Abstract
Abstract. The General Directorate of Surveying and Mapping (GDSM), under the Ministry of Municipal and Rural Affairs (MOMRA) is responsible for the production and dissemination of accurate geospatial data for all the metropolitan cities, towns and rural settlements in the Kingdom of Saudi Arabia. GDSM maintains digital geospatial databases that support the production of conventional line and orthophoto maps at scales ranging from 1:1,000 to 1:20,000. The current procedures for the acquisition of new aerial imagery cover a long time cycle of three or more years. Consequently, the availability of recently acquired High Resolution Satellite Imagery (HRSI) presents an attractive alternative image data source for rapid response to updated geospatial data needs. The direct sensor orientation of HRSI is not accurate enough requiring ground control points (GCP). A field survey of GCP is time consuming and costly. Seeking an alternative approach, a research study has recently been completed to use existing image and data base information instead of traditional ground control for the orthoprojection of HRSI in order to automate and speed up as much as possible the whole process. Based on a series of practical experiments, the ability for automated matching of aerial and satellite images by using the Speeded-Up Robust Features (SURF) algorithm is demonstrated to be useful for this task. Practical results from matching with SURF validate the ability for multi-scale, multi-sensor and multi-season matching of aerial and satellite images. The matched tie points are then used to transform the satellite orthophoto to the aerial orthophoto through a 2D affine coordinate transformation. GeoEye-1 and IKONOS imagery, when geo-referenced through SURF-based matching and transformed meet the MOMRA Map Accuracy Standards for 1:10,000 and 1:20,000 scale. However, a similarly processed SPOT-5 image does not meet these standards. This research has led to the development of a simple and efficient tool for the geo-referencing of HRSI of 0,5 m to 1 m ground sampling distance (GSD) that can be used for updating map information. The process completely eliminates the need for any ground control as well as image measurements by human operators.
Highlights
The Kingdom of Saudi Arabia has been covered by small and large scale topographic mapping using photogrammetric procedures
The map accuracy standards used by Ministry of Municipal and Rural Affairs (MOMRA) (Table 1) are very high in relation to common international standards which are in the range of 0.2mm up to 0.3mm in the presentation map scale
It could be shown in this study that the existing 0.5m resolution aerial orthophoto database can effectively be used as control for geo-referencing of recently acquired satellite imagery of 0.5m to 1m resolution to generate and update 1:10,000 scale line maps and orthophotos with 0.5m ground sampling distance (GSD)
Summary
The Kingdom of Saudi Arabia has been covered by small and large scale topographic mapping using photogrammetric procedures. The resulting network of 700 monumented geodetic stations was adequate to meet the required accuracy for national mapping at the desired scale, but is not suited for mapping at larger scales needed for urbanized and settlement areas. Large scale urban mapping efforts are assigned to the Ministry of Municipal and Rural Affairs (MOMRA). For this task MOMRA developed a new geodetic network. Latest photogrammetric technologies have been implemented to meet kingdom wide mapping requirements and to maintain the large scale topographic map database. Using current photogrammetric technology and methods, high quality topographic maps at 1:1,000, 1:2,500, 1:10,000 and 1:20,000 scales have been produced. The required horizontal standard deviations with 0.12 to 0.14mm in the map scale are quite challenging
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