{"content_id":"xheydcycch","slug":"cheugugi-1442-rainfall-measurement-system","locale":"en","schema_type":"Article","category":"knowledge_base","category_name":"Knowledge Base","title":"Cheugugi: Standardizing Rainfall Observation in 1442","summary":"Joseon developed Cheugugi to improve on the practice of estimating rainfall from the depth to which rainwater soaked into the ground. In 1442, it formalized a nationwide observation system by setting instrument specifications, measurement units, responsible officials, and items to record.","sponsorship_disclosure":null,"affiliate_disclosure":null,"commerce_disclosure":null,"author":{"name":"Injoys Editorial Team","url":"https://injoys.com/ko/about"},"key_points":["Cheugugi is an instrument that measures rainfall by the depth of rainwater collected in a cylindrical container.","Discussions about making it in 1441 began with the problem that rainwater soaked to different depths depending on soil conditions.","The 1442 regulations specified a length of 1 cheok 5 chon and a diameter of 7 chon, using the jucheok standard.","Responsibility for direct observation was assigned to Seoun-gwan officials in Seoul and local magistrates elsewhere.","The system recorded the dates and times of rainfall and clearing skies, along with water depth, providing a basis for comparing observations."],"content_markdown":"Joseon struggled to measure rainfall accurately, which was necessary for responding to drought. It developed the Cheugugi in 1441 and refined its measurement and reporting standards in 1442. This system is remembered for establishing a basis for comparing observations across regions.\n\nThis article follows the records in the National Institute of Korean History's *Annals of King Sejong*, checked in November 2026.\n\n## Why the Cheugugi Was Developed and the Limits of Earlier Observations\n\nThe instrument was developed because rainfall was difficult to determine from the depth of rainwater that had seeped into the ground alone. Joseon was already receiving reports on rainfall in the provinces. But the ability to submit reports and the accuracy of the measurements were separate matters.\n\nThe way rainwater seeped into the soil varied depending on how dry or wet it was. The depth of wet soil therefore could not be equated directly with rainfall. A 1441 memorial from the Ministry of Taxation pointed out this limitation in measurement.\n\nDetermining how much rain had fallen for agriculture was fundamental to responding to drought. The aim was not to improve the natural phenomenon of rainfall itself. It was to improve the method used to observe and measure it.\n\n| Category | Examining the depth of seepage into the ground | Measuring rainwater collected in a vessel |\n| --- | --- | --- |\n| What was measured | Depth of soil penetrated by rainwater | Depth of water collected in the vessel |\n| Effect of soil conditions | Dryness or wetness affected the assessment | No seepage into soil was involved |\n| How standards were aligned | Differences in soil conditions made comparisons difficult | Instrument specifications and ruler standards were set |\n| Nature of the record | Observations of how wet the soil was | Rainfall measured with a standardized instrument |\n\nThis shift is also explained in Uriyeoksanet's [“Making the Cheugugi” commentary](https://contents.history.go.kr/front/hm/view.do?levelId=hm_092_0030).\n\n## Timeline from Development in 1441 to Refinement of the System in 1442\n\nIn 1441, instrument-based observation was pursued, and in 1442, specifications and operating standards were detailed. Combining the two years into a single event obscures the process by which the system was refined. All dates from the annals below use the lunar calendar.\n\n| Date | Recorded details | Source |\n| --- | --- | --- |\n| 18th day of the 8th lunar month, 1441 | The Ministry of Taxation identified the limitations of existing measurements and proposed observations using an iron vessel | *Annals of King Sejong*, volume 93, entry 4 |\n| 18th day of the 8th lunar month, 1441 | Proposed placing a vessel 2 cheok long and 8 chon in diameter on a platform at Seoun-gwan | The same Ministry of Taxation memorial |\n| 8th day of the 5th lunar month, 1442 | Revised the specifications to a length of 1 cheok 5 chon and a diameter of 7 chon, explicitly naming the jucheok as the standard | *Annals of King Sejong*, volume 96, entry 1 |\n| 8th day of the 5th lunar month, 1442 | Defined observation responsibilities in the capital and provinces, the information to be recorded, and how records were to be kept | The same Ministry of Taxation memorial |\n\nThe key historical source is the Ministry of Taxation memorial dated **the 8th day of the 5th lunar month, 1442**. A memorial is a report submitted by an official to the king. This entry also records that the king accepted the ministry's proposal.\n\n## How the Cheugugi Worked and the Role of Each Part\n\nThe measurement principle was to use a ruler to read the depth of rainwater collected in a cylindrical vessel. The volume of water entering the vessel was not itself reported. The observed value was a length indicating how high the collected water stood.\n\nThis principle is easy to understand when the area receiving the rainwater equals the cross-sectional area in which the water collects. Dividing the volume of collected water by the receiving area gives the water depth. In a straight-sided cylinder, therefore, the water depth represents the amount of rain that fell at that location.\n\n| Component | Role | Distinguishing feature |\n| --- | --- | --- |\n| Cheugugi body | Received and collected rainwater | A cylindrical vessel for measuring rainfall |\n| Cheugudae | Supported the body | A structure separate from the vessel holding rainwater |\n| Jucheok | Measured the depth of collected water | A ruler based on the length standard designated for common use in observations |\n\nCheok, chon, and bun are the units of length used in the records. Converting them into modern millimeters requires a conversion standard for the jucheok. This article retains the specifications and recording units used in the annals.\n\n## Observation Standards for the Capital and Provinces in 1442\n\nThe 1442 rules allowed materials to vary by region while requiring consistent measurement standards. The instrument specified for use in the capital was made of iron. Local districts were allowed to use porcelain or earthenware vessels made to the same specifications.\n\n| Item | Capital | Provinces |\n| --- | --- | --- |\n| Reference instruments | An iron Cheugugi | One set consisting of an iron Cheugugi and a jucheok sent to each province |\n| Actual construction | Length of 1 cheok 5 chon and diameter of 7 chon, based on the jucheok | Each district to make a porcelain or earthenware vessel according to the standard |\n| Installation site | On a platform at Seoun-gwan | On a platform built in the courtyard of the guesthouse |\n| Measuring tool | Jucheok | A bamboo or wooden ruler made in advance to the same standard |\n| Responsibility for observations | Seoun-gwan officials | Local magistrates |\n| Recorded information | Dates and times when rain began and cleared, and water depth in chon and bun | Dates and times when rain began and cleared, and water depth in cheok, chon, and bun |\n| Handling of records | Report immediately and enter in a ledger | Report immediately and enter in a ledger as a reference for the future |\n\nSeoun-gwan was the government office responsible for astronomy, weather, and related matters at the time. Guesthouses were facilities for receiving visitors at local government offices. The rules explicitly made the responsible officials accountable for examining rainfall conditions themselves.\n\nThe observation duties described in the memorial can be organized in the following sequence.\n\n1. Prepare an instrument and ruler that meet the specified standards.\n2. Install the instrument on a platform at the designated location.\n3. After rainfall, have the responsible official personally examine rainfall conditions.\n4. Measure the water depth with the jucheok and record the dates and times when rain began and cleared.\n5. Report the measurements and preserve them in a ledger.\n\nThe standardization of specifications and observation procedures stands out more than uniformity of materials. Construction methods were left open so that local districts could also obtain instruments meeting the standard. At the same time, responsibility for records was assigned, making the system part of administrative work.\n\n## Achievements of Institutionalization and the Surviving Artifact\n\nThe achievement of institutionalization was the creation of a framework for measuring and recording rainfall according to consistent standards. If instruments alone had been distributed, observation times and recording methods could have varied. The 1442 rules addressed these matters together.\n\nHowever, these rules alone do not show how much drought damage was reduced. The memorial also does not state how much agricultural production increased. The achievement that can be confirmed is the development of a detailed observation and reporting system.\n\nThe system established under Sejong did not continue without interruption thereafter. The National Meteorological Museum explains that the system was interrupted by war and revived under Yeongjo. This history can be traced in the [National Meteorological Museum's Cheugugi guide](https://science.kma.go.kr/museum/files/leaflet_RainGauge_KOR.pdf).\n\nThe only known surviving Cheugugi from the Joseon period is the Rain Gauge of Chungcheong Provincial Office, Gongju. This artifact was made in **1837**. It is not an original instrument made under Sejong.\n\nAccording to Korea Heritage Service records, the artifact was returned from Japan in 1971. It is currently managed by the National Meteorological Museum. Its designation as a National Treasure on February 27, 2020, is also documented. The source is the [artifact record in the National Heritage Digital Service](https://digital.khs.go.kr/heri/heriDetail.do?ctptNo=1111103290000\u0026ctptUid=13898859673172200624).\n\n## Records and Interpretation\n\nThe rules recorded in the annals should be distinguished from later historical assessments. The rules show what people were instructed to do at the time. They do not prove every aspect of actual operation and results.\n\n### What the Records State Directly\n\nThe 1442 memorial specified instrument dimensions and observation duties in detail. It also explicitly required the use of the jucheok and personal observation by the responsible officials. The dates and times when rain began and cleared were to be recorded alongside the water depth.\n\nThe king's acceptance of the proposal is also recorded. However, this entry does not say when every district completed installation. How many local observation ledgers survive must also be checked separately.\n\n### Significance Assigned in Historical Commentary\n\nUriyeoksanet's commentary emphasizes the nationwide implementation of a system for measuring rainfall quantitatively. This assessment highlights the combination of an invented instrument with administrative recordkeeping. It interprets the system as an attempt to record natural phenomena in comparable numerical terms.\n\nThe Korea Heritage Service presents the Cheugugi as the world's first scientific rainfall-measuring instrument. This is that institution's assessment of its significance in the history of science. This article focuses on the development and refinement of the system that can be confirmed through the annals.\n\n### What Can Be Confirmed About the Inventor and Detailed Circumstances\n\nUriyeoksanet's commentary explains that the crown prince, who later became Munjong, was involved in the invention. However, the 1442 memorial itself is not an account of an individual's development process. This entry alone cannot establish that a particular person was the sole inventor.\n\nNo basis is therefore established here for describing it as Jang Yeong-sil's sole invention. The memorial also does not describe the specific experiments involved in reducing the instrument's size. Unverified details should not be filled in with dialogue or anecdotes about historical figures.\n\n## Distinctions Needed When Reading Observation Records as Data\n\nThe date when an observation system began and the extent of the material available today are different matters. The 1442 rules provide evidence that records were required. They do not mean that observations from every region have been preserved without gaps from that year onward.\n\nThis is an interpretation of the rules in the annals from a modern data perspective. An isolated water-depth value makes it difficult to identify the location and time of observation. To compare records, the conditions attached to the figures must also be preserved.\n\n| Information to transfer into data | Why the distinction matters |\n| --- | --- |\n| Observation region and location | Prevents measurements from different sites from being mixed together |\n| Dates and times when rain began and cleared | Identifies the rainfall event to which the water depth belongs |\n| Water depth and original units | Prevents the distinctions among cheok, chon, and bun from being lost by retaining numbers alone |\n| Instrument specifications and measurement standards | Provides a basis for checking whether values were obtained in the same way |\n| Whether a record exists | Prevents the absence of an observation from being treated as an absence of rain |\n\nIn particular, the absence of a record is different from a conclusion that rainfall was 0. Filling gaps in the material with arbitrary figures can distort past weather. This is why the existence of a system, the performance of observations, and the preservation of records must be considered separately.\n\n## What This Means for Understanding Rainfall Observation Today\n\nEven today, the meaning of an observation depends on measurement standards and recording conditions. Figures with the same name still require care in comparison if their units or observation periods differ. The 1442 rules offer a historical example for understanding these issues.\n\nThe significance of this example lies not only in the form of the invention. It also lies in the decision to specify who would measure and what would be recorded. Both instruments and recording procedures must be in place for observations to serve as evidence in the future.","content_html":"\u003cp\u003eJoseon struggled to measure rainfall accurately, which was necessary for responding to drought. It developed the Cheugugi in 1441 and refined its measurement and reporting standards in 1442. This system is remembered for establishing a basis for comparing observations across regions.\u003c/p\u003e\n\u003cp\u003eThis article follows the records in the National Institute of Korean History's \u003cem\u003eAnnals of King Sejong\u003c/em\u003e, checked in November 2026.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#why-the-cheugugi-was-developed-and-the-limits-of-earlier-observations\" class=\"anchor\" id=\"why-the-cheugugi-was-developed-and-the-limits-of-earlier-observations\"\u003e\u003c/a\u003eWhy the Cheugugi Was Developed and the Limits of Earlier Observations\u003c/h2\u003e\n\u003cp\u003eThe instrument was developed because rainfall was difficult to determine from the depth of rainwater that had seeped into the ground alone. Joseon was already receiving reports on rainfall in the provinces. But the ability to submit reports and the accuracy of the measurements were separate matters.\u003c/p\u003e\n\u003cp\u003eThe way rainwater seeped into the soil varied depending on how dry or wet it was. The depth of wet soil therefore could not be equated directly with rainfall. A 1441 memorial from the Ministry of Taxation pointed out this limitation in measurement.\u003c/p\u003e\n\u003cp\u003eDetermining how much rain had fallen for agriculture was fundamental to responding to drought. The aim was not to improve the natural phenomenon of rainfall itself. It was to improve the method used to observe and measure it.\u003c/p\u003e\n\u003cdiv class=\"overflow-x-auto\"\u003e\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eCategory\u003c/th\u003e\n\u003cth\u003eExamining the depth of seepage into the ground\u003c/th\u003e\n\u003cth\u003eMeasuring rainwater collected in a vessel\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Category\"\u003eWhat was measured\u003c/td\u003e\n\u003ctd data-label=\"Examining the depth of seepage into the ground\"\u003eDepth of soil penetrated by rainwater\u003c/td\u003e\n\u003ctd data-label=\"Measuring rainwater collected in a vessel\"\u003eDepth of water collected in the vessel\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Category\"\u003eEffect of soil conditions\u003c/td\u003e\n\u003ctd data-label=\"Examining the depth of seepage into the ground\"\u003eDryness or wetness affected the assessment\u003c/td\u003e\n\u003ctd data-label=\"Measuring rainwater collected in a vessel\"\u003eNo seepage into soil was involved\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Category\"\u003eHow standards were aligned\u003c/td\u003e\n\u003ctd data-label=\"Examining the depth of seepage into the ground\"\u003eDifferences in soil conditions made comparisons difficult\u003c/td\u003e\n\u003ctd data-label=\"Measuring rainwater collected in a vessel\"\u003eInstrument specifications and ruler standards were set\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Category\"\u003eNature of the record\u003c/td\u003e\n\u003ctd data-label=\"Examining the depth of seepage into the ground\"\u003eObservations of how wet the soil was\u003c/td\u003e\n\u003ctd data-label=\"Measuring rainwater collected in a vessel\"\u003eRainfall measured with a standardized instrument\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\u003c/div\u003e\n\u003cp\u003eThis shift is also explained in Uriyeoksanet's \u003ca href=\"https://contents.history.go.kr/front/hm/view.do?levelId=hm_092_0030\"\u003e“Making the Cheugugi” commentary\u003c/a\u003e.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#timeline-from-development-in-1441-to-refinement-of-the-system-in-1442\" class=\"anchor\" id=\"timeline-from-development-in-1441-to-refinement-of-the-system-in-1442\"\u003e\u003c/a\u003eTimeline from Development in 1441 to Refinement of the System in 1442\u003c/h2\u003e\n\u003cp\u003eIn 1441, instrument-based observation was pursued, and in 1442, specifications and operating standards were detailed. Combining the two years into a single event obscures the process by which the system was refined. All dates from the annals below use the lunar calendar.\u003c/p\u003e\n\u003cdiv class=\"overflow-x-auto\"\u003e\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eDate\u003c/th\u003e\n\u003cth\u003eRecorded details\u003c/th\u003e\n\u003cth\u003eSource\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Date\"\u003e18th day of the 8th lunar month, 1441\u003c/td\u003e\n\u003ctd data-label=\"Recorded details\"\u003eThe Ministry of Taxation identified the limitations of existing measurements and proposed observations using an iron vessel\u003c/td\u003e\n\u003ctd data-label=\"Source\"\u003e\n\u003cem\u003eAnnals of King Sejong\u003c/em\u003e, volume 93, entry 4\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Date\"\u003e18th day of the 8th lunar month, 1441\u003c/td\u003e\n\u003ctd data-label=\"Recorded details\"\u003eProposed placing a vessel 2 cheok long and 8 chon in diameter on a platform at Seoun-gwan\u003c/td\u003e\n\u003ctd data-label=\"Source\"\u003eThe same Ministry of Taxation memorial\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Date\"\u003e8th day of the 5th lunar month, 1442\u003c/td\u003e\n\u003ctd data-label=\"Recorded details\"\u003eRevised the specifications to a length of 1 cheok 5 chon and a diameter of 7 chon, explicitly naming the jucheok as the standard\u003c/td\u003e\n\u003ctd data-label=\"Source\"\u003e\n\u003cem\u003eAnnals of King Sejong\u003c/em\u003e, volume 96, entry 1\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Date\"\u003e8th day of the 5th lunar month, 1442\u003c/td\u003e\n\u003ctd data-label=\"Recorded details\"\u003eDefined observation responsibilities in the capital and provinces, the information to be recorded, and how records were to be kept\u003c/td\u003e\n\u003ctd data-label=\"Source\"\u003eThe same Ministry of Taxation memorial\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\u003c/div\u003e\n\u003cp\u003eThe key historical source is the Ministry of Taxation memorial dated \u003cstrong\u003ethe 8th day of the 5th lunar month, 1442\u003c/strong\u003e. A memorial is a report submitted by an official to the king. This entry also records that the king accepted the ministry's proposal.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#how-the-cheugugi-worked-and-the-role-of-each-part\" class=\"anchor\" id=\"how-the-cheugugi-worked-and-the-role-of-each-part\"\u003e\u003c/a\u003eHow the Cheugugi Worked and the Role of Each Part\u003c/h2\u003e\n\u003cp\u003eThe measurement principle was to use a ruler to read the depth of rainwater collected in a cylindrical vessel. The volume of water entering the vessel was not itself reported. The observed value was a length indicating how high the collected water stood.\u003c/p\u003e\n\u003cp\u003eThis principle is easy to understand when the area receiving the rainwater equals the cross-sectional area in which the water collects. Dividing the volume of collected water by the receiving area gives the water depth. In a straight-sided cylinder, therefore, the water depth represents the amount of rain that fell at that location.\u003c/p\u003e\n\u003cdiv class=\"overflow-x-auto\"\u003e\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eComponent\u003c/th\u003e\n\u003cth\u003eRole\u003c/th\u003e\n\u003cth\u003eDistinguishing feature\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Component\"\u003eCheugugi body\u003c/td\u003e\n\u003ctd data-label=\"Role\"\u003eReceived and collected rainwater\u003c/td\u003e\n\u003ctd data-label=\"Distinguishing feature\"\u003eA cylindrical vessel for measuring rainfall\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Component\"\u003eCheugudae\u003c/td\u003e\n\u003ctd data-label=\"Role\"\u003eSupported the body\u003c/td\u003e\n\u003ctd data-label=\"Distinguishing feature\"\u003eA structure separate from the vessel holding rainwater\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Component\"\u003eJucheok\u003c/td\u003e\n\u003ctd data-label=\"Role\"\u003eMeasured the depth of collected water\u003c/td\u003e\n\u003ctd data-label=\"Distinguishing feature\"\u003eA ruler based on the length standard designated for common use in observations\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\u003c/div\u003e\n\u003cp\u003eCheok, chon, and bun are the units of length used in the records. Converting them into modern millimeters requires a conversion standard for the jucheok. This article retains the specifications and recording units used in the annals.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#observation-standards-for-the-capital-and-provinces-in-1442\" class=\"anchor\" id=\"observation-standards-for-the-capital-and-provinces-in-1442\"\u003e\u003c/a\u003eObservation Standards for the Capital and Provinces in 1442\u003c/h2\u003e\n\u003cp\u003eThe 1442 rules allowed materials to vary by region while requiring consistent measurement standards. The instrument specified for use in the capital was made of iron. Local districts were allowed to use porcelain or earthenware vessels made to the same specifications.\u003c/p\u003e\n\u003cdiv class=\"overflow-x-auto\"\u003e\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eItem\u003c/th\u003e\n\u003cth\u003eCapital\u003c/th\u003e\n\u003cth\u003eProvinces\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eReference instruments\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eAn iron Cheugugi\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eOne set consisting of an iron Cheugugi and a jucheok sent to each province\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eActual construction\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eLength of 1 cheok 5 chon and diameter of 7 chon, based on the jucheok\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eEach district to make a porcelain or earthenware vessel according to the standard\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eInstallation site\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eOn a platform at Seoun-gwan\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eOn a platform built in the courtyard of the guesthouse\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eMeasuring tool\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eJucheok\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eA bamboo or wooden ruler made in advance to the same standard\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eResponsibility for observations\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eSeoun-gwan officials\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eLocal magistrates\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eRecorded information\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eDates and times when rain began and cleared, and water depth in chon and bun\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eDates and times when rain began and cleared, and water depth in cheok, chon, and bun\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Item\"\u003eHandling of records\u003c/td\u003e\n\u003ctd data-label=\"Capital\"\u003eReport immediately and enter in a ledger\u003c/td\u003e\n\u003ctd data-label=\"Provinces\"\u003eReport immediately and enter in a ledger as a reference for the future\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\u003c/div\u003e\n\u003cp\u003eSeoun-gwan was the government office responsible for astronomy, weather, and related matters at the time. Guesthouses were facilities for receiving visitors at local government offices. The rules explicitly made the responsible officials accountable for examining rainfall conditions themselves.\u003c/p\u003e\n\u003cp\u003eThe observation duties described in the memorial can be organized in the following sequence.\u003c/p\u003e\n\u003col\u003e\n\u003cli\u003ePrepare an instrument and ruler that meet the specified standards.\u003c/li\u003e\n\u003cli\u003eInstall the instrument on a platform at the designated location.\u003c/li\u003e\n\u003cli\u003eAfter rainfall, have the responsible official personally examine rainfall conditions.\u003c/li\u003e\n\u003cli\u003eMeasure the water depth with the jucheok and record the dates and times when rain began and cleared.\u003c/li\u003e\n\u003cli\u003eReport the measurements and preserve them in a ledger.\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe standardization of specifications and observation procedures stands out more than uniformity of materials. Construction methods were left open so that local districts could also obtain instruments meeting the standard. At the same time, responsibility for records was assigned, making the system part of administrative work.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#achievements-of-institutionalization-and-the-surviving-artifact\" class=\"anchor\" id=\"achievements-of-institutionalization-and-the-surviving-artifact\"\u003e\u003c/a\u003eAchievements of Institutionalization and the Surviving Artifact\u003c/h2\u003e\n\u003cp\u003eThe achievement of institutionalization was the creation of a framework for measuring and recording rainfall according to consistent standards. If instruments alone had been distributed, observation times and recording methods could have varied. The 1442 rules addressed these matters together.\u003c/p\u003e\n\u003cp\u003eHowever, these rules alone do not show how much drought damage was reduced. The memorial also does not state how much agricultural production increased. The achievement that can be confirmed is the development of a detailed observation and reporting system.\u003c/p\u003e\n\u003cp\u003eThe system established under Sejong did not continue without interruption thereafter. The National Meteorological Museum explains that the system was interrupted by war and revived under Yeongjo. This history can be traced in the \u003ca href=\"https://science.kma.go.kr/museum/files/leaflet_RainGauge_KOR.pdf\"\u003eNational Meteorological Museum's Cheugugi guide\u003c/a\u003e.\u003c/p\u003e\n\u003cp\u003eThe only known surviving Cheugugi from the Joseon period is the Rain Gauge of Chungcheong Provincial Office, Gongju. This artifact was made in \u003cstrong\u003e1837\u003c/strong\u003e. It is not an original instrument made under Sejong.\u003c/p\u003e\n\u003cp\u003eAccording to Korea Heritage Service records, the artifact was returned from Japan in 1971. It is currently managed by the National Meteorological Museum. Its designation as a National Treasure on February 27, 2020, is also documented. The source is the \u003ca href=\"https://digital.khs.go.kr/heri/heriDetail.do?ctptNo=1111103290000\u0026amp;ctptUid=13898859673172200624\"\u003eartifact record in the National Heritage Digital Service\u003c/a\u003e.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#records-and-interpretation\" class=\"anchor\" id=\"records-and-interpretation\"\u003e\u003c/a\u003eRecords and Interpretation\u003c/h2\u003e\n\u003cp\u003eThe rules recorded in the annals should be distinguished from later historical assessments. The rules show what people were instructed to do at the time. They do not prove every aspect of actual operation and results.\u003c/p\u003e\n\u003ch3\u003e\n\u003ca href=\"#what-the-records-state-directly\" class=\"anchor\" id=\"what-the-records-state-directly\"\u003e\u003c/a\u003eWhat the Records State Directly\u003c/h3\u003e\n\u003cp\u003eThe 1442 memorial specified instrument dimensions and observation duties in detail. It also explicitly required the use of the jucheok and personal observation by the responsible officials. The dates and times when rain began and cleared were to be recorded alongside the water depth.\u003c/p\u003e\n\u003cp\u003eThe king's acceptance of the proposal is also recorded. However, this entry does not say when every district completed installation. How many local observation ledgers survive must also be checked separately.\u003c/p\u003e\n\u003ch3\u003e\n\u003ca href=\"#significance-assigned-in-historical-commentary\" class=\"anchor\" id=\"significance-assigned-in-historical-commentary\"\u003e\u003c/a\u003eSignificance Assigned in Historical Commentary\u003c/h3\u003e\n\u003cp\u003eUriyeoksanet's commentary emphasizes the nationwide implementation of a system for measuring rainfall quantitatively. This assessment highlights the combination of an invented instrument with administrative recordkeeping. It interprets the system as an attempt to record natural phenomena in comparable numerical terms.\u003c/p\u003e\n\u003cp\u003eThe Korea Heritage Service presents the Cheugugi as the world's first scientific rainfall-measuring instrument. This is that institution's assessment of its significance in the history of science. This article focuses on the development and refinement of the system that can be confirmed through the annals.\u003c/p\u003e\n\u003ch3\u003e\n\u003ca href=\"#what-can-be-confirmed-about-the-inventor-and-detailed-circumstances\" class=\"anchor\" id=\"what-can-be-confirmed-about-the-inventor-and-detailed-circumstances\"\u003e\u003c/a\u003eWhat Can Be Confirmed About the Inventor and Detailed Circumstances\u003c/h3\u003e\n\u003cp\u003eUriyeoksanet's commentary explains that the crown prince, who later became Munjong, was involved in the invention. However, the 1442 memorial itself is not an account of an individual's development process. This entry alone cannot establish that a particular person was the sole inventor.\u003c/p\u003e\n\u003cp\u003eNo basis is therefore established here for describing it as Jang Yeong-sil's sole invention. The memorial also does not describe the specific experiments involved in reducing the instrument's size. Unverified details should not be filled in with dialogue or anecdotes about historical figures.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#distinctions-needed-when-reading-observation-records-as-data\" class=\"anchor\" id=\"distinctions-needed-when-reading-observation-records-as-data\"\u003e\u003c/a\u003eDistinctions Needed When Reading Observation Records as Data\u003c/h2\u003e\n\u003cp\u003eThe date when an observation system began and the extent of the material available today are different matters. The 1442 rules provide evidence that records were required. They do not mean that observations from every region have been preserved without gaps from that year onward.\u003c/p\u003e\n\u003cp\u003eThis is an interpretation of the rules in the annals from a modern data perspective. An isolated water-depth value makes it difficult to identify the location and time of observation. To compare records, the conditions attached to the figures must also be preserved.\u003c/p\u003e\n\u003cdiv class=\"overflow-x-auto\"\u003e\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eInformation to transfer into data\u003c/th\u003e\n\u003cth\u003eWhy the distinction matters\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Information to transfer into data\"\u003eObservation region and location\u003c/td\u003e\n\u003ctd data-label=\"Why the distinction matters\"\u003ePrevents measurements from different sites from being mixed together\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Information to transfer into data\"\u003eDates and times when rain began and cleared\u003c/td\u003e\n\u003ctd data-label=\"Why the distinction matters\"\u003eIdentifies the rainfall event to which the water depth belongs\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Information to transfer into data\"\u003eWater depth and original units\u003c/td\u003e\n\u003ctd data-label=\"Why the distinction matters\"\u003ePrevents the distinctions among cheok, chon, and bun from being lost by retaining numbers alone\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Information to transfer into data\"\u003eInstrument specifications and measurement standards\u003c/td\u003e\n\u003ctd data-label=\"Why the distinction matters\"\u003eProvides a basis for checking whether values were obtained in the same way\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd data-label=\"Information to transfer into data\"\u003eWhether a record exists\u003c/td\u003e\n\u003ctd data-label=\"Why the distinction matters\"\u003ePrevents the absence of an observation from being treated as an absence of rain\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\u003c/div\u003e\n\u003cp\u003eIn particular, the absence of a record is different from a conclusion that rainfall was 0. Filling gaps in the material with arbitrary figures can distort past weather. This is why the existence of a system, the performance of observations, and the preservation of records must be considered separately.\u003c/p\u003e\n\u003ch2\u003e\n\u003ca href=\"#what-this-means-for-understanding-rainfall-observation-today\" class=\"anchor\" id=\"what-this-means-for-understanding-rainfall-observation-today\"\u003e\u003c/a\u003eWhat This Means for Understanding Rainfall Observation Today\u003c/h2\u003e\n\u003cp\u003eEven today, the meaning of an observation depends on measurement standards and recording conditions. Figures with the same name still require care in comparison if their units or observation periods differ. The 1442 rules offer a historical example for understanding these issues.\u003c/p\u003e\n\u003cp\u003eThe significance of this example lies not only in the form of the invention. It also lies in the decision to specify who would measure and what would be recorded. Both instruments and recording procedures must be in place for observations to serve as evidence in the future.\u003c/p\u003e\n","tags":["Joseon period","Cultural heritage"],"faqs":[{"question":"What does a cheugugi measure?","answer":"A cheugugi is an instrument that measures rainfall by the depth of rainwater collected in a cylindrical vessel. This differs from measuring the depth to which water has seeped into the ground."},{"question":"Why was the cheugugi created?","answer":"Because the depth to which rainwater seeped into the soil varied depending on how dry or wet the soil was. Joseon sought to use a more consistent standard to obtain the rainfall data needed to respond to drought."},{"question":"What is the significance of 1441 and 1442, respectively?","answer":"In 1441, efforts were made to measure rainfall using iron vessels. In 1442, the instrument's specifications, measurement units, responsibilities for observation, and recording procedures were defined in detail."},{"question":"What dimensions were set for the cheugugi in 1442?","answer":"The specifications in the Sejong Sillok are a length of 1 cheok 5 chon and a diameter of 7 chon, based on the jucheok standard. When converting these dimensions into modern units of length, the conversion standard used for the jucheok must also be stated."},{"question":"Were all cheugugi in the provinces also made of iron?","answer":"Local towns could use porcelain or earthenware vessels of the same specifications. Each province was to receive one iron cheugugi and one jucheok ruler to serve as standards for production."},{"question":"Who measured rainfall?","answer":"In Seoul, officials of the Seoun-gwan were instructed to conduct observations themselves. In the provinces, local magistrates were assigned responsibility for personally observing rainfall conditions and measuring the water depth."},{"question":"What was entered in the observation ledgers?","answer":"They recorded the dates and times when it rained and when the weather cleared, along with the depth of the collected water. After the measurements were reported, they were to be entered in ledgers for future reference."},{"question":"How does a cheugugi differ from a cheugudae?","answer":"A cheugugi is a vessel that collects rainwater. A cheugudae is the supporting structure on which the instrument is placed. A separate ruler called a jucheok was used to read the water depth."},{"question":"Can the cheugugi be considered the invention of Jang Yeong-sil alone?","answer":"The 1442 memorial submitted by the Hojo does not support the claim that Jang Yeong-sil invented it alone. The commentary on Uriyeoksanet explains the involvement of the crown prince, who later became Munjong. An individual's role in making the instrument must be distinguished from the state's development of an observation system."},{"question":"Did the invention of the cheugugi solve drought?","answer":"The cheugugi was a tool for determining the amount of rainfall. It was not a device that made rain fall or supplied water for agriculture. The extent of any reduction in drought damage cannot be determined from that memorial alone."},{"question":"Was the surviving cheugugi made during Sejong's reign?","answer":"The surviving cheugugi from the Chungcheong Provincial Office in Gongju was made in 1837. It is not an instrument made during Sejong's reign. The Korea Heritage Service describes this artifact as the only currently known cheugugi from the Joseon period."},{"question":"Do all nationwide rainfall records survive from 1442 onward?","answer":"The fact that observation rules were established does not mean that all records have been preserved. The periods covered by surviving records and the gaps in those records must be checked separately for each region."}],"sources":[{"url":"https://sillok.history.go.kr/id/kda_12405008_001","title":"National Institute of Korean History, Annals of the Joseon Dynasty, Annals of King Sejong, vol. 96, 24th year of King Sejong's reign, 5th lunar month, 8th day, entry 1","type":"source"},{"url":"https://contents.history.go.kr/front/hm/view.do?levelId=hm_092_0030","title":"National Institute of Korean History, Our History Net, Korean History Through Historical Sources, \"Making the Rain Gauge\"","type":"source"},{"url":"https://science.kma.go.kr/museum/files/leaflet_RainGauge_KOR.pdf","title":"Korea Meteorological Administration, National Meteorological Museum, rain gauge information materials","type":"source"},{"url":"https://digital.khs.go.kr/heri/heriDetail.do?ctptNo=1111103290000\u0026ctptUid=13898859673172200624","title":"Korea Heritage Service, National Heritage Digital Service, Rain Gauge of Chungcheong Provincial Office, Gongju","type":"source"}],"images":[{"id":2683,"url":"https://injoys.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDEyNzksInB1ciI6ImJsb2JfaWQifX0=--0ecd775a147838e3da06ece93546bf97d2e0ab78/ai-7f64e3cb.webp","is_representative":false,"generation_method":"ai_semi","license":"ai_generated","mime_type":"image/webp","width":1536,"height":1024,"translations":{"ko":{"alt":"비 내리는 기와집 마당에서 돌 받침 위의 원통형 측우기가 빗물을 받고 있다.","caption":"강우량은 땅에 스며든 깊이 대신 직접 모은 빗물의 깊이로 측정하게 되었다.","description":null},"en":{"alt":"Rain falls on a cylindrical rain gauge on a stone pedestal in a courtyard surrounded by tiled-roof buildings.","caption":"Rainfall came to be measured by the depth of collected rainwater rather than how deeply it soaked into the soil.","description":null},"ja":{"alt":"瓦屋根の建物に囲まれた雨の中庭で、石台に据えた円筒形の測雨器が雨水を受けている。","caption":"降水量は地中に染み込んだ深さではなく、直接集めた雨水の深さで測るようになった。","description":null},"es":{"alt":"Pluviómetro cilíndrico sobre una base de piedra en un patio con edificios de tejados de tejas, bajo la lluvia.","caption":"La lluvia pasó a medirse por la profundidad del agua recogida, no por cuánto penetraba en el suelo.","description":null},"id":{"alt":"Hujan membasahi penakar hujan silinder di atas alas batu di halaman yang dikelilingi bangunan beratap genteng.","caption":"Curah hujan mulai diukur dari kedalaman air yang ditampung langsung, bukan kedalaman resapannya ke tanah.","description":null},"pt":{"alt":"Chuva sobre um pluviômetro cilíndrico numa base de pedra, em um pátio cercado por edifícios com telhados de telhas.","caption":"A chuva passou a ser medida pela profundidade da água recolhida, em vez de sua infiltração no solo.","description":null},"zh-hant":{"alt":"雨中的瓦頂建築庭院裡，石座上的圓筒形測雨器正承接雨水。","caption":"降雨量改以直接收集的雨水深度測量，不再依據雨水滲入土壤的深度判斷。","description":null},"de":{"alt":"Regen fällt auf einen zylindrischen Regenmesser auf einem Steinsockel im Hof zwischen ziegelgedeckten Gebäuden.","caption":"Die Niederschlagsmenge wurde nun anhand der Höhe des gesammelten Regenwassers statt seiner Eindringtiefe im Boden bestimmt.","description":null}}},{"id":2684,"url":"https://injoys.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDEyODYsInB1ciI6ImJsb2JfaWQifX0=--b656c9f2d75c87d59fbe4d1d06682f2f4754f03b/ai-6da3fef5.webp","is_representative":false,"generation_method":"ai_semi","license":"ai_generated","mime_type":"image/webp","width":1536,"height":1024,"translations":{"ko":{"alt":"비 갠 조선시대 관청 마당에서 수령이 측우기에 나무자를 넣어 재고, 뒤편에서는 서리가 기록하는 모습","caption":"1442년 규정은 지방의 수령이 직접 강우량을 관측하도록 책임을 정했다.","description":null},"en":{"alt":"A Joseon official measures a rain gauge with a wooden ruler in a wet courtyard while a clerk writes nearby.","caption":"The 1442 regulations made local magistrates personally responsible for measuring rainfall.","description":null},"ja":{"alt":"雨上がりの朝鮮時代の役所の庭で、守令が測雨器に木製の物差しを入れて測り、奥では書吏が記録している。","caption":"1442年の規定では、地方の守令が自ら雨量を観測する責任を負った。","description":null},"es":{"alt":"Un funcionario de Joseon mide un pluviómetro con una regla en un patio mojado mientras un escribiente toma notas.","caption":"Las normas de 1442 responsabilizaron a los magistrados locales de medir personalmente las precipitaciones.","description":null},"id":{"alt":"Pejabat Joseon mengukur penakar hujan dengan penggaris kayu di halaman basah, sementara juru tulis mencatat.","caption":"Aturan tahun 1442 mewajibkan kepala daerah mengukur curah hujan secara langsung.","description":null},"pt":{"alt":"Um oficial de Joseon mede um pluviômetro com uma régua num pátio molhado enquanto um escrivão faz anotações.","caption":"As normas de 1442 atribuíram aos magistrados locais a responsabilidade de medir pessoalmente a precipitação.","description":null},"zh-hant":{"alt":"雨後的朝鮮官署庭院中，守令將木尺伸入測雨器測量，後方的書吏正在記錄。","caption":"1442年的規定明定，地方守令須親自負責觀測雨量。","description":null},"de":{"alt":"Ein Joseon-Beamter misst im nassen Hof mit einem Holzlineal im Regenmesser, während ein Schreiber Notizen macht.","caption":"Die Vorschriften von 1442 verpflichteten die örtlichen Amtsvorsteher, den Niederschlag persönlich zu messen.","description":null}}}],"published_at":"2026-11-11T03:10:55+09:00","updated_at":"2026-11-11T03:10:55+09:00","license":"cc_by","translation_status":"reviewed","available_locales":["ko","en","ja","es"],"data_locales":["ko","en","ja","es","id","pt","zh-hant","de"],"url":"https://injoys.com/en/articles/cheugugi-1442-rainfall-measurement-system"}