13.3.1 Orthophoto Production
13.3.1.1 Geodetic Works
Turkey initiated the study first on geodetic issues. The total area of Turkey was
divided into 67 blocks to facilitate the optimal organization of data acquisition and
the Notice to Airmen (NOTAM) authorization process and to organize the subsequent processes of ground control point (GCP) surveys, aerial triangulation, and
orthophoto production into unified units of manageable size in terms of the number
of images and data size (Fig. 13.1). Each block is the size of 1.0
latitude and 1.5
longitude in transverse Mercator zones; 3
-wide transverse Mercator zones are
specified as the official reference map projection of the LPIS project. In addition,
the longitudinal size of 1.5
was chosen to ensure optimal flying time over a single
line limited by inertial measurement unit (IMU) drift. With turboprop aircraft, such
lines can be flown in 20 minutes, which ensures the minimal accumulation of errors
caused by IMU drift (Demirkol 2015).
Geodetic works included documentation, pre-signalization, and global navigation
satellite system (GNSS) surveying as well as continuously operating reference
stations (CORS) static GNSS data processing and adjustment starting from the
western region of Turkey and progressing eastward covering the entire country.
Prior to the LPIS GNSS survey campaign, comprehensive test surveys and computations were performed in the field in order to design the survey plan and to assure
the accuracy of the resulting GCP coordinates. According to the results of the test
work, it was concluded that an observation time of 1 h with a 1.0-second recording
interval (RCI) at each GCP was required.
Geodetic coordinates (latitude, longitude, and ellipsoidal height) of the GCPs in
ITRF96 datum at 2005.0 reference epoch were computed using GNSS data from
CORS in Turkey (CORS-TR /TUSAGA-AKTIF). This computation began in
October 2014, restarted in early March 2015 after the winter season, continued
Fig. 13.1 Photogrammetric blocks and final GCP distribution
238
H. Erden and M. Aslan
13.3.1.1 Geodetic Works
Turkey initiated the study first on geodetic issues. The total area of Turkey was
divided into 67 blocks to facilitate the optimal organization of data acquisition and
the Notice to Airmen (NOTAM) authorization process and to organize the subsequent processes of ground control point (GCP) surveys, aerial triangulation, and
orthophoto production into unified units of manageable size in terms of the number
of images and data size (Fig. 13.1). Each block is the size of 1.0
latitude and 1.5
longitude in transverse Mercator zones; 3
-wide transverse Mercator zones are
specified as the official reference map projection of the LPIS project. In addition,
the longitudinal size of 1.5
was chosen to ensure optimal flying time over a single
line limited by inertial measurement unit (IMU) drift. With turboprop aircraft, such
lines can be flown in 20 minutes, which ensures the minimal accumulation of errors
caused by IMU drift (Demirkol 2015).
Geodetic works included documentation, pre-signalization, and global navigation
satellite system (GNSS) surveying as well as continuously operating reference
stations (CORS) static GNSS data processing and adjustment starting from the
western region of Turkey and progressing eastward covering the entire country.
Prior to the LPIS GNSS survey campaign, comprehensive test surveys and computations were performed in the field in order to design the survey plan and to assure
the accuracy of the resulting GCP coordinates. According to the results of the test
work, it was concluded that an observation time of 1 h with a 1.0-second recording
interval (RCI) at each GCP was required.
Geodetic coordinates (latitude, longitude, and ellipsoidal height) of the GCPs in
ITRF96 datum at 2005.0 reference epoch were computed using GNSS data from
CORS in Turkey (CORS-TR /TUSAGA-AKTIF). This computation began in
October 2014, restarted in early March 2015 after the winter season, continued
Fig. 13.1 Photogrammetric blocks and final GCP distribution
238
H. Erden and M. Aslan