/en

13 Data was obtained from Climate Change, Agriculture and Food Security, Consortium for Spatial Information (CGIAR-CSI) online database, https://srtm.csi.cgiar.org

The extensive research available on Hanoi’s

geo-morphology, water network, and urban history

demon-strates that the geomorphology around the Imperial Citadel

of Thang Long has changed little between the 11th century

and the present.14 To reconstruct the historical

geo-morphology, we utilised data from 29 archaeological sites in

the Hanoi area that have been excavated with cultural

layers dating back to the Ly dynasty (Tống, 2020, pp

169e225), as well as regional-scale contemporary

geomor-phological data

2.2 Methodology

In ancient China’s urban planning and construction

prac-tice, especially in capital cities, the spatial layout and axis

systems were closely related to natural and cultural

fac-tors This theoretical perspective is usually interpreted at

two levels: (1) At the astronomical level, the spatial

pattern of the palace cities simulates the symbolic and

typical astronomical phenomena, such as the cases of the

Mausoleum of Qin Shihuang, Qin Xianyang, Han Chang’an,

and Yuan Dadu (Guo, 2019, pp 92e103;Xu, 2019a, p 25)

(2) At the geographical level, the city axis system embodies

the natural environment’s characteristics From the Qin to

the Yuan dynasties, Chinese emperors and planners used

collineation measurement to determine the spatial

orien-tation of the capital space (Guo, 2019, pp 68e72; Wu

et al., 2019, p 115, pp 132e216)

Moreover, scholars of architecture and urban planning

considered the collineation measurement as a tradition of

ancient Chinese urban planning After examining 1400

ancient Chinese cities, Wang Shusheng (2019) proposed the

’Siwang’, a human-centered approach to the environmental

observation that focuses on city-landscape interaction It

could provide the foundation for designing the urban

pattern and site selection for important buildings Based on

3940 local gazetteers from the Tang Dynasty to the Republic

of China, Xu Bin (2019b) confirmed collineation

measure-ment as a technical method to determine the orientation of

urban axes and arrange the landscape order in ancient

China The above findings and theoretical framework

pro-vide the foundation for this research

In light of the experience of human settlements in East

Asia, this paper examines the design and construction

process of the spatial orientation of the Imperial City of

Thang Long and its design concept of integrating with

na-ture This paper uses a mixed-method of historical archives,

fieldwork, and simulation models First, it introduces the

theory and application of collineation measurement,

several practice cases in the 11th-13th centuries Second, it

uses hypothesis testing with empirical evidence to address

the research issue, which entails two research steps: (1)

The statistical analysis is used to examine the orientation of

the Imperial Citadel of Thang Long using historical archives

to create a hypothetical description; (2) The evidence

verification is to evaluate the feasibility of the hypothetical

description by creating a simulation model on the

Geographic Information System (GIS) platform and Land-scape Information Modeling(LIM) Moreover, the fieldwork method has also been used to restore and verify findings The second step is an exclusion or identification of statis-tical analysis findings Third, the paper concludes with a summary of the logic and techniques used to construct the Thang Long City and establish the orientation of the Im-perial Citadel Further, it discusses the planning ideology behind this process in harmony with nature

3 Collineation measurement: a general method for establishing the orientation in the Sinophere countries

As per the history of the 11e13th century in Sinosphere countries, collineation measurement is a general method of establishing the orientation of buildings It is a three-point one-line measuring method unique among linear measure-ment techniques The planner draws on the natural co-ordinates and combines the artificial coco-ordinates to establish the plane, size, and orientation system of projects

on the city scale Mountain peaks, valleys, and huge trees are among the natural coordinates; and wooden poles, stacked stones, and other high-ceilinged structures such as pavilions, towers, and gate houses serve as artificial co-ordinates The book Ten Computational Canons details the theory and application of this technique

Question: Now for (the purpose of) looking at a sea is-land, erect two poles of the same height, 3 zhang (on the ground), the distance between the front and rear (poles) being a thousand bu Assume that the rear and front poles are aligned (with the island) By moving away 123 bu from the rear pole and observing the island’s peak from ground level, it is noticed that the tip of the front pole coincides with the peak Then by moving backward 127 bu from the rear pole and observing the island’s peak from ground level again, the tip of the back pole also coincides with the peak What is the height of the island, and how far is

it from the pole?

Answer:The height of the island is 4 li 55 bu; it is 120 li

150 bu from the pole.15 This text is the opening chapter in the book Ten Computational Canons, describing the most straightforward and primary method of using collineation measurement The human observer, the top of the pole, and the mountain peak form a three-point one-line measurement The Chi-nese in the Eastern Han Dynasty established these two lines

of measurement, combined with the triangulation tech-nique and inferred data, such as the proximity and eleva-tion of the relevant terrain (Fig 2)

There are many cases applying the method of collinea-tion measurement in practice Albeit limited, this paper explain two examples from the 11the13th century period

to illustrate the application and ideology The sacred tree

14 Based on the contents of the city, the mountains, the rivers,

the geo-potential and landform in the books of Atlas of Hongduc,

Dai Nam’s comprehensive encyclopaedia and descriptive geography

of the Emperor Ðồng Kha´nh.

直。从前表却行123步, 人目著地取望岛峯, 与表末参合。从后表却行 127步, 人目著地取望岛峯, 亦与表末参合。问岛高及去表各几何？答 曰:岛高4里55步;去表102里150步.’see, Se and Swetz 1986 , p 105.

was assigned to the south and used as a placement point to

define the forbidden city’s centreline while building the

capital city Yuan Dadu in 1266 by the planner Liu Bingzhong

(Wu et al., 2018, pp 68e70) The ancient book, Chronicles

of Capital City Dadu in the Yuan Dynasty (Xijinzhi Jiyi),

which Xiong Mengxiang compiled, recorded that Liu

Bingz-hong determined the orientation of the imperial palace of

Yuan Dadu:

When Kublai Khan was constructing the Yuan Dynasty’s

capital, he sought counsel from Liu Bingzhong, a Grand

Guardian, on the city’s orientation The emperor

con-sented, calling the tree The Sacred Tree and awarding it

a gold medal as a reference point and benchmark Liu

Bingzhong responded that he would use a tree south of

the third bridge outside the Lizheng Gate as a reference

point, and the emperor agreed.16

In addition to the large trees in the south, Liu Bingzhong

used the Yangshan Mountain peak as the coordinate point at

an angle of 60

from the central axis and used the Niutiling

peak as the coordinate point along the central axis (Fig 3)

In this process, the planner placed the capital in the order

of the mountains and rivers by investigating the surrounding mountains’ location, shape, and cultural connotations, thus creating a great harmony of ’heaven-earth-city-human’ (Wu et al., 2018, pp 68e71)

In another instance, the designers of Qiyin Temple in Mentougou, Beijing (the 1100s), surveyed the mountain from the north to south and selected the summits as placement sites The placement and orientation of Qiyin Temple’s structure were built based on the linkage of these two positioning points Finally, the project obtained a mountain view in front and behind, a pagoda for Buddhist relics was added to the placement in the north, on the Jiji Peak This case is a decentralized plan that seeks to unite the temple with the surrounding peaks Based on GIS date (Wu et al., 2018, p 69), further analysis of the positional relationships among the elements effortlessly reveals a three-point measuring line, whose three points include (1) the Buddha’s relic pagoda residing on the Jiji Peak; (2) Qiyin Temple; and (3) the Bijia Peak located at the south-ernmost point of the overall pattern (seeFig 4) The stele

of reconstruction of Qiyin Temple in Yangshan has a detailed record of these dialectical relationships:

The peak on the north side is called Jiji Peak, and the name comes from the fact that it is very high and steep and has a Buddha relic pagoda on the top Bijia Peak lies directly south of the lake beyond the temple The temple entrance was constructed to face the southern Bijia Peak, serving as a placement point throughout the construction Three spikes seem to be lined up from the south to the north when viewed from above 17

The above two cases reveal that the collineation mea-surement approach, in terms of practical application, could

be divided into two main types: one is for determining the orientation of the imperial palace, and the other is for shaping the landscape What they have in common is the designer’s observation and thinking about the natural landscape in the creation of artificial buildings, thus establishing a harmonious relationship between ’nature-human-city (building)’ It could be regarded as the philo-sophical foundation of ancient urban planning and design in the Sinosphere countries

4 Historical backgrounds of the Imperial Citadel of Thang Long

4.1 Construction of the Imperial Citadel of Thang Long

The construction of the Imperial Citadel of Thang Long took place during the regime change in Vietnam Leˆ Long Ð~ınh, the last emperor of Ti^ee`n Leˆ dynasty, died on 20 November

1009, in the capital city of Hoa Lư.18 Ly´ Coˆng Uẩn (974e1028), an emperor with military strength, took over

Fig 2 Survey of a sea island Source:https://en.wikipedia

org/wiki/Haidao_Suanjing

Xiong Mengxiang, Xilu Zhi Jiyi析津志辑佚 [Chronicles of Capital City

Dadu in the Yuan Dynasty] (Beijing: Beijing Guji Chuban She,

1983), p 213 see Xiong, 1983 , p 213.

et al., 2018 , p 69.

18 Hoa Lư is a district of Ninh Bı`nh Province in the Hồng River Delta region of Vietnam Before 1010, Hoa Lư served as the capital of Ðại

Cồ Việt.

and established the Ly´ dynasty, known as Ly´ Tha´i Tổ (Leˆ

et al., 1998, p 109) Wary of the previous dynasty’s

re-sidual influence, Ly´ Tha´i Tổ chose to relocate the capital of

Ðại Việt to the site of the Ðại La Citadel, which is now

modern Hanoi, in March 1010.19The emperor and his court

completed the relocation of the capital and changed the

name of Ðại La to Thang Long in August and September of

the same year, respectively (Leˆ et al., 1998, p 110) During

the early construction phases, the rulers temporarily used the remaining palaces and infrastructure of Ðại La while building the new capital (Bu`i and Tống, 2010, pp 27e31) The Imperial Citadel of Thang Long was roughly built

in three phases: (1) survey and site selection, which took place from the winter of 1009 to the spring of 1010; (2) implementation, which was accomplished during the early winter of 1010 to the late winter of 1017 and included the completion of palace projects for the administration and service of the emperor as well as the construction of the city wall; and (3) construction of the residential area from 1017 to 1030 (Phạm, 2013, pp 91e94; Momoki, 2010, p 2)

Royal chronicles detailed the site selection, planning, and construction of Thang Long city:

1010, Feb Furthermore, Dai La citadel, the ancient citadel of lord Gao Pian, is situated in the space be-tween Heaven and Earth, where the dragon is coiled and the tiger crouching The capital is laid out on North-South East-West axes and is favourably situated concerning the mountains and river The site is large and flat, the fields high and well enough exposed The population is protected against high water and floods Everything there flourishes and prospers It is a beau-tiful site where men and riches from the four cardinal points converge.20

1010 in the Th
ang Long Imperial City, Tri^ee`u Nguyễn palace was built, Tập Hi^eeˆ`n was built on its left, Giảng Vo˜ was built on its right Phi Long Gate was open on the left, Ðan Phượng Gate was open on the right In the middle area of the south, Cao Palace was built with a terrace called Long Trı` behind the Tri^ee`u Nguyễn palace, Long An and Long Thụy were built Nhật Quang was built on right and Nguyệt Minh was built on its left, Thu´y Hoa was built behind Four gates were opened on the four sides of the city: Tường Phu` on the east, Quảng Phu´c on the west, Ðại Hưng on the south, and Diệu Ðức on the north Hưng

Fig 3 The landscape order of Dadu, Source: Wu et al., p 70

Fig 4 The collineation lines of Qinyin Temple Source:

Wu et al., p 69

19 Ðại La was the southernmost province of China in Tang Dynasty

from 679 to 866 Jiedushi Gao Pian constructed Ðại La in 866 It was

the seat of Tống Bı`nh County during the Tang dynasty, and was the

capital of the T~ınh Hải qua ˆn Ðại La was favoured because of its

central and convenient location, defensible terrain, and relatively

dry climate.

也), 民居蔑昏墊之困, 萬物極蕃阜之豐 遍覽越邦, 斯為勝地 誠四方 輻輳之要會.’ see Le ˆ et al., 1998 , p 109.

Thieˆn Temple and Ng~u Phụng Observatory were built in

the city, and Th
aa˘´ng Nghieˆm Temple was built on the

south side of the city.21

The two paragraphs above reveal that the site selection

of Thang Long city took into consideration geo-potential and

landform, and safety, production, transportation, and

land-scape aesthetics The logic of the site selection is similar to

that of Sui and Tang Dynasties’ capitals Chang’an (Now

Xi’an) in China and Heian-kyo (now Kyoto) in Japan The

planning and design method begins in the middle and

pro-gresses from left to right and front to rear This method

reflects a clear notion of overall orientation by overlapping

the geographical order with the ritual order

4.2 Urban from and structure

Phan Huy Leˆ (2010a, p 21), Tống Trung Tı´n (2020,

pp 172e3), and Nguyễn Quang Ngọc (2010, p 97)

recov-ered the plan of the capital city of Thang Long (Fig 5)

Thang Long was located in the districts of Ba Ðı`nh, Hoa`n

Kiếm, Ðống Ða, and Hai Ba` Trưng of modern Hanoi The city

wall divided the city space into three functional areasdthe Imperial Citadel, the Royal City, and the Capital City The Imperial Citadel was located in the northern part

of the walled city and had a rectangular structure with

Nu`ng Mountain at its centre and the emperors residence

on top of it The four city walls surrounding the Imperial Citadel are 770m long (Phan, 2010a, p 46) Although the emperor’s residence was rebuilt several times, its posi-tion and orientaposi-tion remained unchanged At present, only the base of the emperor’s residence remains, which

is the site of Kı´nh Thieˆn Palace The Royal City, located west of the Imperial Citadel and south of West Lake, was where the royal army drilled, hunted, and relaxed The Royal City surrounds the Forbidden City, and is a rect-angular plan with short east-west sides and long north-south sides, maintained by the city walls The eastern wall of the Imperial City was located at the present-day Thuốc B
aa˘´c (Trần and V~u, 1966, p 42), the northern wall

of the Imperial City was located at Phan Ðı`nh Phu`ng), the western wall was located at present-day Ngọc Ha`, and the southern wall crossed present-day Lenin Square (Tống, 2020, p 172) The highest topographical location was the mountain of Kha´n, the commanding platform for troop exercises and is now the site of the Presidential Palace, in the Royal City The Capital City, situated in the southern part, was the living space for the residents 4.3 A 9 deviation of orientation system

It is important to stress that the ruler of the Ly´ Dynasty abandoned the former orientation system of the Ðại La Citadel and created a new one for the capital city

Fig 5 The urban structure of the capital city of Thang Long in the Ly´ dynasty Source:Leˆ, 1490, p 172

丹鳳門。正陽啟髙殿階曰龍墀。墀內翼以逥廊周匝四面。朝元殿後置

四門。東曰祥符, 西曰廣福, 南曰大興, 北曰耀德。又於城內起興天

寺、五鳳星樓。離方創勝嚴寺 ’ in Anonymous, 1300s Việt SửLược

[The concise summary of the Vietnamese historical records]

reproduced in the online version of the Siku Quanshu in the Kanseki

Repository, Kyoto University’s online database of premodern

Chi-nese texts http://www.kanripo.org/text/KR2i0023/002#1a,pp.

002-3b, 002-4a.

According to archaeological evidence, the Ðại La Citadel is

located under the ruins of the Imperial Citadel of Thang

Long and has its orientation system (along an azimuth of

176

) (Tống and Bu`i, 2010, pp 42e3) The orientations of

the two cities have a 9deviation Assuredly, changing the

orientation system posed a great challenge to the project

In most cases, if a ruler wanted to construct a new citadel

on top of the foundations of an existing one, the most

cost-effective and practical option would be to utilize the base

for expansion or creation; because of the new spatial

orientation, there were no amenities at the time that could

be used Presumably done deliberately for the rulers of the

Ly´ Dynasty, designing the new orientation and layout was of

great political significance

5 Statistical analysis: historical clues and

design perspectives related to the spatial

orientation

5.1 Historical clues related to the collineation

measurement

The materials from the 11th to 13th centuries, record the

construction or renovation of the palace city, provide a

comprehensive understanding of the planning process in

Vietnam during that period Both Concise summary and

Complete book point out that the method of collineation

measurement22was applied to determine the orientation of

Imperial Citadel in the Ly Dynasty of Vietnam The

following are two historical texts:

In July 1071, [the craftsmen] established artificial

coordinates (libiao) to build five buildings, including the

Trường Quảng Gate, Tha´i Bı`nh Gate, Thủy Ha` Thượng

Gate, Ngheˆnh Thu Shrine and Quy Nhaˆn Post.23

In January 1237, Hence, [Thu Do] collineated the

peak of Tuyet Mountain(biaojueshanzhong), designed

here would be Thieˆn An palace, there would be Ðoạn

Minh tower, ordered the craftsmen to build it.24

The Chinese terms libiao and biaojueshanzhong are

important evidence in the above-mentioned historical

sour-ces In 1072, during an enlargement project of Imperial

Citadel of Thang Long, the first task was libiao (meaning the

establishment of artificial coordinates) Additionally, the

second text in 1237 described a plan that failed to be

imple-mented by Trần Tha´i Toˆng (1218e1277), the first monarch of

the Trần Dynasty, who usurped the throne from the Ly royal family Unable to deal with the regime transition, he left Thang Long city and lived in seclusion in Yeˆn Tử Mountain Trần Thủ Ðộ, as the imperial master, planned a new palace city in

Yeˆn Tử Mountain district The central axis of the royal city’s design was the line from Thieˆn An Palace to Ðoạn Minh Palace, and biaojueshanzhong (meaning collineating the peak of Tuyet Mountain) was the essential technique for establishing the axis orientation as documented

Mountain and river landscapes are shaped in part by the method of collineation measurement, which is useful for establishing orientation and creating the landscape The his-torical elements of Vietnamese poetry provide the exempli-fications, such as ’the spacious fields stretched out in front of the mausoleum feud, and the tiered peaks of the mountain facing the capital’s gates’ (Ða`o et al., 1978, p 143)

5.2 Three design perspectives related to the natural landscape

Royal geographical and historical materials indicate a dia-lectical relationship between the orientation of the Impe-rial Citadel and the surrounding mountains The results of clue statistics reveal three essential design perspectives related to orientation issues:(1) the highland, (2) the cen-tral mountains, and (3) the Hall of Brightness

5.2.1 The highland The highland involves the location of Tản Vieˆn Mountain,

Nu`ng Mountain, and the Imperial Citadel of Thang Long It refers to a lengthy stretch of highland that runs from west

to east on a regional scale Following are some of the most important historical documents:

This is the land where the Dragon Vein is, reaching from the mountain of Tản Vieˆn, and ending at the River of Hồng.25

In the past, Hanoi was the town of Thang Long Geomantic principles define this stretch of land as reaching from Tản Vieˆn Mountain in the province of Sơn

Taˆy From there, it follows the winding course of the Ha´t River before crossing it and ending at Nu`ng Mountain The main building of the emperor’s residence is located

on Nu`ng Mountain.26 These two descriptions suggest a highland originating from Tản Vieˆn Mountain, extending eastward and ending at

Nu`ng Mountain The location of the Imperial Citadel of Thang Long appears to be closely related to this highland (Fig 6) This highland is a natural feature in historical, poetic writings, forming a binary antithesis to the Hồng river (meaning The Red River) The mountains are associ-ated with dryness and safety, and the Hồng river with wetness and fertility In addition, from the perspective of waterway transportation, the highland was an isolated is-land on a large swamp, resulting in a beautiful is-landscape

22 Collineation measurement was one of the construction

tech-niques of the 11th-13th centuries in the Sinosphere countries For

details of the Zhongdu of the Jin Dynasty (1151) and Dadu of the

Yuan Dynasty (1267), see Wu et al., 2018

Anonymous, 1300s Việt Sử Lược [The concise summary of the

Vietnamese historical records] reproduced in the online version of

the Siku Quanshu in the Kanseki Repository, Kyoto University’s

online database of premodern Chinese texts

http://www.kanri-po.org/text/KR2i0023/002#1a, p 002-22a.

1998 , p 172.

1882 , p 29.

山而止。今為行宮正殿.’see Ngo ˆ et al., 2004 , p 1450.

effect This content may be found in a poem written by

Vietnamese poets, such as ’In the early morning, following

the Nhi river (the Hồng river) as it flows eastwards, [I] look

back and see the Tan Linh Mountain and Nung Son, which

are faintly visible in the clouds’27and ’ Tản Vieˆn Mountain

has been famous from ancient times, looking from the city

into the distance in a mass that looks like round

umbrellas’.28

5.2.2 The central mountains

The second is on the central mountains, involving Nu`ng

Mountain, Tam Mountain, Khan Mountain, and the

em-peror’s Palace The books of Descriptive Geography of Việt

Kingdom and Complete Atlas of the Ðại Việt Kingdom

indicate that Nu`ng Mountain was placed at the centre of

the Imperial Citadel:

The mountain of Nu`ng is located in the centre of the

city When the Ly´ Dynasty set the capital, Nu`ng Mountain

was used as the foundation of the Emperor’s residence,

where the palace of Kı´nh Thieˆn is located The mountain

of Tam is located on the north side of Nu`ng Mountain in

the Thang Long city and is the pillow of Nu`ng Mountain.29

The base of the palace of the Kı´nh Thieˆn is a flat plateau

protruding from the level ground The mountain of Nu`ng

is located in the middle, where the palace is located,

and behind it is Tam Mountain, with Khan Mountain on

the right.30

These indicate that Nu`ng Mountain was the base of the

emperor’s residence and the centre of the Imperial Citadel

Tam Mountain, behind (north) Nu`ng Mountain, is likened to

the pillows of the Imperial Citadel On the right (west) of

Nu`ng Mountain, Khan Mountain is recognized as the viewing

platform of the citadel In the dialectical whole of the

three, the existence of Tam Mountain and Khan Mountain is

to emphasize the central consciousness of Nu`ng Mountain

and the Imperial Citadel (Fig 7)

5.2.3 The Hall of Brightness The third is the viewpoint of the Hall of Brightness (Min-gtang in Chinese), which connects the region that can directly be seen along with the mountains of Ðội and Ðiệt from the emperor’s residence The following passage de-scribes the view from the emperor’s residence: a hinterland with visible sunrise and sunsets, runoff from three rivers, and vast landscapes (Fig 8)

Facing south from [the Emperor’s residence], [one] could see the mountains of Ðội and Ðiệt The impetuous

Toˆ Lịch River runs past on the right, and the Nhuệ, Ngưu, and Toˆ Rivers embrace the town in front Their currents meet at the Luong confluence and empty into the Hồng

Fig 6 The axis or ‘highland’ of the Imperial Citadel of Thang

Long Source: Self-painted by author

Fig 7 The centre of the Imperial Citadel of Thang Long Source: Self-painted by author

Fig 8 The Brightland of the Imperial Citadel of Thang Long Source: Self-painted by author

106.

枕 ’see Le ˆ 1833 , p 18.

River before flowing down to Hưng Yeˆn, Nam Ðịnh, and

the sea These areas are the Hall of Brightness of the Ha`

Nội region.31

6 Evidence verification: interpreting the

design logic of the orientation system

By importing the information about the city walls and

mountains listed above into GIS, this paper recovers

and locates them using geographical data from the

Atlas of Hongduc and The Descriptive Geography of

the Emperor Dong Khanh (Ngoˆ et al., 2004, pp 5e22;

Leˆ,1490, pp 5e6) This section uses the following four

steps to verify the three perspectives mentioned above

(part 5.2)

6.1 The geographic positioning of mountain peaks

Nu`ng Mountain was located under the site of Kı´nh

Thieˆn Palace (21.03662

N, 105.84027

E) Tam Mountain was located north of Nu`ng Mountain and east of the

North Gate of the modern Hanoi Citadel (21.04069

N, 105.84189

E) Kha´n Mountain was east of Nu`ng

Mountain and at the entrance of the modern

Presidential Palace (21.03929

N, 105.83449E) Tản Vieˆn Mountain was located at the Ba Vı` National Park

(21.06979

N, 105.35641

E), west of modern Hanoi city and

50 km away from Nu`ng Mountain The two peaks of Long

Ðội Mountain were Ðội Mountain and Ðiệp Mountain,

located in Duy Tieˆn County, Ha` Nam Province (20.58529

N,

105.97426

E), south of modern Hanoi City and 52 km from

Nu`ng Mountain (Fig 9).32 In sunny weather, people can see the scenery of Tản Vieˆn Mountain when looking west from the relics of the Imperial Citadel of Thang Long (Fig 10)

6.2 The identification of the highland

The highland of the Imperial Citadel of Thang Long was a long, bar-shaped geological vein that originated from Tản Vieˆn Mountain and stretched from west to east It can be regarded as a rare natural dike located in the Hồng river basin that provided a habitat close to the mainstream without fearing flood The archaeological and geological data (Bu`i and Nguyễn, 2015;Tống, 2020), imported into the GIS platform, reveal a dependency between the location of the Imperial Citadel and the highland Nu`ng Mountain is a highland rising from its proximity to the Hồng river The Imperial Citadel and Royal City were located above the highland, and the Royal City had a long east-west and nar-row north-south pattern (Fig 11) The northern wall of the capital city also spreads in the direction of its elongation 6.3 The identification of the central mountains Historical sources emphasize that Nu`ng Mountain was the center of the Imperial Citadel Nevertheless, geographic information analysis provides comprehensive visual data on its layout The ground surrounding Nu`ng mountain displays numerous slope hillocks with a west-east tendency, with a hillock in each of the four directions of the mountain, influenced by the stratigraphic structure The northern

Fig 9 Distribution and geographic information of mountains around the Imperial Citadel of Thang Long Source: Self-painted by author

为悍气流过右边, 与鋭江、牛江、苏江濴迴其前, 同注于良三岐, 出珥

局之明堂水.’ see Ngo ˆ et al., 2004 , pp 1450e1.

32 The positioning data in this paper are based on the geocentric coordinate system and IERS Reference Meridian coordinate system.