The Northern Manitoba Theoretical Township/Quarter-Section Grid File Structure The above grid consists of a series of topologically structured Mastertiles and Subtiles. A Mastertile is 4 townships deep (24 miles) and extends province wide from the Manitoba/Saskatchewan boundary to the Manitoba/Ontario boundary. There are presently 25 Mastertiles in the grid with Mastertile 1 being the most northerly full 4 townships in the province and the Mastertile numbers increasing by one for each 4 townships one proceeds southwards. A Subtile is a subset of the Mastertile and generally consists of a block 4 townships deep by 10 ranges wide (40 townships in all). The actual number of townships in a Subtile will vary when a particular tile closes on a meridian, an interprovincial boundary, or large natural water body such as Hudson Bay. Each Subtile bears the Mastertile name followed by a letter designation. The letter "A" has been assigned to the most westerly Subtile with Subtiles "B", "C", "D" and so on occurring as one proceeds easterly. General Coverage The theoretical township/quarter-section grid covers approximately townships 35 to 127 north-south and ranges 1-30 Wpm, ranges 1-24 Epm and ranges 1-31 E2ME east-west. There is additional coverage east of Lake Winnipeg between townships 19 to 34, ranges 7 to 17 Epm and projected through the two major lakes - Lake Winnipeg and Lake Manitoba [south part only]. How the Grid Was Created The Manitoba theoretical township/quarter-section grid is a computed grid. It is governed by the Third System of Survey under which all road allowances are 66 feet in width. These road allowances occur every mile east-west but only every second mile north- south. Horizontal (MANOR) survey control adjustments were completed for all surveyed baselines and meridians based on measurements shown on Director of Surveys Plans or other records available within the office of the Director of Surveys. These adjustments were constrained to the most accurate federal and provincial geodetic survey control available at the time of the computations. In northern Manitoba this control was predominantly either ISS or Doppler technology based. A specialized software program was written to determine mathematically the coordinate positions for the four corners of each standard theoretical township (6 miles wide by 6 miles deep) northerly and southerly from each surveyed baseline accommodating for the proper widths of road allowances at correction lines. The interior sections for each theoretical township were created by mathematically subdividing into 36 units each computed theoretical township block. Graphics software was used to connect the computed points and output a graphical representation of each theoretical township together with a standard DLS key for each theoretical township and each of its interior sections. This was the original grid. It has since been value added in that it has been further subdivided and topologically structured to the quarter-section level. Unique 9 digit parcel identification numbers or PINS have been assigned to each theoretical quarter-section parcel to facilitate use of the graphics grid with tabular data in a relational database. The PIN serves as the primary linkage mechanism between the two. A graphical change in the product was made by showing all road allowances as double width lines rather than single lines. Datum NAD83 (nmip94 adjustment) Accuracy The estimated accuracy of the grid is plus or minus 100 metres. However this accuracy fluctuates throughout the grid depending on the density of the geodetic control available at the time of computations and the accuracy of the governing meridian and baseline surveys on which the computations were based. Some of the older original baseline surveys were done using baseline transit and chain. The Hudson Bay shoreline used in the product comes from the Branch's 1:500,000 topographical base map. Known Weaknesses in the Grid The northern Manitoba Theoretical Township/Quarter-Section grid was developed to meet general DLS parcel referencing needs for Northern Manitoba. It was produced intermittently on an ad hoc basis over some 8 years and has only recently undergone rigorous topological structuring. Although the grid topology has been checked there has been no quality control done on polygon annotation due to the large number of polygons involved (800,000 or so). The mathematical solution used in the grid's production was not a unique solution as professional judgement had to be used as to how to deal with any misclosures which became evident when undertaking the MANOR adjustments of the baseline and meridian surveys on which the grid is based. This is particularly true when computing theoretical township positions in the Lake Winnipeg and Lake Winnipegosis areas which contain some of the province's weaker baseline surveys. Proportioning of the misclosures was a common solution but not used in every instance as intermittent retracement surveys often impacted decision making and the final grid layout. A known weakness of the grid is the fact that it has been perpetuated through several of the surveyed townships in Northern Manitoba. This is particularly true in the area around The Pas (Tps 50 to 60) and along the predominant railway system which stretches from Clearwater Park to Gillam to Thompson to Churchill. Time and resources did not permit the undertaking of the labor intensive computations required to derive graphical representations of each surveyed township in northern Manitoba. End users are cautioned to respect the existence of these surveyed townships and that use of this grid for parcel referencing in these areas should be undertaken only as a last resort. Data Formats The Manitoba Theoretical Township/Quarter-Section Grid is available in two of today's common spatial referencing data formats - AutoCAD DXF or ESRI Shape Files. GIS USE The Manitoba Theoretical Township/Quarter-Section Grid has been topologically structured to the quarter-section level. Each quarter-section polygon is a spatially referenced entity with a unique 9 digit parcel identification number or PIN. As attribute data each quarter-section polygon has a DLS key in standard format -section/township/range/meridian. As such it provides an excellent GIS support tool for users who wish to relate tabular data or spatially referenced land parcel data to a theoretical DLS fabric.