Determining How Many Tiles You Need For A Project

If purchasing EDX Cirrus high-resolution data tiles, with access to large terrain and clutter datasets, determining the smallest number of tiles you need for a project can be confusing. This article aims to demystify tile naming practices and help determining how to easily find the number of tiles needed.

EDX packages terrain and clutter data by square degree. It is usually named using the following convention: long_lat_resolution.extension. For example, a 10m Cirrus terrain file might be named 123w43n_10m.pte.

Cirrus 5m and 1m clutter is further sub-divided into 16 sub-tiles for each square degree. A representative Cirrus clutter sub-tile would be named 124w44n_r4_c4_us1m_ds5.gce.


Using EDX SignalPro to Determine Needed Tiles

Open your map layers and highlight the Reference Grid layer, then click the Style button to display the following dialog box.

Ensure the grid spacing is set to 1 degree, then click OK. Make sure the reference grid layer is above any Bing map or extracted terrain/clutter layers. Click OK to exit back to the main map window.

If you don’t see the reference grid layer, you can re-add it by choosing Add layer… then selecting it from the middle left window.

Zoom out until you can easily see the reference grid lines. You can pan the map until you’re in your area of interest. In the example below, say we’re interested in data for the Eugene/Springfield area. Notice how Eugene/Springfield is covered by at least 2 tiles, possibly 4 if we want to cover down through Pleasant Hill.

To find the latitude and longitude, look in lower right of the status bar to see the coordinates. For example, if I the mouse cursor is placed on Eugene, it reports 44.049955n, -123.107221. Ignore the decimals, and you’re looking at tile -123w44n.

The origin of EDX data files are the lower-left corner. This means that in the northern/western hemisphere, the tile 44n, -123w actually covers from 44n to 45n, and -123w to -122w. So for the above example, to cover Eugene, we need the tile -124w44n to cover that area.

If we wanted all 4 tiles from the above picture, we’d need tiles:

123w43n, 123w44n, 124w43n, 124w44n to cover our area.

Using EDX TileSelector to Determine Needed Tiles

The EDX tiles selector is installed when the SignalPro software is installed and is located at C:\Program Files\EDX\Cirrus TileSelector\EDXTilesSelector.exe. Launch the tile selector, then like above, pan and zoom the map in to encompass your project area. This time, when you point to a tile, there is a field in the left of the status bar named Tile Origin (SW). This is the tile reference origin. You don’t need to offset this value.

Once you’ve determined the number of tiles necessary, you can search your data folders for the necessary tiles to move into your project location, or you can use the Tile Selector to purchase and/or download tiles from you subscription.