How To Interpret MapWarehouse File Names

RAQ's: Rarely asked questions

Anyone's who purchased aerial imagery or mapping data through MapWarehouse is familiar with the quick delivery of a zip folder containing a bunch of cryptically named files.


Did you know the string of numbers actually means something useful? By interpreting the file names you can find:

  • The data type (orthophoto, parcel, contours...)
  • The UTM coordinates of the file's insertion point
  • The year the data was produced
  • The data provider (FBS, Teranet, TRCA...)

Understanding how to use the UTM coordinates of the file's insertion point all starts with understanding the common grid.

Most data types like orthophoto, parcels, and DEM are sold in 500m x 500m tiles that are pre-clipped to a common grid that extends across Southern Ontario. Some data types like Ontario Base Maps are sold in other tile sizes, pre-clipped to a product-specific grid. Some data types like Floodplains are sold in item-specific coverage areas.

The common grid makes it easy to purchase complementary data sets à la carte for your area of interest with complete, identical map coverage.

When using two products together, such as orthophoto and parcels that are using the common grid, the insertion points and coverage areas will be identical when the data is added to your map project.

Now here's where the UTM coordinates in the file name come in handy.

If you are using a software that does not automatically read the insertion coordinates from the auxillary *.wld world file, you'll need to enter those parameters manually. Here's a CAD example:


Use the Command IMAGEATTACH and select the images to add one by one. For each image review the Easting and Northing in the file name.

Add the four digit Easting coordinate plus two zeros as the X insertion point. Add the five digit Northing coordinate plus two zeros as the Y insertion point. The scale will be 500 since the tile covers 500m x 500m. Click OK and the tile will be inserted in it's proper location.

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