Accuracy Assessment of Geospatial Data for Cadastral Application: A Case of Addis Ababa City, Ethiopia
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Date
2022-07
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Addis Ababa University
Abstract
Datum transformation is the transformation of coordinate points from one known coordinate
reference system into another. The recent practice of geospatial data collection, management,
and analysis in Ethiopia is in geocentric coordinates of a point defined based on a global datum
(WGS84). However, Ethiopia uses Adindan as the recognized local datum. The current official
transformation parameters in use by Ethiopia are slightly different from the parameters
determined by previous research and adopted in widely used geospatial software packages. In
addition to this, the rotation and scale changes are ignored in the transformation parameters.
The current practice of cadaster in Addis Ababa city is below the accuracy level of all local and
global geospatial data standard guidelines. The main purpose of this study is to assess and
evaluate the Accuracy Assessment of Geospatial Data for Cadastral Application: A Case of
Addis Ababa City, Ethiopia. Statistical analyses have been done for second-order GCP,
orthophoto, and cadastral parcel accuracy assessment analysis based on ASPRS 2014
standards. The positional accuracy of second-order ground control points, orthophoto, and
cadastral parcels evaluated by checkpoints is determined as 0.47m, 1.326m, and 1.87m
respectively at a 95 % confidence level. Finally, the software packages used to convert from
global to local reference datum differ from one another, causing major changes in the values of
specific points. Coordinates values of Orthophoto and static GCPs were converted from WGS84
to Adindan using (X = 162m, Y = 12m, and Z = -206m); the RMS error of easting and northing
values were 0.32 m and 0.69 m respectively. On the other hand, the static GCPs coordinates
were converted by using (X = 165 m, Y =11 m, and Z = -206 m) and compared with orthophoto
coordinates, the RMS error of easting and northing values were 2.65 m and 0.78 m respectively.
And, according to Molodensky-Badekas seven transformation parameters using (169.674 m in
X, 14.801m in y, and -204.841 in Z), the RMS error of easting and northing values were 3.055m
and 0.697 m respectively. Finally, the researcher recommends these parameters shall utilize as
unique and constant values to improve data integrity for geospatial work such as cadastral
application.
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Keywords
Adindan, Cadaster, Coordinate System, Ground Control Point, WGS84