Reliance on ground coordinate measurements produced by DGPS post-processing

الملخص EN

Some users of the GPS take the coordinates and the distances between points as they are in the field and try to joint work with the total station, but they found a difference between the coordinates and the distances.

The reason is that these measurements are three-dimensional Coordinates : where they are represented on the model of the Earth, while the total station based on the theory of plan survey are two-dimensional coordinates.

And other causes the distortion resulting from the projection itself.

From the scientific point of view, all the solutions applied for this problem are not accurately enough, but serve their purpose.

Where as in this research we are trying to cancel the differences in the coordinates and the distances between the GPS and the total station measurements.

Where work on a project using both techniques (GPS, and Total station) .The coordinates of the project are measured on the site by considering the total length of the project (35km) and ten control points as base line points had been distributed along the route including the X and Y coordinates corresponding to the zone N38.

It was found that the DGPS Software (Topcon Tools v7) or other data collection software can be used to convert the coordinates from grid coordinates to ground coordinates and then these coordinates can be used with the total station in the field for small distances.

But for large distances the ground coordinates that obtained from Total station instrument must be used to avoid accumulative error.

And must also take into account when choosing sites of the control network in the field where it should be direct view between the control network points to get rid of random errors resulting from the use total station this in turn leads to obtain high accuracy results for the ground coordinates.