Map revision is an important factor in virtually all types of map production. Its true aim is to keep up-to-date the changes and this task is only theoretically possible even with many times the resources normally devoted to it. A map is a symbolic depiction highlighting relationship between elements of some space, such as objects regions and themes. Many maps are static two dimensional geographically accurate representations of three dimensional space; while others are dynamic or interactive, even three dimensional. Although, most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale e.g. brain mapping, ONA Mapping and extraterrestrial mapping (Wikipedia, 2023).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitation of the study and Definition of technical terms.
1.2 Background of Study
Maps are graphical representation that gives information of place, features in a particular environment on paper. They are representation of the real world drawn on a flat surface but many times smaller than the place itself. Every culture in all part of the world makes and uses maps. For planning, navigation etc. The art and science of making maps is known as cartography.
Cartography concerns the art, science and techniques of making maps or charts. Conventionally, the term map is used for terrestrial area and chart for marine areas, but they are both maps in the sense the word is used here. In statistical or analytical fields, charts provide the pictorial representation of statistical data, but this does not form part of the discussion in this write-up rather we are concern in digital conversion (revisio/update) of map.
According to Bjrn Kellsrom (2007), a map is a geographical representation of a portion of the earth’s surface drawn to scale. It uses colours, symbols and labels to represent features found on the ground. Much of town planning is done using maps, therefore any operation requires a supply of maps; however, the finest maps available are worthless, the map user knows how to read them (Kraak and Ormeling, 1996).
Map making or cartography has been greatly assisted by technological advancement since World War II. The most important and easier approach has been the use of technological advancement that create room for better techniques to capture data of physical features without touching them. These techniques include aerial photography remote sensing and satellite imagery which has reduced error in determining the exact location of paint on the earth surface.
Digital conversion and revision of map is the process of using a computer and the relevant software in map production in such a way that map production is enhanced and can be understood by its readers not minding their intelligence.
The concept of revision is to keep all published maps up-to-date with changes taking place on the environment; thus making maps maintain their usefulness. The process of maintaining maps in an up-to-date condition is known as revision. The task of map revision can be quite immense notably in those areas where changes are likely to be extensive and rapid, notably urban and highly developed areas.
The term base map is see often in GIS and refers to a collection of GIS data and or ortho-rectified imagery that form the background setting detail necessary to orient the location of the map. Base maps also add to the aesthetic appeal of a map (Caitlin Dempsy; GIS Lounge, 2011)
One produced; this graphic image (map) becomes static, therefore it should be expected that a map may be partly outdated by the time of its publication and it may have to continue in this state for a period of time (Krentes, 1973). Thus, in order to ensure that all maps are up-to-date with all the information and changes which may have taken place with respect to time, the need for map revision and up-to-date will not be overlooked. Therefore, it is of a great importance that maps are been updated in order for its relevance to be appreciated.
1.3 Statement of Problems
Investigation revealed that in most part of the country and in Imo State in particular, most base maps produced several years back and majority of new artificial features such as buildings of different purposes (bank, Hotel, Schools etc.) and roads etc. between when the map is produced and the present times is not properly accounted for and depicted. Thus, making such existing map obsolete and out dated and these maps appear in analogue form. Therefore, no new information can be extracted from the maps like street names, building petrol stations, churches, schools, hotels, fast foods, recreational centers, commercial areas etc. which leads to estimation of expected revenue by the planning authority.
Map revision is essential here because once a map is produced, the graphic image is static and there is a constant need to provide the map with information on changes at the same time reducing defect. Hence, there is need to digitize and update the analogue map of Owerri, Imo State using GIS technique in order to ensure proper planning and development of the area.
1.4 Aim and Objectives of Study
The aim of the study is to produce an updated map of Owerri municipal and Environ using digital techniques. In achieving this aim, the following specific objectives were laid out as follows:
- To use digital technique to update Owerri map.
- To project this map into a given coordinate system.
- To acquire the base map of the study area
- To digitize the acquired maps
- Demonstrating through various analyses, the potential of GIS in the revision and update of the map.
1.5 Scope and Limitation of Study
This project involves the digital revision and update of Owerri map in GIS environment. The scope also outline reconnaissance, acquisition satellite imagery data covering the study area, geo-referencing/rectifying of the scanned Owerri Street Guide map using Arc GIS software, vectorizing the features in the imagery within the extent of the area, cartographic embellishment, initial printing of the updated map.
The work is capital intensive bond requires some amount of man power but less compare to convention technique which is not readily available. Also, it was not easy for the researcher to acquire the coordinate of places. This work has been limited to the use of satellite imagery, old Owerri Street Guide and the use of ground control point from GPS.
1.6 Significance of Study
Maps are produce to show natural and artificial features information especially to visitors and researchers, considering this, there is need to produce maps from data that can portray reality as accurate as possible, in order for the rapid nature of changes is to be accommodated in the map. GIS, an acceptable method of keeping inventory of the earth’s resources offers such powerful data gathering tool. When digitally acquired data is used to produce a map, it will take a new form, encourage new uses and users, and cartographic visualization can be possible with adequate software image manipulation and analysis can be achieved.
The result of the research will reveal the impact of digital mapping. It will also assist other researchers in their work and serve as reference material.