Matching a set of digitized cadastral maps

Errors inherent in the digitizing process inevitably lead to variations in the locations of boundaries of neighboring cadastral blocks. It then becomes necessary to adjust the digitized data to compensate for discrepancies and discontinuities in the digitized cadastral information. For this purpose it is proposed that a procedure commonly used in aerial triangulation be adopted. Each map is regarded as an equivalent to a single photograph and a set of neighboring maps as a photogrammetric block. A system of appropriate equations is formed to adjust the “block”. Points lying on boundaries of adjacent cadastral blocks are the substitute for the transfer and tie points used in photogrammetry, and traverse or trigpoints available on the maps constitute the control data. The results of this procedure are: “orientation” data for each map to transform its content to the state plane coordinate system and adjusted coordinates of points positioned on boundaries shared by neighboring maps.

Logan '92: an expedition to measure the height of canada’s tallest mountain

To mark the 150th anniversary of the Geological Survey of Canada (GSC), as well as Canada’s 125th birthday and the 50th anniversary of the Alaska Highway, the Royal Canadian Geographical Society, in partnership with the Geological Survey of Canada, the Surveys, Mapping and Remote Sensing Sector (both of the Department of Energy, Mines and Resources) and the Canadian Parks Service (Environment Canada) undertook an expedition to determine the exact elevation of Mount Logan. In addition to measuring the elevation of the mountain the expedition also collected rock samples and positioned brass survey markers on the mountain. Since the first recorded sighting of the mountain in 1890 a number of different values for the height of the mountain have been quoted. Most of these values centered around 5950 metres. However a value of 6050 metres was very widely used. The differences in elevation can in large measure be attributed to the difficulties associated with conducting surveys in the extreme remoteness of the Saint Elias Mountains combined with measuring techniques of varying accuracies. The Logan '92 Expedition was the first expedition to attempt to measure the height of Mt. Logan using the Global Positioning System (GPS).

Where has sable island been for the past 200 years?

The location of Sable Island (44°N, 60°W) has been positioned by six independent surveys over the past 200 years. This paper correlates the surveys based on the limited number of common points and comments on the surveying methods that were employed and concludes that the various positions are more due to the quality of surveying than to the shifting of the island. The implications, both in terms of hydrographic charting and legal basis of sovereignty of maritime areas, are also discussed.

Logan '92: an expedition to measure the height of canada’s tallest mountain

To mark the 150th anniversary of the Geological Survey of Canada (GSC), as well as Canada’s 125th birthday and the 50th anniversary of the Alaska Highway, the Royal Canadian Geographical Society, in partnership with the Geological Survey of Canada, the Surveys, Mapping and Remote Sensing Sector (both of the Department of Energy, Mines and Resources) and the Canadian Parks Service (Environment Canada) undertook an expedition to determine the exact elevation of Mount Logan. In addition to measuring the elevation of the mountain the expedition also collected rock samples and positioned brass survey markers on the mountain. Since the first recorded sighting of the mountain in 1890 a number of different values for the height of the mountain have been quoted. Most of these values centered around 5950 metres. However a value of 6050 metres was very widely used. The differences in elevation can in large measure be attributed to the difficulties associated with conducting surveys in the extreme remoteness of the Saint Elias Mountains combined with measuring techniques of varying accuracies. The Logan '92 Expedition was the first expedition to attempt to measure the height of Mt. Logan using the Global Positioning System (GPS).

Selection criteria for archiving non-current data in land information system

An important consideration in developing a temporal component for spatial information systems lies in determining which data sets are worthy of archiving and which ones need not be retained after their currency ceases. For many natural resource and socio-economic based systems (often termed Geographical Information Systems), the choice is usually clear since certain historical data will usually be needed as the basis for longitudinal analysis. However in the case of parcel-based Land Information Systems (LIS) established for administrative purposes, the answer is not always so obvious. This is compounded by the difficulty in assessing what the likely value of non-current data, within this latter type of system, may be in the years to come and who the potential users might be. The purpose of this paper is to present and discuss the selection criteria which professional archivists use in making such decisions and to examine the application of these procedures in the context of LIS.