The issue

CAD cannot tile imagery thus is unable to add large orthomosaics over 500 MB. Most orthomosaics are many Gigs. As a result, the surveyor, civil engineer is unable to use your data in CAD. Some CAD users will ‘crap’ the data to very low resolution and loose the projection which at that point the imagery is essentially worthless

the CAD operator will have difficulty determining which image tiles to add. Fortunately, ArcGIS provides a function to generate a image tile key.

A Solution

Photogrammetry tools like Pix4D also generates a folder ‘tiles’ along with the orthomosaic. In the folder, you guessed it, are several hundred or thousand image tiles each no more than 50MB thus can be added into CAD.

However, ArcGIS Pro has a function to generate a image tile key, similar to the Thomas Brothers Mapbook which identifies what page is what location and adjacent pages.

Thomas Brothers mapbook. The initial pages give a key to what page is what location. For example, page 49 appears to be the Santa Monica pier and Venice Beach.

Thomas Brothers mapbook. The initial pages give a key to what page is what location. For example, page 49 appears to be the Santa Monica pier and Venice Beach.

In the example below, there are over 2000 tiles, some tiles entirely grass. In future exercises I will determine if the size of the tiles can be double the size to reduce the number of tiles yet keep each image under the 500MB limit CAD has with imagery. Each grid is labeled to enable the surveyor, designer, civil, landscape architect etc to determine “what grid do I need to add into CAD?”

image tiles identifying what ortho tile

image tiles identifying what ortho tile

Abbreviated steps to create image key

<aside> 💡 Note: unfortunately this option started with release ArcGIS pro 3.1 :-/

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  1. Create Catalog Dataset (toolbox under analysis menu). Search for the tool “Catalog Dataset.” This makes an empty dataset that we will place the grid polygons.

    1. make sure the output goes to perhaps the default database

    2. provide a catalog name

    3. identify what is the projection (use the same one that images use from Pix4D. In this example, its Rio Hondo College and I use the NAD 2011 State Plane Zone 5 in feet.

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    4. Select Run. Notice in the table of contents you now have the dataset.

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  2. Add Items to Catalog Dataset. The input are all the tiles (could be many thousand tiles). Select Run

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  3. Polygon features are generated for the image footprints including the image name and path (see below)

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  4. Export the Footprint to shapefile to shapefile ‘Imagekey.’ Remember where you place the shapefile file, you’ll need to know when you add this layer / shapefile into the Civil3D (only optional given many of us are unfamiliar with CAD .. at least for now)

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  1. Examine the attribute table of the new shapefile ImageKey. Each image tile name can be very lengthy which presents a problem when labeling the tiles. Create a new field (string / text with number of characters 6). Copy over the right 4 characters to the new field.

    addfield.mp4

  2. Label the shapefile using the new field to determine if this works (as displayed below)

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Deliverable to the CAD operators

There are two options for the CAD user to use your data. One option is to give them the folder from Pix4D (outputs) including the orthomosaic and tiles, contours, etc. The second option is to host the features and images online (Cloud) so they can add the data via the ArcGIS for AutoCAD Connector.

Deliverable for the Class