This summary file
is ODBM.rtf; read MNRDTDB.rtf for the complete text issued by the Ministry
of Natural Resources.
ODBM files available in the Department of Earth Sciences include:
Garson Sudbury region iomega(350Y):\50-V12\50V12.ZIP
Garson Sudbury region iomega(350Y):\51-V12\51V12.ZIP
Wahnapaetei Sudbury iomega(350Y):\OBM52514\52005140.zip and the unzipped .DXF files; also unzipped in C:\aacrse\350\digsud1, and E:\DIGSUD1\
Four ODBM tiles maps for the Pinery have been archived in \\Users\wrchurch\pinery\1017425047850, 1017430047850, 1017430047900, 1017435047950, and some but not all of the contents of 1017425047850 have been placed on computer GIS6 and GIS 8 (room 53) in d:\autocadmap2\pinery; and (PONTY)c:\aacrse\505\ODBM\Pinery.
The province is divided into four UTM zones, where
UTM is a mathematically accurate reterencing grid system used worldwide.
It is particularly relevant to topographic mapping and surveying purposes.
The UTM evolved from the Mercator projection system, influenced by the
Gaussian cylindrical perspective projection. The basis for UTM is a grid
system which transverses the globe in zones six degrees wide along the
lines of longitude.
Data are then partitioned into tiles, conforming to the Ontario Basic Map.
Mapping is produced at the scales of 1:10 000 in Southern Ontario and 1:20000 in Northern Ontario. Each map measures 50cm x 50cm for both scales, providing a physical coverage of:
5,000 m x 5,000 m, or 25 sq. km for a 1:10 000 scale sheet; and.
10,000 m x 10,000 m, or 100 sq. km for a 1:20 000 scale sheet .
By using the OBM numbering system. the tiles are uniquely identified by a geocode which is a combination of scale, zone, and the UTM coordinates of the southwest corner of the sheet, viz,
UTM Zone number 17
UTM easting (southwest corner of map) 4050
UTM northing 47450
Geocode = 10 17 4050 47450
The tile file name 1017405047450 would be read
as 10=scale 1:10000, 17 = zone 17, 405000 m (405 km east of the zone 17
western boundary), 4745000
m (4745 km north of the equator)
In Autocad the coordinates would appear as 405000.0 (4.050000+05) and 745000.0 (7.450000+05) because although the co-ordinates are stored in UTM values 4 million is subtracted from the northing (latitude, Y) values (expressed to one metre), i.e. 4745000 appears as 745000.
The data for each tile is further divided into thematic layers of information with common themes or structures. The current 18 layers of information per tile are defined in Table 1.
Layer 16/DTM (Digital Terrain Model) - contains a series of point data, with x,y and z values stored against each point.
This layer is maintained and delivered for digital tiles compiled through photogrammetric compilation methods.
Layer 17/Contour - contains a series of line data, with x,y coordinates of a particular contour. The z value is attached to each contour line. This layer is maintained and delivered for digital files compiled through automation methods. (Contours contained in this layer are treated as cartographic features, therefore mathematical connectivity between map sheets is not performed on these features.) A more detailed description of the contents of each layer is supplied in Appendix A.
Horizontal datums for all data is NAD27 (May 1976 Adjustment). It is anticipated that this datum will shortly be replaced by NAD83. Vertical datum is derived from mean sea level, as established by the Geodetic Survey Division, Energy, Mines and Resources Canada.
3.4 Resolution and Accuracy
Features are stored on the UTM co-ordinate base. Co-ordinate information is stored in UTM X/Y pairs. Hypsographic information (elevations) is stored as attributes for selected features, ie. DTM points, contours, spot heights, and vertical control points.
Co-ordinates are stored in full UTM values with 4 million subtracted from the northing values (expressed to one metre). (Due to internal storage restrictions and numerical round off, four million metres is translated (subtracted) from the northing values. This translation allows for the processing of the co-ordinate information without any loss of precision, and thus maintaining the one-metre feature placement accuracy).
Use the Pinery data set in //PUBLIC/505/PINERY or the folder 'd:\autocadmap2\pinery' on GIS6 and GIS8. (Note: if permissions are not set, the data can only be read.)
ODBM files are sold as .DXF files, and as such
do not contain data about the datum in which they were formatted. It is
therefore necessary to first define the projection and datum for the map.
Click Map -> Map Tools -> 'Assign Global Cordinate System'.
Assigning a global coordinate system for the project
In the 'Assign....' box, click the 'To Current Work session' button, click the 'Codes' box, select UTM-NAD27 from the 'Categories' drop down list (towards the bottom of the list), and 'Zone 17 North, Meter' as the UTM zone in the 'Available Global Coordinate System' drop down list. Then click OK twice.
In some cases (e.g. NTDB maps) .DXF files can be overlaid on an existing active .DXF image using the command DXFIN. However should you get the message - "AutoCAD cannot DXFIN this file" when attempting this procedure, it will be necessary to import (DXFIN) each .DXF file into a new drawing, save each drawing as a .DWG file, and then carry out the following procedure:
MAP -> Drawing -> Define Drawing Set;
the 'Define/Modify Drawing Set' window will appear.
The 'Define/Attach drawing file' window and the 'Select Drawings to attach' window
Click Attach to bring up the 'Select Drawing to Attach' window. If an alias has not been defined, click -> 'Edit Aliases' to fetch the 'Drive Alias Administration' window. Provide a drive alias name in the requisite box, and define the path in the 'Drive Alias Details' box (use BROWSE to define the path) --> click Add followed by Close.
Repeat to create aliases for other directories (tiles), and add the files for these aliases to the Selected Drawings box. [NOTE: aliases, GIS8PINERY1, ...2, ...3 have already been created for the directory D:\acadmap2\Pinery\1017425047850, ...1017430047850. ...1017430047900 (Tiles 1017425047850, 1017430047850, 1017430047900)]
Select the alias name in the Drive Alias box in the 'Select Drawing to Attach' window . A list of .DWG files in the directory represented by the alias name will appear in the File Name selection box -> click SELECT ALL, followed by ADD, and then OK twice.
To plot the maps to the screen, make the selection sequence:
Map -> Query -> Define query to call the Query window. Query window
Click 'Property' to select a specific layer (e.g. Property -> Elevation to select a specific contour), or a select group of Layers, OR 'Location' to get you to the 'Location Condition' window. In the latter case click 'All' and OK to select all objects in the attached .dwg files. Location Condition window
Click the DRAW button in the Query Mode box -> and the Execute Query button. Carry out a 'Zoom (z) Extents (e)' to display the image.
Because 4 million
is subtracted from the northing (latitude, Y) values in the
ODB map it is necessary to add 4000000 to the Autocad Y coordinate values.
Run the MOVE command from the command line and in response to 'Select Objects'
enter 'all', in response to 'Base Point or Displacement' enter 0,4000000,
and in response to 'Second Point of displacement' press the ENTER key.
Save the file under a new name, e.g.map1nad27.
Start a new file and assign the coordinates as NAD-83. Attach the file map1nad27you have just created and in the Define/Modify Drawing set Window' click the 'Drawing Settings' button. In the Active Drawing box, the datum assoicated with the file will appear to the right of the file name. Carry out the Query procedure to bring the map to the screen. It will now be plotted as a NAD-83 map. Save again under a new name, e.g. map1nad83.
An alternative procedure
for the import of .DXF files involves opening a .DWG file (followed by
zoom -> extents to make the map visible), and then using INSERT -> BLOCK
-> File (Select drawing File -> Open) -> Deselect "Specify parameters on
screen" in the Options box, and select the Explode option -> click OK.
The inserted DXF file will be added to the original DXF file.