SaLIS Vol. 65, No. 4

December 2005

 

Rainfall Trends in the Badia Region of Jordan

Nadhir Al-Ansari and Serwan M.J. Baban

 

In Jordan, like in other semi-arid countries in the region, water resources are increasingly becoming an important factor in its stability, growth, and national security. This study examines the rainfall record of 25 stations during the period 1967-1995 to determine periodicity and interrelations between stations using power spectral, harmonic analysis, and correlation coefficient techniques. The ARIMA model is used to forecast rainfall trends in individual stations up to the year 2020. The outcomes show that the intensity of rainfall has been decreasing with time since 1967, and this trend is likely to continue into the future. The average annual rainfall is relatively low (90 mm/y), and there are some significant differences in rainfall values between the stations due mainly to topography. Stations with the same altitude that are close geographically tend to have a strong statistical association and show a similar rainfall trend. Furthermore, a statistically significant relationship was established between vegetation index (derived from remotely sensed data) and rainfall intensity. The outcomes from this study can be used as a basis for planning future agricultural, economic, and social development in Jordan and in the Badia region, in particular.

KEYWORDS: Rainfall, forecasting, Jordan

 

 

Updating Geospatial Data: A Theoretical Framework

J. Raul Ramirez

 

The currency of geospatial data is critical for the analysis and visualization of the environment. Out-of-date geospatial data have historical value, but if the data are used to analyze current events, the results could be contaminated to a point where they are incorrect or completely wrong. There are two possible solutions to the problem of outdated geospatial data. The first solution is to collect the data again and then generate new maps or any other type of geospatial data visualization. This approach is very costly, especially for countries that are of medium to large size. The second solution is the identification of changes to the landscape and the replacement of these changes by new data. This paper presents the theoretical framework for updating geospatial data. Two major issues are discussed: (1) how to detect changes in the data, and (2) how to correct the changes.

 

 

Computation of Reservoir Storage Capacity and Submergence Using GIS

Ritesh Vijay, Apurba Gupta, and Sukumar Devotta

 

Measurement of volumes is an important task in many civil engineering projects. In designing dams, the volumes that need to be determined are storage and submergence. In this paper, a GIS-based algorithm has been developed to compute storage capacities and submergence scenarios of reservoirs with varying dam height. The computation is based on a digital elevation model (DEM) of the topography and triangulated irregular networks (TIN). The method requires that real-world coordinates are used for the computations, which highlights the need for surveying.

KEYWORDS: Storage, submergence, DEM, TIN, GIS

 

 

Developing a GIS Database for the Gray Fossil Site, Tennessee, Based on Modern Surveying

Jerry W. Nave, Tarig A. Ali, and Steven C. Wallace

 

The selection of an appropriate data acquisition method is a significant phase of GIS design, because the data determine the scale and accuracy of the analysis in the GIS.  In the case of fossils, the method selected must provide precise mapping of all sizes of fossils uncovered at the paleontological site. Historically, paleontologists have used different methods to establish the approximate locations of fossils. A commonly used method consisted of string line grids and measuring tapes to provide arbitrary x, y and z coordinates. The maps produced using these methods often lacked accuracy were not replicable and did not provide any information about the conditions of the site. We studied how modern land surveying can enable fast accurate, replicable and precise mapping of fossils in 3D. First, the horizontal control monuments in the site were fixed using Global Positioning System (GPS), and a vertical control network was established by running an accurate, level loop from nearby state traverse control stations to the monuments within the site. Based on that, control stations were established throughout the project site, locating the existing geologic strata and providing a control network for the site base map. One challenge we faced was the design of a linkage mechanism that establishes unique identifiers for the fossils uncovered at the site. These identifiers are essential for determining fossil attributes and ensuring the consistency, integrity and completeness of the GIS database. The integration of modern land surveying techniques with GIS in this project has provided researchers with additional tools for spatial analysis, evaluation of site conditions and accurate relocation of fossils in the field.

 

 

The Quilt and the Rain: Vignettes of Historical Consciousness, by a Land Surveyor

Joseph T. Stuart

 

The past is very important to surveyors for the successful completion of their jobs. But the connection between land surveying and history goes much deeper. Learning to “think historically” can yield a more accurate and a more just understanding of the surveying profession. Furthermore, knowledge of the past can not only give one a new perspective on one’s job, but it can also begin to deepen one’s personal experience of the present (symbolized in this article by a quilt and the rain), and make life so much richer.