Topographic maps analysis and digital update in Wasit Governorate

Topographic maps are among the most important types of maps used in a wide range of scientific and practical applications. The term topography refers to the detailed description of the Earth's surface and its natural and human-made features, whether the area concerned is an entire city or a relatively small part of the Earth's surface. Topographic maps are generally produced at relatively large scales, allowing natural and human features to be represented with a high degree of spatial accuracy. One of their most important characteristics is their ability to represent terrain and elevation in a three-dimensional manner on a two-dimensional surface using contour lines. This distinguishes topographic maps from general maps, which mainly represent the spatial distribution of features without providing the same level of detail regarding elevation and terrain. Topographic maps have extensive practical applications, including land-use classification, agricultural and urban planning, assessment of agricultural and urban areas, mineral exploration, irrigation-project studies, soil-erosion assessment, selection of sites for power lines and towers, design of dams, drainage channels and ports, pipeline planning, and the construction of airports, railway networks, and transportation routes. They also constitute an essential base for producing various thematic maps. Furthermore, contour lines provide valuable information for identifying landforms and understanding the geomorphological and geological characteristics of a study area. Cartographic generalization is a fundamental process in the production and updating of topographic maps. It aims to reduce unnecessary details while preserving and emphasizing the principal features according to the map scale and its intended purpose. This process is applied both during the production of the original map and when converting maps between different scales. In this study, cartographic generalization was applied using previous and updated topographic maps at a scale of 1:50,000, which was considered appropriate for the extent of the study area and for representing its major natural and human features. The generalization process included feature selection and elimination, simplification, enhancement, aggregation, reduction, exaggeration, displacement, classification, and symbolization, as well as the generalization of point, line, and polygon features and the placement and generalization of map text. The study area is located in Wasit Governorate, in the eastern part of central Iraq. It extends between latitudes 31°55′11″–33°31′41″ N and longitudes 44°30′43″–46°34′32″ E. The governorate is bounded by Baghdad Governorate to the northwest, Diyala Governorate to the north, Babil and Al-Qadisiyah Governorates to the west, Dhi Qar Governorate to the south, Maysan Governorate to the southeast, and the Islamic Republic of Iran to the east. The total area of Wasit Governorate is approximately 17,153 km², representing about 3.95% of the total area of Iraq. The temporal extent of the study represents the most recent period available for updating the maps using remote-sensing data and satellite imagery to detect spatial changes in the study area. To achieve the objectives of the study, a systematic methodological framework was adopted. The work began with the collection of spatial and descriptive data, including previous and updated topographic maps, satellite imagery with appropriate spatial resolution, and Digital Elevation Models (DEMs) used to derive terrain characteristics. A geographic database was subsequently established through scanning the paper maps, performing georeferencing using a unified coordinate system and ground control points, digitizing geographic features, and organizing them into multiple spatial layers within a Geographic Information System (GIS) environment. Spatial changes between different time periods were then detected, and the topographic map elements were updated according to established cartographic standards to produce more accurate and functional digital maps. The study employed several specialized software applications for spatial-data processing, satellite-image analysis, and digital map production, including ArcGIS 10.4.1, ArcCatalog, ArcMap, ERDAS IMAGINE, Google Earth Pro, and Microsoft Excel. Geographic Information System and remote-sensing techniques were also used to analyze spatial data and produce updated digital maps. The results showed that Wasit Governorate exhibits considerable spatial variation in its natural and human characteristics. From a topographic perspective, the study area can generally be divided into a hilly region, occupying the eastern part of the governorate, and a plain region, covering most of the remaining area. The hilly region generally slopes from the northeast toward the southwest, whereas the plain region is characterized by a gentle slope toward the southwest. The study area also contains a network of permanent and seasonal rivers, several wetlands and marsh areas, and diverse geomorphological features of structural, erosional, depositional, aeolian, and evaporitic origins. From the human perspective, the digital maps revealed spatial variations in the distribution and extent of residential areas and agricultural lands, including both cultivated and uncultivated areas. The governorate also contains an extensive network of primary and secondary roads, some of which are operational while others remain under construction, in addition to numerous steel and concrete bridges distributed throughout the governorate. The study demonstrates the importance of updating topographic maps digitally using Geographic Information Systems (GIS) and remote-sensing techniques, as these technologies provide an accurate spatial database that can support spatial planning, sustainable development, natural and human resource management, and decision-making in Wasit Governorate.