1.5. DEFINING UE4 LANDSCAPE EXTENTS

This section of the tutorial is about how to load GIS data into Global Mapper, and how to define our UE4 landscape’s extents.

We Need:
  • The DTM, aerial imagery, and vector data we downloaded in the previous tutorial.
  • Global Mapper (or similar GIS tool)
  • Photoshop (or similar image editing software)
Step 1:

Extract the zip files:

  • Extract all the “USGS_NED_*” files into the same folder.
  • You can overwrite any files with duplicate names – we don’t need them.
  • Next extract the ‘Transport’ files into separate folders – you don’t want to overwrite files with the same name in those (if you have more than 1).
Step 2:

Load DTM files into Global Mapper:

  • GM stores data in layers – first loaded appear at the bottom, so we’ll load the DTM data first.
  • Launch Global Mapper (“GM”).
  • Select all the .img files in your folder.
  • Drag them into the main workspace area in GM.

It should look something like this. (If you don’t see all the data, hit the ‘Full View’ button.)

[NOTE: The USGS National Elevation Data (NED) is stored in a Cartesian coordinate system known as UTM, and uses the North American Datum defined in 1983 (NAD83). GM automatically sets the projection and datum for its workspace to those of the first data sets you load, so by loading the NED data first, we’re already working in a local Cartesian coordinate system. (See the status bar in the bottom right of the screenshot below to verify.)

If you’re using your own data, you may need to adjust the projection to a Cartesian system. UTM is a projection that splits the world into local Cartesian ‘Zones’ and is our preferred option. We don’t go into to how to do the reprojection here, but let us know if you’re stuck and we’ll help you out.]

Step 3:

Load the aerial imagery files into Global Mapper:

  • Select all the .jp2 files in Windows Explorer.
  • Drag them into the main GM window on top of the loaded DTM files.
Step 4:

Load the vector files:

  • When you extracted the “TRAN_*.zip files”, a “Shape” directory should have been created in a sub-folder.
  • Select the “Trans_RoadSegment.shp”, “Trans_RailFeature.shp”, and “Trans_TrailSegment.shp” files and drag them into GM:

It should look like this:

Step 5:

Next we need to create a box to use as a template to export the data for the area we want to model:

  • Click the ‘Digitizer Tool’ icon.
  • Click ‘Create Rectangular/Square Area’ icon.
  • Create a square area approximately covering your AOI (hold + and drag mouse).
  • A ‘Modify Feature Info’ box will appear when you release. Type ‘AOI’ into the ‘Name:’ box.
  • Then click ‘OK’.

It should look like this:

Step 6:

UE4 needs image tiles to be specific sizes. We chose 8,129px by 8,129px and we want a resolution of 1m per pixel, so we need to make sure our AOI is 8,128m x 8,128m because our pixel values start a 0. To do this you need to edit the vertices of the AOI shape you just created:

To edit the AOI shape:

  • Click the ‘Digitizer Tool’ icon.
  • Click on the ‘AOI’ area feature to select it (it will fill with a cross-hatch).
  • Next <right-click> on the object (with ‘Digitizer Tool’ still selected) and select ‘Edit Area Feature’.
  • Then click ‘Vertices…’ to the right of the ‘Name’ in the ‘Modify Feature Info’ window that appears.
  • In the ‘Feature Vertex List’, select the first vertex, then ‘Edit Position…’
  • A ‘Select Location’ window will appear. We’re going to round these numbers down to the nearest 500m make the maths easier, then click ‘OK’ (Don’t worry about the location at the moment – we’ll move it to define our export area next.)
  • Next we need to move the other vertices.
  • Select the second vertex and ‘Edit Position’.
  • We started in the top left, vertex 2 is top right, so we need to add 8,128 to the previous X-coordinate value, and change the Y-coordinate value to the same value as vertex 1:
  • Vertex 3 is bottom right, so we need to subtract 8,128 from the Y-coordinate and set the X-coordinate to the same as vertex 2.
  • Vertex 4 it bottom left so we need to use the same X-coordinate as vertex 1 and the same Y-coordinate as vertex 3.
  • Vertex 5 closes the shape and should be the same as vertex 1.
  • Your ‘Feature Vertex List’ box should look like this when complete:
  • Click ‘OK’ to close the ‘Feature Vertex List’ window.
  • Click ‘OK’ to close the ‘Modify Feature Info’ window.
Step 7:
  • Next thing to do is to move the ‘AOI’ area feature to the location for your UE4 landscape.
  • With the ‘Digitizer Tool’ selected, <right-click> the ‘AOI’ area feature and ‘Move Area Feature’.
  • The cursor will change and you can click to drag the AOI where you want it to be.
  • When you’re happy, <right-click> to complete the operation. 

Here’s mine:

Step 8:

Now we’re ready to export the data.

Before you do that though, save the workspace:

  • In GM: ‘File’ > ‘Save Workspace As…’
  • Give it a useful name in case you need to refer back to it.