Historical Survey Sheet Digitization

Project Overview

This project documents the georeferencing and digitization of historical engineering survey sheets of the Allai Irrigation Scheme in Mutur, Trincomalee District. The original analogue survey maps, prepared between 1943 and 1955, were converted into a GIS-ready digital dataset to preserve terrain information for future irrigation and engineering analysis.

Project Background

During my internship at the GIS Branch, Irrigation Department Head Office, Colombo 07, I was assigned a set of 71 scanned engineering survey sheets related to the Allai Irrigation Scheme. Due to their age and analogue nature, these maps required careful georeferencing and extensive manual digitization to reconstruct accurate terrain information within a modern GIS environment.

Study Area

The study area covers the Allai Irrigation Scheme located in the Mutur area of the Trincomalee District, Eastern Province of Sri Lanka. The region includes varied terrain with complex elevation patterns that are critical for irrigation planning and water management.

Data Sources

Historical engineering survey sheets (1943–1955) – Irrigation Department of Sri Lanka
Scanned analogue maps (soft copy format)
Reference basemaps for georeferencing

Methodology

Georeferencing of scanned historical survey sheets
Sheet-wise alignment and edge matching
Manual digitization of high-density contour lines
Topology awareness and line continuity checking
Layer organization and quality control in ArcGIS Pro

Project Visualization

Digitized Contour Coverage – Full Extent

Overview of the Allai Scheme showing the complete spatial extent of manually digitized contour lines derived from 71 historical survey sheets.

Contour Digitization

High-Density Contour Digitization – Zoomed Views

Sequential zoomed views showing the density, continuity, and precision of manually digitized contour lines derived from historical survey sheets.

Analogue to Digital Transformation

Comparison between an original scanned engineering survey sheet and its GIS-based digital representation after georeferencing and contour digitization.

Challenges & Solutions

Very old and distorted analogue survey maps
Inconsistent scales and map conditions across sheets
Extremely dense contour networks requiring manual digitization
Time-intensive editing and quality control process

Tools & Skills Demonstrated

ArcGIS Pro
Historical map georeferencing
Manual contour digitization
Terrain data reconstruction
Large multi-sheet dataset management

Conclusion

This project demonstrates practical experience in handling legacy engineering survey data and transforming historical analogue maps into structured GIS datasets. The digitized contour information forms a valuable foundation for future irrigation, hydrological, and terrain analysis in the Allai Scheme area.