Accuracy Assessment Of Preliminary Index Diagrams (PIDS) From High Resolution Orthoimages In Kenya

Abstract

In Kenya, various types of cadastral maps are in use for land administration; the most famous being Registry Index Maps (RIMs) used in the rural areas due to their ease of production by simple surveying techniques and air survey methods. Such RIMs initially intended as a temporary measure to speed up land registration pending preparation of more accurate documents, are still in use today resulting in unreliable and lack of up to-date survey information for better land administration. This study investigates a new system that would facilitate quick production of reliable, accurate and up to-date cadastral maps for land administration through the use of high spatial resolution satellite imagery (QuickBird). Three types of data were acquired and integrated to provide a database; namely QuickBird orthoimage, orthophoto and parcel areas from the RIMs. The evaluation was made by statistically comparing parcel areas from, orthophoto (reference data), QuickBird satellite orthoimage and the official PID Area List. The study has demonstrated that the high spatial resolution satellite imagery can be used as an input for indirect land surveying methodology. Statistical analysis indicated that there was no significant difference between parcel areas from orthophoto and satellite orthoimage while there was significant difference between PID and orthophoto areas. Good results were obtained for large and medium size parcels with an average area difference of 0.3% and 1.0% respectively and 2.6% for smaller sized parcels. However, with regard to the minimum requirements for a Land Registry Index Map to be of sufficient accuracy to perform its core functions of parcel identification, boundary relocation, mutation surveys and area computation, it can be reasonably concluded that PIDs from QuickBird orthoimage at a scale of 1:5000 met these requirements.