CHAPTER ONE
INTRODUCTION
1.0 BACKGROUND TO THE STUDY
1.0.1 MAP
A map is a pictorial, diagram or analogue (or all) of the surface of the earth (or other mappable area) and is a device for transferring selected information about the mapped area to the map user.
The surface of the earth is a vast area 510,900,000sqkm with a greatly variety of surface features. These may be classed as natural topographic (sea, lakes, rivers, mountains, desert, forecast etc.) none of these features is permanently fixed in size and shape. There are always smaller or larger changes in progress. They constitute the main factor in the environment of mankind, and currently increasing demand for more information about our physical environment map serves as a base tool or bedrock for planning and development of an area or a nation as a whole.
Surveying is typically used to locate and measure property lines; to lay out buildings, bridges, channels, highways, sewers, and pipelines for construction; to locate stations for launching and tracking satellites; and to obtain topographic information for mapping and charting. Surveying is the act of making measurement of the relative positions of natural and man made features of the earth surface , and the presentation of this information either, graphically or numerically (A. Bannister and S. Raymond 1993).
However, Surveying can be described as the art of making measurements upon the earth’s surface for the purpose of producing a map, plan, or estimate of an area and thus making measurements in the horizontal plane, and leveling as taking measurements in the vertical plane (A.L Higins 1974).
An alternative definition, per the American Congress on Surveying and Mapping (ACSM), is the science and art of making all essential measurements to determine the relative position of points and/or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points and/or details. Furthermore, as alluded to above, a particular type of surveying known as “land surveying” (also per ACSM) is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats/maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data. The most common is by the way of a plan, a true to scale representation of an area in two dimensions which forms the horizontal plan, the third dimension, height is normal to the horizontal and can be shown on the plans in various ways.
1.0.2 TOPOGRAPHIC SURVEYING
This is a surveying operation carried out for the purpose of determining both planimetric horizontal and vertical coordinates to establish the position and shape of natural and man made features over a given area usually for the purpose of producing a map of the area. Such surveys are usually classified according to the scale of the final map Viz: Small scale, medium scale or large scale.
Topograpic maps support a diversification of applications. Topographic maps are general purpose maps that represent an area of interest based on scale, projection and with the appropriate cartographic general purpose maps (Sewell, 1995).
Heights information is shown with the aid of contour lines. Entities are represented in terms of points, lines and area with the aid of cartographic symbols. Scale, coordinates and legend and the keys for the map interpretation (Thrower, 1996)
Topographic map are being used for planning, earthwork, military and administrative purposes (Tongkul, 2000)
1.0.3 IMPORTANCE OF TOPOGRAPHICAL MAPPING
Topographical maps are an important tool because they can represent the three – dimensional landscape in two dimensions. A person who can read a topographical map can find out the location of peaks, valleys, ridges and saddles, among other land features. Topographic maps can also show you whether you will be travelling uphill or downhill on a particular road or trail.
1.0.4 CONTOUR LINES
Elevations on a topographic map are marked with contour lines, which connects points of equal elevation. Contour lines show elevation and the shape of the terrain. They’re useful because they illustrate the shape of the land surface — its topography– on the map. E.g. Take an object like a ball or a pile of laundry, and shine a redlaser pointer along the object’s side. The line you see will look like a contour line on a topographic map.
In order to keep things simple, topographic maps show lines for certain elevations only. These lines are evenly spaced apart. We call this spacing the contour interval. For example, if your map uses a 10-foot contour interval, you will see contour lines for every 10 feet (3 meters) of elevation — lines at 0, 10, 20, 30, 40, and so on. Different maps use different intervals, depending on the topography. If, for example, the general terrain is quite elevated, the map might run at 80- to even 100-foot (24.4- to 30.5-meter) intervals. This makes it easier to read the map — too many contour lines would be difficult to work with. Look in the margin of your map to find out its contour interval.
To make topographic maps easier to read, every fifth contour line is an index contour. Because it’s impractical to mark the elevation of every contour line on the map, the index contour lines are the only ones labeled. The index contours are a darker or wider brown line in comparison to the regular contour lines. You’ll see the elevations marked on the index contour lines only. To determine elevations, pay attention to the amount of space in between lines. If the contours are close together, you’re looking at a steep slope.
If the contours have wide spaces in between — or aren’t there at all — the terrain is relatively flat.
1.0.5 LAND FEATURES
The shape of the contour lines can tell you the shape of the landform in a particular area. For example, concentric circles show peak, with the smallest circle marking the summit. Contour lines that are close together indicate that the land is very steep, while contour lines that are spread apart shows that the land is relatively flat. Contour lines that encircle two peaks or two sets of concentric circles can indicate the presence of a saddle, or gap, between two peaks.
1.0.6 METHODS INVOLVED IN MAPPING
Traversing
This is a method in the field of surveying to establish control networks. It is also used in geodetic work. Traverse networks involved placing the survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point. It provides horizontal controls and is carried out to determine the position of (coordinate) of a point by their bearings and distances relatively to a reference point.
Leveling
This is the measurement and mapping of the relative heights of points on the earth’s surface showing them in maps, plane and charts as vertical sections or with conventional symbols.
Tachometry
This is a branch of surveying where details are taken and their heights and distance obtain by optical means only. All data information obtained from the field work are then plotted as a topographical map. But for a small scale mapping, the field measurement method may not be sufficient and then the best option is the use of photogrammetric method.
1.1 PROBLEM STATEMENT
Since the inception of (KASU), there has been no up to date detail topographic map covering exclusively the faculty of science. This project is to produce a digital Map of the Faculty of Science and create Land Information that will provide useful information for planning.
1.2 STUDY AREA
Geology and Hydrogeologic Setting of the Study Area
The study area is Kaduna State University (KASU) Faculty of Science main campus, Kaduna State. It is however located along Tafawa Balewa Way, Ungwan Rimi, Kaduna North Local Government area. It is relatively bounded to the East by Ungwan Rimi, and to the west by Marafa, south of Gamji gate and bounded to the north by the golf course. It is located with coordinates: 100 30I 58.6″ N and 70 27I 7.4″E in the National grid. This falls within the general geology of the Basement complex of Nigeria, where two broad geologic units are recognized namely; The older Precambrian unit of metamorphosed sedimentary rocks consists of quartzite, muscovite schist, muscovite biotite schist, biotite gneiss, migmatite and marble and the younger precambrian igneous rocks comprising of biotite granite, and few plugs of diorite, gabbro and syenite (Alagbe, 1979).
The study area has typical savannah climate with distinct wet and dry seasons. The raining season extends from March/April to September/October and dry season between November and March. Average annual rainfall for Kaduna is 1054 mm (Eduvie, 1998). Rainfall generally reaches its peak in August. Temperature varies between less than 15 C around December/ January and 300 C in March/April. Vegetation consists of broadleaved savannah woodland which, when well developed, may be dense enough to suppress the growth of grasses. The hill features in the area are inselbergs and whalebacks which belong to the category of residual hills commonly associated with massive granite bodies (Mc Curry, 1976). One of the major sources of recharge in the study area is from river Kaduna.
The river is a long tributary of the River Niger and is about 550 km (140 miles) long. Rain water is another recharge source which is seasonal. The area is being discharged through river, ditches to river Kaduna (Mamman, 1992). The hydrogeology of the study area is controlled by factors such as geology, climate and structure. The rocks are predominantly gneisses and migmatites, the relief is generally low, while deep weathering is common with attendant wide spread variation in the ground water level. Appreciable porosity, permeability and storability of aquifer in rocks of the basement complex depend primarily on secondary structural features such as fractures, fissures and joints, there and volume together with the thickness of the weathered zone.
1.3 AIMS
The aim of the project is to produce a more detailed exclusive up to date digital topographic map of Kaduna State University, faculty of science coverage area with the view of showing (relief, natural and artificial features in their relative positions) after carrying out all the field work successfully.
1.4 OBJECTIVES
· To provide a precise Benchmark for the control the construction of buildings and the information that will serve as an initial database for general construction and planning
· To map the area at a scale of so as to clearly show the positional relationship of existing artificial and natural features.
· To detail in all physical feature within the site by any survey techniques
· To plot the locations of the relative positions on the site using any survey software suitable for it.
· To produce a topographical map of the faculty of science (KASU) serving as a reference document and use as a research material.
1.5 SPECIFICATIONS
In terms of understanding this survey project, it is however billed to produce a map of the faculty of science area to a suitable scale and that any instrument could be used, provided it serves the purpose and carrying out a comprehensive detailing of the site in order to produce a map.
1.6 METHODOLOGY
The method employed in the exercise is ground survey method and it includes
(a) Office planning
(b) Reconnaissance
(c) Perimeter survey
(d) Control extension
(e) Detailing
(f) Plotting and digitization
1.7 SCOPE AND LIMITATION
The extent of work done covers the following steps:
Identifying control points of the survey area and plan to carry out extension of control by method to where the allotted mapping area will be carried out.
The type of details found in the map includes.
(a) Buildings
(b) Roads (tarred roads, foot paths)
(c) Electric poles
(d) Culvert drainages
(e) Economic trees
1.8 LIMITATION
The project is only restricted to the faculty of science coverage area
1.9 SIGNIFICANCE OF THE STUDY
The work is immensely significant particularly to new researchers in providing information that will serve as initial database or as the base for further survey and construction. The work will also serve as a guide and provide a very good background for understanding topographical mapping survey.
1.10 EXPECTED RESULT
The project work is expected to produce a map of the area at a suitable scale
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