Using Tile

Requirements

Any image, whether it is a spatial image or not, can be tiled using the Tile function. It is recommended that all images be flattened before tiling. If a multi-layered image is tiled without flattening first, it will result in each tile containing all of the layers from the original image. In some cases this may result in blank layers in one or more of the resultant tiles if all layers do not contain image content that covers all image pixels.

 Any non-georeferenced images can be tiled; however, the output files will contain no georeferencing.

Tile Dialog Box

With an open image, click the Tile button in the Geographic Imager panel to open the Tile dialog box.

Tile button

Tiling Schema

The Tile dialog box displays two options for creating tiled images: By Number of Tiles or By Size of Tiles.

By Number of Tiles

This option creates a series of equally-sized georeferenced image tiles from the original image. Specify the number of horizontal and vertical tiles. The total number of tiles are displayed in the Destination frame. Using this option creates tiles that are divided evenly into the extent of the image.

By Size of Tiles

There are two options for creating tiles by a specific size: by number of pixels or by ground units of the coordinate system of the current image. For instance, if an image is in a coordinate system using meters, then the ground units option would be meters. Specify the horizontal and vertical tile dimensions. The total number of tiles are displayed in the Destination frame. Creating tiles by size may create smaller edge tiles that vary in size.

Overlap

Specify the amount of overlap that each tile has with its adjoining tiles. The amount of overlap for each tile can be set to either the number of pixels, ground units, or by a percentage (of the tile). The amount of overlap may be the same for both horizontal and vertical directions or different in each direction. This option is especially useful to guarantee gap-free mosaicking of individually transformed tiles.

Total Files

Displays the total number of tiled image files that will be created for the current tiling operation. This value is updated as the number or size of each tile changes. Check the Keep images open check box to keep the tiled images open after the tile process is completed. It is unchecked by default.

Keep Images Open

By default, this option is unchecked. Check this option to let tiles remain open, however, having many tiles open may cause Adobe Photoshop performance issues.

Naming

There are four naming conventions for tiled image files: Sequential Numbering, Separate Row/Column Numbers, Top - Left Corner Pixel Coordinates, and Top - Left Corner Ground Coordinates. To specify a file name and folder location to save the tiles, click OK in the Tile dialog box after all settings have been made.

The Sequential Numbering option begins numbering at the first tile in the top-left corner of the image and continues left to right, numbering each tile starting with the number 1 (e.g. tile-image_1.tif, tile-image_2.tif, etc). Both reference files and TIFF files are suffixed with the sequential tile number.

The Separate Row/Column Numbers option suffixes both row and column number of the position of each tile, beginning at the top-left corner and moving left to right. The row is the first number and the column is the second number. Both rows and columns start numbering at 1 (e.g. tile-image_1_1.tif, tile-image_1_2.tif, tile-image_2_1.tif, tile-image_2_2.tif, etc).

The Top - Left Corner Pixel Coordinates option suffixes the top-left pixel coordinate of each tile to the file name. In the four-tile example below, the pixel coordinates are shown for each file. The number of decimal places in the file name can be adjusted in the Precision box.

The Top - Left Ground Pixel Coordinates option suffixes the top-left ground coordinate of each tile to the file name. In the four-tile example below, the ground coordinates (in meters) are shown for each file.

Reference File Format

The Reference File Format drop-down list contains available external reference file formats to save with any Adobe Photoshop format: World files, Blue Marble Reference, MapInfo TAB and ERS. When Use internal format if available is checked and a selected image format has internal referencing, the external reference file format won’t be created. Some image formats that have internal referencing are ArcInfo ASCII Grid, BIL, ECW, Geospatial PDF, GeoTIFF/BigTIFF/TIFF, NITF, ERDAS IMAGINE Raster, USGS DEM, and MrSID.

Important Notes

 When tiling an image whose resolution is greater than 72 dpi, ECW and NITF output files will result in 72 dpi. ECW and NITF formats do not support change in storing and restoring resolution values.

 When creating greater than 200 tiles, the Keep images open option will be disabled.