Changing coordinates using appropriate mathematical models from one reference system to another may be influenced if the operation requires the change of datum. A set of transformation parameters has been adopted for ...Changing coordinates using appropriate mathematical models from one reference system to another may be influenced if the operation requires the change of datum. A set of transformation parameters has been adopted for Nigeria. However, the critical concern usually associated with the problem of transformation of coordinates is the issue of recoverability of the original values of transformed coordinates. The recursive effect of variables associated with spatial problems can be aptly modelled with an appropriate algorithm that set out a process to achieve a definite output. Consequently, the main thrust of this paper is to highlight the critical elements of the mathematical algorithm associated with the National Transformation Version 2 (NTv2) model adapted for the Nigerian Datum Transformation process. The adapted NTv2 model adopts the bi-linear interpolation approach and the covariance function obtained were used to generate transformation elements in latitude (Δ<em>φp</em>) and longitude (Δ<em>λp</em>) and corresponding accuracies at the lattice nodes. The mathematical algorithm of this adapted NTv2 model underscores the likely attainment of better and significant values and statistical indicator of the improved accuracy as the average shift values for latitude and longitude for any transformed points in Nigeria. This capability makes the mathematical algorithm to be adaptable and fit for the purpose of the transformation process. The improvement in the positional accuracy is directly attributable to the application of the NTv2 model which provides a flexible and robust system of modelling any inherent systematic error in the national network.展开更多
As there is datum redundancy in tradition database and temporal database in existence and the quantities of temporal database are increasing fleetly. We put forward compress storage tactics for temporal datum which co...As there is datum redundancy in tradition database and temporal database in existence and the quantities of temporal database are increasing fleetly. We put forward compress storage tactics for temporal datum which combine compress technology in existence in order to settle datum redundancy in the course of temporal datum storage and temporal datum of slow acting domain and momentary acting domain are accessed by using each from independence clock method and mutual clock method .We also bring forward strategy of gridding storage to resolve the problems of temporal datum rising rapidly.展开更多
Since 1990, positioning technology has undergone a dramatic improvement in terms of accuracy and accessibility. Prior to 1990, national geodetic datums were considered to be static with fixed coordinates assigned to t...Since 1990, positioning technology has undergone a dramatic improvement in terms of accuracy and accessibility. Prior to 1990, national geodetic datums were considered to be static with fixed coordinates assigned to the datum origin by convention. Datum coordinates were dynamic only as a consequence of re-observation and re-adjustment, or localized disturbance. This strategy has been suitable for terrestrial surveys within stable continental areas. The accessibility of Precise Point Positioning “PPP” is now widespread with the provision of free online processing facilities by various geodetic agencies. Such ready accessibility to a global datum has serious implication for this technology with static geocentric datums. The Geocentric Datum of Egypt (ITRF1994 Epoch 1996 based on GPS Observation Campaign 1996), for example, is now offset by -42.0 to +32.0cm from the ITRF2008 Epoch 2015 due to the inexorable tectonic movements of the Nubian plate since the datum realization in 1996. Unless the local geocentric datums are kept in step with global terrestrial reference frames, discrepancies between the two will increase in magnitude over time and will become discernable, even using PPP. The PPP users nowadays are unaware of this datum offset and incorrectly assume that a coordinated datum monument is in error if there is found to be a disagreement greater than the level of accuracy of the positioning technique. In this study, to avoid the discrepancies between the applied datum and On-Line GNSS Services, a semi-kinematic datum and related deformation mode are proposed for Egypt. The result also confirmed that the PMM model was giving good performance for the other parts out of Egypt. The evaluation study shows the best performances for the Egyptian deformation model over the ITRF2008 PMM.展开更多
文摘Changing coordinates using appropriate mathematical models from one reference system to another may be influenced if the operation requires the change of datum. A set of transformation parameters has been adopted for Nigeria. However, the critical concern usually associated with the problem of transformation of coordinates is the issue of recoverability of the original values of transformed coordinates. The recursive effect of variables associated with spatial problems can be aptly modelled with an appropriate algorithm that set out a process to achieve a definite output. Consequently, the main thrust of this paper is to highlight the critical elements of the mathematical algorithm associated with the National Transformation Version 2 (NTv2) model adapted for the Nigerian Datum Transformation process. The adapted NTv2 model adopts the bi-linear interpolation approach and the covariance function obtained were used to generate transformation elements in latitude (Δ<em>φp</em>) and longitude (Δ<em>λp</em>) and corresponding accuracies at the lattice nodes. The mathematical algorithm of this adapted NTv2 model underscores the likely attainment of better and significant values and statistical indicator of the improved accuracy as the average shift values for latitude and longitude for any transformed points in Nigeria. This capability makes the mathematical algorithm to be adaptable and fit for the purpose of the transformation process. The improvement in the positional accuracy is directly attributable to the application of the NTv2 model which provides a flexible and robust system of modelling any inherent systematic error in the national network.
文摘As there is datum redundancy in tradition database and temporal database in existence and the quantities of temporal database are increasing fleetly. We put forward compress storage tactics for temporal datum which combine compress technology in existence in order to settle datum redundancy in the course of temporal datum storage and temporal datum of slow acting domain and momentary acting domain are accessed by using each from independence clock method and mutual clock method .We also bring forward strategy of gridding storage to resolve the problems of temporal datum rising rapidly.
文摘Since 1990, positioning technology has undergone a dramatic improvement in terms of accuracy and accessibility. Prior to 1990, national geodetic datums were considered to be static with fixed coordinates assigned to the datum origin by convention. Datum coordinates were dynamic only as a consequence of re-observation and re-adjustment, or localized disturbance. This strategy has been suitable for terrestrial surveys within stable continental areas. The accessibility of Precise Point Positioning “PPP” is now widespread with the provision of free online processing facilities by various geodetic agencies. Such ready accessibility to a global datum has serious implication for this technology with static geocentric datums. The Geocentric Datum of Egypt (ITRF1994 Epoch 1996 based on GPS Observation Campaign 1996), for example, is now offset by -42.0 to +32.0cm from the ITRF2008 Epoch 2015 due to the inexorable tectonic movements of the Nubian plate since the datum realization in 1996. Unless the local geocentric datums are kept in step with global terrestrial reference frames, discrepancies between the two will increase in magnitude over time and will become discernable, even using PPP. The PPP users nowadays are unaware of this datum offset and incorrectly assume that a coordinated datum monument is in error if there is found to be a disagreement greater than the level of accuracy of the positioning technique. In this study, to avoid the discrepancies between the applied datum and On-Line GNSS Services, a semi-kinematic datum and related deformation mode are proposed for Egypt. The result also confirmed that the PMM model was giving good performance for the other parts out of Egypt. The evaluation study shows the best performances for the Egyptian deformation model over the ITRF2008 PMM.
