A Combined Method For Digital Terrain Models Generation

الموضوعات

علوم تطبيقية وتكنولوجية

الملخص

Recent studies have shown that the various methods of generating DigitalTerrain Model (DTM) from its discrete form to a continuous one usingsimple functions suffer from the influence of terrain complexity and thedensity of the data points that can introduce significant errors in the finalgenerated model.The interpolation of the grid node is generally carried out using some functions. Thesefunctions are based on the assumption that the measured height values are autocorrelatedi.e. the adjacent points on the surface are expected to have the same value.This assumption is only true when the terrain surface is smooth. However, in the caseof a variable and mountainous terrain, the assumptions made about the underlyingvariation (correlation) of the measured height values can be critical.For a successful application of the simple functions in these terrain the density of themeasured sample data must be increased. The acquisition of this data by groundsurvey methods, photogrammetric method or digitization is time consuming andfinancially constitutes a major cost in the overall process of DTM generation. It canbe seen from the above that the use of the simple functions in DTM genearation in avariable terrain surface would be of no meaning if the number of measured heightvalues is not reduced.In this thesis a new method that can effectively be used in the generation of DTM in avariable terrain surface is proposed. The new method which is known as a combinedmethod uses a few number of discrete sample points in the interpolation of grid nodes.IVThe variations in the measured height values resulting from the variations in terrainsurface are modelled statistically in a function known as covariance function.The covariance function is used for an apriori analysis of the correlation between themeasured heights around the interpolated point and to compute the necessarycovariance matrices which are used to interpolate the value of the unknown point.The height value of each grid node is computed using a combination of least squaressurface fitting and least squares collocation method.The performances of the new method together with performance of the six choseninterpolation methods in two sites were evaluated. The sites considered represent twovariable terrain types. Test points were selected randomly for each site considered,and the interpolated values at the selected points were tested statistically. These testsrevealed in addition to the reduction of the need for measurement of large data points,a high potential of the combined method in relation to a substantial improvement inthe precision. Although, the method may be regarded as an accurate method ofgenerating DTM in variable terrain, there are cases when the performance of themethod decline. This is not a disadvantage of the method itself but is rather due tosparseness of data points.

روابط وملفات

التعريف والنوع

رقم الوثيقة

0e46d0b5-47cf-44aa-9f20-a4595f161619

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل دكتوراة

نوع الملف

pdf text

أسماء الملفات

1637213_1.pdf

بيانات النشر

ألقاب المؤلفين

[{"name_ar":"Elshami M. Masaad","title_ar":"اشراف","title_en":"Supervision"},{"name_ar":"James Janthana Bango","title_ar":"اعداد","title_en":"Preparation"}]

اللغة

English

المصدر والدورية

اسم المصدر

A Combined Method For Digital Terrain Models Generation

المحتوى والصفحات

عدد الصفحات

0

إشراف وإعداد

الإشراف

Elshami M. Masaad

الإعداد

James Janthana Bango

الاقتباسات الببليوغرافية