This paper presents an analysis of four open-source Global Digital Elevation Models (GDEMs) and compares them on two topographic profiles (nearly flat, and hills regions) for mapping and geomatics applications. The ch...This paper presents an analysis of four open-source Global Digital Elevation Models (GDEMs) and compares them on two topographic profiles (nearly flat, and hills regions) for mapping and geomatics applications. The chief intention is to investigate if GDEMs-based heights, contour intervals, slopes, and topographic profiles are valid for all map scales of topographic mapping, which constitutes a major issue in mapping activities. Two case studies, the Nile delta in Egypt and Makkah city in Saudi Arabia, have been utilized to represent flat and moderate-topography patterns. The investigated GDEMs include the most-recent released models: ASTER v.3, ACE 2, SRTMGL1 v.3, and NASADEM_HGT v.1 released in 2019 and 2020 with spatial resolutions of 1 and 3 arc seconds. Available accurate Ground Control Points (GCP) consist of 540 stations in the Nile delta and 175 stations in Makkah. Based on the available datasets in two study areas, it has been found that the accuracy of investigated GDEMs over known checkpoints ranges from ±2.5 and ±5.1 meters in the Nile delta region, while it varies between ±5.1 and ±8.0 meters in the Makkah area. That indicates that the utilization of GDEMs in topographic mapping differs significantly between flat and hilly spatial regions. Therefore, it is recommended to avoid using GDEMs for developing topographic maps of scale 1:25,000 or larger in flat regions and map scale 1:50,000 or larger in hilly regions. Additionally, the accomplished results showed that all GDEM-based slopes do not match with the actual slopes from known GCP over cross section’s length up to 30 kilometers. Thus, it is concluded that GDEMs are not the appropriate heights’ source for topographic mapping at medium and large map scales, and could not be utilized for topographic profiling in precise engineering and geomatics applications.展开更多
Building on a new model proposed recently for calculating constant electro-magnetic field values, the present article explores the electro-magnetic field configuration generated by parallel electrical wires. This impo...Building on a new model proposed recently for calculating constant electro-magnetic field values, the present article explores the electro-magnetic field configuration generated by parallel electrical wires. This imposes a reevaluation of the drawing procedure for constructing field curves with a constant field values around multiple parallel electrical conducting wires. To achieve this, we employ methods akin to those used for creating contours on topographical maps, ensuring a consistent numerical field value along the entire length of the field curves. Subsequent calculations will be conducted for scenarios where wires are not parallel.展开更多
An often unrecognized problem is the geology and glacial history paradigm’s inability to explain topographic map drainage system and erosional landform evidence, which means geology research studies rarely address th...An often unrecognized problem is the geology and glacial history paradigm’s inability to explain topographic map drainage system and erosional landform evidence, which means geology research studies rarely address that type of topographic map evidence. The problem originated in the late 19<sup>th</sup> century with William Morris Davis who is sometimes called the father of geomorphology and was one of the first geologists to interpret what in the late 19<sup>th</sup> century were newly available topographic maps. An 1889 Davis paper describes selected drainage system evidence observed on an advance copy of the 1890 Doylestown (Pennsylvania) topographic map and an 1892 Ward paper written after discussions with Davis describes additional selected drainage system evidence seen on the same map. Both papers fail to mention the majority of the Doylestown map’s drainage system features including most barbed tributaries, asymmetric drainage divides, and through (dry) valleys crossing major drainage divides. Had Davis used all of the map’s drainage system and erosional landform evidence he should have recognized the map evidence shows headward erosion of an east-oriented Neshaminy Creek valley captured southwest-oriented streams which headward erosion of the south-oriented Delaware River valley and its east-oriented tributary Tohickon Creek valley had beheaded. Consciously or unconsciously, Davis chose not to alert future investigators that Doylestown topographic map evidence did not support his yet-to-be-published Pennsylvania and New Jersey erosion history interpretations and instead Davis proceeded to develop and promote erosion history interpretations which the map evidence did not support.展开更多
文摘This paper presents an analysis of four open-source Global Digital Elevation Models (GDEMs) and compares them on two topographic profiles (nearly flat, and hills regions) for mapping and geomatics applications. The chief intention is to investigate if GDEMs-based heights, contour intervals, slopes, and topographic profiles are valid for all map scales of topographic mapping, which constitutes a major issue in mapping activities. Two case studies, the Nile delta in Egypt and Makkah city in Saudi Arabia, have been utilized to represent flat and moderate-topography patterns. The investigated GDEMs include the most-recent released models: ASTER v.3, ACE 2, SRTMGL1 v.3, and NASADEM_HGT v.1 released in 2019 and 2020 with spatial resolutions of 1 and 3 arc seconds. Available accurate Ground Control Points (GCP) consist of 540 stations in the Nile delta and 175 stations in Makkah. Based on the available datasets in two study areas, it has been found that the accuracy of investigated GDEMs over known checkpoints ranges from ±2.5 and ±5.1 meters in the Nile delta region, while it varies between ±5.1 and ±8.0 meters in the Makkah area. That indicates that the utilization of GDEMs in topographic mapping differs significantly between flat and hilly spatial regions. Therefore, it is recommended to avoid using GDEMs for developing topographic maps of scale 1:25,000 or larger in flat regions and map scale 1:50,000 or larger in hilly regions. Additionally, the accomplished results showed that all GDEM-based slopes do not match with the actual slopes from known GCP over cross section’s length up to 30 kilometers. Thus, it is concluded that GDEMs are not the appropriate heights’ source for topographic mapping at medium and large map scales, and could not be utilized for topographic profiling in precise engineering and geomatics applications.
文摘Building on a new model proposed recently for calculating constant electro-magnetic field values, the present article explores the electro-magnetic field configuration generated by parallel electrical wires. This imposes a reevaluation of the drawing procedure for constructing field curves with a constant field values around multiple parallel electrical conducting wires. To achieve this, we employ methods akin to those used for creating contours on topographical maps, ensuring a consistent numerical field value along the entire length of the field curves. Subsequent calculations will be conducted for scenarios where wires are not parallel.
文摘An often unrecognized problem is the geology and glacial history paradigm’s inability to explain topographic map drainage system and erosional landform evidence, which means geology research studies rarely address that type of topographic map evidence. The problem originated in the late 19<sup>th</sup> century with William Morris Davis who is sometimes called the father of geomorphology and was one of the first geologists to interpret what in the late 19<sup>th</sup> century were newly available topographic maps. An 1889 Davis paper describes selected drainage system evidence observed on an advance copy of the 1890 Doylestown (Pennsylvania) topographic map and an 1892 Ward paper written after discussions with Davis describes additional selected drainage system evidence seen on the same map. Both papers fail to mention the majority of the Doylestown map’s drainage system features including most barbed tributaries, asymmetric drainage divides, and through (dry) valleys crossing major drainage divides. Had Davis used all of the map’s drainage system and erosional landform evidence he should have recognized the map evidence shows headward erosion of an east-oriented Neshaminy Creek valley captured southwest-oriented streams which headward erosion of the south-oriented Delaware River valley and its east-oriented tributary Tohickon Creek valley had beheaded. Consciously or unconsciously, Davis chose not to alert future investigators that Doylestown topographic map evidence did not support his yet-to-be-published Pennsylvania and New Jersey erosion history interpretations and instead Davis proceeded to develop and promote erosion history interpretations which the map evidence did not support.
