Journal of Surveying Engineering

The use of a differential global positioning system (GPS) for high‐accuracy road positioning has shown some limitations in terms of outages due to satellite masking that cause poor geometry and loss of carrier phase lock. By integrating a GPS receiver to an inertial navigation system (INS), i.e., GPS/INS, these limitations can be overcome to a large degree. The concept of GPS/INS for positioning is discussed with the emphasis on accuracies at the centimeter level, and an effective cycle‐slip detection and correction strategy using INS is also presented. GPS/INS data collected on a highway near Calgary is used to assess the feasibility of the system in terms of accuracy and reliability. GPS outages are simulated to determine their effect on the accuracy and cycle‐slip detection/correction capabilities. Results show that accuracies of 5 cm are achievable with this system; however, a degradation in performance can be expected when GPS outages occur. A discussion of improved modeling techniques as well as the many applications of this system concludes the paper.

The National Program for Rural Cadasters and Titling (CATIR) is currently undergoing the development of a legal cadastral system for the rural areas in Ecuador. The first phase of the program, which essentially entails the pilot project, consists of implementing a cadastral system in two counties: Salcedo, in the sierra region, and Alfredo Baquerizo Moreno (known locally as Jujan), on the coastal plain. For each rural parcel the pilot project will establish ownership, define shape and area, describe land use, and provide an evaluation. This paper discusses the current status and problems of the Ecuadorean cadastral system, describes the objectives of CATIR, and documents the technical processes of phase I being applied in Salcedo County as of August 1990. The technical processes explained includes surveying engineering methods, cadastral data gathering techniques, and cartographic design. Institutional issues and the current status of the program are addressed in “Ecuador Land Titling Project Evaluation,” a report by Lambert et al. published in 1990.

The advent of the Global Positioning System (GPS) brought about changes in positioning and surveying that are only now being fully exploited. When GPS is in place, positioning accuracy of 100 m or less will be available worldwide, 24 hr/day, in all weather and visibility conditions. The Coast Guard grasped the significance of the potential of the GPS system and has developed a system to improve the accuracy of GPS from 100 m to 5–10 m; this is the differential GPS system, or DGPS. The Short Range Aids to Navigation Division recognized the potential use of DGPS as a new tool for aid positioning. Our present manual buoy‐positioning methods are tedious, time‐consuming, and error‐prone. For these reasons our units must continually check and recheck their positions with electronic navigation aids, radar information, and horizontal sextant angles to place a buoy on station. Automation of this procedure with DGPS input would allow units to obtain real‐time positioning information for navigation and aid placement. The Coast Guard Research & Development Center was tasked with developing an automated navigation aid positioning system. Their efforts provided us with the Laptop Automated Aid Positioning System, or LAAPS. For the Short Range Aids to Navigation Division, LAAPS is everything it was expected to be. The USCGC Bittersweet, out of Woods Hole, Mass., is testing the system and is finding it can find the position of aids to navigation with 2–3 m accuracy. Plans call for nationwide coverage of DGPS by 1996. By that time all Coast Guard aids‐to‐navigation units will have LAAPS ready for operation.