Census Data Capture with OCR Technology Ghanas Experience

Census Data Capture with OCR Technology: Ghana’s Experience Presented at the UNSD Regional Workshop on Census Data Processing Dar es Salaam, Tanzania 9 – 13 June, 2008 Presenter: K. B. Danso-Manu, Ghana Statistical Service

Ghana uses scanning technology for 2000 Census n Ghana used the Optical Character Recognition (OCR) technology to capture the 2000 census forms. n Three Kodak 9500 document scanners used for 12 months. n About 4. 5 million census forms captured. n Total population 18, 912, 079 persons. n Males = 9, 357, 382 males (49. 5%). n Females = 9, 554, 697 females (50. 5%).

Geographical Coding System n n n The 2000 Ghana census was conducted at the household level. A 15 -digit reference code was used to uniquely identify each household. The hierarchical coding system used was as follows:

The hierarchical coding system used Item Position No. of Digits Valid values 1 -2 3 -4 5 -7 8 -10 2 2 3 3 01 - 10 01 - 18 001 - 999 Structure/Building Number 11 -13 3 001 - 999 Household Number 14 -15 2 01 - 99 Region District Locality EA Num

Capturing of census data Steps: n Office editing n Opening and preparation of forms n Scanning n Validation

Office Editing n n n The scanners could not recognize light crossed marks, responses had to be crossed again, deep enough for the scanner to recognize. In rural scattered EAs, some enumerators gave the same locality (A 06) code as that of the base locality. This had to be corrected before scanning. Some enumerators used wrong EA codes for the questionnaire. In many instances, after copying the codes, marking them on the questionnaires was done wrongly or not marked at all. The front-page of some questionnaires especially supplementary forms was blank.

Opening and Preparation of Questionnaires for Scanning n After editing, questionnaires were opened, separated and prepared for scanning. n To ensure that the crosses were dark. n n The 15 -digit reference number was on the inner sheet with the household identification on the outer sheet (this was the only link the two forms had) for each household. Continuation forms follow the original.

OCR Scanning • • Type of scanners: Kodak 9500 D Optical Resolution: 300 dpi • Speed: 120 ppm (A 4) • Interface: SCSI-2 (8 -bit) • Software: Readsoft’s Eyes & Hands

OCR Scanning (cont. ) n n The data capture involved scanning of the questionnaire, interpretation of the scanned marks, transfer of the data and loading the scanned data into an oracle database. Periodic backups of the data and images were made on compact tapes – DLT Tapes 40 GB.

OCR Scanning (cont. ) n n Three 8 -hour shifts, 7 days a week for 4 months, then 6 days a week for 8 months. Forms fed manually to avoid paper jams. Forms scanned in batches of EA within districts and regions. Scanned batch stamped, bagged and returned to the documents room.

Validation n Validation of scanned data was undertaken to correct structural and inconsistency problems identified in the dataset. For every household that failed the structural and/or consistency checks, the image and dataset were recalled. Necessary corrections made to the dataset but not the images.

Validation (cont. ) § § § There was no direct mechanism to retrieve images of the questionnaires form tapes. The validation process became very slow and tedious. The validation teams worked the same shift as the scanning teams.

Difficulties and Challenges Paper weight - different grammage of paper used to print the questionnaires (80 g/m 2, 100 g/m 2 and 120 g/m 2). - sheets got jammed up in the system. - Scanners fed manually.

Difficulties and Challenges (cont. ) - - No Barcodes on census forms An 8 -page questionnaire, consisting of two A 3 sheets was used to design the OCR readable census questionnaire. The company printing them could not print unique barcodes on them.

Difficulties and Challenges (cont. ) - - Number of scanners used Three out of the six scanners planned for the data capture were purchased. All three scanners were used to scan but became idle during interpretation and transfer of data.

Difficulties and Challenges (cont. ) n - - - Output from scanned questionnaires The generated ASCII data file was all numeric and left justified. Fields with 3 or 4 -digit had their leading zeros truncated. The scanners could not pick the 15 digit reference number correctly.

Difficulties and Challenges (cont. ) n - - - Power interruptions Power fluctuations, power cuts and low voltage disturbed the flow of work to the extent that it sometimes became impossible to scan during the day. This led to the destruction of two motherboards of the scanners and damage to a couple of computers and printers. This problem was however resolved when a 100 k. VA generator and a stabilizer were installed.

Thank You … for your time and attention.