The Survey Department Of Sri Lanka

Published Date: 02 Nov 2017

The Survey Department of Sri Lanka was established on 2nd of August 1800. It works as a central point in mapping and surveying. It is an important department in Sri Lanka which mainly conduct GIS and Remote Sensing. It consists of four main units or sections named as topographic unit, GIS unit, photogrammetic unit and remote sensing unit.

In topographic unit of the Survey Department mainly target towards map drawing based on topological factors. Here they concern both man-made and natural objects and develop maps accordingly. The department has completed digitizing 1:250,000 scale map and 1:50,000 topographic map series, and 1:10,000 series is now in progress.

The section which conducts the Geographic Information System at the Survey Department of Sri Lanka mainly focus on database manipulation activities of Geo-referenced data. In order to facilitate this process this section uses the software named ArcGIS.

The Photogrammetic unit in this department initially used air photographs of the scales of 1: 10,000, 1: 20,000 and 1: 40,000. In order to conduct this phtogrammetic process the department has fewer numbers of plotting machines with early models. But currently they upgraded their equipments to certain levels by using semi-analytical plotters with digital encorders and two analytical plotters. The Survey Department has introduced GPS receivers in geodetic type to determine ground control points.

The Centre of Remote Sensing in the Survey Department of Sri Lanka develops Land Use Map series for Sri Lanka using satellite remote sensed images. SPOT, LANDSAT and IRS are the main satellites used by this remote sensing centre when developing the required map series. They conducted this remote sensing process as a joint project between the Sri Lankan Government and the Swiss Government

Geographic Information System

Geographic information system is a computer-based information system which supports all most all geographically referenced data. Using a GIS, geographical data can be captured, modelled, stored, retrieved, shared, manipulated, and presented. In order to manage a GIS, there should be computer hardware, application software, skilled people, appropriate methods and geographically referenced data.

Survey Department of Sri Lanka - GIS unit

The Survey Department of Sri Lanka provides the mapped data which are the base for any Geographic Information System in the Sri Lanka. The modern GIS is a computerized geographic database system with tools for data analysis and data presentation. A GIS is a tool which helps to store and manipulate large data sets and to perform complex operations that would take a human a long time. Algorithms and storage techniques are used for this purpose. Data captured from an aerial photograph have been done digitally since 1992. That can be directly fed into any sort of Geographic Information System. However, the scale of the spatial information should map with the level of accuracy required. The Geographic Information System technology in conjunction with remote sensing and photogrammetric can be used to identify hazards. Land hazard prone areas, flood prone areas, The representation of these hazards can be stored in a GIS database once those hazards had been identified properly.

The Survey Department is the national Surveying & Mapping organization that provides Geo-spatial data to other institutions and individuals for their needs. Since 1992, 1:10,000 topographic map series has been produced using photogrammetric method. Data are available in digital form for all areas to be developed. In 1993 the geodetic control network of Sri Lanka was upgraded by using precise baselines measured using global positioning system. The transformation parameter was computed from the local datum called Everest 1830 to global datum called WGS84. Hence Global Positioning System receivers can be used to obtain the national grid system centimetre level accuracy.

Requirements of Geographical Information

As the population increases in what happens to our natural resources? Of course they deplete. So there is a demand on the Earth’s resources of land, air, water and raw materials. With the realization that better management is required of limited resources, people have become more organized. Complex social and economic patterns have evolved. Human beings have understood the need for better sharing of resources between humans as well as in all forms of life. So we must learn to make the most of our resources. It must be mentioned here that it is not only the natural resources but also the changes brought about through social and technological advances also needs to be monitored constantly. How do we set about doing all this? First we need to understand the spatial & temporal patterns of resources and also spatial & temporal processes governing their availability. Let us see what this means. We need to know exactly where the resources are located (spatial data). Data needs to be monitored continuously. For this reason, we need to obtain data of a resource or a phenomenon at different times (temporal data). The temporal process for obtaining rainfall data can be on a daily basis. The temporal process for obtaining population data can be once in ten years. GIS is all about how we record the information in order to be able to retrieve the data when required.

Application areas of GIS

Geographic Information Systems can be used in multiple sectors. The following table will mention some operational application areas, and social and environmental application areas that can be facilitated through a GIS.

Operational Applications

Social & Environmental applications

Utilities management

Local, National & Global applications

Telecommunication

Healthcare applications

Transportation

Politics

Emergency management

Monitoring land-use

Land administration

Environmental monitoring and assessment

Urban planning

Military applications

Library management

Geographical Information

For everybody to read and understand records or maps it was necessary to have units of geographic information. We can use real symbols and attributes to represent real world objects.

Symbols :

Point: Schools, hospitals etc.

Lines: Contours, streams, roads etc.

Polygons: Land use, Provinces, districts etc.

Attributes :

These any other data relevant to that particular spatial data as indicated by the symbol. They are the non-geographic characteristics of the geographical entities (spatial information) in a GIS.

Geographic data is the information about the earth’s surface and features on it. Feeding the data or the information into the system is referred to as data capture. Before we see how we can capture data, let us first understand what geographic data really are and the different forms in which this data can be represented. Usually data can be represented either in vector data format or in raster data format.

Operations of a GIS

We can observe the following operations using a GIS software,

Point-in polygon queries: When we click the mouse while inside the region of a computerized map, the program must perform a point-in-polygon test to find out what you are interested in

Proximity-based queries: For example if we need to know the number of schools lying within a certain distance from a point, you can create a buffer zone to obtain the result

Network queries: To get at the optimal routes for travel, water pipeline or any other. It can also be network load queries where you try to find out the response of a drainage system to heavy rainfall etc.

Thematic maps: These are methods of presenting information for quick and easy reference. Just having a table of numbers may very often not indicate some important point

At national level we need to have data about different areas in order to decide on priority requirements. The different data figures for different items such as the number of doctors serving each district, the number of school going children with the number of schools in a district and so on can be reflected much better using maps. Townships are complicated complexes where a database is required for many types of information. Location of streets, houses, culverts, electricity, water & sewage line information are just a few.