SELECTION OF THE MOST SUITABLE SIZES OF GROUND CONTROL POINTS IN
THE SATELLITE IMAGES
H.M. Yilmaz ?, M. Yakar ", O. Mutluoglu ^, F. Yildiz ^
* Nigde University, Engineering and Architecture Faculty, Geodesy and Photogrammetry Department, Nigde, TURKEY
(hmyilmaz@nigde.edu.tr
® Selcuk University, Engineering and Architecture Faculty, Geodesy and Photogrammetry Department, 42075 Konya, TURKEY
( yakar, omutluoglu, fyildiz )@selcuk.edu.tr
Commission IV, WG IV/7
KEYWORD: Satellite, Image, control points( GCP), high resolution, orthomosaic, IKONOS
ABSTRACT:
Nowadays, satellite images have been used for many applications intensively. Using of the digital satellite images in relevant
approaches may give more accurate ideas about the researched fields. Besides, different methods could be used for derivation of
maps from relevant digital data in many scientific disciplines. One of these methods is to use satellite images. The most important
reason of using the maps, which are derived from satellite images, is accuracy of data. To obtain maps from satellite images or use
satellite images as map, the satellite images required certain rectification. For a rectification process, ground control points are
plotted in field. In the present study, the most suitable ground control point sizes were investigated for multi-spectral images from
IKONOS satellite of one-meter resolution. The present study showed that the most suitable size of ground control point was 2.5 m
diameter points.
1. INTRODUCTION
High resolution satellite images, as less than 1 m. resolution are
used in many fields. For example, updating existing maps, land
use mapping, urban planning, disaster monitoring, and so on. To
use high resolution satellite images in such fields, they had to be
rectified. Rectification process is done by points, which
coordinates are known in both land and image. The selected
points may indicate either measured points in the field or/and
can be designated as visible points in images. These points may
represent; building corner, road cross, panting objects, etc.
Points which are set up in the field are either acquired from
existing maps or from image matching the research site. The
main purpose of the present study is to identify the most
suitable size of the field points, which might be marked in land
by using ground control points for rectification.
2. IMPORTANT OF CONTROL POINTS
Acquisition of ground control points (GCPs) is particularly
important for geometric correction of high resolution satellite
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images. The commercial high resolution satellite image can be
accurately rectified using the combination of bias-corrected
rational polynomial coefficients (RPCs) and ground control
points (GCPs). With a few precisely measured GCPs accurate
three dimensional measurements can be made from the base
level Ikonos data product. However, the accuracy of the results
is dependent on the precision of the GCPs (Dare et al., 2002).
There are two approaches in geometric correction of high
resolution satellite images. One of them is the bias-correction
procedure for rational polynomial coefficients (RPCs), which
requires a minimum of only a single GCP, but it gives of course
require RPCs. The other is affine model that requires a
minimum of four GCPs per scene, though six as practical
minimum would be recommended (Fraser, 2002).
The control points could be acquired by three different methods
for geometric correction in two and three dimensional of high
resolution satellite images. These are; GCPs from existing
maps, GCPs set up in land, GCPs from image matching.
Kadota and Takagi (2002) had used above mentioned methods
in acquisition of GCPs for geometric correction of high
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