Vector Files Research Articles

Error Tracking in Ikonos Geometric Processing Using a 3D Parametric Model

data, different research studies have addressed the potential of Thirteen panchromatic (Pan) and multiband (XS) Ikonos Geo- high-resolution imagery for mapping. A research study at the product images over seven study sites with various environ- National Mapping Agency of Great Britain used simulated 0.2ments and terrain were tested using different cartographic data m and 1-m Pan images derived from 1:7,500-scale aerial photos and accuracies with a 3D parametric model developed at the and XS 4-m images from the Compact Airborne Spectrographic Canada Centre for Remote Sensing, Natural Resources Canada. Images (Ridley et al., 1997). Some results indicated that the The objectives of this study were to define the relationship future high-resolution satellite imagery would have potential between the final accuracy and the number and accuracy of for improving the existing National Topographic Database of input data, to track error propagation during the full geometric Great Britain from 1-m panchromatic images as well as autocorrection process (bundle adjustment and ortho-rectification), mating the detection of topographic feature change from 4-m XS and to advise on the applicability of the model in opera- images. In another research study, a theoretical analysis based tional environments. on in-track and across-track stereo mapping techniques demonWhen ground control points (GCPs) have an accuracy strated that high-resolution satellite imagery could be used for poorer than 3 m, 20 GCPs over the entire image are a good the generation and updating of national mapping products in compromise to obtain a 3- to 4-m accuracy in the bundle the United States, but only if photogrammetric processing were adjustment. When GCP accuracy is better than 1 m, ten GCPs employed (Li, 1998). Based on this theoretical analysis, an are enough to decrease the bundle adjustment error of either evaluation of the potential accuracy of ground points was panchromatic or multiband images to 2 to 3 m. Because GCP performed using Ikonos stereo images simulated from aerial residuals reflect the input data errors (map and/or plotting), photos (Zhou and Li, 2000). Without ground control points these errors did not propagate through the 3D parametric (GCPs), a positioning accuracy of 12 m in the three axes (X, Y, model, and the internal accuracy of the geometric model is and Z ) was achieved, and with 24 GCPs the accuracy was thus better (around a pixel or less). improved to 3mi n planimetry (X and Y ) and 2 m in elevation. Quantitative and qualitative evaluations of ortho-images More recently, preliminary accuracy tests with real images were thus performed with either independent check points or having a viewing angle of 39 and using a3D parametric geooverlaid digital vector files. Generally, the measured errors metric correction model were performed with few precise confirmed the predicted errors or were even slightly better, GCPs (Toutin and Cheng, 2000; Davies and Wang, 2001). The and a 2- to 4-m positioning accuracy was achieved for the results of the two research studies demonstrated positioning ortho-images depending upon the elevation accuracy (DEM accuracies of 2 to 3 m and confirmed the high mapping potenand grid spacing). To achieve a better final positioning tial of Ikonos images. accuracy, such as 1 m, a DEM with an accuracy of 1 to 2 m This paper expands on the above-mentioned preliminary and with a fine grid spacing is required, in addition to well- results related to the geometric processing and ortho-rectificadefined GCPs with an accuracy of 1 m.

Establishing snowmelt runoff simulating model using remote sensing data and GIS in the west of China

Supported by Geographical Information Systems (GIS), snowmelt runoff simulation models have been built for the large-scale basin in the west of China. Digital Terrain Factors (DTF) were employed for dividing the basin. Using image-processing software, the problems of image correction and match between the satellite image and the images transformed from vector files have been resolved. Meanwhile, the thresholds of snow-pixel in images were achieved by means of a trial-and-error iterative process. Supervising classification techniques were utilized to determine the percentage of snow cover area in different zones and in the whole basin. The experimental watershed of the Qushenan (5286 km 2 ), in the upper reaches of the Yellow River was selected as a test basin. Snowmelt runoff models were developed for each sub-basin from which three vertical zones were simulated separately. The snowmelt runoff was computed by weighting coefficients. The results show that this approach is significant and practical.

Comparison of SAR amplitude vs. coherence flood detection methods - a GIS application

Flood area detection from multipass Synthetic Aperture Radar (SAR) data can be performed via amplitude change detection techniques. These methods allow flooded zones to be discriminated only when they are flooded at the time of the second passage, and not at the time of the first one. Coherence derived from multipass SAR interferometry can be used instead, as an indicator of changes in the electromagnetic scattering behaviour of the surface, thus potentially revealing all the areas affected by the flood event at any time between the two passes. The paper presents a prototype application of such techniques, that is, a flood map obtained from ERS-1/2 data taken over Beziers (Southern France), through proper thresholding of a combination of amplitude and coherence information. Produced in the framework of an ESA project, the map consists of a DXF vector file which can be imported directly into most commercial GIS software.

CT-Generated Porous Hydroxyapatite Orbital Floor Prosthesis as a Prototype Bioimplant

Literature Abstracts: Literature Abstracts-The American Journal of Neuroradiology, 1997: Clinicoanatomic and Pathologic Correlations: PDF Only

Use of Geographical Information Systems in the search for additional populations, or sites suitable for re-establishment, of the endangered Northern Province endemic Euphorbia ctivicola

Euphorbia clivicola R.A. Dyer, an endangered Northern Province endemic, is restricted to only two known populations, both of which are threatened with extinction. The area between and surrounding the known populations, totalling 8874 km 2 , was therefore searched for sites where either unknown populations could exist, or which could represent a suitable habitat for the introduction of a new poputation. A raster-based Geographical Information Systems package, IDRISI for Windows, was utilized to manipulate two point vector files, representing rainfall and altitude of the searched area, digitized within the TOSCANELLI system. The INTERPOL module produced two digital elevation models, from which the SURFACE module created slope and aspect images representative of the searched area RECLASS and OVERLAY modules were finally utilized to identify 12 potential sites, covering only 1.4% of the total searched area. Ground-truthing is now needed to determine the presence or absence of further populations and to assess habitat suitability. This study emphasizes an additional application of GIS techniques to investigations with relevance to the biological sciences, specifically to problems of rare and threatened species. GIS represents a cost-effective alternative method for addressing these problems by focusing ground searching activities to only a small number of potential sites.

TIGER/Line files in teaching GIS

Abstract This paper offers a teaching strategy for incorporating TIGER/Line files into introductory GIS courses where IDRISI and OSUMAP are the primary software packages. TIGER/Line files present a valuable database for teaching GIS. The TIGER data structure aids in teaching concepts related to topological data structures, geocoding and address matching, and the files themselves provide an excellent database for laboratory exercises that incorporate census information along with environmental and natural resource data. Lack of support by commonly-used educational software packages to import TIGER/Line files directly has been a serious impediment in an instructional context. This paper presents software developed to convert TIGER/Line files into simple polygon vector files acceptable by IDRISI and OSUMAP for three alternative census geographic units (tracts, block groups and blocks). The resulting vector files are plotted for visual examination and graphical output. The vector files generated can also be i...

The design of a user friendly statistical software package for the IBM personal computer and compatibles written in Turbo Pascal

The design and features of a user friendly statistical software package for the IBM personal computer and IBM PC compatibles (PC VSTAT) is described. The software package, written in Turbo Pascal, requires an IBM Personal Computer or IBM PC compatible computer with either two floppy disk drives or one fixed (hard) disk and one floppy disk drive, and a line printer to obtain hard copies of the output. The most important feature of this statistical software package is the use of data vector files as storage for the experimental observations. The use of PC VSTAT does not require any previous programming experience and uses a menu format for selection of options. A number of special programming techniques were used to facilitate user input and to make the software package user friendly. PC VSTAT permits the user to name, create, delete, and edit data vectors, list data, sort data, manipulate data mathematically, produce frequency tables and histograms, perform linear regression and correlation, perform nonlinear (quadratic and cubic) regression, produce scatter plots, generate random sampling sequences and generate random numbers, and perform a number or statistical hypothesis tests such as t-tests, F-tests, Chi-Square tests and Kolmogorov-Smirnov tests. Output may be displayed on the screen or directed to a line printer. PC VSTAT uses algorithms to compute the probability values for the corresponding values of the test statistics. User acceptance has been excellent with much positive feedback concerning the speed at which calculations are completed (a feature of the Turbo Pascal programming language) and the friendly interface that exists between the user and the computer via the menu format. This package is well suited for the user in an introductory statistics class and for the analysis of research data which requires basic data manipulation, descriptive statistical measures, simple hypothesis testing and goodness-of-fit testing.

An algorithm for programming electrostatic plotter type devices

AbstractElectrostatic plotter type devices, CRT or hardcopy, are basically printers which allow the ‘paper’ movement only in one direction. As a result, the entire display file has to be created before the process of generating the display can begin. This arrangement differs significantly from the X‐Y plotters where the ‘plotting pencil’ and/or paper may be moved in any direction. An algorithm for generating a display on the electrostatic plotter type devices is described in this paper. This algorithm is based upon creating and maintaining a vector file consisting of end points of visible vectors, sorting these vectors, and then generating the plot—a strip at a time. Only the points that lie within the strip are calculated. The details of implementation and the data structure used are discussed. There is no restriction on the size of the display that can be generated; in fact, plots of size 100 in by 20 in have been produced using this algorithm. No a‐priori knowledge of the extent of the plot is required. The algorithm has been designed to operate in a device independent computer plotting system and has worked very satisfactorily without imposing any restrictions on the users.

A Discriminant Analysis of the Mmpi for Female College Students in Health and Education

THE MAIN purpose of this investigation was to see if a number of curriculum groups in the health related professions could be differentiated from each other on the basis of personality variables as measured by the Minnesota Multiphasic Personality Inventory (MMPI). Considerable effort is being ex pended at the University of Florida's College of Health Related Professions to find personality, ap titude, interest, and other differences among stu dents in the health related professions (i. e. Occu pational Therapy, Physical Therapy) which will ul timately enable counselors to function more effec tively in the advising of students into and out of these professions. There have been a number of studies where the MMPI was used to determine personality differ ences among college majors. Lough (7) found the MMPI to be of little or no value for detecting differ ences among women students in liberal arts, nurs ing, and teacher training. Norman and Redlo (8) found that certain scales differentiated certain cur ricula from each other for seven curriculum groups of female students. Clark (2) found that profiles for each of a large number of college majors (13 majors for males and 12 majors for females) showed few significant differences from the average college pro f i le. It is of interest to note that the majority of these differences were on the Masculinity-Femi ninity scale, which is interpreted by many investi gators as an interest scale. Harder (5) found no MMPI differences among business, education, and engineering students that were useful is describing these groups. The results of these studies have not been partic ularly encouraging. However, in all of the above studies, the data were handled in a most inefficient manner. The most efficient manner to handle mul tivariate data of this nature is through the use of dis criminant function analysis. Discriminant analysis I involves considering the complete test vector or pro file in a single analysis. Univariate analyses such as those used in the above-mentioned studies do not take into account.the intercorrelations among the measures and consequently do not make full use of the data. For example, it is possible that not one single variable out of a number of variables will sig nificantly differentiate among the groups, while a test of significance involving the complete profile will yield significant differences among these groups. Furthermore, discriminant analysis indicates not only whether the groups differ significantly f r o m one another, but also the practicality of these differ ences, e.g. the effectiveness with which individuals can be predicted to belong to various groups on the basis of their test scores. Discriminant analysis answers this question. Excellent re views of dis criminant analysis are given by TatsuokaandTiede man (10) and Creager (4). Theoretical and computa tional details are treated in detail by Rao (9) and Kendall (6). It is possible that the MMPI would yield useful differences among college majors if the data were handled by multivariate techniques. Consequently, discriminant analysis was utilized in the present in vestigation. The college majors of most interest to the pres ent investigator were Medical Technology (MT), Oc cupational Therapy (OT), and Physical Therapy (PT), since these are the undergraduate educational pro grams in the College of Health Related Professions. However, two other groups were included in the analysis for comparison purposes. These groups are Nursing (N) students and Education (E) majors. Although Ns are not in the College of Health Related Professions, their roles are similar to those of stu dents in these professions. The Es, of course, are the furthest removed from the Health Related P r o I fessions.