How to calibrate maps with Land

How to calibrate maps with Land

Many users have digital maps and map images that are not geo-referenced. Today we present a simple and quick way to calibrate our not geo referenced maps with our software Land.

First, we need a not calibrated cartographic map but with geo reference information to calibrate it. In our example, we downloaded a free map from the Canadian Natural Resources website. More specifically it’s the CanTopo 092G13 section, Jervis Inlet area.

Not calibrated map of Canada

Open Land and click on “Maps> Calibrate Map from Image” selecting our map image.

Calibrate maps with Land

Once you’ve opened the map, a window called “calibrating” will appear. To calibrate our image, we will complete the four tabs of this window: projection, frames, point 1 and point 2.

Calibrating maps with Land

The Projection tab requires a couple of essential fields to continue with the calibration: UTM projection and Datum of the map. As the earth globe is not spherical or regular, the datum is responsible for measuring irregularities in each zone of th world. We need to know this information to achieve a correct calibration. In the example, we see that this information comes at the foot of the image: North American Datum 1983. We also have to fill area and hemisphere details.

Datum informationZone and Hemisphere details

Then, click the next tab called “Frames”. This tab allows us to cut the image, basically the part of the map image that we are not interested in (for example the framework). Click “Modify Map Frames” playing with the zoom options to cut the image with maximum detail.

Cut Frameworks

After cutting the image, we just need to mark the points 1 and 2 in order to reference the image map.

Select point 1 tab and with the mouse cursor mark the first reference point for calibrating the map. To facilitate and make the work as accurate as possible, we select an easily identifiable point with map coordinates. In the example we have selected the intersection point between the Eastern 466.000 meters point and Northern 5.540.000 meters point.

Referenced coordinates

Now we just need to select the field “type of coordinates”, because when we click point number 1, the coordinate’s fields are automatically filled.

UTM projection

Select the UTM projection, fill the X point and Y point coordinates, select the number of area (information is on the map) and hemisphere (Being a Canada image is the northern hemisphere).

Then we make the same procedure for point number 2. In this case, simply click on the point, select the type and enter the values of X and Y coordinates. The zone and hemisphere information will be stored as the same as point number 1.

Referenced map points

Now we only need to save the new calibrated image in our computer (file. IMP) in the same folder where is located the original not-referenced map image. We also can create a more optimized raster map (.RMAP format) readable by TwoNav and Land/Air.

Finally, if we return to Land and we open the .IMP (or .RMAP) calibrated file and we compare it, for example, with an orthographic map we will see if the map image is properly calibrated.

Orthographic Map

Calibrated map with Land

Calibrated map above orthographic map

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  • How to calibrate maps with Land

    How to calibrate maps with Land

    Many users have digital maps and map images that are not geo-referenced. Today we present a simple and quick way to ...
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