F. Samadzadegan, A. Talebzadeh
Dept. of Surveying and Geomatics Engineering, Faculty of Engineering,
University of Tehran, Iran
Email: [email protected]
M. A. Hosseini
Iranian Remote Sensing Centre, Tehran, Iran
Email: [email protected]
High and accelerating rate of the urban changes and urban area extensions, in particular in developing countries, calls for an efficient and fast technique for mapping the urban changes with the required accuracy for updating the existing maps. The availability of the new generation commercial one-meter resolution satellite imageries have opened a new era and signaled promising futures for producing and updating large-scale digital maps. Although several investigations have already begun in this subject, still the subject demands more comprehensive tests for the determination of the suitability of such high-resolution images for the purpose of large-scale map revisions. The experiments were conducted on a Geo panchromatic Ikonos scene acquired on October 7, 2000. The main reasons for selecting this area was that: The city faced many changes during last 8 years acquisition time difference between satellite image and aerial photographs.
In this study the following experiments have been conducted to evaluate the suitability of Ikonos images for the large scale map revision: 1- Assessment of the geometric accuracy of the high resolution satellite images. To assess these factors the following strategy is adapted: To evaluate the 2D geometric accuracy of Ikonos image, geo referencing with multiquadric, projective and polynomial mathematical models was carried out. 3D accuracy assessment is performed using DLT, rational and rigorous mathematical models. Since stereo images of the Ikonos were not available, a large scale Digital Surface Model (DSM) of the area under investigation was used to compensate for the relief displacement. The accuracy evaluation of both 2D and 3D cases were achieved using RMSE factors for GCPs as well as checkpoints. 2- Evaluation of the information contents of the IKONOS images. The feature tracing and pointing potentials as regards the feature sharpness compared with the large and medium scale photographs acquired with the standard metric aerial cameras and existing digital maps of the city. The digital 1/1000 and 1/10000 maps information is according to Iranian mapping standards. The assessments of the information content of the image was performed by visual inspection and identifiability of each map feature on the image. This assessment was also quantified using frequency domain analysis. A further assessment was also conducted by generating the object coordinates of some linear features and comparing the results with the object coordinates of the same objects generated by aerial photographs. 3- The assessment of map revision potentials of such high resolution imageries. Map revision potential of images assessed regarding geometric accuracy and image contents. Due to seven years difference between satellite image and aerial photos there were many changed areas in the image. These areas digitized from the image with Bently-Microstation CAD software package.
The overall evaluation has given an indication that map revision for the scale of 1/10000 may be carried out using Ikonos image.