Mining grids are adjustments (calibrations) to regular map projections and are often used on mining and other special construction sites.
Pseudonyms for 'mining grids' are 'construction', 'local' or 'site calibration' grids.
Mining grids coordinates are calculated by applying a translation, rotation and scale factor to a specific origin point.
A mining grid can for instance be applied to a standard state plane coordinate system or UTM projection.
This document shows all the steps required to setup a mining grid in Hydromagic.
Please note that some steps may be optional for your setup.
The Similarity Transformation - Image source: EPSG Guidance Note 7
The first step is to configure the map datum for your mining grid. Please note, that in cases where a standard projection is used as base for your grid (for instance a 'State Plane Coordinate System' or 'SPCS'), you can skip this step. Depending on the map datum transformation that is used, you need the 'Translation', 'Rotation' and 'Scale Factor' settings.
To configure a new map datum, select "Coordinate Systems" => "Manage Map Datums" from the "Options" menu, and click "Add" to enter the new datum parameters.
Please note that the translation values have to be entered in meters. For US Survey Feet, always multiply by 0.3048.
When finished, click the "Save" button to store the new map datum.
Setting up a map datum transformation for the mining grid
To configure a new map grid, select "Coordinate Systems" => "Manage Map Grids" from the "Options" menu, and click the "Add" button to enter the new map grid.
The next step is to setup the regular map projection used for the mining grid. This can be any type of projection such as 'Lambert Conformal Conic' or 'Transverse Mercator'. Depending on the projection method used, fill in the parameters for 'False Easting', 'False Northing', 'Origin Latitude', etc..
As map datum, select the map datum we created in the previous chapter of this document.
Skip this step when the projection used as base for the mining grid is already defined in the software.
Do not forget to select the units used in the map grid. Most of the times projections are defined in 'US Survey Feet, 'Feet' or 'Meters'.
The 'False Easting' and 'False Northing' values are distances, and have to be entered in the units selected at the bottom of the grid configuration screen.
When finished, click the "Save" button to store the new map grid.
Setting up a map grid as base for the mining grid
When the above two steps have been completed, or when you want to apply the mining grid to an existing grid, go back to the list of map grids. To display this list, select "Coordinate Systems" => "Manage Map Grids" from the "Options" menu.
When the mining grid is based upon a regular map grid, it is recommended to create a copy of this grid first. This can be done by right clicking the grid, and selecting the "Add Copy..." function from the popup menu. When you already created a dedicated map grid to be used, just select this one and click the 'Modify...' button.
Click the 'Local...' button to enter mining grid parameters
After clicking 'Modify...' or 'Add Copy...' you will notice that the 'Local...' button is enabled. Click this button to enter the mining grid parameters.
Enter the mining grid parameters
In the dialog that appears you need to enter the origin coordinate, the translation values, scale factor and rotation around the origin.
Make sure that both the origin and translation values are entered in the projected units, in this example US Survey Feet.
When the local grid parameters are not known, they can be calculated from two known coordinate pairs (projected coordinates, local grid coordinates) also called reference points.
When the projected coordinates aren't available, for instance when they are given in geographic coordinates, you can use the built in 'Coordinate Calculator' tool to calculate them.
Example:
Point A: Mining Grid X = 19988.69, Y = -11563.65 Geographic Long = 110 deg 56' 09.99755" W, Lat = 33 deg 07 35.41081" N.
Point B: Mining Grid X = -5813.66, Y = 17571.83 Geographic Long = 110 deg 59' 43.65094" W, Lat = 33 deg 13 15.91767" N.
Launch the 'Coordinate Calculator' by selecting "Coordinate Calculator..." from the "Tools" => "Geodesy Calculations" menu. In the 'Coordinate Calculator' select the mining grid as destination grid. Make sure you use the base grid used for the mining grid.
Enter the geographic coordinates to calculate the projected coordinates as shown below:
Calculating the projected coordinates with the Coordinate Calculator
This should give you the following results:
Point A: Projected Grid X = 17565.211, Y = -15924.403 Mining Grid X = 19988.69, Y = -11563.65
Point B: Projected Grid X = -598.703, Y = 18490.529 Mining Grid X = -5813.66, Y = 17571.83
Now enter these values in the calculation window as shown below and click 'OK' to accept the parameters. When you make a mistake entering these parameters, no worries, they will be saved and shown the next time the calculation windows is displayed.
Calculate the mining grid parameters
When all parameters are entered correctly, the software will calculate and fill in the mining grid parameters automatically:
Enter the mining grid parameters
To test the grid, just create a new project and select the mining grid we just defined.
In the "project Explorer", right-click the "Waypoints" map and select the "Add Waypoint..." option.
In the waypoint dialog that appears, enter the geographic coordinates of one of the test points, or preferably a third point. Check the 'Show position in Easting/Northing coordinates to show the mining grid coordinates. This point should match one of the reference points.
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| Control point's geographic coordinates | Control points local (mining grid) coordinates |